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Kamiya T, Davis NM, Greischar MA, Schneider D, Mideo N. Linking functional and molecular mechanisms of host resilience to malaria infection. eLife 2021; 10:e65846. [PMID: 34636723 PMCID: PMC8510579 DOI: 10.7554/elife.65846] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2020] [Accepted: 08/16/2021] [Indexed: 12/30/2022] Open
Abstract
It remains challenging to understand why some hosts suffer severe illnesses, while others are unscathed by the same infection. We fitted a mathematical model to longitudinal measurements of parasite and red blood cell density in murine hosts from diverse genetic backgrounds to identify aspects of within-host interactions that explain variation in host resilience and survival during acute malaria infection. Among eight mouse strains that collectively span 90% of the common genetic diversity of laboratory mice, we found that high host mortality was associated with either weak parasite clearance, or a strong, yet imprecise response that inadvertently removes uninfected cells in excess. Subsequent cross-sectional cytokine assays revealed that the two distinct functional mechanisms of poor survival were underpinned by low expression of either pro- or anti-inflammatory cytokines, respectively. By combining mathematical modelling and molecular immunology assays, our study uncovered proximate mechanisms of diverse infection outcomes across multiple host strains and biological scales.
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Affiliation(s)
- Tsukushi Kamiya
- Department of Ecology and Evolutionary Biology, University of TorontoTorontoCanada
| | - Nicole M Davis
- Department of Microbiology and Immunology, Stanford UniversityStanfordUnited States
| | - Megan A Greischar
- Department of Ecology and Evolutionary Biology, Cornell UniversityIthacaUnited States
| | - David Schneider
- Department of Microbiology and Immunology, Stanford UniversityStanfordUnited States
| | - Nicole Mideo
- Department of Ecology and Evolutionary Biology, University of TorontoTorontoCanada
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2
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Kamiya T, Greischar MA, Schneider DS, Mideo N. Uncovering drivers of dose-dependence and individual variation in malaria infection outcomes. PLoS Comput Biol 2020; 16:e1008211. [PMID: 33031367 PMCID: PMC7544130 DOI: 10.1371/journal.pcbi.1008211] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2019] [Accepted: 07/31/2020] [Indexed: 01/01/2023] Open
Abstract
To understand why some hosts get sicker than others from the same type of infection, it is essential to explain how key processes, such as host responses to infection and parasite growth, are influenced by various biotic and abiotic factors. In many disease systems, the initial infection dose impacts host morbidity and mortality. To explore drivers of dose-dependence and individual variation in infection outcomes, we devised a mathematical model of malaria infection that allowed host and parasite traits to be linear functions (reaction norms) of the initial dose. We fitted the model, using a hierarchical Bayesian approach, to experimental time-series data of acute Plasmodium chabaudi infection across doses spanning seven orders of magnitude. We found evidence for both dose-dependent facilitation and debilitation of host responses. Most importantly, increasing dose reduced the strength of activation of indiscriminate host clearance of red blood cells while increasing the half-life of that response, leading to the maximal response at an intermediate dose. We also explored the causes of diverse infection outcomes across replicate mice receiving the same dose. Besides random noise in the injected dose, we found variation in peak parasite load was due to unobserved individual variation in host responses to clear infected cells. Individual variation in anaemia was likely driven by random variation in parasite burst size, which is linked to the rate of host cells lost to malaria infection. General host vigour in the absence of infection was also correlated with host health during malaria infection. Our work demonstrates that the reaction norm approach provides a useful quantitative framework for examining the impact of a continuous external factor on within-host infection processes.
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Affiliation(s)
- Tsukushi Kamiya
- Department of Ecology & Evolutionary Biology, University of Toronto, Toronto, ON M5S 3B2, Canada
| | - Megan A. Greischar
- Department of Ecology Evolutionary Biology, Cornell University, United States of America
| | - David S. Schneider
- Program in Immunology, Stanford University, Stanford, California, United States of America
- Department of Microbiology and Immunology, Stanford University, Stanford, California, United States of America
| | - Nicole Mideo
- Department of Ecology & Evolutionary Biology, University of Toronto, Toronto, ON M5S 3B2, Canada
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3
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Wale N, Jones MJ, Sim DG, Read AF, King AA. The contribution of host cell-directed vs. parasite-directed immunity to the disease and dynamics of malaria infections. Proc Natl Acad Sci U S A 2019; 116:22386-22392. [PMID: 31615885 PMCID: PMC6825298 DOI: 10.1073/pnas.1908147116] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Hosts defend themselves against pathogens by mounting an immune response. Fully understanding the immune response as a driver of host disease and pathogen evolution requires a quantitative account of its impact on parasite population dynamics. Here, we use a data-driven modeling approach to quantify the birth and death processes underlying the dynamics of infections of the rodent malaria parasite, Plasmodium chabaudi, and the red blood cells (RBCs) it targets. We decompose the immune response into 3 components, each with a distinct effect on parasite and RBC vital rates, and quantify the relative contribution of each component to host disease and parasite density. Our analysis suggests that these components are deployed in a coordinated fashion to realize distinct resource-directed defense strategies that complement the killing of parasitized cells. Early in the infection, the host deploys a strategy reminiscent of siege and scorched-earth tactics, in which it both destroys RBCs and restricts their supply. Late in the infection, a "juvenilization" strategy, in which turnover of RBCs is accelerated, allows the host to recover from anemia while holding parasite proliferation at bay. By quantifying the impact of immunity on both parasite fitness and host disease, we reveal that phenomena often interpreted as immunopathology may in fact be beneficial to the host. Finally, we show that, across mice, the components of the host response are consistently related to each other, even when infections take qualitatively different trajectories. This suggests the existence of simple rules that govern the immune system's deployment.
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Affiliation(s)
- Nina Wale
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI 48109;
| | - Matthew J Jones
- Center for Infectious Disease Dynamics, Huck Institutes for the Life Sciences, Pennsylvania State University, University Park, PA 16802
| | - Derek G Sim
- Center for Infectious Disease Dynamics, Huck Institutes for the Life Sciences, Pennsylvania State University, University Park, PA 16802
| | - Andrew F Read
- Center for Infectious Disease Dynamics, Huck Institutes for the Life Sciences, Pennsylvania State University, University Park, PA 16802
- Department of Biology, Pennsylvania State University, University Park, PA 16802
- Department of Entomology, Pennsylvania State University, University Park, PA 16802
| | - Aaron A King
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI 48109
- Center for the Study of Complex Systems, University of Michigan, Ann Arbor, MI 48109
- Department of Mathematics, University of Michigan, Ann Arbor, MI 48109
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Akter J, Khoury DS, Aogo R, Lansink LIM, SheelaNair A, Thomas BS, Laohamonthonkul P, Pernold CPS, Dixon MWA, Soon MSF, Fogg LG, Engel JA, Elliott T, Sebina I, James KR, Cromer D, Davenport MP, Haque A. Plasmodium-specific antibodies block in vivo parasite growth without clearing infected red blood cells. PLoS Pathog 2019; 15:e1007599. [PMID: 30811498 PMCID: PMC6411214 DOI: 10.1371/journal.ppat.1007599] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2018] [Revised: 03/11/2019] [Accepted: 01/28/2019] [Indexed: 01/01/2023] Open
Abstract
Plasmodium parasites invade and multiply inside red blood cells (RBC). Through a cycle of maturation, asexual replication, rupture and release of multiple infective merozoites, parasitised RBC (pRBC) can reach very high numbers in vivo, a process that correlates with disease severity in humans and experimental animals. Thus, controlling pRBC numbers can prevent or ameliorate malaria. In endemic regions, circulating parasite-specific antibodies associate with immunity to high parasitemia. Although in vitro assays reveal that protective antibodies could control pRBC via multiple mechanisms, in vivo assessment of antibody function remains challenging. Here, we employed two mouse models of antibody-mediated immunity to malaria, P. yoelii 17XNL and P. chabaudi chabaudi AS infection, to study infection-induced, parasite-specific antibody function in vivo. By tracking a single generation of pRBC, we tested the hypothesis that parasite-specific antibodies accelerate pRBC clearance. Though strongly protective against homologous re-challenge, parasite-specific IgG did not alter the rate of pRBC clearance, even in the presence of ongoing, systemic inflammation. Instead, antibodies prevented parasites progressing from one generation of RBC to the next. In vivo depletion studies using clodronate liposomes or cobra venom factor, suggested that optimal antibody function required splenic macrophages and dendritic cells, but not complement C3/C5-mediated killing. Finally, parasite-specific IgG bound poorly to the surface of pRBC, yet strongly to structures likely exposed by the rupture of mature schizonts. Thus, in our models of humoral immunity to malaria, infection-induced antibodies did not accelerate pRBC clearance, and instead co-operated with splenic phagocytes to block subsequent generations of pRBC. Malaria occurs when Plasmodium parasites replicate inside red blood cells, with the number of parasitised cells (pRBC) correlating with disease severity. Antibodies are highly effective at controlling pRBC numbers in the bloodstream, and yet we know very little about how they function in vivo. Human in vitro studies predict that antibodies may function in a number of ways, including via phagocytes or different complement mechanisms. However, to date it has been challenging to explore how antibodies might control parasite numbers in vivo. Here, we have used a unique method in mice, where clearance and replication of a single cohort of pRBC was closely tracked in the presence of protective antibodies. Surprisingly, antibodies played no role whatsoever in accelerating the removal of pRBC. Instead, antibodies were highly effective at preventing parasites from progressing from one generation of pRBC to the next. This process partly depended on host phagocytes. However, we found no role for complement-mediated direct killing. Together, our in vivo data suggest in mouse models that naturally-acquired antibodies do not clear pRBC, and instead prevent transition from one red blood cell to the next.
