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Balta VA, Stiffler D, Sayeed A, Tripathi AK, Elahi R, Mlambo G, Bakshi RP, Dziedzic AG, Jedlicka AE, Nenortas E, Romero-Rodriguez K, Canonizado MA, Mann A, Owen A, Sullivan DJ, Prigge ST, Sinnis P, Shapiro TA. Clinically relevant atovaquone-resistant human malaria parasites fail to transmit by mosquito. Nat Commun 2023; 14:6415. [PMID: 37828012 PMCID: PMC10570281 DOI: 10.1038/s41467-023-42030-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2023] [Accepted: 09/27/2023] [Indexed: 10/14/2023] Open
Abstract
Long-acting injectable medications, such as atovaquone, offer the prospect of a "chemical vaccine" for malaria, combining drug efficacy with vaccine durability. However, selection and transmission of drug-resistant parasites is of concern. Laboratory studies have indicated that atovaquone resistance disadvantages parasites in mosquitoes, but lack of data on clinically relevant Plasmodium falciparum has hampered integration of these variable findings into drug development decisions. Here we generate atovaquone-resistant parasites that differ from wild type parent by only a Y268S mutation in cytochrome b, a modification associated with atovaquone treatment failure in humans. Relative to wild type, Y268S parasites evidence multiple defects, most marked in their development in mosquitoes, whether from Southeast Asia (Anopheles stephensi) or Africa (An. gambiae). Growth of asexual Y268S P. falciparum in human red cells is impaired, but parasite loss in the mosquito is progressive, from reduced gametocyte exflagellation, to smaller number and size of oocysts, and finally to absence of sporozoites. The Y268S mutant fails to transmit from mosquitoes to mice engrafted with human liver cells and erythrocytes. The severe-to-lethal fitness cost of clinically relevant atovaquone resistance to P. falciparum in the mosquito substantially lessens the likelihood of its transmission in the field.
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Affiliation(s)
- Victoria A Balta
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, The Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, 21205, USA
- The Johns Hopkins Malaria Research Institute, Baltimore, MD, 21205, USA
| | - Deborah Stiffler
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, The Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, 21205, USA
- The Johns Hopkins Malaria Research Institute, Baltimore, MD, 21205, USA
| | - Abeer Sayeed
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, The Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, 21205, USA
- The Johns Hopkins Malaria Research Institute, Baltimore, MD, 21205, USA
| | - Abhai K Tripathi
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, The Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, 21205, USA
- The Johns Hopkins Malaria Research Institute, Baltimore, MD, 21205, USA
| | - Rubayet Elahi
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, The Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, 21205, USA
- The Johns Hopkins Malaria Research Institute, Baltimore, MD, 21205, USA
| | - Godfree Mlambo
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, The Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, 21205, USA
- The Johns Hopkins Malaria Research Institute, Baltimore, MD, 21205, USA
| | - Rahul P Bakshi
- The Johns Hopkins Malaria Research Institute, Baltimore, MD, 21205, USA
- Division of Clinical Pharmacology, Departments of Medicine and of Pharmacology and Molecular Sciences, The Johns Hopkins University, Baltimore, MD, 21205-2186, USA
| | - Amanda G Dziedzic
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, The Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, 21205, USA
| | - Anne E Jedlicka
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, The Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, 21205, USA
| | - Elizabeth Nenortas
- Division of Clinical Pharmacology, Departments of Medicine and of Pharmacology and Molecular Sciences, The Johns Hopkins University, Baltimore, MD, 21205-2186, USA
| | - Keyla Romero-Rodriguez
- Division of Clinical Pharmacology, Departments of Medicine and of Pharmacology and Molecular Sciences, The Johns Hopkins University, Baltimore, MD, 21205-2186, USA
| | - Matthew A Canonizado
- Division of Clinical Pharmacology, Departments of Medicine and of Pharmacology and Molecular Sciences, The Johns Hopkins University, Baltimore, MD, 21205-2186, USA
| | - Alexis Mann
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, The Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, 21205, USA
- The Johns Hopkins Malaria Research Institute, Baltimore, MD, 21205, USA
| | - Andrew Owen
- Centre of Excellence in Long-acting Therapeutics (CELT), Department of Pharmacology and Therapeutics, University of Liverpool, Liverpool, L69 3BX, UK
| | - David J Sullivan
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, The Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, 21205, USA
- The Johns Hopkins Malaria Research Institute, Baltimore, MD, 21205, USA
| | - Sean T Prigge
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, The Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, 21205, USA
- The Johns Hopkins Malaria Research Institute, Baltimore, MD, 21205, USA
| | - Photini Sinnis
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, The Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, 21205, USA
- The Johns Hopkins Malaria Research Institute, Baltimore, MD, 21205, USA
| | - Theresa A Shapiro
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, The Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, 21205, USA.
- The Johns Hopkins Malaria Research Institute, Baltimore, MD, 21205, USA.
- Division of Clinical Pharmacology, Departments of Medicine and of Pharmacology and Molecular Sciences, The Johns Hopkins University, Baltimore, MD, 21205-2186, USA.
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2
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Balta VA, Stiffler D, Sayeed A, Tripathi AK, Elahi R, Mlambo G, Bakshi RP, Dziedzic AG, Jedlicka AE, Nenortas E, Romero-Rodriguez K, Canonizado MA, Mann A, Owen A, Sullivan DJ, Prigge ST, Sinnis P, Shapiro TA. Transmissibility of clinically relevant atovaquone-resistant Plasmodium falciparum by anopheline mosquitoes. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.02.07.527535. [PMID: 36798298 PMCID: PMC9934642 DOI: 10.1101/2023.02.07.527535] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
Abstract
Rising numbers of malaria cases and deaths underscore the need for new interventions. Long-acting injectable medications, such as those now in use for HIV prophylaxis, offer the prospect of a malaria "chemical vaccine", combining the efficacy of a drug (like atovaquone) with the durability of a biological vaccine. Of concern, however, is the possible selection and transmission of drug-resistant parasites. We addressed this question by generating clinically relevant, highly atovaquone-resistant, Plasmodium falciparum mutants competent to infect mosquitoes. Isogenic paired strains, that differ only by a single Y268S mutation in cytochrome b, were evaluated in parallel in southeast Asian (Anopheles stephensi) or African (Anopheles gambiae) mosquitoes, and thence in humanized mice. Fitness costs of the mutation were evident along the lifecycle, in asexual parasite growth in vitro and in a progressive loss of parasites in the mosquito. In numerous independent experiments, microscopic exam of salivary glands from hundreds of mosquitoes failed to detect even one Y268S sporozoite, a defect not rescued by coinfection with wild type parasites. Furthermore, despite uniformly successful transmission of wild type parasites from An. stephensi to FRG NOD huHep mice bearing human hepatocytes and erythrocytes, multiple attempts with Y268S-fed mosquitoes failed: there was no evidence of parasites in mouse tissues by microscopy, in vitro culture, or PCR. These studies confirm a severe-to-lethal fitness cost of clinically relevant atovaquone-resistant P. falciparum in the mosquito, and they significantly lessen the likelihood of their transmission in the field.
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Affiliation(s)
- Victoria A. Balta
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, The Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, 21205
- The Johns Hopkins Malaria Research Institute, Baltimore, MD, 21205
| | - Deborah Stiffler
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, The Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, 21205
- The Johns Hopkins Malaria Research Institute, Baltimore, MD, 21205
| | - Abeer Sayeed
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, The Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, 21205
- The Johns Hopkins Malaria Research Institute, Baltimore, MD, 21205
| | - Abhai K. Tripathi
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, The Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, 21205
- The Johns Hopkins Malaria Research Institute, Baltimore, MD, 21205
| | - Rubayet Elahi
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, The Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, 21205
- The Johns Hopkins Malaria Research Institute, Baltimore, MD, 21205
| | - Godfree Mlambo
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, The Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, 21205
- The Johns Hopkins Malaria Research Institute, Baltimore, MD, 21205
| | - Rahul P. Bakshi
- The Johns Hopkins Malaria Research Institute, Baltimore, MD, 21205
- Division of Clinical Pharmacology, Departments of Medicine and of Pharmacology and Molecular Sciences, The Johns Hopkins University, Baltimore, MD, 21205-2186
| | - Amanda G. Dziedzic
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, The Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, 21205
| | - Anne E. Jedlicka
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, The Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, 21205
| | - Elizabeth Nenortas
- Division of Clinical Pharmacology, Departments of Medicine and of Pharmacology and Molecular Sciences, The Johns Hopkins University, Baltimore, MD, 21205-2186
| | - Keyla Romero-Rodriguez
- Division of Clinical Pharmacology, Departments of Medicine and of Pharmacology and Molecular Sciences, The Johns Hopkins University, Baltimore, MD, 21205-2186
| | - Matthew A. Canonizado
- Division of Clinical Pharmacology, Departments of Medicine and of Pharmacology and Molecular Sciences, The Johns Hopkins University, Baltimore, MD, 21205-2186
| | - Alexis Mann
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, The Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, 21205
- The Johns Hopkins Malaria Research Institute, Baltimore, MD, 21205
| | - Andrew Owen
- Centre of Excellence in Long-acting Therapeutics (CELT), Department of Pharmacology and Therapeutics, University of Liverpool, Liverpool L69 3BX, UK
| | - David J. Sullivan
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, The Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, 21205
- The Johns Hopkins Malaria Research Institute, Baltimore, MD, 21205
| | - Sean T. Prigge
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, The Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, 21205
- The Johns Hopkins Malaria Research Institute, Baltimore, MD, 21205
| | - Photini Sinnis
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, The Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, 21205
- The Johns Hopkins Malaria Research Institute, Baltimore, MD, 21205
| | - Theresa A. Shapiro
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, The Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, 21205
- The Johns Hopkins Malaria Research Institute, Baltimore, MD, 21205
- Division of Clinical Pharmacology, Departments of Medicine and of Pharmacology and Molecular Sciences, The Johns Hopkins University, Baltimore, MD, 21205-2186
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3
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Roobsoong W, Yadava A, Draper SJ, Minassian AM, Sattabongkot J. The challenges of Plasmodium vivax human malaria infection models for vaccine development. Front Immunol 2023; 13:1006954. [PMID: 36685545 PMCID: PMC9849360 DOI: 10.3389/fimmu.2022.1006954] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Accepted: 12/09/2022] [Indexed: 01/07/2023] Open
Abstract
Controlled Human Malaria Infection models (CHMI) have been critical to advancing new vaccines for malaria. Stringent and safe preparation of a challenge agent is key to the success of any CHMI. Difficulty producing the Plasmodium vivax parasite in vitro has limited production of qualified parasites for CHMI as well as the functional assays required to screen and down-select candidate vaccines for this globally distributed parasite. This and other challenges to P. vivax CHMI (PvCHMI), including scientific, logistical, and ethical obstacles, are common to P. vivax research conducted in both non-endemic and endemic countries, with additional hurdles unique to each. The challenges of using CHMI for P. vivax vaccine development and evaluation, lessons learned from previous and ongoing clinical trials, and the way forward to effectively perform PvCHMI to support vaccine development, are discussed.
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Affiliation(s)
- Wanlapa Roobsoong
- Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Anjali Yadava
- Biologics Research & Development, Walter Reed Army Institute of Research, Silver Spring, MD, United States
| | - Simon J. Draper
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | | | - Jetsumon Sattabongkot
- Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
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4
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Salkeld J, Themistocleous Y, Barrett JR, Mitton CH, Rawlinson TA, Payne RO, Hou MM, Khozoee B, Edwards NJ, Nielsen CM, Sandoval DM, Bach FA, Nahrendorf W, Ramon RL, Baker M, Ramos-Lopez F, Folegatti PM, Quinkert D, Ellis KJ, Poulton ID, Lawrie AM, Cho JS, Nugent FL, Spence PJ, Silk SE, Draper SJ, Minassian AM. Repeat controlled human malaria infection of healthy UK adults with blood-stage Plasmodium falciparum: Safety and parasite growth dynamics. Front Immunol 2022; 13:984323. [PMID: 36072606 PMCID: PMC9444061 DOI: 10.3389/fimmu.2022.984323] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Accepted: 08/01/2022] [Indexed: 11/13/2022] Open
Abstract
In endemic settings it is known that natural malaria immunity is gradually acquired following repeated exposures. Here we sought to assess whether similar acquisition of blood-stage malaria immunity would occur following repeated parasite exposure by controlled human malaria infection (CHMI). We report the findings of repeat homologous blood-stage Plasmodium falciparum (3D7 clone) CHMI studies VAC063C (ClinicalTrials.gov NCT03906474) and VAC063 (ClinicalTrials.gov NCT02927145). In total, 24 healthy, unvaccinated, malaria-naïve UK adult participants underwent primary CHMI followed by drug treatment. Ten of these then underwent secondary CHMI in the same manner, and then six of these underwent a final tertiary CHMI. As with primary CHMI, malaria symptoms were common following secondary and tertiary infection, however, most resolved within a few days of treatment and there were no long term sequelae or serious adverse events related to CHMI. Despite detectable induction and boosting of anti-merozoite serum IgG antibody responses following each round of CHMI, there was no clear evidence of anti-parasite immunity (manifest as reduced parasite growth in vivo) conferred by repeated challenge with the homologous parasite in the majority of volunteers. However, three volunteers showed some variation in parasite growth dynamics in vivo following repeat CHMI that were either modest or short-lived. We also observed no major differences in clinical symptoms or laboratory markers of infection across the primary, secondary and tertiary challenges. However, there was a trend to more severe pyrexia after primary CHMI and the absence of a detectable transaminitis post-treatment following secondary and tertiary infection. We hypothesize that this could represent the initial induction of clinical immunity. Repeat homologous blood-stage CHMI is thus safe and provides a model with the potential to further the understanding of naturally acquired immunity to blood-stage infection in a highly controlled setting.
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Affiliation(s)
- Jo Salkeld
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
- The Jenner Institute, University of Oxford, Oxford, United Kingdom
| | | | - Jordan R. Barrett
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
- The Jenner Institute, University of Oxford, Oxford, United Kingdom
| | - Celia H. Mitton
- The Jenner Institute, University of Oxford, Oxford, United Kingdom
| | | | - Ruth O. Payne
- The Jenner Institute, University of Oxford, Oxford, United Kingdom
| | - Mimi M. Hou
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
- The Jenner Institute, University of Oxford, Oxford, United Kingdom
| | - Baktash Khozoee
- The Jenner Institute, University of Oxford, Oxford, United Kingdom
| | - Nick J. Edwards
- The Jenner Institute, University of Oxford, Oxford, United Kingdom
| | - Carolyn M. Nielsen
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
- The Jenner Institute, University of Oxford, Oxford, United Kingdom
| | - Diana Muñoz Sandoval
- Institute of Immunology and Infection Research, University of Edinburgh, Edinburgh, United Kingdom
| | - Florian A. Bach
- Institute of Immunology and Infection Research, University of Edinburgh, Edinburgh, United Kingdom
| | - Wiebke Nahrendorf
- Institute of Immunology and Infection Research, University of Edinburgh, Edinburgh, United Kingdom
| | | | - Megan Baker
- The Jenner Institute, University of Oxford, Oxford, United Kingdom
| | | | | | - Doris Quinkert
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
- The Jenner Institute, University of Oxford, Oxford, United Kingdom
| | | | - Ian D. Poulton
- The Jenner Institute, University of Oxford, Oxford, United Kingdom
| | - Alison M. Lawrie
- The Jenner Institute, University of Oxford, Oxford, United Kingdom
| | - Jee-Sun Cho
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
- The Jenner Institute, University of Oxford, Oxford, United Kingdom
| | - Fay L. Nugent
- The Jenner Institute, University of Oxford, Oxford, United Kingdom
| | - Philip J. Spence
- Institute of Immunology and Infection Research, University of Edinburgh, Edinburgh, United Kingdom
- Centre for Immunity, Infection and Evolution, University of Edinburgh, Edinburgh, United Kingdom
| | - Sarah E. Silk
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
- The Jenner Institute, University of Oxford, Oxford, United Kingdom
| | - Simon J. Draper
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
- The Jenner Institute, University of Oxford, Oxford, United Kingdom
| | - Angela M. Minassian
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
- The Jenner Institute, University of Oxford, Oxford, United Kingdom
- *Correspondence: Angela M. Minassian,
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Kibwana E, Kapulu M, Bejon P. Controlled Human Malaria Infection Studies in Africa-Past, Present, and Future. Curr Top Microbiol Immunol 2022. [PMID: 35704094 DOI: 10.1007/82_2022_256] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Controlled human infection studies have contributed significantly to the understanding of pathogeneses and treatment of infectious diseases. In malaria, deliberately infecting humans with malaria parasites was used as a treatment for neurosyphilis in the early 1920s. More recently, controlled human malaria infection (CHMI) has become a valuable, cost-effective tool to fast-track the development and evaluation of new anti-malarial drugs and/or vaccines. CHMI studies have also been used to define host/parasite interactions and immunological correlates of protection. CHMI involves infecting a small number of healthy volunteers with malaria parasites, monitoring their parasitemia and providing anti-malarial treatment when a set threshold is reached. In this review we discuss the introduction, development, and challenges of modern-day Plasmodium falciparum CHMI studies conducted in Africa, and the impact of naturally acquired immunity on infectivity and vaccine efficacy. CHMIs have shown to be an invaluable tool particularly in accelerating malaria vaccine research. Although there are limitations of CHMI studies for estimating public health impacts and for regulatory purposes, their strength lies in proof-of-concept efficacy data at an early stage of development, providing a faster way to select vaccines for further development and providing valuable insights in understanding the mechanisms of immunity to malarial infection.
