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Friedman-Klabanoff DJ, Adu-Gyasi D, Asante KP. Malaria prevention in children: an update. Curr Opin Pediatr 2024; 36:164-170. [PMID: 38299986 PMCID: PMC10932812 DOI: 10.1097/mop.0000000000001332] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2024]
Abstract
PURPOSE OF REVIEW Malaria cases and deaths decreased from 2000 to 2015 but remain increased since 2019. Several new developments and strategies could help reverse this trend. The purpose of this review is to discuss new World Health Organization (WHO) guidelines and recent research on malaria prevention in children. RECENT FINDINGS Fifteen countries have now rolled out seasonal malaria chemoprophylaxis (SMC) in children at highest risk for severe malaria, and new WHO recommendations provide more flexibility for SMC implementation in terms of target age groups, geographic region, and number of cycles. Recent studies confirm that malaria burden in school aged children, and their contribution to transmission, is high. New guidelines permit expanded chemoprevention options for these children. Two vaccines have been approved for use in malaria endemic countries, RTS,S/AS01 E and R21/Matrix-M. Additionally, pyrethroid-chlorfenapyr bed nets are being deployed to combat resistant mosquitoes. SUMMARY While challenges remain in malaria control towards elimination, new guidelines and recently approved vaccines offer hope. Monitoring for continued vaccine and chemoprevention effectiveness, and for possible epidemiologic shifts in severe malaria presentation and deaths as additional prevention efforts roll out will be paramount.
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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, USA
| | - Dennis Adu-Gyasi
- Kintampo Health Research Centre, Research and Development Division, Ghana Health Service, Kintampo North Municipality, Bono East Region, Ghana
- Centre for Research in Applied Biology, School of Sciences, University of Energy and Natural Resources, Sunyani, Bono Region, Ghana, West Africa
| | - Kwaku Poku Asante
- Kintampo Health Research Centre, Research and Development Division, Ghana Health Service, Kintampo North Municipality, Bono East Region, Ghana
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Locke E, Flores-Garcia Y, Mayer BT, MacGill RS, Borate B, Salgado-Jimenez B, Gerber MW, Mathis-Torres S, Shapiro S, King CR, Zavala F. Establishing RTS,S/AS01 as a benchmark for comparison to next-generation malaria vaccines in a mouse model. NPJ Vaccines 2024; 9:29. [PMID: 38341502 DOI: 10.1038/s41541-024-00819-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2023] [Accepted: 01/24/2024] [Indexed: 02/12/2024] Open
Abstract
New strategies are needed to reduce the incidence of malaria, and promising approaches include vaccines targeting the circumsporozoite protein (CSP). To improve upon the malaria vaccine, RTS,S/AS01, it is essential to standardize preclinical assays to measure the potency of next-generation vaccines against this benchmark. We focus on RTS,S/AS01-induced antibody responses and functional activity in conjunction with robust statistical analyses. Transgenic Plasmodium berghei sporozoites containing full-length P. falciparum CSP (tgPb-PfCSP) allow two assessments of efficacy: quantitative reduction in liver infection following intravenous challenge, and sterile protection from mosquito bite challenge. Two or three doses of RTS,S/AS01 were given intramuscularly at 3-week intervals, with challenge 2-weeks after the last vaccination. Minimal inter- and intra-assay variability indicates the reproducibility of the methods. Importantly, the range of this model is suitable for screening more potent vaccines. Levels of induced anti-CSP antibody 2A10 equivalency were also associated with activity: 105 μg/mL (95% CI: 68.8, 141) reduced liver infection by 50%, whereas 285 μg/mL (95% CI: 166, 404) is required for 50% sterile protection from mosquito bite challenge. Additionally, the liver burden model was able to differentiate between protected and non-protected human plasma samples from a controlled human malaria infection study, supporting these models' relevance and predictive capability. Comparison in animal models of CSP-based vaccine candidates to RTS,S/AS01 is now possible under well controlled conditions. Assessment of the quality of induced antibodies, likely a determinant of durability of protection in humans, should be possible using these methods.
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Affiliation(s)
- Emily Locke
- Center for Vaccine Innovation and Access, PATH, Washington, DC, 20001, USA
| | - Yevel Flores-Garcia
- Department of Molecular Microbiology and Immunology, Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - Bryan T Mayer
- Vaccine and Infectious Disease Division, Fred Hutchison Cancer Research Center, Seattle, WA, 98109, USA
| | - Randall S MacGill
- Center for Vaccine Innovation and Access, PATH, Washington, DC, 20001, USA
| | - Bhavesh Borate
- Vaccine and Infectious Disease Division, Fred Hutchison Cancer Research Center, Seattle, WA, 98109, USA
| | - Berenice Salgado-Jimenez
- Department of Molecular Microbiology and Immunology, Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - Monica W Gerber
- Vaccine and Infectious Disease Division, Fred Hutchison Cancer Research Center, Seattle, WA, 98109, USA
| | - Shamika Mathis-Torres
- Department of Molecular Microbiology and Immunology, Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - Sarah Shapiro
- Department of Molecular Microbiology and Immunology, Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - C Richter King
- Center for Vaccine Innovation and Access, PATH, Washington, DC, 20001, USA
| | - Fidel Zavala
- Department of Molecular Microbiology and Immunology, Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA.