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Affiliation(s)
- Jasmin Akter
- QIMR Berghofer Medical Research Institute, Herston, Brisbane QLD, Australia
| | - David S. Khoury
- Infection Analytics Program, Kirby Institute, UNSW Australia, Kensington NSW, Australia
| | - Rosemary Aogo
- Infection Analytics Program, Kirby Institute, UNSW Australia, Kensington NSW, Australia
| | | | - Arya SheelaNair
- QIMR Berghofer Medical Research Institute, Herston, Brisbane QLD, Australia
| | - Bryce S. Thomas
- QIMR Berghofer Medical Research Institute, Herston, Brisbane QLD, Australia
| | | | | | - Matthew W. A. Dixon
- University of Melbourne, Department of Biochemistry and Molecular Biology, Melbourne, Victoria, Australia
| | - Megan S. F. Soon
- QIMR Berghofer Medical Research Institute, Herston, Brisbane QLD, Australia
| | - Lily G. Fogg
- QIMR Berghofer Medical Research Institute, Herston, Brisbane QLD, Australia
| | - Jessica A. Engel
- QIMR Berghofer Medical Research Institute, Herston, Brisbane QLD, Australia
| | - Trish Elliott
- QIMR Berghofer Medical Research Institute, Herston, Brisbane QLD, Australia
| | - Ismail Sebina
- QIMR Berghofer Medical Research Institute, Herston, Brisbane QLD, Australia
| | - Kylie R. James
- QIMR Berghofer Medical Research Institute, Herston, Brisbane QLD, Australia
| | - Deborah Cromer
- Infection Analytics Program, Kirby Institute, UNSW Australia, Kensington NSW, Australia
| | - Miles P. Davenport
- Infection Analytics Program, Kirby Institute, UNSW Australia, Kensington NSW, Australia
- * E-mail: (MPD); (AH)
| | - Ashraful Haque
- QIMR Berghofer Medical Research Institute, Herston, Brisbane QLD, Australia
- * E-mail: (MPD); (AH)
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Borges da Silva H, Machado de Salles É, Lima-Mauro EF, Sardinha LR, Álvarez JM, D’Império Lima MR. CD28 deficiency leads to accumulation of germinal-center independent IgM+ experienced B cells and to production of protective IgM during experimental malaria. PLoS One 2018; 13:e0202522. [PMID: 30148845 PMCID: PMC6110469 DOI: 10.1371/journal.pone.0202522] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2018] [Accepted: 08/03/2018] [Indexed: 12/04/2022] Open
Abstract
Protective immunity to blood-stage malaria is attributed to Plasmodium-specific IgG and effector-memory T helper 1 (Th1) cells. However, mice lacking the costimulatory receptor CD28 (CD28KO) maintain chronic parasitemia at low levels and do not succumb to infection, suggesting that other immune responses contribute to parasite control. We report here that CD28KO mice develop long-lasting non-sterile immunity and survive lethal parasite challenge. This protection correlated with a progressive increase of anti-parasite IgM serum levels during chronic infection. Serum IgM from chronically infected CD28KO mice recognize erythrocytes infected with mature parasites, and effectively control Plasmodium infection by promoting parasite lysis and uptake. These antibodies also recognize autoantigens and antigens from other pathogens. Chronically infected CD28KO mice have high numbers of IgM+ plasmocytes and experienced B cells, exhibiting a germinal-center independent Fas+GL7-CD38+CD73- phenotype. These cells are also present in chronically infected C57BL/6 mice although in lower numbers. Finally, IgM+ experienced B cells from cured C57BL/6 and CD28KO mice proliferate and produce anti-parasite IgM in response to infected erythrocytes. This study demonstrates that CD28 deficiency results in the generation of germinal-center independent IgM+ experienced B cells and the production of protective IgM during experimental malaria, providing evidence for an additional mechanism by which the immune system controls Plasmodium infection.
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Affiliation(s)
- Henrique Borges da Silva
- Departamento de Imunologia, Instituto de Ciências Biomédicas (ICB), Universidade de São Paulo (USP), São Paulo, Brazil
- * E-mail: (HBdS); (MRDL)
| | - Érika Machado de Salles
- Departamento de Imunologia, Instituto de Ciências Biomédicas (ICB), Universidade de São Paulo (USP), São Paulo, Brazil
| | | | | | - José Maria Álvarez
- Departamento de Imunologia, Instituto de Ciências Biomédicas (ICB), Universidade de São Paulo (USP), São Paulo, Brazil
| | - Maria Regina D’Império Lima
- Departamento de Imunologia, Instituto de Ciências Biomédicas (ICB), Universidade de São Paulo (USP), São Paulo, Brazil
- * E-mail: (HBdS); (MRDL)
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Chukwuocha UM, Fernández-Rivera O, Legorreta-Herrera M. Exploring the antimalarial potential of whole Cymbopogon citratus plant therapy. J Ethnopharmacol 2016; 193:517-523. [PMID: 27693771 DOI: 10.1016/j.jep.2016.09.056] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2016] [Revised: 09/24/2016] [Accepted: 09/28/2016] [Indexed: 06/06/2023]
Abstract
ETHNOPHARMACOLOGICAL RELEVANCE Cymbopogon citratus (lemon grass) has been used in traditional medicine as an herbal infusion to treat fever and malaria. Generally, whole plant extracts possess higher biological activity than purified compounds. However, the antimalarial activity of the whole C. citratus plant has not been experimentally tested. AIM OF THE STUDY To evaluate the antimalarial activity of an herbal infusion and the whole Cymbopogon citratus plant in two experimental models of malaria. MATERIAL AND METHODS The plant was dried for 10 days at room temperature and was then milled and passed through brass sieves to obtain a powder, which was administered to CBA/Ca mice with a patent Plasmodium chabaudi AS or P. berghei ANKA infection. We analysed the effects of two different doses (1600 and 3200mg/kg) compared with those of the herbal infusion and chloroquine, used as a positive control. We also assessed the prophylactic antimalarial activities of the whole C. citratus plant and the combination of the whole plant and chloroquine. RESULTS The C. citratus whole plant exhibited prolonged antimalarial activity against both P. chabaudi AS and P. berghei ANKA. The low dose of the whole C. citratus plant displayed higher antimalarial activity than the high dose against P. berghei ANKA. As a prophylactic treatment, the whole plant exhibited higher antimalarial activity than either the herbal infusion or chloroquine. In addition, the combination of the whole C. citratus plant and chloroquine displayed higher activity than chloroquine alone against P. berghei ANKA patent infection. CONCLUSIONS We demonstrated the antimalarial activity of the whole C. citratus plant in two experimental models. The whole C. citratus plant elicited higher anti-malarial activity than the herbal infusion or chloroquine when used as a prophylactic treatment. The antimalarial activity of the whole C. citratus plant supports continued efforts towards developing whole plant therapies for the management of malaria and other infectious diseases prevalent in resource-poor communities.
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Affiliation(s)
- Uchechukwu M Chukwuocha
- Laboratorio de Inmunología Molecular, FES Zaragoza, Universidad Nacional Autónoma de México, Batalla 5 de Mayo esq. Fuerte de Loreto, Iztapalapa 09230, Ciudad de México, Mexico; Department of Public Health Technology, Federal University of Technology, Owerri PMB 1526, Imo State, Nigeria
| | - Omar Fernández-Rivera
- Laboratorio de Inmunología Molecular, FES Zaragoza, Universidad Nacional Autónoma de México, Batalla 5 de Mayo esq. Fuerte de Loreto, Iztapalapa 09230, Ciudad de México, Mexico
| | - Martha Legorreta-Herrera
- Laboratorio de Inmunología Molecular, FES Zaragoza, Universidad Nacional Autónoma de México, Batalla 5 de Mayo esq. Fuerte de Loreto, Iztapalapa 09230, Ciudad de México, Mexico.
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Carpio VH, Opata MM, Montañez ME, Banerjee PP, Dent AL, Stephens R. IFN-γ and IL-21 Double Producing T Cells Are Bcl6-Independent and Survive into the Memory Phase in Plasmodium chabaudi Infection. PLoS One 2015; 10:e0144654. [PMID: 26646149 PMCID: PMC4672895 DOI: 10.1371/journal.pone.0144654] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2015] [Accepted: 11/20/2015] [Indexed: 11/19/2022] Open
Abstract
CD4 T cells are required to fight malaria infection by promoting both phagocytic activity and B cell responses for parasite clearance. In Plasmodium chabaudi infection, one specific CD4 T cell subset generates anti-parasitic IFN-γ and the antibody-promoting cytokine, IL-21. To determine the lineage of these multifunctional T cells, we followed IFN-γ+ effector T cells (Teff) into the memory phase using Ifng-reporter mice. While Ifng+ Teff expanded, the level of the Th1 lineage-determining transcription factor T-bet only peaked briefly. Ifng+ Teff also co-express ICOS, the B cell area homing molecule CXCR5, and other Tfh lineage-associated molecules including Bcl6, the transcription factor required for germinal center (GC) T follicular helper cells (Tfh) differentiation. Because Bcl6 and T-bet co-localize to the nucleus of Ifng+ Teff, we hypothesized that Bcl6 controls the Tfh-like phenotype of Ifng+ Teff cells in P. chabaudi infection. We first transferred Bcl6-deficient T cells into wildtype hosts. Bcl6-deficient T cells did not develop into GC Tfh, but they still generated CXCR5+IFN-γ+IL-21+IL-10+ Teff, suggesting that this predominant population is not of the Tfh-lineage. IL-10 deficient mice, which have increased IFN-γ and T-bet expression, demonstrated expansion of both IFN-γ+IL-21+CXCR5+ cells and IFN-γ+ GC Tfh cells, suggesting a Th1 lineage for the former. In the memory phase, all Ifng+ T cells produced IL-21, but only a small percentage of highly proliferative Ifng+ T cells maintained a T-bethi phenotype. In chronic malaria infection, serum IFN-γ correlates with increased protection, and our observation suggests Ifng+ T cells are maintained by cellular division. In summary, we found that Ifng+ T cells are not strictly Tfh derived during malaria infection. T cells provide the host with a survival advantage when facing this well-equipped pathogen, therefore, understanding the lineage of pivotal T cell players will aid in the rational design of an effective malaria vaccine.