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Affiliation(s)
- Elizabeth Kibwana
- Bioscience Department, KEMRI-Wellcome Trust Research Program, Kilifi, Kenya
| | - Melissa Kapulu
- Bioscience Department, KEMRI-Wellcome Trust Research Program, Kilifi, Kenya
| | - Philip Bejon
- KEMRI-Wellcome Trust Research Program, Kilifi, Kenya.
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6
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Doolan DL. Malaria research in Australia: looking through the lens of the past towards the future. Int J Parasitol 2021; 51:1255-1263. [PMID: 34780720 DOI: 10.1016/j.ijpara.2021.11.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2021] [Revised: 11/05/2021] [Accepted: 11/05/2021] [Indexed: 10/19/2022]
Abstract
Malaria remains a global health priority, with substantial resources devoted to control and intervention since the causative parasite was first identified in 1880. Major advances have been made in discovery and translational research activities aimed at prevention, treatment and control. Laboratory-based, clinical, and field-based studies have complemented public health approaches. Australian scientists have played important roles, developing and applying innovative approaches, novel research tools and cutting-edge technologies in animal and human models of disease, as well as in disease-endemic settings. This article will provide an insight into 50 years of Australian efforts to discover mechanisms and targets of immunity and pathogenesis; develop new diagnostics, drugs, vaccines, and therapeutics; and assess new public health interventions and control measures in malaria-endemic settings.
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Affiliation(s)
- Denise L Doolan
- Centre for Molecular Therapeutics, Australian Institute of Tropical Health & Medicine, James Cook University, Cairns QLD 4878, Australia.
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7
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Camponovo F, Lee TE, Russell JR, Burgert L, Gerardin J, Penny MA. Mechanistic within-host models of the asexual Plasmodium falciparum infection: a review and analytical assessment. Malar J 2021; 20:309. [PMID: 34246274 PMCID: PMC8272282 DOI: 10.1186/s12936-021-03813-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Accepted: 06/11/2021] [Indexed: 12/03/2022] Open
Abstract
Background Malaria blood-stage infection length and intensity are important drivers of disease and transmission; however, the underlying mechanisms of parasite growth and the host’s immune response during infection remain largely unknown. Over the last 30 years, several mechanistic mathematical models of malaria parasite within-host dynamics have been published and used in malaria transmission models. Methods Mechanistic within-host models of parasite dynamics were identified through a review of published literature. For a subset of these, model code was reproduced and descriptive statistics compared between the models using fitted data. Through simulation and model analysis, key features of the models were compared, including assumptions on growth, immune response components, variant switching mechanisms, and inter-individual variability. Results The assessed within-host malaria models generally replicate infection dynamics in malaria-naïve individuals. However, there are substantial differences between the model dynamics after disease onset, and models do not always reproduce late infection parasitaemia data used for calibration of the within host infections. Models have attempted to capture the considerable variability in parasite dynamics between individuals by including stochastic parasite multiplication rates; variant switching dynamics leading to immune escape; variable effects of the host immune responses; or via probabilistic events. For models that capture realistic length of infections, model representations of innate immunity explain early peaks in infection density that cause clinical symptoms, and model representations of antibody immune responses control the length of infection. Models differed in their assumptions concerning variant switching dynamics, reflecting uncertainty in the underlying mechanisms of variant switching revealed by recent clinical data during early infection. Overall, given the scarce availability of the biological evidence there is limited support for complex models. Conclusions This study suggests that much of the inter-individual variability observed in clinical malaria infections has traditionally been attributed in models to random variability, rather than mechanistic disease dynamics. Thus, it is proposed that newly developed models should assume simple immune dynamics that minimally capture mechanistic understandings and avoid over-parameterization and large stochasticity which inaccurately represent unknown disease mechanisms. Supplementary Information The online version contains supplementary material available at 10.1186/s12936-021-03813-z.
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Affiliation(s)
- Flavia Camponovo
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland.,Center for Communicable Disease Dynamics, Department of Epidemiology, Harvard T. H. Chan School of Public Health, Boston, MA, 02115, USA
| | - Tamsin E Lee
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland
| | - Jonathan R Russell
- Institute of Disease Modeling, Bill & Melinda Gates Foundation, 500 5th Ave N, Seattle, WA, 98109, USA
| | - Lydia Burgert
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland
| | - Jaline Gerardin
- Department of Preventive Medicine and Institute for Global Health, Northwestern University, Chicago, IL, USA
| | - Melissa A Penny
- Swiss Tropical and Public Health Institute, Basel, Switzerland. .,University of Basel, Basel, Switzerland.
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8
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Parkash V, Ashwin H, Sadlova J, Vojtkova B, Jones G, Martin N, Greensted E, Allgar V, Kamhawi S, Valenzuela JG, Layton AM, Jaffe CL, Volf P, Kaye PM, Lacey CJN. A clinical study to optimise a sand fly biting protocol for use in a controlled human infection model of cutaneous leishmaniasis (the FLYBITE study). Wellcome Open Res 2021; 6:168. [PMID: 34693027 PMCID: PMC8506224 DOI: 10.12688/wellcomeopenres.16870.1] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/21/2021] [Indexed: 02/02/2023] Open
Abstract
Background: Leishmaniasis is a globally important yet neglected parasitic disease transmitted by phlebotomine sand flies. With new candidate vaccines in or near the clinic, a controlled human challenge model (CHIM) using natural sand fly challenge would provide a method for early evaluation of prophylactic efficacy. Methods : We evaluated the biting frequency and adverse effects resulting from exposure of human volunteers to bites of either Phlebotomus papatasi or P. duboscqi, two natural vectors of Leishmania major. 12 healthy participants were recruited (mean age 40.2 ± 11.8 years) with no history of significant travel to regions where L. major-transmitting sand flies are prevalent. Participants were assigned to either vector by 1:1 allocation and exposed to five female sand flies for 30 minutes in a custom biting chamber. Bite frequency was recorded to confirm a bloodmeal was taken. Participant responses and safety outcomes were monitored using a visual analogue scale (VAS), clinical examination, and blood biochemistry. Focus groups were subsequently conducted to explore participant acceptability. Results: All participants had at least one successful sand fly bite with none reporting any serious adverse events, with median VAS scores of 0-1/10 out to day 21 post-sand fly bite. Corresponding assessment of sand flies confirmed that for each participant at least 1/5 sand flies had successfully taken a bloodmeal (overall mean 3.67±1.03 bites per participant). There was no significant difference between P. papatasi and P. duboscqi in the number of bites resulting from 5 sand flies applied to human participants (3.3±0.81 vs 3.00±1.27 bites per participant; p=0.56) . In the two focus groups (n=5 per group), themes relating to positive participant-reported experiences of being bitten and the overall study, were identified. Conclusions: These results validate a protocol for achieving successful sand fly bites in humans that is safe, well-tolerated and acceptable for participants. Clinicaltrials.gov registration: NCT03999970 (27/06/2019).
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Affiliation(s)
- Vivak Parkash
- York Biomedical Research Institute, Hull York Medical School, University of York, York, N.Yorks, YO10 5DD, UK
- Department of Infection and Tropical Medicine, Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, UK
| | - Helen Ashwin
- York Biomedical Research Institute, Hull York Medical School, University of York, York, N.Yorks, YO10 5DD, UK
| | - Jovana Sadlova
- Department of Parasitology, Charles University, Prague, Czech Republic
| | - Barbora Vojtkova
- Department of Parasitology, Charles University, Prague, Czech Republic
| | - Georgina Jones
- School of Social Sciences, Leeds Beckett University, Leeds, UK
| | - Nina Martin
- School of Social Sciences, Leeds Beckett University, Leeds, UK
| | - Elizabeth Greensted
- York Biomedical Research Institute, Hull York Medical School, University of York, York, N.Yorks, YO10 5DD, UK
| | - Victoria Allgar
- Peninsula Medical School, University of Plymouth, Plymouth, UK
| | - Shaden Kamhawi
- Laboratory of Malaria and Vector Research, National Institutes of Health, Rockville, MD, USA
| | - Jesus G. Valenzuela
- Laboratory of Malaria and Vector Research, National Institutes of Health, Rockville, MD, USA
| | - Alison M. Layton
- York Biomedical Research Institute, Hull York Medical School, University of York, York, N.Yorks, YO10 5DD, UK
| | - Charles L. Jaffe
- Department of Microbiology and Molecular Genetics, The Hebrew University – Hadassah Medical School, Jerusalem, Israel
| | - Petr Volf
- Department of Parasitology, Charles University, Prague, Czech Republic
| | - Paul M. Kaye
- York Biomedical Research Institute, Hull York Medical School, University of York, York, N.Yorks, YO10 5DD, UK
| | - Charles J. N. Lacey
- York Biomedical Research Institute, Hull York Medical School, University of York, York, N.Yorks, YO10 5DD, UK
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9
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Minassian AM, Silk SE, Barrett JR, Nielsen CM, Miura K, Diouf A, Loos C, Fallon JK, Michell AR, White MT, Edwards NJ, Poulton ID, Mitton CH, Payne RO, Marks M, Maxwell-Scott H, Querol-Rubiera A, Bisnauthsing K, Batra R, Ogrina T, Brendish NJ, Themistocleous Y, Rawlinson TA, Ellis KJ, Quinkert D, Baker M, Lopez Ramon R, Ramos Lopez F, Barfod L, Folegatti PM, Silman D, Datoo M, Taylor IJ, Jin J, Pulido D, Douglas AD, de Jongh WA, Smith R, Berrie E, Noe AR, Diggs CL, Soisson LA, Ashfield R, Faust SN, Goodman AL, Lawrie AM, Nugent FL, Alter G, Long CA, Draper SJ. Reduced blood-stage malaria growth and immune correlates in humans following RH5 vaccination. MED 2021; 2:701-719.e19. [PMID: 34223402 PMCID: PMC8240500 DOI: 10.1016/j.medj.2021.03.014] [Citation(s) in RCA: 51] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2020] [Revised: 02/19/2021] [Accepted: 03/25/2021] [Indexed: 12/27/2022]
Abstract
BACKGROUND Development of an effective vaccine against the pathogenic blood-stage infection of human malaria has proved challenging, and no candidate vaccine has affected blood-stage parasitemia following controlled human malaria infection (CHMI) with blood-stage Plasmodium falciparum. METHODS We undertook a phase I/IIa clinical trial in healthy adults in the United Kingdom of the RH5.1 recombinant protein vaccine, targeting the P. falciparum reticulocyte-binding protein homolog 5 (RH5), formulated in AS01B adjuvant. We assessed safety, immunogenicity, and efficacy against blood-stage CHMI. Trial registered at ClinicalTrials.gov, NCT02927145. FINDINGS The RH5.1/AS01B formulation was administered using a range of RH5.1 protein vaccine doses (2, 10, and 50 μg) and was found to be safe and well tolerated. A regimen using a delayed and fractional third dose, in contrast to three doses given at monthly intervals, led to significantly improved antibody response longevity over ∼2 years of follow-up. Following primary and secondary CHMI of vaccinees with blood-stage P. falciparum, a significant reduction in parasite growth rate was observed, defining a milestone for the blood-stage malaria vaccine field. We show that growth inhibition activity measured in vitro using purified immunoglobulin G (IgG) antibody strongly correlates with in vivo reduction of the parasite growth rate and also identify other antibody feature sets by systems serology, including the plasma anti-RH5 IgA1 response, that are associated with challenge outcome. CONCLUSIONS Our data provide a new framework to guide rational design and delivery of next-generation vaccines to protect against malaria disease. FUNDING This study was supported by USAID, UK MRC, Wellcome Trust, NIAID, and the NIHR Oxford-BRC.
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Affiliation(s)
| | - Sarah E. Silk
- The Jenner Institute, University of Oxford, Oxford OX3 7DQ, UK
| | | | | | - Kazutoyo Miura
- Laboratory of Malaria and Vector Research, NIAID/NIH, Rockville, MD 20852, USA
| | - Ababacar Diouf
- Laboratory of Malaria and Vector Research, NIAID/NIH, Rockville, MD 20852, USA
| | - Carolin Loos
- The Ragon Institute of MGH, MIT, and Harvard, Cambridge, MA 02139, USA
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | | | - Ashlin R. Michell
- The Ragon Institute of MGH, MIT, and Harvard, Cambridge, MA 02139, USA
| | - Michael T. White
- Department of Parasites and Insect Vectors, Institut Pasteur, 25-28 Rue du Dr Roux, 75015 Paris, France
| | - Nick J. Edwards
- The Jenner Institute, University of Oxford, Oxford OX3 7DQ, UK
| | - Ian D. Poulton
- The Jenner Institute, University of Oxford, Oxford OX3 7DQ, UK
| | - Celia H. Mitton
- The Jenner Institute, University of Oxford, Oxford OX3 7DQ, UK
| | - Ruth O. Payne
- The Jenner Institute, University of Oxford, Oxford OX3 7DQ, UK
| | - Michael Marks
- Centre for Clinical Infection and Diagnostics Research, King’s College London and Guy’s & St Thomas’ NHS Foundation Trust, Westminster Bridge Road, London SE1 7EH, UK
| | - Hector Maxwell-Scott
- Centre for Clinical Infection and Diagnostics Research, King’s College London and Guy’s & St Thomas’ NHS Foundation Trust, Westminster Bridge Road, London SE1 7EH, UK
| | - Antonio Querol-Rubiera
- Centre for Clinical Infection and Diagnostics Research, King’s College London and Guy’s & St Thomas’ NHS Foundation Trust, Westminster Bridge Road, London SE1 7EH, UK
| | - Karen Bisnauthsing
- Centre for Clinical Infection and Diagnostics Research, King’s College London and Guy’s & St Thomas’ NHS Foundation Trust, Westminster Bridge Road, London SE1 7EH, UK
| | - Rahul Batra
- Centre for Clinical Infection and Diagnostics Research, King’s College London and Guy’s & St Thomas’ NHS Foundation Trust, Westminster Bridge Road, London SE1 7EH, UK
| | - Tatiana Ogrina
- NIHR Wellcome Trust Clinical Research Facility, University Hospital Southampton NHS Foundation Trust, Faculty of Medicine, University of Southampton, Southampton SO16 6YD, UK
| | - Nathan J. Brendish
- NIHR Wellcome Trust Clinical Research Facility, University Hospital Southampton NHS Foundation Trust, Faculty of Medicine, University of Southampton, Southampton SO16 6YD, UK
| | | | | | | | - Doris Quinkert
- The Jenner Institute, University of Oxford, Oxford OX3 7DQ, UK
| | - Megan Baker
- The Jenner Institute, University of Oxford, Oxford OX3 7DQ, UK
| | | | | | - Lea Barfod
- The Jenner Institute, University of Oxford, Oxford OX3 7DQ, UK
| | | | - Daniel Silman
- The Jenner Institute, University of Oxford, Oxford OX3 7DQ, UK
| | - Mehreen Datoo
- The Jenner Institute, University of Oxford, Oxford OX3 7DQ, UK
| | - Iona J. Taylor
- The Jenner Institute, University of Oxford, Oxford OX3 7DQ, UK
| | - Jing Jin
- The Jenner Institute, University of Oxford, Oxford OX3 7DQ, UK
| | - David Pulido
- The Jenner Institute, University of Oxford, Oxford OX3 7DQ, UK
| | | | - Willem A. de Jongh
- ExpreSion Biotechnologies, SCION-DTU Science Park, Agern Allé 1, Hørsholm 2970, Denmark
| | - Robert Smith
- Clinical BioManufacturing Facility, University of Oxford, Oxford OX3 7JT, UK
| | - Eleanor Berrie
- Clinical BioManufacturing Facility, University of Oxford, Oxford OX3 7JT, UK
| | | | | | | | | | - Saul N. Faust
- NIHR Wellcome Trust Clinical Research Facility, University Hospital Southampton NHS Foundation Trust, Faculty of Medicine, University of Southampton, Southampton SO16 6YD, UK
| | - Anna L. Goodman
- Centre for Clinical Infection and Diagnostics Research, King’s College London and Guy’s & St Thomas’ NHS Foundation Trust, Westminster Bridge Road, London SE1 7EH, UK
| | | | - Fay L. Nugent
- The Jenner Institute, University of Oxford, Oxford OX3 7DQ, UK
| | - Galit Alter
- The Ragon Institute of MGH, MIT, and Harvard, Cambridge, MA 02139, USA
| | - Carole A. Long
- Laboratory of Malaria and Vector Research, NIAID/NIH, Rockville, MD 20852, USA
| | - Simon J. Draper
- The Jenner Institute, University of Oxford, Oxford OX3 7DQ, UK
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10
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Abstract
Jean-Marc Chavatte and Georges Snounou discuss research involving controlled malaria infections.