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Dutta S, Thera MA. Seasonal RTS,S/AS01 E vaccination with or without seasonal malaria chemoprevention. THE LANCET. INFECTIOUS DISEASES 2024; 24:9-11. [PMID: 37625433 DOI: 10.1016/s1473-3099(23)00392-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2023] [Accepted: 06/16/2023] [Indexed: 08/27/2023]
Affiliation(s)
- Sheetij Dutta
- Structural Vaccinology Laboratory, Biologics Research & Development Branch, Walter Reed Army Institute of Research, Silver Spring, MD 20910, USA.
| | - Mahamadou A Thera
- Malaria Research and Training Center, Faculty of Medicine and Odonto-Stomatology, University of Sciences, Techniques and Technologies of Bamako, Bamako, Mali
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Hammershaimb EA, Berry AA. Pre-erythrocytic malaria vaccines: RTS,S, R21, and beyond. Expert Rev Vaccines 2024; 23:49-52. [PMID: 38095048 DOI: 10.1080/14760584.2023.2292204] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2023] [Accepted: 12/04/2023] [Indexed: 12/18/2023]
Affiliation(s)
- Elizabeth Adrianne Hammershaimb
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, MD, USA
- Department of Pediatrics, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Andrea A Berry
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, MD, USA
- Department of Pediatrics, University of Maryland School of Medicine, Baltimore, MD, USA
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Bolton JS, MacGill RS, Locke E, Regules JA, Bergmann-Leitner ES. Novel antibody competition binding assay identifies distinct serological profiles associated with protection. Front Immunol 2023; 14:1303446. [PMID: 38152401 PMCID: PMC10752609 DOI: 10.3389/fimmu.2023.1303446] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2023] [Accepted: 11/21/2023] [Indexed: 12/29/2023] Open
Abstract
Introduction Pre-erythrocytic malaria vaccines hold the promise of inducing sterile protection thereby preventing the morbidity and mortality associated with Plasmodium infection. The main surface antigen of P. falciparum sporozoites, i.e., the circumsporozoite protein (CSP), has been extensively explored as a target of such vaccines with significant success in recent years. Systematic adjuvant selection, refinements of the immunization regimen, and physical properties of the antigen may all contribute to the potential of increasing the efficacy of CSP-based vaccines. Protection appears to be dependent in large part on CSP antibodies. However due to a knowledge gap related to the exact correlates of immunity, there is a critical need to improve our ability to down select candidates preclinically before entering clinical trials including with controlled human malaria infections (CHMI). Methods We developed a novel multiplex competition assay based on well-characterized monoclonal antibodies (mAbs) that target crucial epitopes across the CSP molecule. This new tool assesses both, quality and epitope-specific concentrations of vaccine-induced antibodies by measuring their equivalency with a panel of well-characterized, CSP-epitope-specific mAbs. Results Applying this method to RTS,S-immune sera from a CHMI trial demonstrated a quantitative epitope-specificity profile of antibody responses that can differentiate between protected vs. nonprotected individuals. Aligning vaccine efficacy with quantitation of the epitope fine specificity results of this equivalency assay reveals the importance of epitope specificity. Discussion The newly developed serological equivalence assay will inform future vaccine design and possibly even adjuvant selection. This methodology can be adapted to other antigens and disease models, when a panel of relevant mAbs exists, and could offer a unique tool for comparing and down-selecting vaccine formulations.
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Affiliation(s)
- Jessica S. Bolton
- Biologics Research & Development, Walter Reed Army Institute of Research (WRAIR), Silver Spring, MD, United States
| | - Randall S. MacGill
- Center for Vaccine Innovation and Access, PATH, Washington, DC, United States
| | - Emily Locke
- Center for Vaccine Innovation and Access, PATH, Washington, DC, United States
| | - Jason A. Regules
- Biologics Research & Development, Walter Reed Army Institute of Research (WRAIR), Silver Spring, MD, United States
| | - Elke S. Bergmann-Leitner
- Biologics Research & Development, Walter Reed Army Institute of Research (WRAIR), Silver Spring, MD, United States
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