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Affiliation(s)
- Victor H. Carpio
- Department of Internal Medicine, Division of Infectious Diseases, University of Texas Medical Branch, Galveston, Texas, United States of America
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Michael M. Opata
- Department of Internal Medicine, Division of Infectious Diseases, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Marelle E. Montañez
- Department of Internal Medicine, Division of Infectious Diseases, University of Texas Medical Branch, Galveston, Texas, United States of America
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Pinaki P. Banerjee
- Center for Human Immunobiology of Texas Children’s Hospital, Baylor College of Medicine, Houston, Texas, United States of America
| | - Alexander L. Dent
- Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, Indiana, United States of America
| | - Robin Stephens
- Department of Internal Medicine, Division of Infectious Diseases, University of Texas Medical Branch, Galveston, Texas, United States of America
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas, United States of America
- * E-mail:
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Pollitt LC, Huijben S, Sim DG, Salathé RM, Jones MJ, Read AF. Rapid response to selection, competitive release and increased transmission potential of artesunate-selected Plasmodium chabaudi malaria parasites. PLoS Pathog 2014; 10:e1004019. [PMID: 24763470 PMCID: PMC3999151 DOI: 10.1371/journal.ppat.1004019] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2013] [Accepted: 02/06/2014] [Indexed: 11/19/2022] Open
Abstract
The evolution of drug resistance, a key challenge for our ability to treat and control infections, depends on two processes: de-novo resistance mutations, and the selection for and spread of resistant mutants within a population. Understanding the factors influencing the rates of these two processes is essential for maximizing the useful lifespan of drugs and, therefore, effective disease control. For malaria parasites, artemisinin-based drugs are the frontline weapons in the fight against disease, but reports from the field of slower parasite clearance rates during drug treatment are generating concern that the useful lifespan of these drugs may be limited. Whether slower clearance rates represent true resistance, and how this provides a selective advantage for parasites is uncertain. Here, we show that Plasmodium chabaudi malaria parasites selected for resistance to artesunate (an artemisinin derivative) through a step-wise increase in drug dose evolved slower clearance rates extremely rapidly. In single infections, these slower clearance rates, similar to those seen in the field, provided fitness advantages to the parasite through increased overall density, recrudescence after treatment and increased transmission potential. In mixed infections, removal of susceptible parasites by drug treatment led to substantial increases in the densities and transmission potential of resistant parasites (competitive release). Our results demonstrate the double-edged sword for resistance management: in our initial selection experiments, no parasites survived aggressive chemotherapy, but after selection, the fitness advantage for resistant parasites was greatest at high drug doses. Aggressive treatment of mixed infections resulted in resistant parasites dominating the pool of gametocytes, without providing additional health benefits to hosts. Slower clearance rates can evolve rapidly and can provide a strong fitness advantage during drug treatment in both single and mixed strain infections.
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Affiliation(s)
- Laura C. Pollitt
- Center for Infectious Disease Dynamics, Department of Biology, Pennsylvania State University, University Park, Pennsylvania, United States of America
- Centre for Immunology, Infection and Evolution, The University of Edinburgh, Edinburgh, United Kingdom
- * E-mail:
| | - Silvie Huijben
- Center for Infectious Disease Dynamics, Department of Biology, Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Derek G. Sim
- Center for Infectious Disease Dynamics, Department of Biology, Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Rahel M. Salathé
- Center for Infectious Disease Dynamics, Department of Biology, Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Matthew J. Jones
- Center for Infectious Disease Dynamics, Department of Biology, Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Andrew F. Read
- Center for Infectious Disease Dynamics, Department of Biology, Pennsylvania State University, University Park, Pennsylvania, United States of America
- Department of Entomology, The Pennsylvania State University, University Park, Pennsylvania, United States of America
- Fogarty International Center, National Institutes of Health, Bethesda, Maryland, United States of America
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Abstract
A recent study found that mosquito-transmitted (MT) lines of rodent malaria parasites elicit a more effective immune response than non-transmitted lines maintained by serial blood passage (non-MT), thereby causing lower parasite densities in the blood and less pathology to the host. The authors attribute these changes to higher diversity in expression of antigen-encoding genes in MT cf. non-MT lines. Alternative explanations that are equally parsimonious with these new data, and results from previous studies, suggest that this conclusion may be premature.
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Huijben S, Bell AS, Sim DG, Tomasello D, Mideo N, Day T, Read AF. Aggressive chemotherapy and the selection of drug resistant pathogens. PLoS Pathog 2013; 9:e1003578. [PMID: 24068922 PMCID: PMC3771897 DOI: 10.1371/journal.ppat.1003578] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2013] [Accepted: 07/10/2013] [Indexed: 11/19/2022] Open
Abstract
Drug resistant pathogens are one of the key public health challenges of the 21st century. There is a widespread belief that resistance is best managed by using drugs to rapidly eliminate target pathogens from patients so as to minimize the probability that pathogens acquire resistance de novo. Yet strong drug pressure imposes intense selection in favor of resistance through alleviation of competition with wild-type populations. Aggressive chemotherapy thus generates opposing evolutionary forces which together determine the rate of drug resistance emergence. Identifying treatment regimens which best retard resistance evolution while maximizing health gains and minimizing disease transmission requires empirical analysis of resistance evolution in vivo in conjunction with measures of clinical outcomes and infectiousness. Using rodent malaria in laboratory mice, we found that less aggressive chemotherapeutic regimens substantially reduced the probability of onward transmission of resistance (by >150-fold), without compromising health outcomes. Our experiments suggest that there may be cases where resistance evolution can be managed more effectively with treatment regimens other than those which reduce pathogen burdens as fast as possible. Drug-resistance is a major public health problem. Conventional wisdom on resistance management is to use aggressive chemotherapy to kill pathogens as rapidly as possible so as to prevent them from acquiring resistance. This is the reason why physicians frequently exhort patients to finish drug courses even after they no longer feel sick. However, this approach is based on the notion that we need only prevent new resistant mutants from arising. We hypothesize that in the situation where such mutants are already present at the time of treatment, more aggressive chemotherapy will select for these the fastest by rapidly killing all sensitive competitors. Here we demonstrate in a rodent malaria model that such selection indeed occurs more intensely following aggressive treatment than following less aggressive treatment, without any benefit to host health or infectivity. This suggests that aggressive chemotherapy will not be the best way to retard resistance evolution in some - perhaps many - circumstances. We suggest that an evidence-based approach across a wide range of infectious diseases is needed to manage resistance evolution.
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Affiliation(s)
- Silvie Huijben
- Center for Infectious Disease Dynamics, Departments of Biology and Entomology, Pennsylvania State University, University Park, Pennsylvania, United States of America
- * E-mail: (SH); (AFR)
| | - Andrew S. Bell
- Center for Infectious Disease Dynamics, Departments of Biology and Entomology, Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Derek G. Sim
- Center for Infectious Disease Dynamics, Departments of Biology and Entomology, Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Danielle Tomasello
- Center for Infectious Disease Dynamics, Departments of Biology and Entomology, Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Nicole Mideo
- Center for Infectious Disease Dynamics, Departments of Biology and Entomology, Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Troy Day
- Departments of Mathematics, Statistics and Biology, Jeffery Hall, Queen's University, Kingston, Ontario, Canada
| | - Andrew F. Read
- Center for Infectious Disease Dynamics, Departments of Biology and Entomology, Pennsylvania State University, University Park, Pennsylvania, United States of America
- Fogarty International Center, National Institutes of Health, Bethesda, Maryland, United States of America
- * E-mail: (SH); (AFR)
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Elfawal MA, Towler MJ, Reich NG, Golenbock D, Weathers PJ, Rich SM. Dried whole plant Artemisia annua as an antimalarial therapy. PLoS One 2012; 7:e52746. [PMID: 23289055 PMCID: PMC3527585 DOI: 10.1371/journal.pone.0052746] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2012] [Accepted: 11/21/2012] [Indexed: 12/11/2022] Open
Abstract
Drugs are primary weapons for reducing malaria in human populations. However emergence of resistant parasites has repeatedly curtailed the lifespan of each drug that is developed and deployed. Currently the most effective anti-malarial is artemisinin, which is extracted from the leaves of Artemisia annua. Due to poor pharmacokinetic properties and prudent efforts to curtail resistance to monotherapies, artemisinin is prescribed only in combination with other anti-malarials composing an Artemisinin Combination Therapy (ACT). Low yield in the plant, and the added cost of secondary anti-malarials in the ACT, make artemisinin costly for the developing world. As an alternative, we compared the efficacy of oral delivery of the dried leaves of whole plant (WP) A. annua to a comparable dose of pure artemisinin in a rodent malaria model (Plasmodium chabaudi). We found that a single dose of WP (containing 24 mg/kg artemisinin) reduces parasitemia more effectively than a comparable dose of purified drug. This increased efficacy may result from a documented 40-fold increase in the bioavailability of artemisinin in the blood of mice fed the whole plant, in comparison to those administered synthetic drug. Synergistic benefits may derive from the presence of other anti-malarial compounds in A. annua. If shown to be clinically efficacious, well-tolerated, and compatible with the public health imperative of forestalling evolution of drug resistance, inexpensive, locally grown and processed A. annua might prove to be an effective addition to the global effort to reduce malaria morbidity and mortality.
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Affiliation(s)
- Mostafa A. Elfawal
- Laboratory of Medical Zoology, Department of Microbiology, University of Massachusetts, Amherst, Massachusetts, United States of America
| | - Melissa J. Towler
- Department of Biology and Biotechnology, Worcester Polytechnic Institute, Worcester, Massachusetts, United States of America
| | - Nicholas G. Reich
- Division of Biostatistics and Epidemiology, School of Public Health and Health Sciences, University of Massachusetts, Amherst, Massachusetts, United States of America
| | - Douglas Golenbock
- Infectious Diseases and Immunology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - Pamela J. Weathers
- Department of Biology and Biotechnology, Worcester Polytechnic Institute, Worcester, Massachusetts, United States of America
| | - Stephen M. Rich
- Laboratory of Medical Zoology, Department of Microbiology, University of Massachusetts, Amherst, Massachusetts, United States of America
- * E-mail:
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Maretty L, Sharp RE, Andersson M, Kurtzhals JAL. Intravenous ferric carboxymaltose accelerates erythropoietic recovery from experimental malarial anemia. J Infect Dis 2012; 205:1173-7. [PMID: 22357662 DOI: 10.1093/infdis/jis020] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Iron restriction has been proposed as a cause of erythropoietic suppression in malarial anemia; however, the role of iron in malaria remains controversial, because it may increase parasitemia. To investigate the role of iron-restricted erythropoiesis, A/J mice were infected with Plasmodium chabaudi AS, treated with intravenous ferric carboxymaltose at different times, and compared with untreated controls. Iron treatment significantly increased weight and hemoglobin nadirs and provided enhanced reticulocytosis and faster recovery, compared with controls. Our findings challenge the restrictive use of iron therapy in malaria and show the need for trials of intravenous ferric carboxymaltose as an adjunctive treatment for severe malarial anemia.