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Affiliation(s)
- Jean-Marc Chavatte
- Malaria Reference Centre–National Public Health Laboratory, National Centre for Infectious Diseases, Singapore
- * E-mail: (J-MC); (GS)
| | - Georges Snounou
- Commissariat à l’Energie Atomique et aux Energies Alternatives-Université Paris Sud 11-INSERM U1184, Immunology of Viral Infections and Autoimmune Diseases (IMVA-HB), Infectious Disease Models and Innovative Therapies (IDMIT) Department, Institut de Biologie François Jacob (IBFJ), Direction de la Recherche Fondamentale (DRF), Fontenay-aux-Roses, France
- * E-mail: (J-MC); (GS)
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11
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Milne K, Ivens A, Reid AJ, Lotkowska ME, O'Toole A, Sankaranarayanan G, Munoz Sandoval D, Nahrendorf W, Regnault C, Edwards NJ, Silk SE, Payne RO, Minassian AM, Venkatraman N, Sanders MJ, Hill AVS, Barrett M, Berriman M, Draper SJ, Rowe JA, Spence PJ. Mapping immune variation and var gene switching in naive hosts infected with Plasmodium falciparum. eLife 2021; 10:e62800. [PMID: 33648633 PMCID: PMC7924948 DOI: 10.7554/elife.62800] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2020] [Accepted: 02/09/2021] [Indexed: 02/06/2023] Open
Abstract
Falciparum malaria is clinically heterogeneous and the relative contribution of parasite and host in shaping disease severity remains unclear. We explored the interaction between inflammation and parasite variant surface antigen (VSA) expression, asking whether this relationship underpins the variation observed in controlled human malaria infection (CHMI). We uncovered marked heterogeneity in the host response to blood challenge; some volunteers remained quiescent, others triggered interferon-stimulated inflammation and some showed transcriptional evidence of myeloid cell suppression. Significantly, only inflammatory volunteers experienced hallmark symptoms of malaria. When we tracked temporal changes in parasite VSA expression to ask whether variants associated with severe disease rapidly expand in naive hosts, we found no transcriptional evidence to support this hypothesis. These data indicate that parasite variants that dominate severe malaria do not have an intrinsic growth or survival advantage; instead, they presumably rely upon infection-induced changes in their within-host environment for selection.
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Affiliation(s)
- Kathryn Milne
- Institute of Immunology and Infection Research, University of EdinburghEdinburghUnited Kingdom
| | - Alasdair Ivens
- Institute of Immunology and Infection Research, University of EdinburghEdinburghUnited Kingdom
- Centre for Immunity, Infection and Evolution, University of EdinburghEdinburghUnited Kingdom
| | - Adam J Reid
- Wellcome Sanger InstituteCambridgeUnited Kingdom
| | | | - Aine O'Toole
- Centre for Immunity, Infection and Evolution, University of EdinburghEdinburghUnited Kingdom
- Institute of Evolutionary Biology, University of EdinburghEdinburghUnited Kingdom
| | | | - Diana Munoz Sandoval
- Institute of Immunology and Infection Research, University of EdinburghEdinburghUnited Kingdom
- Instituto de Microbiologia, Universidad San Francisco de QuitoQuitoEcuador
| | - Wiebke Nahrendorf
- Institute of Immunology and Infection Research, University of EdinburghEdinburghUnited Kingdom
| | - Clement Regnault
- Wellcome Centre for Integrative Parasitology, University of GlasgowGlasgowUnited Kingdom
- Glasgow Polyomics, University of GlasgowGlasgowUnited Kingdom
| | - Nick J Edwards
- The Jenner Institute, University of OxfordOxfordUnited Kingdom
| | - Sarah E Silk
- The Jenner Institute, University of OxfordOxfordUnited Kingdom
| | - Ruth O Payne
- The Jenner Institute, University of OxfordOxfordUnited Kingdom
| | | | | | | | - Adrian VS Hill
- The Jenner Institute, University of OxfordOxfordUnited Kingdom
| | - Michael Barrett
- Wellcome Centre for Integrative Parasitology, University of GlasgowGlasgowUnited Kingdom
- Glasgow Polyomics, University of GlasgowGlasgowUnited Kingdom
| | | | - Simon J Draper
- The Jenner Institute, University of OxfordOxfordUnited Kingdom
| | - J Alexandra Rowe
- Institute of Immunology and Infection Research, University of EdinburghEdinburghUnited Kingdom
- Centre for Immunity, Infection and Evolution, University of EdinburghEdinburghUnited Kingdom
| | - Philip J Spence
- Institute of Immunology and Infection Research, University of EdinburghEdinburghUnited Kingdom
- Centre for Immunity, Infection and Evolution, University of EdinburghEdinburghUnited Kingdom
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12
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Woolley SD, Fernandez M, Rebelo M, Llewellyn SA, Marquart L, Amante FH, Jennings HE, Webster R, Trenholme K, Chalon S, Moehrle JJ, McCarthy JS, Barber BE. Development and evaluation of a new Plasmodium falciparum 3D7 blood stage malaria cell bank for use in malaria volunteer infection studies. Malar J 2021; 20:93. [PMID: 33593375 PMCID: PMC7885253 DOI: 10.1186/s12936-021-03627-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Accepted: 02/05/2021] [Indexed: 11/23/2022] Open
Abstract
Background New anti-malarial therapeutics are required to counter the threat of increasing drug resistance. Malaria volunteer infection studies (VIS), particularly the induced blood stage malaria (IBSM) model, play a key role in accelerating anti-malarial drug development. Supply of the reference 3D7-V2 Plasmodium falciparum malaria cell bank (MCB) is limited. This study aimed to develop a new MCB, and compare the safety and infectivity of this MCB with the existing 3D7-V2 MCB, in a VIS. A second bank (3D7-V1) developed in 1995 was also evaluated. Methods The 3D7-V2 MCB was expanded in vitro using a bioreactor to produce a new MCB designated 3D7-MBE-008. This bank and 3D7-V1 were then evaluated using the IBSM model, where healthy participants were intravenously inoculated with blood-stage parasites. Participants were treated with artemether-lumefantrine when parasitaemia or clinical thresholds were reached. Safety, infectivity and parasite growth and clearance were evaluated. Results The in vitro expansion of 3D7-V2 produced 200 vials of the 3D7-MBE-008 MCB, with a parasitaemia of 4.3%. This compares to 0.1% in the existing 3D7-V2 MCB, and < 0.01% in the 3D7-V1 MCB. All four participants (two per MCB) developed detectable P. falciparum infection after inoculation with approximately 2800 parasites. For the 3D7-MBE-008 MCB, the parasite multiplication rate of 48 h (PMR48) using non-linear mixed effects modelling was 34.6 (95% CI 18.5–64.6), similar to the parental 3D7-V2 line; parasitaemia in both participants exceeded 10,000/mL by day 8. Growth of the 3D7-V1 was slower (PMR48 of 11.5 [95% CI 8.5–15.6]), with parasitaemia exceeding 10,000 parasites/mL on days 10 and 8.5. Rapid parasite clearance followed artemether-lumefantrine treatment in all four participants, with clearance half-lives of 4.01 and 4.06 (weighted mean 4.04 [95% CI 3.61–4.57]) hours for 3D7-MBE-008 and 4.11 and 4.52 (weighted mean 4.31 [95% CI 4.16–4.47]) hours for 3D7-V1. A total of 59 adverse events occurred; most were of mild severity with three being severe in the 3D7-MBE-008 study. Conclusion The safety, growth and clearance profiles of the expanded 3D7-MBE-008 MCB closely resemble that of its parent, indicating its suitability for future studies. Trial Registration: Australian New Zealand Clinical Trials registry numbers: P3487 (3D7-V1): ACTRN12619001085167. P3491 (3D7-MBE-008): ACTRN12619001079134
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Affiliation(s)
- Stephen D Woolley
- QIMR Berghofer Medical Research Institute, Brisbane, QLD, Australia.,Centre for Defence Pathology, Royal Centre for Defence Medicine, Joint Hospital Group, ICT Building, Birmingham Research Park, Vincent Drive, Birmingham, UK.,Clinical Sciences Department, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, UK
| | | | - Maria Rebelo
- QIMR Berghofer Medical Research Institute, Brisbane, QLD, Australia
| | | | - Louise Marquart
- QIMR Berghofer Medical Research Institute, Brisbane, QLD, Australia
| | - Fiona H Amante
- QIMR Berghofer Medical Research Institute, Brisbane, QLD, Australia
| | - Helen E Jennings
- QIMR Berghofer Medical Research Institute, Brisbane, QLD, Australia
| | - Rebecca Webster
- QIMR Berghofer Medical Research Institute, Brisbane, QLD, Australia
| | - Katharine Trenholme
- QIMR Berghofer Medical Research Institute, Brisbane, QLD, Australia.,School of Medicine, University of Queensland, Herston, QLD, Australia
| | - Stephan Chalon
- Medicines for Malaria Venture, 20 Route de Pre-Bois, PO Box 1826, 1215, Geneva 15, Switzerland
| | - Joerg J Moehrle
- Medicines for Malaria Venture, 20 Route de Pre-Bois, PO Box 1826, 1215, Geneva 15, Switzerland
| | - James S McCarthy
- QIMR Berghofer Medical Research Institute, Brisbane, QLD, Australia
| | - Bridget E Barber
- QIMR Berghofer Medical Research Institute, Brisbane, QLD, Australia.
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13
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Safety and feasibility of apheresis to harvest and concentrate parasites from subjects with induced blood stage Plasmodium vivax infection. Malar J 2021; 20:43. [PMID: 33446191 PMCID: PMC7807416 DOI: 10.1186/s12936-021-03581-w] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Accepted: 01/04/2021] [Indexed: 11/27/2022] Open
Abstract
Background In the absence of a method to culture Plasmodium vivax, the only way to source parasites is ex vivo. This hampers many aspects of P. vivax research. This study aimed to assess the safety of apheresis, a method for selective removal of specific components of blood as a means of extracting and concentrating P. vivax parasites. Methods An iterative approach was employed across four non-immune healthy human subjects in single subject cohorts. All four subjects were inoculated with ~ 564 blood stage P. vivax (HMP013-Pv) and subjected to apheresis 10 to 11 days later. Blood samples collected during apheresis (haematocrit layers 0.5% to 11%) were tested for the presence and concentration of P. vivax by microscopy, flow cytometry, 18S rDNA qPCR for total parasites, and pvs25 qRT-PCR for female gametocyte transcripts. Safety was determined by monitoring adverse events. Malaria transmission to mosquitoes was assessed by membrane feeding assays. Results There were no serious adverse events and no significant safety concerns. Apheresis concentrated asexual parasites by up to 4.9-fold (range: 0.9–4.9-fold) and gametocytes by up to 1.45-fold (range: 0.38–1.45-fold) compared to pre-apheresis densities. No single haematocrit layer contained > 40% of all the recovered P. vivax asexual parasites. Ex vivo concentration of parasites by Percoll gradient centrifugation of whole blood achieved greater concentration of gametocytes than apheresis. Mosquito transmission was enhanced by up to fivefold in a single apheresis sample compared to pre-apheresis. Conclusion The modest level of parasite concentration suggests that the use of apheresis may not be an ideal method for harvesting P. vivax. Trial Registration Australia New Zealand Clinical Trials Registry (ANZCTR) Trial ID: ACTRN12617001502325 registered on 19th October 2017. https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=373812.
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14
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Wockner LF, Hoffmann I, Webb L, Mordmüller B, Murphy SC, Kublin JG, O'Rourke P, McCarthy JS, Marquart L. Growth Rate of Plasmodium falciparum: Analysis of Parasite Growth Data From Malaria Volunteer Infection Studies. J Infect Dis 2020; 221:963-972. [PMID: 31679015 PMCID: PMC7198127 DOI: 10.1093/infdis/jiz557] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Accepted: 10/29/2019] [Indexed: 12/16/2022] Open
Abstract
Background Growth rate of malaria parasites in the blood of infected subjects is an important
measure of efficacy of drugs and vaccines. Methods We used log-linear and sine-wave models to estimate the parasite growth rate of the 3D7
strain of Plasmodium falciparum using data from 177 subjects from 14
induced blood stage malaria (IBSM) studies conducted at QIMR Berghofer. We estimated
parasite multiplication rate per 48 hour (PMR48), PMR per life-cycle
(PMRLC), and parasite life-cycle duration. We compared these parameters to
those from studies conducted elsewhere with infections induced by IBSM (n=66),
sporozoites via mosquito bite (n=336) or injection (n=51). Results The parasite growth rate of 3D7 in QIMR Berghofer studies was 0.75/day (95% CI:
0.73–0.77/day), PMR48 was 31.9 (95% CI: 28.7–35.4),
PMRLC was 16.4 (95% CI: 15.1–17.8) and parasite life-cycle was 38.8
hour (95% CI: 38.3–39.2 hour). These parameters were similar to estimates from
IBSM studies elsewhere (0.71/day, 95% CI: 0.67–0.75/day; PMR48 26.6,
95% CI: 22.2–31.8), but significantly higher (P < 0.001)
than in sporozoite studies (0.47/day, 95% CI: 0.43–0.50/day; PMR48
8.6, 95% CI: 7.3–10.1). Conclusions Parasite growth rates were similar across different IBSM studies and higher than
infections induced by sporozoite.
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Affiliation(s)
- Leesa F Wockner
- QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia
| | - Isabell Hoffmann
- QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia
| | - Lachlan Webb
- QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia
| | | | - Sean C Murphy
- Departments of Laboratory Medicine and Microbiology, University of Washington, Seattle, Washington, USA
| | - James G Kublin
- Fred Hutchinson Cancer Research Center, Seattle, Washington, USA
| | - Peter O'Rourke
- QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia
| | - James S McCarthy
- QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia.,School of Medicine, The University of Queensland, Brisbane, Queensland, Australia
| | - Louise Marquart
- QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia
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15
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Estimation of parasite age and synchrony status in Plasmodium falciparum infections. Sci Rep 2020; 10:10925. [PMID: 32616767 PMCID: PMC7331735 DOI: 10.1038/s41598-020-67817-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Accepted: 06/11/2020] [Indexed: 12/24/2022] Open
Abstract
Human malaria parasites have complex but poorly understood population dynamics inside their human host. In some but not all infections, parasites progress synchronously through the 48 h lifecycle following erythrocyte invasion, such that at any one time there is a limited spread of parasites at a particular time (hours) post-invasion. Patients presenting with older parasites, and with asynchronous infections, have been reported to have higher risks of fatal outcomes, associated with higher parasite biomass and multiplication rates respectively. However, practical tools to assess synchrony and estimate parasite age post-invasion in patient samples are lacking. We have developed a novel method based on three genes differentially expressed over the parasite intra-erythrocytic lifecycle, and applied it to samples from patients with uncomplicated malaria attending two health clinics in Ghana. We found that most patients presented with synchronous infections, and with parasites within 12 h of erythrocyte invasion. Finally we investigated if clinical features such as fever and parasite density could act as predictors of parasite age and synchrony. The new method is a simple and practicable approach to study parasite dynamics in naturally-infected patients, and is a significant improvement on the subjective microscopical methods for parasite staging in vivo, aiding patient management.