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Affiliation(s)
- Lasse Maretty
- Centre for Medical Parasitology, Department of Clinical Microbiology, Copenhagen University Hospital (Rigshospitalet), University of Copenhagen, Copenhagen, Denmark
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13
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Mideo N, Savill NJ, Chadwick W, Schneider P, Read AF, Day T, Reece SE. Causes of variation in malaria infection dynamics: insights from theory and data. Am Nat 2011; 178:E174-E188. [PMID: 22089879 PMCID: PMC3937740 DOI: 10.1086/662670] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Parasite strategies for exploiting host resources are key determinants of disease severity (i.e., virulence) and infectiousness (i.e., transmission between hosts). By iterating the development of theory and empirical tests, we investigated whether variation in parasite traits across two genetically distinct clones of the rodent malaria parasite, Plasmodium chabaudi, explains differences in within-host infection dynamics and virulence. First, we experimentally tested key predictions of our earlier modeling work. As predicted, the more virulent genotype produced more progeny parasites per infected cell (burst size), but in contrast to predictions, invasion rates of red blood cells (RBCs) did not differ between the genotypes studied. Second, we further developed theory by confronting our earlier model with these new data, testing a new set of models that incorporate more biological realism, and developing novel theoretical tools for identifying differences between parasite genotypes. Overall, we found robust evidence that differences in burst sizes contribute to variation in dynamics and that differential interactions between parasites and host immune responses also play a role. In contrast to previous work, our model predicts that RBC age structure is not important for explaining dynamics. Integrating theory and empirical tests is a potentially powerful way of progressing understanding of disease biology.
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Affiliation(s)
- Nicole Mideo
- Centre for Immunity, Infection and Evolution, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JT, United Kingdom
| | - Nicholas J. Savill
- Centre for Immunity, Infection and Evolution, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JT, United Kingdom
- Institute of Immunity and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JT, United Kingdom
| | - William Chadwick
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JT, United Kingdom
| | - Petra Schneider
- Centre for Immunity, Infection and Evolution, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JT, United Kingdom
| | - Andrew F. Read
- Center for Infectious Disease Dynamics, Departments of Biology and Entomology, Pennsylvania State University, University Park, Pennsylvania 16802; and Fogarty International Center, National Institutes of Health, Bethesda, Maryland 20892
| | - Troy Day
- Departments of Biology and Mathematics and Statistics, Queen’s University, Kingston, Ontario K7L 3N6, Canada
| | - Sarah E. Reece
- Centre for Immunity, Infection and Evolution, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JT, United Kingdom
- Institute of Immunity and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JT, United Kingdom
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JT, United Kingdom
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14
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Geurts N, Martens E, Verhenne S, Lays N, Thijs G, Magez S, Cauwe B, Li S, Heremans H, Opdenakker G, Van den Steen PE. Insufficiently defined genetic background confounds phenotypes in transgenic studies as exemplified by malaria infection in Tlr9 knockout mice. PLoS One 2011; 6:e27131. [PMID: 22096530 PMCID: PMC3214040 DOI: 10.1371/journal.pone.0027131] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2011] [Accepted: 10/11/2011] [Indexed: 01/09/2023] Open
Abstract
The use of genetically modified mice, i.e. transgenic as well as gene knockout (KO) and knock-in mice, has become an established tool to study gene function in many animal models for human diseases . However, a gene functions in a particular genomic context. This implies the importance of a well-defined homogenous genetic background for the analysis and interpretation of phenotypes associated with genetic mutations. By studying a Plasmodium chabaudi chabaudi AS (PcAS) malaria infection in mice bearing a TLR9 null mutation, we found an increased susceptibility to infection, i.e. higher parasitemia levels and increased mortality. However, this was not triggered by the deficient TLR9 gene itself. Instead, this disease phenotype was dependent on the heterogeneous genetic background of the mice, which appeared insufficiently defined as determined by single nucleotide polymorphism (SNP) analysis. Hence, it is of critical importance to study gene KO phenotypes on a homogenous genetic background identical to that of their wild type (WT) control counterparts. In particular, to avoid problems related to an insufficiently defined genetic background, we advocate that for each study involving genetically modified mice, at least a detailed description of the origin and genetic background of both the WT control and the altered strain of mice is essential.
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Affiliation(s)
- Nathalie Geurts
- Laboratory of Immunobiology, Rega Institute for Medical Research, University of Leuven, Leuven, Belgium
| | - Erik Martens
- Laboratory of Immunobiology, Rega Institute for Medical Research, University of Leuven, Leuven, Belgium
| | - Sebastien Verhenne
- Laboratory of Immunobiology, Rega Institute for Medical Research, University of Leuven, Leuven, Belgium
| | - Natacha Lays
- Laboratory of Immunobiology, Rega Institute for Medical Research, University of Leuven, Leuven, Belgium
| | - Greet Thijs
- Laboratory of Immunobiology, Rega Institute for Medical Research, University of Leuven, Leuven, Belgium
| | - Stefan Magez
- Laboratory for Cellular and Molecular Immunology, Vrije Universiteit Brussel, Brussels, Belgium
| | - Bénédicte Cauwe
- Laboratory of Immunobiology, Rega Institute for Medical Research, University of Leuven, Leuven, Belgium
| | - Sandra Li
- Laboratory of Immunobiology, Rega Institute for Medical Research, University of Leuven, Leuven, Belgium
| | - Hubertine Heremans
- Laboratory of Immunobiology, Rega Institute for Medical Research, University of Leuven, Leuven, Belgium
| | - Ghislain Opdenakker
- Laboratory of Immunobiology, Rega Institute for Medical Research, University of Leuven, Leuven, Belgium
| | - Philippe E. Van den Steen
- Laboratory of Immunobiology, Rega Institute for Medical Research, University of Leuven, Leuven, Belgium
- * E-mail:
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15
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Miller MR, Råberg L, Read AF, Savill NJ. Quantitative analysis of immune response and erythropoiesis during rodent malarial infection. PLoS Comput Biol 2010; 6:e1000946. [PMID: 20941388 PMCID: PMC2947982 DOI: 10.1371/journal.pcbi.1000946] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2010] [Accepted: 08/31/2010] [Indexed: 12/20/2022] Open
Abstract
Malarial infection is associated with complex immune and erythropoietic responses in the host. A quantitative understanding of these processes is essential to help inform malaria therapy and for the design of effective vaccines. In this study, we use a statistical model-fitting approach to investigate the immune and erythropoietic responses in Plasmodium chabaudi infections of mice. Three mouse phenotypes (wildtype, T-cell-deficient nude mice, and nude mice reconstituted with T-cells taken from wildtype mice) were infected with one of two parasite clones (AS or AJ). Under a Bayesian framework, we use an adaptive population-based Markov chain Monte Carlo method and fit a set of dynamical models to observed data on parasite and red blood cell (RBC) densities. Model fits are compared using Bayes' factors and parameter estimates obtained. We consider three independent immune mechanisms: clearance of parasitised RBCs (pRBC), clearance of unparasitised RBCs (uRBC), and clearance of parasites that burst from RBCs (merozoites). Our results suggest that the immune response of wildtype mice is associated with less destruction of uRBCs, compared to the immune response of nude mice. There is a greater degree of synchronisation between pRBC and uRBC clearance than between either mechanism and merozoite clearance. In all three mouse phenotypes, control of the peak of parasite density is associated with pRBC clearance. In wildtype mice and AS-infected nude mice, control of the peak is also associated with uRBC clearance. Our results suggest that uRBC clearance, rather than RBC infection, is the major determinant of RBC dynamics from approximately day 12 post-innoculation. During the first 2-3 weeks of blood-stage infection, immune-mediated clearance of pRBCs and uRBCs appears to have a much stronger effect than immune-mediated merozoite clearance. Upregulation of erythropoiesis is dependent on mouse phenotype and is greater in wildtype and reconstitited mice. Our study highlights the informative power of statistically rigorous model-fitting techniques in elucidating biological systems.
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Affiliation(s)
- Martin R. Miller
- Centre for Infectious Diseases, Institute of Immunology and Infection Research, University of Edinburgh, Edinburgh, United Kingdom
| | - Lars Råberg
- Department of Animal Ecology, Lund University, Lund, Sweden
| | - Andrew F. Read
- Center for Infectious Disease Dynamics and Departments of Biology and Entomology, Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Nicholas J. Savill
- Centre for Infectious Diseases, Institute of Immunology and Infection Research, University of Edinburgh, Edinburgh, United Kingdom
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16
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Delić D, Warskulat U, Borsch E, Al-Qahtani S, Al-Quraishi S, Häussinger D, Wunderlich F. Loss of ability to self-heal malaria upon taurine transporter deletion. Infect Immun 2010; 78:1642-9. [PMID: 20100858 PMCID: PMC2849432 DOI: 10.1128/iai.01159-09] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2009] [Revised: 11/24/2009] [Accepted: 01/18/2010] [Indexed: 12/31/2022] Open
Abstract
Deletion of the taurine transporter gene (taut) results in lowered levels of taurine, the most abundant amino acid in mammals. Here, we show that taut-/- mice have lost their ability to self-heal blood-stage infections with Plasmodium chabaudi malaria. All taut-/- mice succumb to infections during crisis, while about 90% of the control taut(+/+) mice survive. The latter retain unchanged taurine levels even at peak parasitemia. Deletion of taut, however, results in the lowering of circulating taurine levels from 540 to 264 micromol/liter, and infections cause additional lowering to 192 micromol/liter. Peak parasitemia levels in taut-/- mice are approximately 60% higher than those in taut(+/+) mice, an elevation that is associated with increased systemic tumor necrosis factor alpha (TNF-alpha) and interleukin-1beta (IL-1beta) levels, as well as with liver injuries. The latter manifest as increased systemic ammonia levels, a perturbed capacity to entrap injected particles, and increased expression of genes encoding TNF-alpha, IL-1beta, IL-6, inducible nitric oxide synthase (iNOS), NF-kappaB, and vitamin D receptor (VDR). Autopsy reveals multiorgan failure as the cause of death for malaria-infected taut-/- mice. Our data indicate that taut-controlled taurine homeostasis is essential for resistance to P. chabaudi malaria. Taurine deficiency due to taut deletion, however, impairs the eryptosis of P. chabaudi-parasitized erythrocytes and expedites increases in systemic TNF-alpha, IL-1beta, and ammonia levels, presumably contributing to multiorgan failure in P. chabaudi-infected taut-/- mice.
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Affiliation(s)
- Denis Delić
- Division of Molecular Parasitology, Department of Biology, and Biologisch-Medizinisches Forschungszentrum, Heinrich-Heine- University, Universitätsstr. 1, Clinic for Gastroenterology, Hepatology, and Infectiology, Heinrich-Heine-University, Moorenstr. 5, 40225 Düsseldorf, Germany, Teacher College, Zoology Department, College of Science, King Saud University, 11352 Riyadh, Saudi Arabia
| | - Ulrich Warskulat
- Division of Molecular Parasitology, Department of Biology, and Biologisch-Medizinisches Forschungszentrum, Heinrich-Heine- University, Universitätsstr. 1, Clinic for Gastroenterology, Hepatology, and Infectiology, Heinrich-Heine-University, Moorenstr. 5, 40225 Düsseldorf, Germany, Teacher College, Zoology Department, College of Science, King Saud University, 11352 Riyadh, Saudi Arabia
| | - Elena Borsch
- Division of Molecular Parasitology, Department of Biology, and Biologisch-Medizinisches Forschungszentrum, Heinrich-Heine- University, Universitätsstr. 1, Clinic for Gastroenterology, Hepatology, and Infectiology, Heinrich-Heine-University, Moorenstr. 5, 40225 Düsseldorf, Germany, Teacher College, Zoology Department, College of Science, King Saud University, 11352 Riyadh, Saudi Arabia
| | - Saad Al-Qahtani
- Division of Molecular Parasitology, Department of Biology, and Biologisch-Medizinisches Forschungszentrum, Heinrich-Heine- University, Universitätsstr. 1, Clinic for Gastroenterology, Hepatology, and Infectiology, Heinrich-Heine-University, Moorenstr. 5, 40225 Düsseldorf, Germany, Teacher College, Zoology Department, College of Science, King Saud University, 11352 Riyadh, Saudi Arabia
| | - Saleh Al-Quraishi
- Division of Molecular Parasitology, Department of Biology, and Biologisch-Medizinisches Forschungszentrum, Heinrich-Heine- University, Universitätsstr. 1, Clinic for Gastroenterology, Hepatology, and Infectiology, Heinrich-Heine-University, Moorenstr. 5, 40225 Düsseldorf, Germany, Teacher College, Zoology Department, College of Science, King Saud University, 11352 Riyadh, Saudi Arabia
| | - Dieter Häussinger
- Division of Molecular Parasitology, Department of Biology, and Biologisch-Medizinisches Forschungszentrum, Heinrich-Heine- University, Universitätsstr. 1, Clinic for Gastroenterology, Hepatology, and Infectiology, Heinrich-Heine-University, Moorenstr. 5, 40225 Düsseldorf, Germany, Teacher College, Zoology Department, College of Science, King Saud University, 11352 Riyadh, Saudi Arabia
| | - Frank Wunderlich
- Division of Molecular Parasitology, Department of Biology, and Biologisch-Medizinisches Forschungszentrum, Heinrich-Heine- University, Universitätsstr. 1, Clinic for Gastroenterology, Hepatology, and Infectiology, Heinrich-Heine-University, Moorenstr. 5, 40225 Düsseldorf, Germany, Teacher College, Zoology Department, College of Science, King Saud University, 11352 Riyadh, Saudi Arabia
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17
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Fairlie-Clarke KJ, Lamb TJ, Langhorne J, Graham AL, Allen JE. Antibody isotype analysis of malaria-nematode co-infection: problems and solutions associated with cross-reactivity. BMC Immunol 2010; 11:6. [PMID: 20163714 PMCID: PMC2838755 DOI: 10.1186/1471-2172-11-6] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2009] [Accepted: 02/17/2010] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND Antibody isotype responses can be useful as indicators of immune bias during infection. In studies of parasite co-infection however, interpretation of immune bias is complicated by the occurrence of cross-reactive antibodies. To confidently attribute shifts in immune bias to the presence of a co-infecting parasite, we suggest practical approaches to account for antibody cross-reactivity. The potential for cross-reactive antibodies to influence disease outcome is also discussed. RESULTS Utilising two murine models of malaria-helminth co-infection we analysed antibody responses of mice singly- or co-infected with Plasmodium chabaudi chabaudi and Nippostrongylus brasiliensis or Litomosoides sigmodontis. We observed cross-reactive antibody responses that recognised antigens from both pathogens irrespective of whether crude parasite antigen preparations or purified recombinant proteins were used in ELISA. These responses were not apparent in control mice. The relative strength of cross-reactive versus antigen-specific responses was determined by calculating antibody titre. In addition, we analysed antibody binding to periodate-treated antigens, to distinguish responses targeted to protein versus carbohydrate moieties. Periodate treatment affected both antigen-specific and cross-reactive responses. For example, malaria-induced cross-reactive IgG1 responses were found to target the carbohydrate component of the helminth antigen, as they were not detected following periodate treatment. Interestingly, periodate treatment of recombinant malaria antigen Merozoite Surface Protein-119 (MSP-119) resulted in increased detection of antigen-specific IgG2a responses in malaria-infected mice. This suggests that glycosylation may have been masking protein epitopes and that periodate-treated MSP-119 may more closely reflect the natural non-glycosylated antigen seen during infection. CONCLUSIONS In order to utilize antibody isotypes as a measure of immune bias during co-infection studies, it is important to dissect antigen-specific from cross-reactive antibody responses. Calculating antibody titre, rather than using a single dilution of serum, as a measure of the relative strength of the response, largely accomplished this. Elimination of the carbohydrate moiety of an antigen that can often be the target of cross-reactive antibodies also proved useful.
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Affiliation(s)
- Karen J Fairlie-Clarke
- Institutes of Evolution, Immunology and Infection Research, School of Biological Sciences, King's Buildings, University of Edinburgh, West Mains Road, Edinburgh, EH9 3JT, UK
| | - Tracey J Lamb
- Current address: School of Biological Sciences, The University of Reading, Reading, Berks RG6 6UB, UK
| | - Jean Langhorne
- Division of Parasitology, National Institute for Medical Research, The Ridgeway Mill Hill, NW7 1AA, UK
| | - Andrea L Graham
- Institutes of Evolution, Immunology and Infection Research, School of Biological Sciences, King's Buildings, University of Edinburgh, West Mains Road, Edinburgh, EH9 3JT, UK
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544, USA
| | - Judith E Allen
- Institutes of Evolution, Immunology and Infection Research, School of Biological Sciences, King's Buildings, University of Edinburgh, West Mains Road, Edinburgh, EH9 3JT, UK
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18
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Abstract
One theory of why some pathogens are virulent (i.e., they damage their host) is that they need to extract resources from their host in order to compete for transmission to new hosts, and this resource extraction can damage the host. Here we describe our studies in malaria that test and support this idea. We go on to show that host immunity can exacerbate selection for virulence and therefore that vaccines that reduce pathogen replication may select for more virulent pathogens, eroding the benefits of vaccination and putting the unvaccinated at greater risk. We suggest that in disease contexts where wild-type parasites can be transmitted through vaccinated hosts, evolutionary outcomes need to be considered.
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Affiliation(s)
- M J Mackinnon
- Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK.
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19
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Lefèvre T, Sanchez M, Ponton F, Hughes D, Thomas F. Virulence and resistance in malaria: who drives the outcome of the infection? Trends Parasitol 2007; 23:299-302. [PMID: 17493874 DOI: 10.1016/j.pt.2007.04.012] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2006] [Revised: 03/29/2007] [Accepted: 04/24/2007] [Indexed: 11/26/2022]
Abstract
Theoretical and experimental studies have established the dynamic nature of virulence and that, like all traits, it has evolved. Understanding parasite evolution offers a conceptual framework for diverse fields and can contribute greatly to decision-making in disease control. Recently, Grech et al. investigated the effects of host genotype-by-parasite genotype interactions on the expression of virulence in an artificial rodent-malaria system. They found that both parasite and host effects explained most of the variance in the virulence, resistance and transmission potential. These findings are a major contribution to the emerging debate on the pros and cons of a coevolutionary approach of virulence evolution; they also hold great potential for more effective control strategies.
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Affiliation(s)
- Thierry Lefèvre
- Génétique et Evolution des Maladies Infectieuses, UMR CNRS/IRD 2724, IRD, 911 Avenue Agropolis, BP 64501, 34394 Montpellier Cedex 5, France
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20
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Long GH, Chan BHK, Allen JE, Read AF, Graham AL. Parasite genetic diversity does not influence TNF-mediated effects on the virulence of primary rodent malaria infections. Parasitology 2006; 133:673-84. [PMID: 16978451 DOI: 10.1017/s003118200600117x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2006] [Revised: 06/17/2006] [Accepted: 06/21/2006] [Indexed: 12/20/2022]
Abstract
The pro-inflammatory cytokine tumour necrosis factor alpha (TNF-alpha) is associated with malaria virulence (disease severity) in both rodents and humans. We are interested in whether parasite genetic diversity influences TNF-mediated effects on malaria virulence. Here, primary infections with genetically distinct Plasmodium chabaudi chabaudi (P.c.c.) clones varied in the virulence and cytokine responses induced in female C57BL/6 mice. Even when parasitaemia was controlled for, a greater day 7 TNF-alpha response was induced by infection with more virulent P.c.c. clones. Since many functions of TNF-alpha are exerted through TNF receptor 1 (TNFR1), a TNFR-1 fusion protein (TNFR-Ig) was used to investigate whether TNFR1 blockade eliminated clone virulence differences. We found that TNFR-1 blockade ameliorated the weight loss but not the anaemia induced by malaria infection, regardless of P.c.c. clone. We show that distinct P.c.c. infections induced significantly different plasma interferon gamma (IFN-gamma), interleukin 6 (IL-6) and interleukin 10 (IL-10) levels. Our results demonstrate that regardless of P.c.c. genotype, blocking TNFR1 signalling protected against weight loss, but had negligible effects on both anaemia and asexual parasite kinetics. Thus, during P.c.c. infection, TNF-alpha is a key mediator of weight loss, independent of parasite load and across parasite genotypes.