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16
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Chughlay MF, Akakpo S, Odedra A, Csermak-Renner K, Djeriou E, Winnips C, Leboulleux D, Gaur AH, Shanks GD, McCarthy J, Chalon S. Liver Enzyme Elevations in Plasmodium falciparum Volunteer Infection Studies: Findings and Recommendations. Am J Trop Med Hyg 2020; 103:378-393. [PMID: 32314694 PMCID: PMC7356411 DOI: 10.4269/ajtmh.19-0846] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Malaria volunteer infection studies (VISs) accelerate new drug and vaccine development. In the induced blood-stage malaria (IBSM) model, volunteers are inoculated with erythrocytes infected with Plasmodium falciparum. Observations of elevated liver enzymes in the IBSM model with new chemical entities (NCEs) promoted an analysis of available data. Data were reviewed from eight IBSM studies of seven different NCEs, plus two studies with the registered antimalarial piperaquine conducted between June 2013 and January 2017 at QIMR Berghofer, Brisbane, Australia. Alanine aminotransferase (ALT) was elevated (> 2.5 times the upper limit of normal [×ULN]) in 20/114 (17.5%) participants. Of these, 8.9% (10/114) had moderate increases (> 2.5–5 × ULN), noted in seven studies of six different NCEs ± piperaquine or piperaquine alone, and 8.9% (10/114) had severe elevations (> 5 × ULN), occurring in six studies of six different NCEs ± piperaquine. Aspartate aminotransferase (AST) was elevated (> 2.5 × ULN) in 11.4% (13/114) of participants, across six of the 10 studies. Bilirubin was > 2 × ULN in one participant. Published data from other VIS models, using sporozoite inoculation by systemic administration or mosquito feeding, also showed moderate/severe liver enzyme elevations. In conclusion, liver enzyme elevations in IBSM studies are most likely multifactorial and could be caused by the model conditions, that is, malaria infection/parasite density and/or effective parasite clearance, or by participant-specific risk factors, acetaminophen administration, or direct hepatotoxicity of the test drug. We make recommendations that may mitigate the risk of liver enzyme elevations in future VISs and propose measures to assist their interpretation, should they occur.
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Affiliation(s)
| | | | - Anand Odedra
- QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia
| | | | | | | | | | - Aditya H Gaur
- St. Jude Children's Research Hospital, Memphis, Tennessee
| | - G Dennis Shanks
- QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia
| | - James McCarthy
- QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia
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17
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Atmar RL, Keitel WA. Searching for Improved Flu Vaccines-The Time Is Now. J Infect Dis 2020; 221:1-4. [PMID: 31665360 DOI: 10.1093/infdis/jiz545] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Accepted: 10/14/2019] [Indexed: 12/21/2022] Open
Affiliation(s)
- Robert L Atmar
- Departments of Medicine and Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas, USA
| | - Wendy A Keitel
- Departments of Medicine and Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas, USA
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18
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Friedman-Klabanoff DJ, Laurens MB, Berry AA, Travassos MA, Adams M, Strauss KA, Shrestha B, Levine MM, Edelman R, Lyke KE. The Controlled Human Malaria Infection Experience at the University of Maryland. Am J Trop Med Hyg 2019; 100:556-565. [PMID: 30675854 PMCID: PMC6402913 DOI: 10.4269/ajtmh.18-0476] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2018] [Accepted: 12/03/2018] [Indexed: 11/07/2022] Open
Abstract
Controlled human malaria infection (CHMI) is a powerful tool to evaluate the efficacy of malaria vaccines and pharmacologics. Investigators at the University of Maryland, Baltimore, Center for Vaccine Development (UMB-CVD) pioneered the technique in the 1970s and continue to advance the frontiers of CHMI research. We reviewed the records of 338 malaria-naive volunteers who underwent CHMI at UMB-CVD with Plasmodium falciparum from 1971 until 2017. These 338 volunteers underwent 387 CHMI events, including 60 via intradermal injection or direct venous inoculation (DVI) of purified, cryopreserved sporozoites. No volunteer suffered an unplanned hospitalization or required intravenous therapy related to CHMI. Median prepatency period was longer in challenges using NF54 (9 days) than in those using 7G8 (8 days), P = 0.0006 by the log-rank test. With dose optimization of DVI, the prepatent period did not differ between DVI and mosquito bite challenge (log-rank test, P = 0.66). Polymerase chain reaction (PCR) detected P. falciparum infection 3 days earlier than thick smears (P < 0.001), and diagnosis by ultrasensitive PCR was associated with less severe symptoms than smear-based diagnosis (39% versus 0%, P = 0.0003). Historical studies with NF54 showed a shorter median prepatency period of 10.3 days than more recent studies (median 11.0 days, P = 0.02) despite significantly lower salivary gland scores in earlier studies, P = 0.0001. The 47-year experience of CHMI at UMB-CVD has led to advancements in sporozoite delivery, diagnostics, and use of heterologous challenge. Additional studies on new challenge strains and genomic data to reflect regional heterogeneity will help advance the use of CHMI as supporting data for vaccine licensure.
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Affiliation(s)
- DeAnna J. Friedman-Klabanoff
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, Maryland
| | - Matthew B. Laurens
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, Maryland
| | - Andrea A. Berry
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, Maryland
| | - Mark A. Travassos
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, Maryland
| | - Matthew Adams
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, Maryland
| | - Kathy A. Strauss
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, Maryland
| | - Biraj Shrestha
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, Maryland
| | - Myron M. Levine
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, Maryland
| | - Robert Edelman
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, Maryland
| | - Kirsten E. Lyke
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, Maryland
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Cooper MM, Loiseau C, McCarthy JS, Doolan DL. Human challenge models: tools to accelerate the development of malaria vaccines. Expert Rev Vaccines 2019; 18:241-251. [PMID: 30732492 DOI: 10.1080/14760584.2019.1580577] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
INTRODUCTION Malaria challenge models, where healthy human volunteers are intentionally infected with Plasmodium species parasites under controlled conditions, can be undertaken in several well-defined ways. These challenge models enable evaluation of the kinetics of parasite growth and clearance, host-pathogen interactions and the host immune response. They can facilitate discovery of candidate diagnostic biomarkers and novel vaccine targets. As translational tools they can facilitate testing of candidate vaccines and drugs and evaluation of diagnostic tests. AREAS COVERED Until recently, malaria human challenge models have been limited to only a few Plasmodium falciparum strains and used exclusively in malaria-naïve volunteers in non-endemic regions. Several recent advances include the use of alternate P. falciparum strains and other species of Plasmodia, as well as strains attenuated by chemical, radiation or genetic modification, and the conduct of studies in pre-exposed individuals. Herein, we discuss how this diversification is enabling more thorough vaccine efficacy testing and informing rational vaccine development. EXPERT OPINION The ability to comprehensively evaluate vaccine efficacy in controlled settings will continue to accelerate the translation of candidate malaria vaccines to the clinic, and inform the development and optimisation of potential vaccines that would be effective against multiple strains in geographically and demographically diverse settings.
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Affiliation(s)
- Martha M Cooper
- a Centre for Molecular Therapeutics, Australian Institute of Tropical Health and Medicine , James Cook University , Cairns , Australia
| | - Claire Loiseau
- a Centre for Molecular Therapeutics, Australian Institute of Tropical Health and Medicine , James Cook University , Cairns , Australia
| | - James S McCarthy
- b Infectious Diseases Programme , QIMR Berghofer Medical Research Institute , Brisbane , Australia
| | - Denise L Doolan
- a Centre for Molecular Therapeutics, Australian Institute of Tropical Health and Medicine , James Cook University , Cairns , Australia
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20
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Abstract
The blood stage of the malaria parasite life cycle is responsible for all the clinical symptoms of malaria. During the blood stage, Plasmodium merozoites invade and multiply within host red blood cells (RBCs). Here, we review the progress made, challenges faced, and new strategies available for the development of blood stage malaria vaccines. We discuss our current understanding of immune responses against blood stages and the status of clinical development of various blood stage malaria vaccine candidates. We then discuss possible paths forward to develop effective blood stage malaria vaccines. This includes a discussion of protective immune mechanisms that can be elicited to target blood stage parasites, novel delivery systems, immunoassays and animal models to optimize vaccine candidates in preclinical studies, and use of challenge models to get an early readout of vaccine efficacy.
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21
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Berna AZ, McCarthy JS, Wang XR, Michie M, Bravo FG, Cassells J, Trowell SC. Diurnal variation in expired breath volatiles in malaria-infected and healthy volunteers. J Breath Res 2018; 12:046014. [PMID: 30129561 PMCID: PMC7753889 DOI: 10.1088/1752-7163/aadbbb] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2018] [Revised: 08/17/2018] [Accepted: 08/21/2018] [Indexed: 12/16/2022]
Abstract
We previously showed that thioether levels in the exhaled breath volatiles of volunteers undergoing controlled human malaria infection (CHMI) with P. falciparum increase as infection progresses. In this study, we show that thioethers have diurnal cyclical increasing patterns and their levels are significantly higher in P. falciparum CHMI volunteers compared to those of healthy volunteers. The synchronized cycle and elevation of thioethers were not present in P. vivax-infection, therefore it is likely that the thioethers are associated with unique factors in the pathology of P. falciparum. Moreover, we found that time-of-day of breath collection is important to accurately predict (98%) P. falciparum-infection. Critically, this was achieved when the disease was asymptomatic and parasitemia was below the level detectable by microscopy. Although these findings are encouraging, they show limitations because of the limited and logistically difficult diagnostic window and its utility to P. falciparum malaria only. We looked for new biomarkers in the breath of P. vivax CHMI volunteers and found that a set of terpenes increase significantly over the course of the malaria infection. The accuracy of predicting P. vivax using breath terpenes was up to 91%. Moreover, some of the terpenes were also found in the breath of P. falciparum CHMI volunteers (accuracy up to 93.5%). The results suggest that terpenes might represent better biomarkers than thioethers to predict malaria as they were not subject to malaria pathogens diurnal changes.
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Affiliation(s)
- Amalia Z Berna
- Department of Pediatrics, Washington University School of Medicine, St. Louis, MO 63110, United States of America. CSIRO Health and Biosecurity, Clunies-Ross Street, Acton ACT 2601, Australia
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22
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Pawliw R, Farrow R, Sekuloski S, Jennings H, Healer J, Phuong T, Sathe P, Pasay C, Evans K, Cowman AF, Schofield L, Chen N, McCarthy J, Trenholme K. A bioreactor system for the manufacture of a genetically modified Plasmodium falciparum blood stage malaria cell bank for use in a clinical trial. Malar J 2018; 17:283. [PMID: 30081913 PMCID: PMC6080485 DOI: 10.1186/s12936-018-2435-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2018] [Accepted: 07/30/2018] [Indexed: 11/22/2022] Open
Abstract
Background Although the use of induced blood stage malaria infection has proven to be a valuable tool for testing the efficacy of vaccines and drugs against Plasmodium falciparum, a limiting factor has been the availability of Good Manufacturing Practice (GMP)—compliant defined P. falciparum strains for in vivo use. The aim of this study was to develop a cost-effective method for the large-scale production of P. falciparum cell banks suitable for use in clinical trials. Methods Genetically-attenuated parasites (GAP) were produced by targeted deletion of the gene encoding the knob associated histidine rich protein (kahrp) from P. falciparum strain 3D7. A GAP master cell bank (MCB) was manufactured by culturing parasites in an FDA approved single use, closed system sterile plastic bioreactor. All components used to manufacture the MCB were screened to comply with standards appropriate for in vivo use. The cryopreserved MCB was subjected to extensive testing to ensure GMP compliance for a phase 1 investigational product. Results Two hundred vials of the GAP MCB were successfully manufactured. At harvest, the GAP MCB had a parasitaemia of 6.3%, with 96% of parasites at ring stage. Testing confirmed that all release criteria were met (sterility, absence of viral contaminants and endotoxins, parasite viability following cryopreservation, identity and anti-malarial drug sensitivity of parasites). Conclusion Large-scale in vitro culture of P. falciparum parasites using a wave bioreactor can be achieved under GMP-compliant conditions. This provides a cost-effective methodology for the production of malaria parasites suitable for administration in clinical trials.
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Affiliation(s)
- Rebecca Pawliw
- Clinical Tropical Medicine Laboratory, QIMR Berghofer Medical Research Institute, 300 Herston Rd, Herston, Brisbane, QLD, Australia
| | - Rebecca Farrow
- Clinical Tropical Medicine Laboratory, QIMR Berghofer Medical Research Institute, 300 Herston Rd, Herston, Brisbane, QLD, Australia
| | - Silvana Sekuloski
- Clinical Tropical Medicine Laboratory, QIMR Berghofer Medical Research Institute, 300 Herston Rd, Herston, Brisbane, QLD, Australia
| | - Helen Jennings
- Clinical Tropical Medicine Laboratory, QIMR Berghofer Medical Research Institute, 300 Herston Rd, Herston, Brisbane, QLD, Australia
| | - Julie Healer
- The Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia
| | - Thuan Phuong
- Clinical Tropical Medicine Laboratory, QIMR Berghofer Medical Research Institute, 300 Herston Rd, Herston, Brisbane, QLD, Australia
| | - Pri Sathe
- The Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia
| | - Cielo Pasay
- Clinical Tropical Medicine Laboratory, QIMR Berghofer Medical Research Institute, 300 Herston Rd, Herston, Brisbane, QLD, Australia
| | - Krystal Evans
- The Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia
| | - Alan F Cowman
- The Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia
| | - Louis Schofield
- The Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia.,Australian Institute of Tropical Health and Medicine, James Cook University, Cairns, Australia
| | - Nanhua Chen
- Department of Drug Resistance and Diagnostics, Australian Army Malaria Institute, Brisbane, Australia
| | - James McCarthy
- Clinical Tropical Medicine Laboratory, QIMR Berghofer Medical Research Institute, 300 Herston Rd, Herston, Brisbane, QLD, Australia.,School of Medicine, University of Queensland, Brisbane, Australia
| | - Katharine Trenholme
- Clinical Tropical Medicine Laboratory, QIMR Berghofer Medical Research Institute, 300 Herston Rd, Herston, Brisbane, QLD, Australia. .,School of Medicine, University of Queensland, Brisbane, Australia.
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23
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Reuling IJ, van de Schans LA, Coffeng LE, Lanke K, Meerstein-Kessel L, Graumans W, van Gemert GJ, Teelen K, Siebelink-Stoter R, van de Vegte-Bolmer M, de Mast Q, van der Ven AJ, Ivinson K, Hermsen CC, de Vlas S, Bradley J, Collins KA, Ockenhouse CF, McCarthy J, Sauerwein RW, Bousema T. A randomized feasibility trial comparing four antimalarial drug regimens to induce Plasmodium falciparum gametocytemia in the controlled human malaria infection model. eLife 2018; 7:31549. [PMID: 29482720 PMCID: PMC5828662 DOI: 10.7554/elife.31549] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2017] [Accepted: 01/14/2018] [Indexed: 12/16/2022] Open
Abstract
Background Malaria elimination strategies require a thorough understanding of parasite transmission from human to mosquito. A clinical model to induce gametocytes to understand their dynamics and evaluate transmission-blocking interventions (TBI) is currently unavailable. Here, we explore the use of the well-established Controlled Human Malaria Infection model (CHMI) to induce gametocyte carriage with different antimalarial drug regimens. Methods In a single centre, open-label randomised trial, healthy malaria-naive participants (aged 18–35 years) were infected with Plasmodium falciparum by bites of infected Anopheles mosquitoes. Participants were randomly allocated to four different treatment arms (n = 4 per arm) comprising low-dose (LD) piperaquine (PIP) or sulfadoxine-pyrimethamine (SP), followed by a curative regimen upon recrudescence. Male and female gametocyte densities were determined by molecular assays. Results Mature gametocytes were observed in all participants (16/16, 100%). Gametocytes appeared 8.5–12 days after the first detection of asexual parasites. Peak gametocyte densities and gametocyte burden was highest in the LD-PIP/SP arm, and associated with the preceding asexual parasite biomass (p=0.026). Male gametocytes had a mean estimated circulation time of 2.7 days (95% CI 1.5–3.9) compared to 5.1 days (95% CI 4.1–6.1) for female gametocytes. Exploratory mosquito feeding assays showed successful sporadic mosquito infections. There were no serious adverse events or significant differences in the occurrence and severity of adverse events between study arms (p=0.49 and p=0.28). Conclusions The early appearance of gametocytes indicates gametocyte commitment during the first wave of asexual parasites emerging from the liver. Treatment by LD-PIP followed by a curative SP regimen, results in the highest gametocyte densities and the largest number of gametocyte-positive days. This model can be used to evaluate the effect of drugs and vaccines on gametocyte dynamics, and lays the foundation for fulfilling the critical unmet need to evaluate transmission-blocking interventions against falciparum malaria for downstream selection and clinical development. Funding Funded by PATH Malaria Vaccine Initiative (MVI). Clinical trial number NCT02836002.