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Affiliation(s)
- G H Long
- Institutes of Evolution, Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, King's Buildings, West Mains Road, Edinburgh EH9 3JT, Scotland.
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21
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Abstract
A rich body of theory on the evolution of virulence (disease severity) attempts to predict the conditions that cause parasites to harm their hosts, and a central assumption to many of these models is that the relative virulence of pathogen strains is stable across a range of host types. In contrast, a largely nonoverlapping body of theory on coevolution assumes that the fitness effects of parasites on hosts is not stable across host genotype, but instead depends on host genotype by parasite genotype interactions. If such genetic interactions largely determine virulence, it becomes difficult to predict the strength and direction of selection on virulence. In this study, we tested for host-by-parasite interactions in a medically relevant vertebrate disease model: the rodent malaria parasite Plasmodium chabaudi in laboratory mice. We found that parasite and particularly host main effects explained most of the variance in virulence (anaemia and weight loss), resistance (parasite burden) and transmission potential. Host-by-parasite interactions were of limited influence, but nevertheless had significant effects. This raises the possibility that host heterogeneity may affect the rate of any parasite response to selection on virulence. This study of rodent malaria is one of the first tests for host-by-parasite interactions in any vertebrate disease; host-by-parasite interactions typical of those assumed in coevolutionary models were present, but were by no means pervasive.
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Affiliation(s)
- K Grech
- Institutes of Evolution, Immunology and Infection Research, School of Biological Sciences, Ashworth Laboratories, University of Edinburgh, Edinburgh, UK.
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22
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Raberg L, de Roode JC, Bell AS, Stamou P, Gray D, Read AF. The Role of Immune‐Mediated Apparent Competition in Genetically Diverse Malaria Infections. Am Nat 2006; 168:41-53. [PMID: 16874614 DOI: 10.1086/505160] [Citation(s) in RCA: 113] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2005] [Accepted: 03/17/2006] [Indexed: 11/03/2022]
Abstract
Competitive interactions between coinfecting genotypes of the same pathogen can impose selection on virulence, but the direction of this selection depends on the mechanisms behind the interactions. Here, we investigate how host immune responses contribute to competition between clones in mixed infections of the rodent malaria parasite Plasmodium chabaudi. We studied single and mixed infections of a virulent and an avirulent clone and compared the extent of competition in immunodeficient and immunocompetent mice (nude mice and T cell-reconstituted nude mice, respectively). In immunocompetent mice, the avirulent clone suffered more from competition than did the virulent clone. The competitive suppression of the avirulent clone was alleviated in immunodeficient mice. Moreover, the relative density of the avirulent clone in mixed infections was higher in immunodeficient than in immunocompetent mice. We conclude that immune-mediated interactions contributed to competitive suppression of the avirulent clone, although other mechanisms, presumably competition for resources such as red blood cells, must also be important. Because only the avirulent clone suffered from immune-mediated competition, this mechanism should contribute to selection for increased virulence in mixed infections in this host-parasite system. As far as we are aware, this is the first direct experimental evidence of immune-mediated apparent competition in any host-parasite system.
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Affiliation(s)
- Lars Raberg
- Institutes of Evolution, Immunology, and Infection Research, School of Biological Sciences, University of Edinburgh, King's Buildings, West Mains Road, Edinburgh EH9 3JT, Scotland, United Kingdom.
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Hernandez-Valladares M, Naessens J, Musoke AJ, Sekikawa K, Rihet P, Ole-Moiyoi OK, Busher P, Iraqi FA. Pathology of Tnf-deficient mice infected with Plasmodium chabaudi adami 408XZ. Exp Parasitol 2006; 114:271-8. [PMID: 16716303 DOI: 10.1016/j.exppara.2006.04.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2006] [Revised: 04/05/2006] [Accepted: 04/06/2006] [Indexed: 10/24/2022]
Abstract
Tumor necrosis factor alpha (Tnf) plays a pleiotropic role in murine malaria. Some investigations have correlated Tnf with hypothermia, hyperlactatemia, hypoglycemia, and a suppression of the erythropoietic response, although others have not. In this study, we have evaluated parasitemia, survival rate and several pathological features in C57BL/6JTnf(-/-) and C57BL/6JTnf(+/+) mice after infection with Plasmodium chabaudi adami 408XZ. Compared to the C57BL/6JTnf(+/+) mice, C57BL/6JTnf(-/-) mice showed increased parasitemia and decreased survival rate, whereas blood glucose, blood lactate and body weight were not significantly different. However, C57BL/6JTnf(-/-) mice suffered significantly more from severe anemia and hypothermia than C57BL/6JTnf(+/+) mice. These results suggest that Tnf is an important mediator of parasite control, but not of anemia development. We hypothesize that the high mortality observed in the Tnf knock-out mice is due to increased anemia and pathology as a direct result of increased levels of parasitemia.
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Affiliation(s)
- M Hernandez-Valladares
- International Livestock Research Institute (ILRI), Naivasha Road, P.O. Box 30709, 00100 Nairobi, Kenya.
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24
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Weidanz WP, Batchelder JM, Flaherty P, LaFleur G, Wong C, van der Heyde HC. Plasmodium chabaudi adami: use of the B-cell-deficient mouse to define possible mechanisms modulating parasitemia of chronic malaria. Exp Parasitol 2005; 111:97-104. [PMID: 16087175 DOI: 10.1016/j.exppara.2005.06.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2005] [Revised: 06/23/2005] [Accepted: 06/26/2005] [Indexed: 11/25/2022]
Abstract
Our previous observation that B-cell-deficient JH-/- mice utilize T cell-dependent immunity to suppress acute Plasmodium chabaudi adami-induced malaria but then develop chronic low-level parasitemia prompted this study of control mechanisms for chronic parasitemia. When we infected JH-/- mice with blood-stage parasites, chronic parasitemia exacerbated after the 6th month and persisted for up to 17 months. This exacerbation of parasitemia could not be attributed to host aging because the time-course of acute infection in naïve aged mice was nearly identical to that seen in young mice. Nor could exacerbated parasitemia be attributed to mutation in the parasite genome resulting in increased virulence; when subinoculated into naïve JH-/- mice, parasites from chronically infected JH-/- mice with exacerbated parasitemia produced acute stage parasitemia profiles in most recipients comparable to those seen in JH-/- mice upon infection with the original stabilate material. Of the pro-inflammatory cytokines measured, including IFNgamma, TNFalpha, IL-12p70, and MCP-1beta, none were significantly different in the sera of mice with exacerbated parasitemia compared to uninfected controls. Levels of IL-6 were significantly (P=0.002) less in the sera of mice with exacerbated parasitemia. Serum levels of the anti-inflammatory cytokine, TGFbeta, were significantly depressed in chronically infected JH-/- mice compared to uninfected controls. In contrast, IL-10 levels were markedly increased. These findings suggest that the cytokine balance may be disturbed during chronic malaria, thereby impacting on mechanisms that modulate levels of parasitemia.
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Affiliation(s)
- William P Weidanz
- Department of Medical Microbiology and Immunology, University of Wisconsin, Madison, WI 53706 1532, USA.
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25
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Abstract
Compared to C57BL/6 wild-type mice, interleukin-15(-/-) (IL-15(-/-)) mice showed delayed clearance of Plasmodium chabaudi AS infection, lower type 1 cytokine production, impaired dendritic cell and NK cell functions, and lower titers of malaria-specific antibodies. Thus, IL-15 supports early control and timely resolution of blood-stage malaria through promotion of Th1-dependent innate and adaptive immune responses.
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Affiliation(s)
- Rebecca Ing
- Centre for the Study of Host Resistance, Research Institute of the McGill University Health Centre, 1650 Cedar Ave., Montreal, Quebec H3G 1A4, Canada
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26
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Abstract
Drug-resistant mutant forms of an organism are likely to be less fit than their wild-type strains in the absence of selection. Experimental work on prokaryotic organisms suggests that this is the case, but that compensatory mutations may occur which restore the fitness of mutants to that of sensitive forms. Here, we review experimental and field studies on this subject in malaria. In the rodent model Plasmodium chabaudi, a pyrimethamine-resistant mutant has been found to grow more slowly in mice than its drug-sensitive progenitor; however, following passage in the absence of the drug it grew faster, suggesting the occurrence of compensatory mutations. Similar findings were made with a chloroquine-resistant mutant. Field studies on Plasmodium falciparum have provided circumstantial evidence of a loss of fitness of chloroquine-resistant mutants, which appear to become less frequent in the parasite population following withdrawal of the drug. However, the occurrence of frequent recombination in the life-cycle of this parasite means that in natural conditions, a gene conferring resistance, once it has arisen, can then spread into a diversity of genetically distinct backgrounds which will influence its fitness and capacity to survive in the parasite population.
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Affiliation(s)
- David Walliker
- Institute of Infection and Immunology Research, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JT, UK.