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Affiliation(s)
- Isaie J Reuling
- Department of Medical Microbiology, Radboud university medical center, Nijmegen, Netherlands
| | - Lisanne A van de Schans
- Department of Medical Microbiology, Radboud university medical center, Nijmegen, Netherlands
| | - Luc E Coffeng
- Department of Public Health, Erasmus MC, University Medical Center Rotterdam, Rotterdam, Netherlands
| | - Kjerstin Lanke
- Department of Medical Microbiology, Radboud university medical center, Nijmegen, Netherlands
| | | | - Wouter Graumans
- Department of Medical Microbiology, Radboud university medical center, Nijmegen, Netherlands
| | - Geert-Jan van Gemert
- Department of Medical Microbiology, Radboud university medical center, Nijmegen, Netherlands
| | - Karina Teelen
- Department of Medical Microbiology, Radboud university medical center, Nijmegen, Netherlands
| | - Rianne Siebelink-Stoter
- Department of Medical Microbiology, Radboud university medical center, Nijmegen, Netherlands
| | | | - Quirijn de Mast
- Department of Internal Medicine, Radboud University Medical Center, Nijmegen, Netherlands
| | - André J van der Ven
- Department of Internal Medicine, Radboud University Medical Center, Nijmegen, Netherlands
| | - Karen Ivinson
- PATH Malaria Vaccine Initiative, Washington, United States
| | - Cornelus C Hermsen
- Department of Medical Microbiology, Radboud university medical center, Nijmegen, Netherlands
| | - Sake de Vlas
- Department of Public Health, Erasmus MC, University Medical Center Rotterdam, Rotterdam, Netherlands
| | - John Bradley
- MRC Tropical Epidemiology Group, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | | | | | - James McCarthy
- Clinical Tropical Medicine Laboratory, QIMR Berghofer, Brisbane, Australia
| | - Robert W Sauerwein
- Department of Medical Microbiology, Radboud university medical center, Nijmegen, Netherlands
| | - Teun Bousema
- Department of Medical Microbiology, Radboud university medical center, Nijmegen, Netherlands
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24
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Abstract
Controlled human malaria infection (CHMI) entails deliberate infection with malaria parasites either by mosquito bite or by direct injection of sporozoites or parasitized erythrocytes. When required, the resulting blood-stage infection is curtailed by the administration of antimalarial drugs. Inducing a malaria infection via inoculation with infected blood was first used as a treatment (malariotherapy) for neurosyphilis in Europe and the United States in the early 1900s. More recently, CHMI has been applied to the fields of malaria vaccine and drug development, where it is used to evaluate products in well-controlled early-phase proof-of-concept clinical studies, thus facilitating progression of only the most promising candidates for further evaluation in areas where malaria is endemic. Controlled infections have also been used to immunize against malaria infection. Historically, CHMI studies have been restricted by the need for access to insectaries housing infected mosquitoes or suitable malaria-infected individuals. Evaluation of vaccine and drug candidates has been constrained in these studies by the availability of a limited number of Plasmodium falciparum isolates. Recent advances have included cryopreservation of sporozoites, the manufacture of well-characterized and genetically distinct cultured malaria cell banks for blood-stage infection, and the availability of Plasmodium vivax-specific reagents. These advances will help to accelerate malaria vaccine and drug development by making the reagents for CHMI more widely accessible and also enabling a more rigorous evaluation with multiple parasite strains and species. Here we discuss the different applications of CHMI, recent advances in the use of CHMI, and ongoing challenges for consideration.
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25
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Pegha-Moukandja I, Imboumy-Limoukou RK, Tchitoula-Makaya N, Mouinga-Ondeme AG, Biteghe-Bi-Essone JC, Mba DN, Lekana-Douki JB, Ndouo FST. High Level of Specific Anti- Plasmodium Falciparum Merozoite IgG1 Antibodies in Rural Asymptomatic Individuals of Dienga, South-Eastern Gabon. Eur J Microbiol Immunol (Bp) 2017; 7:247-260. [PMID: 29403652 PMCID: PMC5793693 DOI: 10.1556/1886.2017.00010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2017] [Accepted: 06/12/2017] [Indexed: 01/01/2023] Open
Abstract
Plasmodium falciparum merozoite antigens (PfMAgs) play an essential role in the development of immunity to malaria. Currently, P. falciparum: protein 113 (Pf 113), apical membrane antigen 1 (AMA1), erythrocyte binding antigens (EBA175), and reticulocyte binding protein homologue 5 (RH5) are among the most PfMAgs studied. A comparative analysis of naturally acquired antibodies against these antigens in children would increase our knowledge about the development of protective immunity. Analysis of antibodies to Pf113, PfAMA1, PfEBA175, and PfRH5 was conducted in rural population during 2013 and 2014. Both prevalence and levels of total IgG anti-PfAMA1 were higher than that of IgG anti-PfEBA175, anti-PfRH5, and anti-Pf113. Seroconversion to PfAMA1 and PfEBA175 occurred moderately in young children and reached to the maximum in adolescent and in adults. High prevalence of IgG anti-Pf113 was observed in young children of 3 to 6 years old in 2013. The four antigens were recognized by IgG 1, 2, 3, and 4 antibodies from a large proportion of the subjects, and all of them induced high levels of specific IgG1 against PfAMA1, PfEBA175, fewer by Pf113 and PfRH5. Many asymptomatic children had specific IgG1 recognizing multiple antigens, and these IgG1 antibodies could be associated with a reduced risk of developing malaria symptoms.
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Affiliation(s)
- Irène Pegha-Moukandja
- Centre International de Recherches Médicales de Franceville (CIRMF), BP 769, Franceville Gabon, Africa.,Département de Parasitologie-Mycologie et Médecine Tropicale, Faculté de Médecine, Université des Sciences de la Santé, BP 4009, Libreville, Gabon, Africa.,Ecole Doctorale Régionale en Infectiologie Tropicale d'Afrique Centrale (ECODRAC), BP 876, Franceville, Gabon, Africa
| | - Roméo-Karl Imboumy-Limoukou
- Centre International de Recherches Médicales de Franceville (CIRMF), BP 769, Franceville Gabon, Africa.,Ecole Doctorale Régionale en Infectiologie Tropicale d'Afrique Centrale (ECODRAC), BP 876, Franceville, Gabon, Africa
| | - Nina Tchitoula-Makaya
- Ecole Doctorale Régionale en Infectiologie Tropicale d'Afrique Centrale (ECODRAC), BP 876, Franceville, Gabon, Africa
| | | | - Jean Claude Biteghe-Bi-Essone
- Centre International de Recherches Médicales de Franceville (CIRMF), BP 769, Franceville Gabon, Africa.,Ecole Doctorale Régionale en Infectiologie Tropicale d'Afrique Centrale (ECODRAC), BP 876, Franceville, Gabon, Africa
| | - Dieudonne Nkoghe Mba
- Centre International de Recherches Médicales de Franceville (CIRMF), BP 769, Franceville Gabon, Africa
| | - Jean-Bernard Lekana-Douki
- Centre International de Recherches Médicales de Franceville (CIRMF), BP 769, Franceville Gabon, Africa.,Département de Parasitologie-Mycologie et Médecine Tropicale, Faculté de Médecine, Université des Sciences de la Santé, BP 4009, Libreville, Gabon, Africa.,Ecole Doctorale Régionale en Infectiologie Tropicale d'Afrique Centrale (ECODRAC), BP 876, Franceville, Gabon, Africa
| | - Fousseyni S Toure Ndouo
- Centre International de Recherches Médicales de Franceville (CIRMF), BP 769, Franceville Gabon, Africa
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26
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Wockner LF, Hoffmann I, O'Rourke P, McCarthy JS, Marquart L. Comparison of statistical models to estimate parasite growth rate in the induced blood stage malaria model. Malar J 2017; 16:352. [PMID: 28841864 PMCID: PMC5574106 DOI: 10.1186/s12936-017-1999-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2017] [Accepted: 08/20/2017] [Indexed: 11/28/2022] Open
Abstract
Background The efficacy of vaccines aimed at inhibiting the growth of malaria parasites in the blood can be assessed by comparing the growth rate of parasitaemia in the blood of subjects treated with a test vaccine compared to controls. In studies using induced blood stage malaria (IBSM), a type of controlled human malaria infection, parasite growth rate has been measured using models with the intercept on the y-axis fixed to the inoculum size. A set of statistical models was evaluated to determine an optimal methodology to estimate parasite growth rate in IBSM studies. Methods Parasite growth rates were estimated using data from 40 subjects published in three IBSM studies. Data was fitted using 12 statistical models: log-linear, sine-wave with the period either fixed to 48 h or not fixed; these models were fitted with the intercept either fixed to the inoculum size or not fixed. All models were fitted by individual, and overall by study using a mixed effects model with a random effect for the individual. Results Log-linear models and sine-wave models, with the period fixed or not fixed, resulted in similar parasite growth rate estimates (within 0.05 log10 parasites per mL/day). Average parasite growth rate estimates for models fitted by individual with the intercept fixed to the inoculum size were substantially lower by an average of 0.17 log10 parasites per mL/day (range 0.06–0.24) compared with non-fixed intercept models. Variability of parasite growth rate estimates across the three studies analysed was substantially higher (3.5 times) for fixed-intercept models compared with non-fixed intercept models. The same tendency was observed in models fitted overall by study. Modelling data by individual or overall by study had minimal effect on parasite growth estimates. Conclusions The analyses presented in this report confirm that fixing the intercept to the inoculum size influences parasite growth estimates. The most appropriate statistical model to estimate the growth rate of blood-stage parasites in IBSM studies appears to be a log-linear model fitted by individual and with the intercept estimated in the log-linear regression. Future studies should use this model to estimate parasite growth rates. Electronic supplementary material The online version of this article (doi:10.1186/s12936-017-1999-1) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Leesa F Wockner
- QIMR Berghofer Medical Research Institute, Brisbane, QLD, 4006, Australia
| | - Isabell Hoffmann
- QIMR Berghofer Medical Research Institute, Brisbane, QLD, 4006, Australia.,Institute of Medical Biostatistics, Epidemiology and Informatics, Medical Center of Johannes Gutenberg University, 55101, Mainz, Germany
| | - Peter O'Rourke
- QIMR Berghofer Medical Research Institute, Brisbane, QLD, 4006, Australia
| | - James S McCarthy
- QIMR Berghofer Medical Research Institute, Brisbane, QLD, 4006, Australia. .,School of Medicine, University of Queensland, Brisbane, QLD, 4072, Australia. .,Q-Pharm Pty Ltd, Brisbane, QLD, 4006, Australia.
| | - Louise Marquart
- QIMR Berghofer Medical Research Institute, Brisbane, QLD, 4006, Australia
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27
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Bliss CM, Drammeh A, Bowyer G, Sanou GS, Jagne YJ, Ouedraogo O, Edwards NJ, Tarama C, Ouedraogo N, Ouedraogo M, Njie-Jobe J, Diarra A, Afolabi MO, Tiono AB, Yaro JB, Adetifa UJ, Hodgson SH, Anagnostou NA, Roberts R, Duncan CJA, Cortese R, Viebig NK, Leroy O, Lawrie AM, Flanagan KL, Kampmann B, Imoukhuede EB, Sirima SB, Bojang K, Hill AVS, Nébié I, Ewer KJ. Viral Vector Malaria Vaccines Induce High-Level T Cell and Antibody Responses in West African Children and Infants. Mol Ther 2017; 25:547-559. [PMID: 28153101 PMCID: PMC5368405 DOI: 10.1016/j.ymthe.2016.11.003] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Revised: 11/15/2016] [Accepted: 11/15/2016] [Indexed: 12/31/2022] Open
Abstract
Heterologous prime-boosting with viral vectors encoding the pre-erythrocytic antigen thrombospondin-related adhesion protein fused to a multiple epitope string (ME-TRAP) induces CD8+ T cell-mediated immunity to malaria sporozoite challenge in European malaria-naive and Kenyan semi-immune adults. This approach has yet to be evaluated in children and infants. We assessed this vaccine strategy among 138 Gambian and Burkinabe children in four cohorts: 2- to 6-year olds in The Gambia, 5- to 17-month-olds in Burkina Faso, and 5- to 12-month-olds and 10-week-olds in The Gambia. We assessed induction of cellular immunity, taking into account the distinctive hematological status of young infants, and characterized the antibody response to vaccination. T cell responses peaked 7 days after boosting with modified vaccinia virus Ankara (MVA), with highest responses in infants aged 10 weeks at priming. Incorporating lymphocyte count into the calculation of T cell responses facilitated a more physiologically relevant comparison of cellular immunity across different age groups. Both CD8+ and CD4+ T cells secreted cytokines. Induced antibodies were up to 20-fold higher in all groups compared with Gambian and United Kingdom (UK) adults, with comparable or higher avidity. This immunization regimen elicited strong immune responses, particularly in young infants, supporting future evaluation of efficacy in this key target age group for a malaria vaccine.
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Affiliation(s)
- Carly M Bliss
- The Jenner Institute Laboratories, University of Oxford, Old Road Campus Research Building, Oxford OX3 7DQ, UK
| | | | - Georgina Bowyer
- The Jenner Institute Laboratories, University of Oxford, Old Road Campus Research Building, Oxford OX3 7DQ, UK
| | - Guillaume S Sanou
- Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, 01 BP 2208 Ouagadougou, Burkina Faso
| | | | - Oumarou Ouedraogo
- Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, 01 BP 2208 Ouagadougou, Burkina Faso
| | - Nick J Edwards
- The Jenner Institute Laboratories, University of Oxford, Old Road Campus Research Building, Oxford OX3 7DQ, UK
| | - Casimir Tarama
- Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, 01 BP 2208 Ouagadougou, Burkina Faso
| | - Nicolas Ouedraogo
- Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, 01 BP 2208 Ouagadougou, Burkina Faso
| | - Mireille Ouedraogo
- Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, 01 BP 2208 Ouagadougou, Burkina Faso
| | | | - Amidou Diarra
- Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, 01 BP 2208 Ouagadougou, Burkina Faso
| | | | - Alfred B Tiono
- Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, 01 BP 2208 Ouagadougou, Burkina Faso
| | - Jean Baptiste Yaro
- Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, 01 BP 2208 Ouagadougou, Burkina Faso
| | | | - Susanne H Hodgson
- Centre for Clinical Vaccinology and Tropical Medicine, The Jenner Institute, Churchill Hospital, Oxford OX3 7LE, UK
| | - Nicholas A Anagnostou
- Centre for Clinical Vaccinology and Tropical Medicine, The Jenner Institute, Churchill Hospital, Oxford OX3 7LE, UK
| | - Rachel Roberts
- Centre for Clinical Vaccinology and Tropical Medicine, The Jenner Institute, Churchill Hospital, Oxford OX3 7LE, UK
| | - Christopher J A Duncan
- Centre for Clinical Vaccinology and Tropical Medicine, The Jenner Institute, Churchill Hospital, Oxford OX3 7LE, UK
| | | | - Nicola K Viebig
- European Vaccine Initiative, Universitäts Klinikum Heidelberg, Voßstr. 2, 69115 Heidelberg, Germany
| | - Odile Leroy
- European Vaccine Initiative, Universitäts Klinikum Heidelberg, Voßstr. 2, 69115 Heidelberg, Germany
| | - Alison M Lawrie
- Centre for Clinical Vaccinology and Tropical Medicine, The Jenner Institute, Churchill Hospital, Oxford OX3 7LE, UK
| | | | - Beate Kampmann
- Medical Research Council Unit, Fajara, The Gambia; Department of Paediatrics, Imperial College London SW7 2AZ, UK
| | - Egeruan B Imoukhuede
- Centre for Clinical Vaccinology and Tropical Medicine, The Jenner Institute, Churchill Hospital, Oxford OX3 7LE, UK
| | - Sodiomon B Sirima
- Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, 01 BP 2208 Ouagadougou, Burkina Faso
| | | | - Adrian V S Hill
- The Jenner Institute Laboratories, University of Oxford, Old Road Campus Research Building, Oxford OX3 7DQ, UK; Centre for Clinical Vaccinology and Tropical Medicine, The Jenner Institute, Churchill Hospital, Oxford OX3 7LE, UK
| | - Issa Nébié
- Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, 01 BP 2208 Ouagadougou, Burkina Faso
| | - Katie J Ewer
- The Jenner Institute Laboratories, University of Oxford, Old Road Campus Research Building, Oxford OX3 7DQ, UK.
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Payne RO, Griffin PM, McCarthy JS, Draper SJ. Plasmodium vivax Controlled Human Malaria Infection - Progress and Prospects. Trends Parasitol 2017; 33:141-150. [PMID: 27956060 PMCID: PMC5270241 DOI: 10.1016/j.pt.2016.11.001] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2016] [Revised: 11/01/2016] [Accepted: 11/04/2016] [Indexed: 02/06/2023]
Abstract
Modern controlled human malaria infection (CHMI) clinical trials have almost entirely focussed on Plasmodium falciparum, providing a highly informative means to investigate host-pathogen interactions as well as assess potential new prophylactic and therapeutic interventions. However, in recent years, there has been renewed interest in Plasmodium vivax, with CHMI models developed by groups in Colombia, the USA, and Australia. This review summarizes the published experiences, and examines the advantages and disadvantages of the different models that initiate infection either by mosquito bite or using a blood-stage inoculum. As for P. falciparum, CHMI studies with P. vivax will provide a platform for early proof-of-concept testing of drugs and vaccines, accelerating the development of novel interventions.
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Affiliation(s)
- Ruth O Payne
- The Jenner Institute Laboratories, Old Road Campus Research Building, University of Oxford, Oxford, OX3 7DQ, UK; The Centre for Clinical Vaccinology and Tropical Medicine, University of Oxford, Oxford, OX3 7LE, UK.
| | - Paul M Griffin
- QIMR Berghofer Medical Research Institute, 300 Herston Rd, Herston, Queensland 4006, Australia; Q-Pharm Pty Ltd, Brisbane, Australia; Department of Medicine and Infectious Diseases, Mater Hospital and Mater Medical Research Institute, Brisbane, Australia; The University of Queensland, Brisbane, Australia
| | - James S McCarthy
- QIMR Berghofer Medical Research Institute, 300 Herston Rd, Herston, Queensland 4006, Australia; The University of Queensland, Brisbane, Australia
| | - Simon J Draper
- The Jenner Institute Laboratories, Old Road Campus Research Building, University of Oxford, Oxford, OX3 7DQ, UK.
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The Power of Malaria Vaccine Trials Using Controlled Human Malaria Infection. PLoS Comput Biol 2017; 13:e1005255. [PMID: 28081133 PMCID: PMC5230743 DOI: 10.1371/journal.pcbi.1005255] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2016] [Accepted: 11/21/2016] [Indexed: 11/25/2022] Open
Abstract
Controlled human malaria infection (CHMI) in healthy human volunteers is an important and powerful tool in clinical malaria vaccine development. However, power calculations are essential to obtain meaningful estimates of protective efficacy, while minimizing the risk of adverse events. To optimize power calculations for CHMI-based malaria vaccine trials, we developed a novel non-linear statistical model for parasite kinetics as measured by qPCR, using data from mosquito-based CHMI experiments in 57 individuals. We robustly account for important sources of variation between and within individuals using a Bayesian framework. Study power is most dependent on the number of individuals in each treatment arm; inter-individual variation in vaccine efficacy and the number of blood samples taken per day matter relatively little. Due to high inter-individual variation in the number of first-generation parasites, hepatic vaccine trials required significantly more study subjects than erythrocytic vaccine trials. We provide power calculations for hypothetical malaria vaccine trials of various designs and conclude that so far, power calculations have been overly optimistic. We further illustrate how upcoming techniques like needle-injected CHMI may reduce required sample sizes. Controlled human malaria infection (CHMI) in healthy human volunteers is an important and powerful tool in clinical malaria vaccine development. However, to obtain meaningful estimates of protective efficacy, it is important to include an appropriate minimum number of participants, while minimizing the risks and burden for volunteers. Existing power calculations have limited value due to important influential assumptions. To optimize power calculations for malaria vaccine trials, we developed a non-linear, Bayesian statistical model for parasite kinetics as measured by quantitative real-time polymerase chain reaction, using existing data from mosquito-based CHMI experiments. Using our model, we provide improved, robust power calculations for various hypothetical malaria vaccine trials, taking account of important sources of variation between and within individuals. We conclude that so far, power calculations for malaria vaccine trials have been overly optimistic. We further illustrate how upcoming techniques like needle-injected CHMI may reduce required sample sizes.
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Griffin P, Pasay C, Elliott S, Sekuloski S, Sikulu M, Hugo L, Khoury D, Cromer D, Davenport M, Sattabongkot J, Ivinson K, Ockenhouse C, McCarthy J. Safety and Reproducibility of a Clinical Trial System Using Induced Blood Stage Plasmodium vivax Infection and Its Potential as a Model to Evaluate Malaria Transmission. PLoS Negl Trop Dis 2016; 10:e0005139. [PMID: 27930652 PMCID: PMC5145139 DOI: 10.1371/journal.pntd.0005139] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Accepted: 10/26/2016] [Indexed: 12/12/2022] Open
Abstract
Background Interventions to interrupt transmission of malaria from humans to mosquitoes represent an appealing approach to assist malaria elimination. A limitation has been the lack of systems to test the efficacy of such interventions before proceeding to efficacy trials in the field. We have previously demonstrated the feasibility of induced blood stage malaria (IBSM) infection with Plasmodium vivax. In this study, we report further validation of the IBSM model, and its evaluation for assessment of transmission of P. vivax to Anopheles stephensi mosquitoes. Methods Six healthy subjects (three cohorts, n = 2 per cohort) were infected with P. vivax by inoculation with parasitized erythrocytes. Parasite growth was monitored by quantitative PCR, and gametocytemia by quantitative reverse transcriptase PCR (qRT-PCR) for the mRNA pvs25. Parasite multiplication rate (PMR) and size of inoculum were calculated by linear regression. Mosquito transmission studies were undertaken by direct and membrane feeding assays over 3 days prior to commencement of antimalarial treatment, and midguts of blood fed mosquitoes dissected and checked for presence of oocysts after 7–9 days. Results The clinical course and parasitemia were consistent across cohorts, with all subjects developing mild to moderate symptoms of malaria. No serious adverse events were reported. Asymptomatic elevated liver function tests were detected in four of six subjects; these resolved without treatment. Direct feeding of mosquitoes was well tolerated. The estimated PMR was 9.9 fold per cycle. Low prevalence of mosquito infection was observed (1.8%; n = 32/1801) from both direct (4.5%; n = 20/411) and membrane (0.9%; n = 12/1360) feeds. Conclusion The P. vivax IBSM model proved safe and reliable. The clinical course and PMR were reproducible when compared with the previous study using this model. The IBSM model presented in this report shows promise as a system to test transmission-blocking interventions. Further work is required to validate transmission and increase its prevalence. Trial Registration Anzctr.org.au ACTRN12613001008718 Blocking the transmission of malaria from infected individuals to mosquitoes is an appealing approach to malaria elimination. However, at present there is no reliable experimental model to test the efficacy of transmission blocking interventions. In this study, we assessed the safety and reproducibility of our clinical trial model, in which we inject blood cells infected with malaria parasites into healthy volunteers. Furthermore, we tested if our clinical trial model could be used as a tool to evaluate malaria transmission. We infected healthy volunteers with Plasmodium vivax parasites and monitored parasite growth by molecular methods. When we detected the parasite stage that is infective to mosquitoes (the sexual stage), blood from infected volunteers was fed to mosquitoes. Then, we investigated the presence of parasites in the midgut of mosquitoes. The results from this study show that our clinical trial model is safe and reproducible. Moreover, we observed low levels of transmission of the malaria parasite from infected volunteers to mosquitoes. We need to validate this finding and to optimize it to increase the rate of malaria transmission. Altogether, our clinical trial model seems to be a reliable system to assess interventions to block malaria transmission, which has enormous public health significance.
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Affiliation(s)
- Paul Griffin
- Clinical Tropical Medicine Laboratory, QIMR Berghofer, Brisbane, Australia
- Q-Pharm Pty Ltd, Brisbane, Australia
- Department of Medicine and Infectious Diseases, Mater Hospital and Mater Medical Research Institute, Brisbane, Australia
- The University of Queensland, Brisbane, Australia
| | - Cielo Pasay
- Clinical Tropical Medicine Laboratory, QIMR Berghofer, Brisbane, Australia
| | | | - Silvana Sekuloski
- Clinical Tropical Medicine Laboratory, QIMR Berghofer, Brisbane, Australia
| | - Maggy Sikulu
- Clinical Tropical Medicine Laboratory, QIMR Berghofer, Brisbane, Australia
| | - Leon Hugo
- Clinical Tropical Medicine Laboratory, QIMR Berghofer, Brisbane, Australia
| | - David Khoury
- University of New South Wales, Sydney, Australia
| | | | | | - Jetsumon Sattabongkot
- Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Karen Ivinson
- PATH, Malaria Vaccine Initiative, Washington, DC, United States
| | | | - James McCarthy
- Clinical Tropical Medicine Laboratory, QIMR Berghofer, Brisbane, Australia
- The University of Queensland, Brisbane, Australia
- * E-mail:
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Infectivity of Plasmodium falciparum in Malaria-Naive Individuals Is Related to Knob Expression and Cytoadherence of the Parasite. Infect Immun 2016; 84:2689-96. [PMID: 27382019 DOI: 10.1128/iai.00414-16] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2016] [Accepted: 06/27/2016] [Indexed: 11/20/2022] Open
Abstract
Plasmodium falciparum is the most virulent human malaria parasite because of its ability to cytoadhere in the microvasculature. Nonhuman primate studies demonstrated relationships among knob expression, cytoadherence, and infectivity. This has not been examined in humans. Cultured clinical-grade P. falciparum parasites (NF54, 7G8, and 3D7B) and ex vivo-derived cell banks were characterized. Knob and knob-associated histidine-rich protein expression, CD36 adhesion, and antibody recognition of parasitized erythrocytes (PEs) were evaluated. Parasites from the cell banks were administered to malaria-naive human volunteers to explore infectivity. For the NF54 and 3D7B cell banks, blood was collected from the study participants for in vitro characterization. All parasites were infective in vivo However, infectivity of NF54 was dramatically reduced. In vitro characterization revealed that unlike other cell bank parasites, NF54 PEs lacked knobs and did not cytoadhere. Recognition of NF54 PEs by immune sera was observed, suggesting P. falciparum erythrocyte membrane protein 1 expression. Subsequent recovery of knob expression and CD36-mediated adhesion were observed in PEs derived from participants infected with NF54. Knobless cell bank parasites have a dramatic reduction in infectivity and the ability to adhere to CD36. Subsequent infection of malaria-naive volunteers restored knob expression and CD36-mediated cytoadherence, thereby showing that the human environment can modulate virulence.
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Dimonte S, Bruske EI, Hass J, Supan C, Salazar CL, Held J, Tschan S, Esen M, Flötenmeyer M, Koch I, Berger J, Bachmann A, Sim BKL, Hoffman SL, Kremsner PG, Mordmüller B, Frank M. Sporozoite Route of Infection Influences In Vitro var Gene Transcription of Plasmodium falciparum Parasites From Controlled Human Infections. J Infect Dis 2016; 214:884-94. [PMID: 27279526 DOI: 10.1093/infdis/jiw225] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2016] [Accepted: 05/19/2016] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND Antigenic variation in Plasmodium falciparum is mediated by the multicopy var gene family. Each parasite possesses about 60 var genes, and switching between active var loci results in antigenic variation. In the current study, the effect of mosquito and host passage on in vitro var gene transcription was investigated. METHODS Thirty malaria-naive individuals were inoculated by intradermal or intravenous injection with cryopreserved, isogenic NF54 P. falciparum sporozoites (PfSPZ) generated from 1 premosquito culture. Microscopic parasitemia developed in 22 individuals, and 21 in vitro cultures were established. The var gene transcript levels were determined in early and late postpatient cultures and in the premosquito culture. RESULTS At the early time point, all cultures preferentially transcribed 8 subtelomeric var genes. Intradermal infections had higher var gene transcript levels than intravenous infections and a significantly longer intrahost replication time (P = .03). At the late time point, 9 subtelomeric and 8 central var genes were transcribed at the same levels in almost all cultures. Premosquito and late postpatient cultures transcribed the same subtelomeric and central var genes, except for var2csa CONCLUSIONS The duration of intrahost replication influences in vitro var gene transcript patterns. Differences between premosquito and postpatient cultures decrease with prolonged in vitro growth.
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Affiliation(s)
- Sandra Dimonte
- Institute of Tropical Medicine University of Tübingen and German Center for Infection Research, Partner Site Tübingen
| | - Ellen I Bruske
- Institute of Tropical Medicine University of Tübingen and German Center for Infection Research, Partner Site Tübingen
| | - Johanna Hass
- Institute of Tropical Medicine University of Tübingen and German Center for Infection Research, Partner Site Tübingen
| | - Christian Supan
- Institute of Tropical Medicine University of Tübingen and German Center for Infection Research, Partner Site Tübingen
| | - Carmen L Salazar
- Institute of Tropical Medicine University of Tübingen and German Center for Infection Research, Partner Site Tübingen
| | - Jana Held
- Institute of Tropical Medicine University of Tübingen and German Center for Infection Research, Partner Site Tübingen
| | - Serena Tschan
- Institute of Tropical Medicine University of Tübingen and German Center for Infection Research, Partner Site Tübingen
| | - Meral Esen
- Institute of Tropical Medicine University of Tübingen and German Center for Infection Research, Partner Site Tübingen
| | | | - Iris Koch
- Max Planck Institute for Developmental Biology, Tübingen
| | - Jürgen Berger
- Max Planck Institute for Developmental Biology, Tübingen
| | - Anna Bachmann
- Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany
| | | | | | - Peter G Kremsner
- Institute of Tropical Medicine University of Tübingen and German Center for Infection Research, Partner Site Tübingen Centre de Recherches Médicales de Lambaréné (CERMEL), Fondation Internationale de l'Hôpital Albert Schweitzer, Lambaréné, Gabon
| | - Benjamin Mordmüller
- Institute of Tropical Medicine University of Tübingen and German Center for Infection Research, Partner Site Tübingen
| | - Matthias Frank
- Institute of Tropical Medicine University of Tübingen and German Center for Infection Research, Partner Site Tübingen
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Pegha Moukandja I, Biteghe Bi Essone JC, Sagara I, Kassa Kassa RF, Ondzaga J, Lékana Douki JB, Bouyou Akotet M, Nkoghe Mba D, Touré Ndouo FS. Marked Rise in the Prevalence of Asymptomatic Plasmodium falciparum Infection in Rural Gabon. PLoS One 2016; 11:e0153899. [PMID: 27228058 PMCID: PMC4881998 DOI: 10.1371/journal.pone.0153899] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2016] [Accepted: 04/05/2016] [Indexed: 11/29/2022] Open
Abstract
Control strategies implemented a decade ago led to a marked reduction in the prevalence of malaria in many countries. In Dienga, southeastern Gabon, the prevalence of microscopic P. falciparum infection was 7% in 2003, close to the pre-elimination threshold of 5%. The aim of this work was to determine the prevalence of P. falciparum infection in the same community a decade later. A cohort of 370 individuals aged from 3 to 85 years living in Dienga was investigated for P. falciparum infection; during six passages (P) in 15-month period. Demographic data were collected, along with behaviors and attitudes towards malaria. Plasmodium infection was diagnosed by microscopy (ME), followed by PCR to detect submicroscopic infection. The prevalence of P. falciparum infection in P1, P2, P3, P4, P5 and P6 was respectively 43.5% (25.1% ME+, 18.4% PCR+); 40.9% (27.0% ME+, 13.9% PCR+), 52.7% (26.1% ME+, 26.6% PCR+); 34.1% (14.1% ME+, 20% PCR+), 57.7% (25.4.% ME+, 32.3% PCR+); and 46.2% (21.4% ME+, 24.8% PCR+) with an overall average of 45.9% (95%CI [37.0–54.7], 23.2% ME+ and 22.7% PCR+). P4 and P5 prevalences were statically different throughout the six passages. Microscopic prevalence was significantly higher than that observed ten years ago (23% [n = 370] vs 7% [n = 323], p < 0.001). Asymptomatic infections were the most frequent (96%). Gametocytes were detected in levels ranging from 5.9% to 13.9%. Insecticide-treated nets, indoor residual insecticides, and self-medication were used by respectively 33.2% (95%CI [29.0–37.4]), 17.7% (95%CI [15.5–19.9]) and 12.1% (95%CI [10.6–13.6]) of the study population. A near-threefold increase in P. falciparum infection has been observed in a rural area of southeastern Gabon during a 10-year period. Most infections were asymptomatic, but these subjects likely represent a parasite reservoir. These findings call for urgent reinforcement of preventive measures.