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27
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de Roode JC, Pansini R, Cheesman SJ, Helinski MEH, Huijben S, Wargo AR, Bell AS, Chan BHK, Walliker D, Read AF. Virulence and competitive ability in genetically diverse malaria infections. Proc Natl Acad Sci U S A 2005; 102:7624-8. [PMID: 15894623 PMCID: PMC1140419 DOI: 10.1073/pnas.0500078102] [Citation(s) in RCA: 276] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Explaining parasite virulence is a great challenge for evolutionary biology. Intuitively, parasites that depend on their hosts for their survival should be benign to their hosts, yet many parasites cause harm. One explanation for this is that within-host competition favors virulence, with more virulent strains having a competitive advantage in genetically diverse infections. This idea, which is well supported in theory, remains untested empirically. Here we provide evidence that within-host competition does indeed select for high parasite virulence. We examine the rodent malaria Plasmodium chabaudi in laboratory mice, a parasite-host system in which virulence can be easily monitored and competing strains quantified by using strain-specific real-time PCR. As predicted, we found a strong relationship between parasite virulence and competitive ability, so that more virulent strains have a competitive advantage in mixed-strain infections. In transmission experiments, we found that the strain composition of the parasite populations in mosquitoes was directly correlated with the composition of the blood-stage parasite population. Thus, the outcome of within-host competition determined relative transmission success. Our results imply that within-host competition is a major factor driving the evolution of virulence and can explain why many parasites harm their hosts.
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Affiliation(s)
- Jacobus C de Roode
- Institutes of Evolution, Immunology, and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JT, Scotland, UK.
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28
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Hernandez-Valladares M, Naessens J, Nagda S, Musoke AJ, Rihet P, Ole-Moiyoi OK, Iraqi FA. Comparison of pathology in susceptible A/J and resistant C57BL/6J mice after infection with different sub-strains of Plasmodium chabaudi. Exp Parasitol 2005; 108:134-41. [PMID: 15582510 DOI: 10.1016/j.exppara.2004.07.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2004] [Revised: 04/08/2004] [Accepted: 07/27/2004] [Indexed: 11/29/2022]
Abstract
Susceptible A/J and more resistant C57BL/6J mice were infected with Plasmodium chabaudi chabaudi 54X, P.c. chabaudi AS and Plasmodium chabaudi adami 408XZ. As expected, most C57BL/6J mice survived the infections with the different isolates. But in contrast to previous observations, not all A/J mice succumbed to infection: just over 50% of A/J mice survived infections with P.c. chabaudi 54X, while 80% survived P.c. chabaudi AS. The more virulent parasite, P.c. adami 408XZ, was able to kill all A/J mice and 20% of C57BL/6J mice after an intravenous infection with 10(5) pRBC. A detailed study of four parameters of pathology (body weight, body temperature, blood glucose and RBC counts) in both mouse strains after a P.c. adami 408XZ infection showed similar patterns to those previously reported after infection with P.c. chabaudi AS. These data suggest that environmental factors as well as parasite polymorphisms might influence the severity of malaria between susceptible and resistant mice.
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Affiliation(s)
- M Hernandez-Valladares
- International Livestock Research Institute , Naivasha Road, P.O. Box 30709, 00100 Nairobi, Kenya
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29
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Mackinnon MJ, Bell A, Read AF. The effects of mosquito transmission and population bottlenecking on virulence, multiplication rate and rosetting in rodent malaria. Int J Parasitol 2005; 35:145-53. [PMID: 15710435 DOI: 10.1016/j.ijpara.2004.11.011] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2004] [Revised: 11/08/2004] [Accepted: 11/11/2004] [Indexed: 10/26/2022]
Abstract
Malaria parasites vary in virulence, but the effects of mosquito transmission on virulence phenotypes have not been systematically analysed. Using six lines of malaria parasite that varied widely in virulence, three of which had been serially blood-stage passaged many times, we found that mosquito transmission led to a general reduction in malaria virulence. Despite that, the between-line variation in virulence remained. Forcing serially passaged lines through extreme population bottlenecks (<5 parasites) reduced virulence in only one of two lines. That reduction was to a level intermediate between that of the virulent parental and avirulent ancestral line. Mosquito transmission did not reverse the increased parasite replication rates that had accrued during serial passage, but it did increase rosetting frequencies. Re-setting of asexual stage genes during the sexual stages of the life cycle, coupled with stochastic sampling of parasites with variable virulence during population bottlenecks, could account for the virulence reductions and increased rosetting induced by mosquito transmission.
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Affiliation(s)
- M J Mackinnon
- School of Biological Sciences, University of Edinburgh, West Mains Road, Edinburgh EH9 3JT, UK.
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30
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Graham AL, Lamb TJ, Read AF, Allen JE. Malaria-filaria coinfection in mice makes malarial disease more severe unless filarial infection achieves patency. J Infect Dis 2004; 191:410-21. [PMID: 15633101 DOI: 10.1086/426871] [Citation(s) in RCA: 121] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2004] [Accepted: 08/18/2004] [Indexed: 11/03/2022] Open
Abstract
Coinfections are common in natural populations, and the literature suggests that helminth coinfection readily affects how the immune system manages malaria. For example, type 1-dependent control of malaria parasitemia might be impaired by the type 2 milieu of preexisting helminth infection. Alternatively, immunomodulatory effects of helminths might affect the likelihood of malarial immunopathology. Using rodent models of lymphatic filariasis (Litomosoides sigmodontis) and noncerebral malaria (clone AS Plasmodium chabaudi chabaudi), we quantified disease severity, parasitemia, and polyclonal splenic immune responses in BALB/c mice. We found that coinfected mice, particularly those that did not have microfilaremia (Mf(-)), had more severe anemia and loss of body mass than did mice with malaria alone. Even when controlling for parasitemia, malaria was most severe in Mf(-) coinfected mice, and this was associated with increased interferon- gamma responsiveness. Thus, in Mf(-) mice, filariasis upset a delicate immunological balance in malaria infection and exacerbated malaria-induced immunopathology.
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Affiliation(s)
- Andrea L Graham
- Institutes of Evolution, Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, Scotland.
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31
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Hernandez-Valladares M, Naessens J, Gibson JP, Musoke AJ, Nagda S, Rihet P, Ole-MoiYoi OK, Iraqi FA. Confirmation and dissection of QTL controlling resistance to malaria in mice. Mamm Genome 2004; 15:390-8. [PMID: 15170228 DOI: 10.1007/s00335-004-3042-4] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2003] [Accepted: 12/17/2003] [Indexed: 11/25/2022]
Abstract
We developed an F(11) AIL population from an F(1) cross of A/J (susceptible) and C57BL/6J (resistant) mouse strains. One thousand F(11) mice were challenged with P.c. chabaudi 54X, and 340 mice selected from the phenotypic extremes for susceptibility and resistance were genotyped for microsatellite markers on Chromosomes (Chrs) 5, 8, and 17. QTL originally detected in backcross and F(2) populations were confirmed on the three chromosomes within narrower genomic regions, by maximum likelihood and regression analyses. Each of the previously mapped QTL on Chrs 5 and 17 resolved into two linked QTLs. The distal and proximal QTLs on Chrs 5 and 17, respectively, map to the previously reported QTL.
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32
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Gillman BM, Batchelder J, Flaherty P, Weidanz WP. Suppression of Plasmodium chabaudi parasitemia is independent of the action of reactive oxygen intermediates and/or nitric oxide. Infect Immun 2004; 72:6359-66. [PMID: 15501765 PMCID: PMC523046 DOI: 10.1128/iai.72.11.6359-6366.2004] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2004] [Revised: 07/04/2004] [Accepted: 08/09/2004] [Indexed: 12/29/2022] Open
Abstract
The killing of blood-stage malaria parasites in vivo has been attributed to reactive intermediates of oxygen (ROI) and of nitrogen (RNI). However, in the case of the latter, this contention is challenged by recent observations that parasitemia was not exacerbated in nitric oxide synthase (NOS) knockout (KO) (NOS2-/- or NOS3-/-) mice or in mice treated with NOS inhibitors. We now report that the time course shows that Plasmodium chabaudi parasitemia in NADPH oxidase KO (p47phox-/-) mice also was not exacerbated, suggesting a minimal role for ROI-mediated killing of blood-stage parasites. It is possible that the production of protective antibodies during malaria may mask the function of ROI and/or RNI. However, parasitemia in B-cell-deficient JH-/- x NOS2-/- or JH-/- x p47phox-/- mice was not exacerbated. In contrast, the magnitude of peak parasitemia was significantly enhanced in p47phox-/- mice treated with the xanthine oxidase inhibitor allopurinol, but the duration of patent parasitemia was not prolonged. Whereas the time course of parasitemia in NOS2-/- x p47phox-/- mice was nearly identical to that seen in normal control mice, allopurinol treatment of these double-KO mice also enhanced the magnitude of peak parasitemia. Thus, ROI generated via the xanthine oxidase pathway contribute to the control of ascending P. chabaudi parasitemia during acute malaria but alone are insufficient to suppress parasitemia to subpatent levels. Together, these results indicate that ROI or RNI can contribute to, but are not essential for, the suppression of parasitemia during blood-stage malaria.
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Affiliation(s)
- Brad M Gillman
- Department of Medical Microbiology and Immunology, University of Wisconsin Medical School, 1300 University Ave., Madison 53706, USA
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33
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Pouniotis DS, Proudfoot O, Bogdanoska V, Apostolopoulos V, Fifis T, Plebanski M. Dendritic cells induce immunity and long-lasting protection against blood-stage malaria despite an in vitro parasite-induced maturation defect. Infect Immun 2004; 72:5331-9. [PMID: 15322030 PMCID: PMC517485 DOI: 10.1128/iai.72.9.5331-5339.2004] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Dendritic cells (DC) suffer a maturation defect following interaction with erythrocytes infected with malaria parasites and become unable to induce protective malaria liver-stage immunity. Here we show that, by contrast, maturation-arrested DC in vitro are capable of the successful induction of antigen-specific gamma interferon (IFN-gamma) and interleukin 4 (IL-4) T-cell responses, antibody responses, and potent protection against lethal blood-stage malaria challenge in vivo. Similar results were found with DC pulsed with intact parasitized Plasmodium yoelii or Plasmodium chabaudi erythrocytes. Cross-strain protection was also induced. High levels of protection (80 to 100%) against lethal challenge were evident from 10 days after a single immunization and maintained up to 120 days. Interestingly, correlation studies versus blood-stage protection at different time points suggest that the immune effector mechanisms associated with protection could change over time. Antibody-independent, T-cell- and IL-12-associated protection was observed early after immunization, followed by antibody and IL-4-associated, IFN-gamma-independent protection in long-term studies. These results indicate that DC, even when clearly susceptible to parasite-induced maturation defect effects in vitro, can be central to the induction of protection against blood-stage malaria in vivo.