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Affiliation(s)
- Irène Pegha Moukandja
- Centre International de Recherches Médicales de Franceville (CIRMF) B.P. 769 Franceville, Gabon
- Ecole Doctorale Régionale (EDR) en Infectiologie Tropicale, BP: 876 Franceville, Gabon
| | - Jean Claude Biteghe Bi Essone
- Centre International de Recherches Médicales de Franceville (CIRMF) B.P. 769 Franceville, Gabon
- Ecole Doctorale Régionale (EDR) en Infectiologie Tropicale, BP: 876 Franceville, Gabon
| | - Issaka Sagara
- Département d'Epidémiologie et des Affections Parasitaires, MRTC, Faculté de Médecine et d'Odontostomatologie, Université de Bamako, BP 1805 Bamako, Mali
| | | | - Julien Ondzaga
- Centre International de Recherches Médicales de Franceville (CIRMF) B.P. 769 Franceville, Gabon
| | - Jean-Bernard Lékana Douki
- Centre International de Recherches Médicales de Franceville (CIRMF) B.P. 769 Franceville, Gabon
- Ecole Doctorale Régionale (EDR) en Infectiologie Tropicale, BP: 876 Franceville, Gabon
- Département de Parasitologie-Mycologie Médecine Tropicale, Faculté de Médecine, Université des Sciences de la Santé, B.P. 4009 Libreville, Gabon
| | - Marielle Bouyou Akotet
- Département de Parasitologie-Mycologie Médecine Tropicale, Faculté de Médecine, Université des Sciences de la Santé, B.P. 4009 Libreville, Gabon
| | - Dieudonne Nkoghe Mba
- Centre International de Recherches Médicales de Franceville (CIRMF) B.P. 769 Franceville, Gabon
| | - Fousseyni S. Touré Ndouo
- Centre International de Recherches Médicales de Franceville (CIRMF) B.P. 769 Franceville, Gabon
- * E-mail:
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Linking Murine and Human Plasmodium falciparum Challenge Models in a Translational Path for Antimalarial Drug Development. Antimicrob Agents Chemother 2016; 60:3669-75. [PMID: 27044554 PMCID: PMC4879391 DOI: 10.1128/aac.02883-15] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Accepted: 03/30/2016] [Indexed: 11/20/2022] Open
Abstract
Effective progression of candidate antimalarials is dependent on optimal dosing in clinical studies, which is determined by a sound understanding of pharmacokinetics and pharmacodynamics (PK/PD). Recently, two important translational models for antimalarials have been developed: the NOD/SCID/IL2Rγ−/− (NSG) model, whereby mice are engrafted with noninfected and Plasmodium falciparum-infected human erythrocytes, and the induced blood-stage malaria (IBSM) model in human volunteers. The antimalarial mefloquine was used to directly measure the PK/PD in both models, which were compared to previously published trial data for malaria patients. The clinical part was a single-center, controlled study using a blood-stage Plasmodium falciparum challenge inoculum in volunteers to characterize the effectiveness of mefloquine against early malaria. The study was conducted in three cohorts (n = 8 each) using different doses of mefloquine. The characteristic delay in onset of action of about 24 h was seen in both NSG and IBSM systems. In vivo 50% inhibitory concentrations (IC50s) were estimated at 2.0 μg/ml and 1.8 μg/ml in the NSG and IBSM models, respectively, aligning with 1.8 μg/ml reported previously for patients. In the IBSM model, the parasite reduction ratios were 157 and 195 for the 10- and 15-mg/kg doses, within the range of previously reported clinical data for patients but significantly lower than observed in the mouse model. Linking mouse and human challenge models to clinical trial data can accelerate the accrual of critical data on antimalarial drug activity. Such data can guide large clinical trials required for development of urgently needed novel antimalarial combinations. (This trial was registered at the Australian New Zealand Clinical Trials Registry [http://anzctr.org.au] under registration number ACTRN12612000323820.)
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Chang HH, Childs LM, Buckee CO. Variation in infection length and superinfection enhance selection efficiency in the human malaria parasite. Sci Rep 2016; 6:26370. [PMID: 27193195 PMCID: PMC4872237 DOI: 10.1038/srep26370] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2015] [Accepted: 04/28/2016] [Indexed: 01/08/2023] Open
Abstract
The capacity for adaptation is central to the evolutionary success of the human malaria parasite Plasmodium falciparum. Malaria epidemiology is characterized by the circulation of multiple, genetically diverse parasite clones, frequent superinfection, and highly variable infection lengths, a large number of which are chronic and asymptomatic. The impact of these characteristics on the evolution of the parasite is largely unknown, however, hampering our understanding of the impact of interventions and the emergence of drug resistance. In particular, standard population genetic frameworks do not accommodate variation in infection length or superinfection. Here, we develop a population genetic model of malaria including these variations, and show that these aspects of malaria infection dynamics enhance both the probability and speed of fixation for beneficial alleles in complex and non-intuitive ways. We find that populations containing a mixture of short- and long-lived infections promote selection efficiency. Interestingly, this increase in selection efficiency occurs even when only a small fraction of the infections are chronic, suggesting that selection can occur efficiently in areas of low transmission intensity, providing a hypothesis for the repeated emergence of drug resistance in the low transmission setting of Southeast Asia.
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Affiliation(s)
- Hsiao-Han Chang
- Center for Communicable Disease Dynamics, Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, MA 02115, USA
| | - Lauren M Childs
- Center for Communicable Disease Dynamics, Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, MA 02115, USA
| | - Caroline O Buckee
- Center for Communicable Disease Dynamics, Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, MA 02115, USA
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Pasay CJ, Rockett R, Sekuloski S, Griffin P, Marquart L, Peatey C, Wang CYT, O'Rourke P, Elliott S, Baker M, Möhrle JJ, McCarthy JS. Piperaquine Monotherapy of Drug-Susceptible Plasmodium falciparum Infection Results in Rapid Clearance of Parasitemia but Is Followed by the Appearance of Gametocytemia. J Infect Dis 2016; 214:105-13. [PMID: 27056954 PMCID: PMC4907420 DOI: 10.1093/infdis/jiw128] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2015] [Accepted: 03/24/2016] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND Piperaquine, coformulated with dihydroartemisinin, is a component of a widely used artemisinin combination therapy. There is a paucity of data on its antimalarial activity as a single agent. Such data, if available, would inform selection of new coformulations. METHODS We undertook a study in healthy subjects, using the induced blood stage malaria (IBSM) model to test the antimalarial activity of single doses of piperaquine (960, 640, and 480 mg) in 3 cohorts. In a pilot study in the third cohort, gametocyte clearance following administration of 15 mg, or 45 mg or no primaquine was investigated. RESULTS Parasite clearance over the 48-hour period after piperaquine administration was more rapid in the 960 mg cohort, compared with the 640 mg cohort (parasite reduction ratio, 2951 [95% confidence interval {CI}, 1520-5728] vs 586 [95% CI, 351-978]; P < .001). All 24 subjects developed gametocytemia as determined by pfs25 transcripts. Clearance of pfs25 was significantly faster in those receiving primaquine than in those not receiving primaquine (P < .001). CONCLUSIONS Piperaquine possesses rapid parasite-clearing activity, but monotherapy is followed by the appearance of gametocytemia, which could facilitate the spread of malaria. This new information should be taken into account when developing future antimalarial coformulations. CLINICAL TRIALS REGISTRATION ACTRN12613000565741.
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Affiliation(s)
| | - Rebecca Rockett
- School of Chemistry and Molecular Biosciences Queensland Pediatric Infectious Diseases Laboratory
| | | | - Paul Griffin
- QIMR Berghofer Medical Research Institute School of Medicine, University of Queensland Q-Pharm Department of Infectious Diseases, Mater Health Services and Mater Research Institute
| | | | | | | | | | | | | | | | - James S McCarthy
- QIMR Berghofer Medical Research Institute School of Medicine, University of Queensland Q-Pharm
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Birkett AJ. Building an effective malaria vaccine pipeline to address global needs. Vaccine 2015; 33:7538-43. [PMID: 26469721 DOI: 10.1016/j.vaccine.2015.09.111] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2015] [Revised: 09/25/2015] [Accepted: 09/29/2015] [Indexed: 02/08/2023]
Abstract
Despite impressive gains over the last 15 years in reducing the mortality associated with malaria, it remains a public health emergency. New interventions, such as vaccines, are needed to ensure that previous gains serve as a foundation for future progress. Vaccines have the potential to prevent severe disease and death in those most vulnerable, and to accelerate elimination and eradication by breaking the cycle of parasite transmission. The pipeline is as healthy as it has ever been, with approaches targeting different stages of the parasite lifecycle using an array of technologies. This article reviews recent progress and reviews key considerations in the quest to develop products that are aligned with the unmet medical need.
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Affiliation(s)
- Ashley J Birkett
- PATH Malaria Vaccine Initiative (MVI), 455 Massachusetts Avenue NW, Suite 1000, Washington, DC 20001-2621, USA.
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Berna AZ, McCarthy JS, Wang RX, Saliba KJ, Bravo FG, Cassells J, Padovan B, Trowell SC. Analysis of Breath Specimens for Biomarkers of Plasmodium falciparum Infection. J Infect Dis 2015; 212:1120-8. [PMID: 25810441 PMCID: PMC4559192 DOI: 10.1093/infdis/jiv176] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2015] [Accepted: 03/06/2015] [Indexed: 11/15/2022] Open
Abstract
Currently, the majority of diagnoses of malaria rely on a combination of the patient's clinical presentation and the visualization of parasites on a stained blood film. Breath offers an attractive alternative to blood as the basis for simple, noninvasive diagnosis of infectious diseases. In this study, breath samples were collected from individuals during controlled malaria to determine whether specific malaria-associated volatiles could be detected in breath. We identified 9 compounds whose concentrations varied significantly over the course of malaria: carbon dioxide, isoprene, acetone, benzene, cyclohexanone, and 4 thioethers. The latter group, consisting of allyl methyl sulfide, 1-methylthio-propane, (Z)-1-methylthio-1-propene, and (E)-1-methylthio-1-propene, had not previously been associated with any disease or condition. Before the availability of antimalarial drug treatment, there was evidence of concurrent 48-hour cyclical changes in the levels of both thioethers and parasitemia. When thioether concentrations were subjected to a phase shift of 24 hours, a direct correlation between the parasitemia and volatile levels was revealed. Volatile levels declined monotonically approximately 6.5 hours after initial drug treatment, correlating with clearance of parasitemia. No thioethers were detected in in vitro cultures of Plasmodium falciparum. The metabolic origin of the thioethers is not known, but results suggest that interplay between host and parasite metabolic pathways is involved in the production of these thioethers.
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Affiliation(s)
| | - James S McCarthy
- QIMR Berghofer Medical Research Institute
- Infectious Diseases Unit, Royal Brisbane and Women舗s Hospital, Brisbane
| | | | - Kevin J Saliba
- Research School of Biology, Australian National University, Canberra, Australia
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Viebig NK, D'Alessio F, Draper SJ, Sim BKL, Mordmüller B, Bowyer PW, Luty AJF, Jungbluth S, Chitnis CE, Hill AVS, Kremsner P, Craig AG, Kocken CHM, Leroy O. Workshop report: Malaria vaccine development in Europe--preparing for the future. Vaccine 2015; 33:6137-44. [PMID: 26431986 DOI: 10.1016/j.vaccine.2015.09.074] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2015] [Revised: 09/03/2015] [Accepted: 09/22/2015] [Indexed: 10/23/2022]
Abstract
The deployment of a safe and effective malaria vaccine will be an important tool for the control of malaria and the reduction in malaria deaths. With the launch of the 2030 Malaria Vaccine Technology Roadmap, the malaria community has updated the goals and priorities for the development of such a vaccine and is now paving the way for a second phase of malaria vaccine development. During a workshop in Brussels in November 2014, hosted by the European Vaccine Initiative, key players from the European, North American and African malaria vaccine community discussed European strategies for future malaria vaccine development in the global context. The recommendations of the European malaria community should guide researchers, policy makers and funders of global health research and development in fulfilling the ambitious goals set in the updated Malaria Vaccine Technology Roadmap.
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Affiliation(s)
- Nicola K Viebig
- European Vaccine Initiative, UniversitätsKlinikum Heidelberg, Im Neuenheimer Feld 326, 69120 Heidelberg, Germany.
| | - Flavia D'Alessio
- European Vaccine Initiative, UniversitätsKlinikum Heidelberg, Im Neuenheimer Feld 326, 69120 Heidelberg, Germany
| | - Simon J Draper
- The Jenner Institute, University of Oxford , Old Road Campus Research Building, Roosevelt Drive, Oxford, OX3 7DQ, UK
| | - B Kim Lee Sim
- Sanaria Inc., 9800 Medical Center Drive, Suite A209, Rockville, MD 20850, USA
| | - Benjamin Mordmüller
- Institut für Tropenmedizin, Universitätsklinikum Tübingen, Wilhelmstraße 27, 72074 Tübingen, Germany; Centre de Recherches Médicales de Lambaréné, B.P. 118 Lambaréné, Gabon
| | - Paul W Bowyer
- The National Institute for Biological Standards and Control (NIBSC), Blanche Lane, South Mimms, Potters Bar, Hertfordshire, EN6 3QG, UK
| | - Adrian J F Luty
- IRD MERIT UMR 216, 75006 Paris, France; COMUE Sorbonne Paris Cité, Université Paris Descartes, Faculté des Sciences Pharmaceutiques et Biologiques, 75270 Paris, France
| | - Stefan Jungbluth
- European Vaccine Initiative, UniversitätsKlinikum Heidelberg, Im Neuenheimer Feld 326, 69120 Heidelberg, Germany
| | - Chetan E Chitnis
- Institut Pasteur, 25-28 Rue du Docteur Roux, 75015 Paris, France
| | - Adrian V S Hill
- The Jenner Institute, University of Oxford , Old Road Campus Research Building, Roosevelt Drive, Oxford, OX3 7DQ, UK
| | - Peter Kremsner
- Institut für Tropenmedizin, Universitätsklinikum Tübingen, Wilhelmstraße 27, 72074 Tübingen, Germany; Centre de Recherches Médicales de Lambaréné, B.P. 118 Lambaréné, Gabon
| | - Alister G Craig
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK
| | - Clemens H M Kocken
- Biomedical Primate Research Centre, Department of Parasitology, Lange Kleiweg 161, 2288 GJ Rijswijk, The Netherlands
| | - Odile Leroy
- European Vaccine Initiative, UniversitätsKlinikum Heidelberg, Im Neuenheimer Feld 326, 69120 Heidelberg, Germany
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Stanisic DI, Liu XQ, De SL, Batzloff MR, Forbes T, Davis CB, Sekuloski S, Chavchich M, Chung W, Trenholme K, McCarthy JS, Li T, Sim BKL, Hoffman SL, Good MF. Development of cultured Plasmodium falciparum blood-stage malaria cell banks for early phase in vivo clinical trial assessment of anti-malaria drugs and vaccines. Malar J 2015; 14:143. [PMID: 25890156 PMCID: PMC4392471 DOI: 10.1186/s12936-015-0663-x] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2014] [Accepted: 03/24/2015] [Indexed: 11/18/2022] Open
Abstract
Background The ability to undertake controlled human malaria infection (CHMI) studies for preliminary evaluation of malaria vaccine candidates and anti-malaria drug efficacy has been limited by the need for access to sporozoite infected mosquitoes, aseptic, purified, cryopreserved sporozoites or blood-stage malaria parasites derived ex vivo from malaria infected individuals. Three different strategies are described for the manufacture of clinical grade cultured malaria cell banks suitable for use in CHMI studies. Methods Good Manufacturing Practices (GMP)-grade Plasmodium falciparum NF54, clinically isolated 3D7, and research-grade P. falciparum 7G8 blood-stage malaria parasites were cultured separately in GMP-compliant facilities using screened blood components and then cryopreserved to produce three P. falciparum blood-stage malaria cell banks. These cell banks were evaluated according to specific criteria (parasitaemia, identity, viability, sterility, presence of endotoxin, presence of mycoplasma or other viral agents and in vitro anti-malarial drug sensitivity of the cell bank malaria parasites) to ensure they met the criteria to permit product release according to GMP requirements. Results The P. falciparum NF54, 3D7 and 7G8 cell banks consisted of >78% ring stage parasites with a ring stage parasitaemia of >1.4%. Parasites were viable in vitro following thawing. The cell banks were free from contamination with bacteria, mycoplasma and a broad panel of viruses. The P. falciparum NF54, 3D7 and 7G8 parasites exhibited differential anti-malarial drug susceptibilities. The P. falciparum NF54 and 3D7 parasites were susceptible to all anti-malaria compounds tested, whereas the P. falciparum 7G8 parasites were resistant/had decreased susceptibility to four compounds. Following testing, all defined release criteria were met and the P. falciparum cell banks were deemed suitable for release. Ethical approval has been obtained for administration to human volunteers. Conclusions The production of cultured P. falciparum blood-stage malaria cell banks represents a suitable approach for the generation of material suitable for CHMI studies. A key feature of this culture-based approach is the ability to take research-grade material through to a product suitable for administration in clinical trials. Electronic supplementary material The online version of this article (doi:10.1186/s12936-015-0663-x) contains supplementary material, which is available to authorized users.
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Affiliation(s)
| | - Xue Q Liu
- Institute for Glycomics, Griffith University, Southport, QLD, Australia.
| | - Sai Lata De
- Institute for Glycomics, Griffith University, Southport, QLD, Australia.
| | - Michael R Batzloff
- Institute for Glycomics, Griffith University, Southport, QLD, Australia.
| | - Tanya Forbes
- Institute for Glycomics, Griffith University, Southport, QLD, Australia.
| | | | - Silvana Sekuloski
- Clinical Tropical Medicine Laboratory, QIMR Berghofer Medical Research Institute, University of Queensland, Herston, Australia.
| | | | - Wendy Chung
- Clinical Tropical Medicine Laboratory, QIMR Berghofer Medical Research Institute, University of Queensland, Herston, Australia.
| | - Katharine Trenholme
- Clinical Tropical Medicine Laboratory, QIMR Berghofer Medical Research Institute, University of Queensland, Herston, Australia.
| | - James S McCarthy
- Clinical Tropical Medicine Laboratory, QIMR Berghofer Medical Research Institute, University of Queensland, Herston, Australia.
| | - Tao Li
- Sanaria Inc, Rockville, MD, USA.
| | | | | | - Michael F Good
- Institute for Glycomics, Griffith University, Southport, QLD, Australia.
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Hofmann N, Mwingira F, Shekalaghe S, Robinson LJ, Mueller I, Felger I. Ultra-sensitive detection of Plasmodium falciparum by amplification of multi-copy subtelomeric targets. PLoS Med 2015; 12:e1001788. [PMID: 25734259 PMCID: PMC4348198 DOI: 10.1371/journal.pmed.1001788] [Citation(s) in RCA: 232] [Impact Index Per Article: 25.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/18/2014] [Accepted: 01/08/2015] [Indexed: 01/09/2023] Open
Abstract
BACKGROUND Planning and evaluating malaria control strategies relies on accurate definition of parasite prevalence in the population. A large proportion of asymptomatic parasite infections can only be identified by surveillance with molecular methods, yet these infections also contribute to onward transmission to mosquitoes. The sensitivity of molecular detection by PCR is limited by the abundance of the target sequence in a DNA sample; thus, detection becomes imperfect at low densities. We aimed to increase PCR diagnostic sensitivity by targeting multi-copy genomic sequences for reliable detection of low-density infections, and investigated the impact of these PCR assays on community prevalence data. METHODS AND FINDINGS Two quantitative PCR (qPCR) assays were developed for ultra-sensitive detection of Plasmodium falciparum, targeting the high-copy telomere-associated repetitive element 2 (TARE-2, ∼250 copies/genome) and the var gene acidic terminal sequence (varATS, 59 copies/genome). Our assays reached a limit of detection of 0.03 to 0.15 parasites/μl blood and were 10× more sensitive than standard 18S rRNA qPCR. In a population cross-sectional study in Tanzania, 295/498 samples tested positive using ultra-sensitive assays. Light microscopy missed 169 infections (57%). 18S rRNA qPCR failed to identify 48 infections (16%), of which 40% carried gametocytes detected by pfs25 quantitative reverse-transcription PCR. To judge the suitability of the TARE-2 and varATS assays for high-throughput screens, their performance was tested on sample pools. Both ultra-sensitive assays correctly detected all pools containing one low-density P. falciparum-positive sample, which went undetected by 18S rRNA qPCR, among nine negatives. TARE-2 and varATS qPCRs improve estimates of prevalence rates, yet other infections might still remain undetected when absent in the limited blood volume sampled. CONCLUSIONS Measured malaria prevalence in communities is largely determined by the sensitivity of the diagnostic tool used. Even when applying standard molecular diagnostics, prevalence in our study population was underestimated by 8% compared to the new assays. Our findings highlight the need for highly sensitive tools such as TARE-2 and varATS qPCR in community surveillance and for monitoring interventions to better describe malaria epidemiology and inform malaria elimination efforts.
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Affiliation(s)
- Natalie Hofmann
- Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
| | - Felista Mwingira
- Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
- Biological Sciences Department, Dar es Salaam University College of Education, Dar es Salaam, Tanzania
| | | | - Leanne J. Robinson
- Papua New Guinea Institute of Medical Research, Madang and Maprik, Papua New Guinea
- Walter and Eliza Hall Institute, Parkville, Victoria, Australia
- Department of Medical Biology, University of Melbourne, Parkville, Victoria, Australia
| | - Ivo Mueller
- Walter and Eliza Hall Institute, Parkville, Victoria, Australia
- Department of Medical Biology, University of Melbourne, Parkville, Victoria, Australia
- Centre de Recerca en Salut Internacional de Barcelona, Barcelona, Spain
| | - Ingrid Felger
- Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
- * E-mail:
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Pinkevych M, Chelimo K, Vulule J, Kazura JW, Moormann AM, Davenport MP. Time-to-infection by Plasmodium falciparum is largely determined by random factors. BMC Med 2015; 13:19. [PMID: 25633459 PMCID: PMC4311447 DOI: 10.1186/s12916-014-0252-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/07/2014] [Accepted: 12/10/2014] [Indexed: 11/24/2022] Open
Abstract
BACKGROUND The identification of protective immune responses to P. falciparum infection is an important goal for the development of a vaccine for malaria. This requires the identification of susceptible and resistant individuals, so that their immune responses may be studied. Time-to-infection studies are one method for identifying putative susceptible individuals (infected early) versus resistant individuals (infected late). However, the timing of infection is dependent on random factors, such as whether the subject was bitten by an infected mosquito, as well as individual factors, such as their level of immunity. It is important to understand how much of the observed variation in infection is simply due to chance. METHODS We analyse previously published data from a treatment-time-to-infection study of 201 individuals aged 0.5 to 78 years living in Western Kenya. We use a mathematical modelling approach to investigate the role of immunity versus random factors in determining time-to-infection in this cohort. We extend this analysis using a modelling approach to understand what factors might increase or decrease the utility of these studies for identifying susceptible and resistant individuals. RESULTS We find that, under most circumstances, the observed distribution of time-to-infection is consistent with this simply being a random process. We find that age, method for detection of infection (PCR versus microscopy), and underlying force of infection are all factors in determining whether time-to-infection is a useful correlate of immunity. CONCLUSIONS Many epidemiological studies of P. falciparum infection assume that the observed variation in infection outcomes, such as time-to-infection or presence or absence of infection, is determined by host resistance or susceptibility. However, under most circumstances, this distribution appears largely due to the random timing of infection, particularly in children. More direct measurements, such as parasite growth rate, may be more useful than time-to-infection in segregating patients based on their level of immunity.
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Affiliation(s)
| | | | | | | | | | - Miles P Davenport
- Centre for Vascular Research, University of New South Wales Australia, Kensington NSW 2052, Sydney, Australia.
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Kamau E, Alemayehu S, Feghali KC, Komisar J, Regules J, Cowden J, Ockenhouse CF. Measurement of parasitological data by quantitative real-time PCR from controlled human malaria infection trials at the Walter Reed Army Institute of Research. Malar J 2014; 13:288. [PMID: 25066459 PMCID: PMC4128310 DOI: 10.1186/1475-2875-13-288] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2014] [Accepted: 07/14/2014] [Indexed: 11/26/2022] Open
Abstract
Background The use of quantitative real-time PCR (qPCR) has allowed for precise quantification of parasites in the prepatent period and greatly improved the reproducibility and statistical power of controlled human malaria infection (CHMI) trials. Parasitological data presented here are from non-immunized, control-challenged subjects who participated in two CHMI trials conducted at the Walter Reed Army Institute of Research (WRAIR). Methods Standardized sporozoite challenge was achieved through the bite of five Anopheles stephensi mosquitoes infected with the 3D7clone of the NF54 strain of Plasmodium falciparum. Blood smears were scored positive when two unambiguous parasites were found. Analysis of parasitological PCR data was performed on log-transformed data using an independent sample t-test when comparing the two studies. The multiplication rate of blood-stage parasites was estimated using the linear model. Results On average, parasites were detected 4.91 days (95% CI = 4.190 to 5.627) before smears. The earliest parasites were detected within 120 hours (5.01 days) after challenge. Parasite densities showed consistent cyclic patterns of blood-stage parasite growth in all volunteers. The parasite multiplication rates for both studies was 8.18 (95% CI = 6.162 to 10.20). Data showed that at low parasite densities, a combination of sequestration and stochastic effects of low copy number DNA may impact qPCR detection and the parasite detection limit. Conclusion Smear positive is an endpoint which antimalarial rescue is imperative whereas early detection of parasitological data by qPCR can allow for better anticipation of the endpoint. This would allow for early treatment to reduce clinical illness and risk for study participants. To use qPCR as the primary endpoint in CHMI trials, an algorithm of two positives by qPCR where one of the positives must have parasite density of at least 2 parasites/μL is proposed.
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Affiliation(s)
- Edwin Kamau
- Military Malaria Research Program, Malaria Vaccine Branch, Walter Reed Army Institute of Research, 503 Robert Grant Ave, Silver Spring, Maryland, USA.
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Abstract
The within-host dynamics of an infection with the malaria parasite Plasmodium falciparum are the result of a complex interplay between the host immune system and parasite. Continual variation of the P. falciparum erythrocyte membrane protein (PfEMP1) antigens displayed on the surface of infected red blood cells enables the parasite to evade the immune system and prolong infection. Despite the importance of antigenic variation in generating the dynamics of infection, our understanding of the mechanisms by which antigenic variation generates long-term chronic infections is still limited. We developed a model to examine the role of cross-reactivity in generating infection dynamics that are comparable to those of experimental infections. The hybrid computational model we developed is attuned to the biology of malaria by mixing discrete replication events, which mimics the synchrony of parasite replication and invasion, with continuous interaction with the immune system. Using simulations, we evaluated the dynamics of a single malaria infection over time. We then examined three major mechanisms by which the dynamics of a malaria infection can be structured: cross-reactivity of the immune response to PfEMP1, differences in parasite clearance rates, and heterogeneity in the rate at which antigens switch. The results of our simulations demonstrate that cross-reactive immune responses play a primary role in generating the dynamics observed in experimentally untreated infections and in lengthening the period of infection. Importantly, we also find that it is the primary response to the initially expressed PfEMP1, or small subset thereof, that structures the cascading cross-immune dynamics and allows for elongation of the infection.
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Held J, Kreidenweiss A, Mordmüller B. Novel approaches in antimalarial drug discovery. Expert Opin Drug Discov 2013; 8:1325-37. [PMID: 24090219 DOI: 10.1517/17460441.2013.843522] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
INTRODUCTION The development of new antimalarial drugs remains of the utmost importance, since Plasmodium falciparum has developed resistance against nearly all chemotherapeutics in clinical use. In an effort to contain the resistance of P. falciparum against artemisinins and to further eradication efforts, studies are ongoing to identify novel and more efficacious approaches to develop antimalarials. AREAS COVERED The authors review the classical and new approaches to antimalarial drug discovery, with a special emphasis on the various stages of the parasite's life cycle and the different Plasmodium species. The authors discuss the methodologies and strategies for early efficacy testing that aim to narrow down the portfolio of promising compounds. EXPERT OPINION The increased efforts in the discovery and development of new antimalarial compounds have led to the recognition of new promising hits. However, there is still major roadblock of selecting the most promising compounds and then further testing them in early clinical trials, especially in the current restricted economy. Controlled human malaria infection has much potential for speeding-up the early development process of many drug candidates including those which target the pre-erythrocytic stages.
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Affiliation(s)
- Jana Held
- University of Tübingen, Institute of Tropical Medicine , Wilhelmstraße 27, D-72074 Tübingen , Germany +49 7071 29 82364 ; +49 7071 295189 ;
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McCarthy JS, Griffin PM, Sekuloski S, Bright AT, Rockett R, Looke D, Elliott S, Whiley D, Sloots T, Winzeler EA, Trenholme KR. Experimentally induced blood-stage Plasmodium vivax infection in healthy volunteers. J Infect Dis 2013; 208:1688-94. [PMID: 23908484 DOI: 10.1093/infdis/jit394] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
BACKGROUND Major impediments to development of vaccines and drugs for Plasmodium vivax malaria are the inability to culture this species and the extreme difficulty in undertaking clinical research by experimental infection. METHODS A parasite bank was collected from a 49-year-old woman with P. vivax infection, characterized, and used in an experimental infection study. RESULTS The donor made a full recovery from malaria after collection of a parasite bank, which tested negative for agents screened for in blood donations. DNA sequence analysis of the isolate indicated that it was clonal. Two subjects inoculated with the isolate became polymerase chain reaction positive on days 8 and 9, with onset of symptoms and positive blood smears on day 14, when they were treated with artemether-lumefantrine, with rapid clinical and parasitologic response. Transcripts of the parasite gene pvs25 that is expressed in gametocytes, the life cycle stage infectious to mosquitoes, were first detected on days 11 and 12. CONCLUSIONS This experimental system results in in vivo parasite growth, probably infectious to mosquitoes. It offers the opportunity to undertake studies previously impossible in P. vivax that will facilitate a better understanding of the pathology of vivax malaria and development of antimalarial drugs and vaccines. Trial Registration. ANZCTR: 12612001096842.
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Good MF, Reiman JM, Rodriguez IB, Ito K, Yanow SK, El-Deeb IM, Batzloff MR, Stanisic DI, Engwerda C, Spithill T, Hoffman SL, Lee M, McPhun V. Cross-species malaria immunity induced by chemically attenuated parasites. J Clin Invest 2013; 123:66634. [PMID: 23863622 PMCID: PMC4011145 DOI: 10.1172/jci66634] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2012] [Accepted: 04/26/2013] [Indexed: 01/29/2023] Open
Abstract
Vaccine development for the blood stages of malaria has focused on the induction of antibodies to parasite surface antigens, most of which are highly polymorphic. An alternate strategy has evolved from observations that low-density infections can induce antibody-independent immunity to different strains. To test this strategy, we treated parasitized red blood cells from the rodent parasite Plasmodium chabaudi with seco-cyclopropyl pyrrolo indole analogs. These drugs irreversibly alkylate parasite DNA, blocking their ability to replicate. After administration in mice, DNA from the vaccine could be detected in the blood for over 110 days and a single vaccination induced profound immunity to different malaria parasite species. Immunity was mediated by CD4+ T cells and was dependent on the red blood cell membrane remaining intact. The human parasite, Plasmodium falciparum, could also be attenuated by treatment with seco-cyclopropyl pyrrolo indole analogs. These data demonstrate that vaccination with chemically attenuated parasites induces protective immunity and provide a compelling rationale for testing a blood-stage parasite-based vaccine targeting human Plasmodium species.
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Sheehy SH, Douglas AD, Draper SJ. Challenges of assessing the clinical efficacy of asexual blood-stage Plasmodium falciparum malaria vaccines. Hum Vaccin Immunother 2013; 9:1831-40. [PMID: 23778312 PMCID: PMC3906345 DOI: 10.4161/hv.25383] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
In the absence of any highly effective vaccine candidate against Plasmodium falciparum malaria, it remains imperative for the field to pursue all avenues that may lead to the successful development of such a formulation. The development of a subunit vaccine targeting the asexual blood-stage of Plasmodium falciparum malaria infection has proven particularly challenging with only limited success to date in clinical trials. However, only a fraction of potential blood-stage vaccine antigens have been evaluated as targets, and a number of new promising candidate antigen formulations and delivery platforms are approaching clinical development. It is therefore essential that reliable and sensitive methods of detecting, or ruling out, even modest efficacy of blood-stage vaccines in small clinical trials be established. In this article we evaluate the challenges facing blood-stage vaccine developers, assess the appropriateness and limitations of various in vivo approaches for efficacy assessment and suggest future directions for the field.
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Protection against malaria after immunization by chloroquine prophylaxis and sporozoites is mediated by preerythrocytic immunity. Proc Natl Acad Sci U S A 2013; 110:7862-7. [PMID: 23599283 DOI: 10.1073/pnas.1220360110] [Citation(s) in RCA: 147] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Volunteers immunized under chloroquine chemoprophylaxis with Plasmodium falciparum sporozoites (CPS) develop complete, long-lasting protection against homologous sporozoite challenge. Chloroquine affects neither sporozoites nor liver-stages, but kills only asexual forms in erythrocytes once released from the liver into the circulation. Consequently, CPS immunization exposes the host to antigens from both preerythrocytic and blood stages, and induced immunity might target either of these stages. We therefore explored the life cycle stage specificity of CPS-induced protection. Twenty-five malaria-naïve volunteers were enrolled in a clinical trial, 15 of whom received CPS immunization. Five immunized subjects and five controls received a sporozoite challenge by mosquito bites, whereas nine immunized and five control subjects received an i.v. challenge with P. falciparum-infected erythrocytes. The latter approach completely bypasses preerythrocytic stages, enabling a direct comparison of protection against either life cycle stage. CPS-immunized subjects (13 of 14) developed anticircumsporozoite antibodies, whereas only one volunteer generated minimal titers against typical blood-stage antigens. IgG from CPS-immunized volunteers did not inhibit asexual blood-stage growth in vitro. All CPS-immunized subjects (5 of 5) were protected against sporozoite challenge. In contrast, nine of nine CPS-immunized subjects developed parasitemia after blood-stage challenge, with identical prepatent periods and blood-stage multiplication rates compared with controls. Intravenously challenged CPS-immunized subjects showed earlier fever and increased plasma concentrations of inflammatory markers D-dimer, IFN-γ, and monokine induced by IFN-γ than i.v. challenged controls. The complete lack of protection against blood-stage challenge indicates that CPS-induced protection is mediated by immunity against preerythrocytic stages. However, evidence is presented for immune recognition of P. falciparum-infected erythrocytes, suggesting memory responses unable to generate functional immunity.
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