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Affiliation(s)
- Dodie S Pouniotis
- Vaccine and Infectious Diseases Unit, The Austin Research Institute, Austin Campus Heidelberg, Victoria 3084, Australia
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34
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Abstract
Malaria parasites cause much morbidity and mortality to their human hosts. From our evolutionary perspective, this is because virulence is positively associated with parasite transmission rate. Natural selection therefore drives virulence upwards, but only to the point where the cost to transmission caused by host death begins to outweigh the transmission benefits. In this review, we summarize data from the laboratory rodent malaria model, Plasmodium chabaudi, and field data on the human malaria parasite, P. falciparum, in relation to this virulence trade-off hypothesis. The data from both species show strong positive correlations between asexual multiplication, transmission rate, infection length, morbidity and mortality, and therefore support the underlying assumptions of the hypothesis. Moreover, the P. falciparum data show that expected total lifetime transmission of the parasite is maximized in young children in whom the fitness cost of host mortality balances the fitness benefits of higher transmission rates and slower clearance rates, thus exhibiting the hypothesized virulence trade-off. This evolutionary explanation of virulence appears to accord well with the clinical and molecular explanations of pathogenesis that involve cytoadherence, red cell invasion and immune evasion, although direct evidence of the fitness advantages of these mechanisms is scarce. One implication of this evolutionary view of virulence is that parasite populations are expected to evolve new levels of virulence in response to medical interventions such as vaccines and drugs.
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Affiliation(s)
- Margaret J Mackinnon
- School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JT, Scotland, UK.
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35
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de Roode JC, Culleton R, Cheesman SJ, Carter R, Read AF. Host heterogeneity is a determinant of competitive exclusion or coexistence in genetically diverse malaria infections. Proc Biol Sci 2004; 271:1073-80. [PMID: 15293862 PMCID: PMC1691691 DOI: 10.1098/rspb.2004.2695] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
During an infection, malaria parasites compete for limited amounts of food and enemy-free space. Competition affects parasite growth rate, transmission and virulence, and is thus important for parasite evolution. Much evolutionary theory assumes that virulent clones outgrow avirulent ones, favouring the evolution of higher virulence. We infected laboratory mice with a mixture of two Plasmodium chabaudi clones: one virulent, the other avirulent. Using real-time quantitative PCR to track the two parasite clones over the course of the infection, we found that the virulent clone overgrew the avirulent clone. However, host genotype had a major effect on the outcome of competition. In a relatively resistant mouse genotype (C57B1/6J), the avirulent clone was suppressed below detectable levels after 10 days, and apparently lost from the infection. By contrast, in more susceptible mice (CBA/Ca), the avirulent clone was initially suppressed, but it persisted, and during the chronic phase of infection it did better than it did in single infections. Thus, the qualitative outcome of competition depended on host genotype. We suggest that these differences may be explained by different immune responses in the two mouse strains. Host genotype and resistance could therefore play a key role in the outcome of within-host competition between parasite clones and in the evolution of parasite virulence.
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Affiliation(s)
- Jacobus C de Roode
- Institute of Cell, Animal and Population Biology, University of Edinburgh, Kings Buildings, West Mains Road, Edinburgh EH9 3JT, UK.
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36
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Abstract
Evolutionary models predict that host immunity will shape the evolution of parasite virulence. While some assumptions of these models have been tested, the actual evolutionary outcome of immune selection on virulence has not. Using the mouse malaria model, Plasmodium chabaudi, we experimentally tested whether immune pressure promotes the evolution of more virulent pathogens by evolving parasite lines in immunized and nonimmunized ("naïve") mice using serial passage. We found that parasite lines evolved in immunized mice became more virulent to both naïve and immune mice than lines evolved in naïve mice. When these evolved lines were transmitted through mosquitoes, there was a general reduction in virulence across all lines. However, the immune-selected lines remained more virulent to naïve mice than the naïve-selected lines, though not to immunized mice. Thus, immune selection accelerated the rate of virulence evolution, rendering parasites more dangerous to naïve hosts. These results argue for further consideration of the evolutionary consequences for pathogen virulence of vaccination.
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Affiliation(s)
- Margaret J Mackinnon
- School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom.
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37
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Bradbury J. Malaria vaccination could drive parasite evolution. Lancet Infect Dis 2004; 4:479. [PMID: 15298023 DOI: 10.1016/s1473-3099(04)01092-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/30/2023]
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38
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Akimitsu N, Kim HS, Hamamoto H, Kamura K, Fukuma N, Arimitsu N, Ono K, Wataya Y, Torii M, Sekimizu K. Duffy antigen is important for the lethal effect of the lethal strain of Plasmodium yoelii 17XL. Parasitol Res 2004; 93:499-503. [PMID: 15278442 DOI: 10.1007/s00436-004-1165-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2004] [Accepted: 06/08/2004] [Indexed: 12/14/2022]
Abstract
We studied the potential role of the Duffy antigen and glycophorin A as receptors for rodent malaria parasite invasion of erythrocytes. Parasitemia increased exponentially after infection with Plasmodium berghei NK65, P. chabaudi, and P. vinckei in Duffy antigen knockout, glycophorin A knockout, and wild-type mice, indicating that the Duffy antigen and glycophorin A are not essential for these malaria parasites. However, parasitemia of the Duffy antigen knockout mice infected with P. yoelii 17XL remained constant from day 5 to 14 after infection, and then decreased, resulting in autotherapy. The treatment of P. yoelii 17XL-infected Duffy antigen knockout mice with anti-CD4 antibody increased the parasitemia 15 days after infection and the mice eventually died, indicating that CD-4-positive cells play an important role in the clearance of P. yoelii 17XL at the late stage of the infection.
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Affiliation(s)
- Nobuyoshi Akimitsu
- Laboratory of Developmental Biochemistry, Graduate School of Pharmaceutical Sciences, University of Tokyo, 3-1, 7-Chome, Hongo, Bunkyo-ku, 113-0033, Japan
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39
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Abstract
During a Plasmodium chabaudi infection in interleukin-10 (IL-10) knockout mice, there is greater parasite sequestration, more severe cerebral edema, and a high frequency of cerebral hemorrhage compared with infection of C57BL/6 mice. Anti-tumor necrosis factor alpha treatment ameliorated both cerebral edema and hemorrhages, suggesting that proinflammatory responses contributed to cerebral complications in infected IL-10(-/-) mice.
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Affiliation(s)
- Latifu A Sanni
- Division of Parasitology, MRC National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, United Kingdom
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40
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Abstract
Several laboratory studies of malaria parasites (Plasmodium sp.) and some field observations suggest that parasite virulence, defined as the harm a parasite causes to its vertebrate host, is positively correlated with transmission. Given this advantage, what limits the continual evolution of higher parasite virulence? One possibility is that while more virulent strains are more infectious, they are also more lethal to mosquitoes. In this study, we tested whether the virulence of the rodent malaria parasite P. chabaudi in the laboratory mouse was correlated with the fitness of mosquitoes it subsequently infected. Mice were infected with one of seven genetically distinct clones of P. chabaudi that differ in virulence. Weight loss and anemia in infected mice were monitored for 16-17 days before Anopheles stephensi mosquitoes were allowed to take a blood meal from them. Infection virulence in mice was positively correlated with transmission to mosquitoes (infection rate) and weakly associated with parasite burden (number of oocysts). Mosquito survival fell with increasing oocyst burden, but there was no overall statistically significant relationship between virulence in mice and mosquito mortality. Thus, there was no evidence that more virulent strains are more lethal to mosquitoes. Both vector survival and fecundity depended on parasite clone, and contrary to expectations, mosquitoes fed on infections more virulent to mice were more fecund. The strong parasite genetic effects associated with both fecundity and survival suggests that vector fitness could be an important selective agent shaping malaria population genetics and the evolution of phenotypes such as virulence in the vector.
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Affiliation(s)
- H M Ferguson
- Institute of Cell, Animal and Population Biology, University of Edinburgh, West Mains Road, Edinburgh EH9 3JT, United Kingdom.
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41
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De Roode JC, Read AF, Chan BHK, Mackinnon MJ. Rodent malaria parasites suffer from the presence of conspecific clones in three-clone Plasmodium chabaudi infections. Parasitology 2004; 127:411-8. [PMID: 14653530 DOI: 10.1017/s0031182003004001] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
We studied infection dynamics of Plasmodium chabaudi in mice infected with 3 genetically distinct clones--1 less virulent than the other 2--either on their own or in mixtures. During the acute phase of infection, total numbers of asexual parasites in mixed-clone infections were equal to those produced by the 3 clones alone, suggesting strong in-host competition among clones. During the chronic phase of the infection, mixed-clone infections produced more asexual parasites than single-clone infections, suggesting lower levels of competition than during the acute phase, and indicating that a genetically diverse infection is harder to control by the host immune system. Transmission potential over the whole course of infection was lower from mixed-clone infections than from the average of the 3 single-clone infections. These results suggest that in-host competition reduces both growth rate and probability of transmission for individual parasite clones.
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Affiliation(s)
- J C De Roode
- Institute of Cell, Animal and Population Biology, University of Edinburgh, Ashworth Laboratories, King's Buildings, West Mains Road, Edinburgh EH9 3JT, Scotland, UK.
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42
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Abstract
An important aspect of malaria vaccine development is the identification of an appropriate adjuvant which is both capable of stimulating a protective immune response and safe for use by humans. Here, we investigated the feasibility of using novel immunostimulatory molecules as adjuvants combined with a crude antigen preparation and coadsorbed to aluminum hydroxide (alum) as a vaccine against blood-stage Plasmodium chabaudi AS malaria. Prior to challenge infection, immunization of genetically susceptible A/J mice with the combination of malaria antigen plus recombinant interleukin-12 (IL-12) in alum induced a Th1 immune response with production of high levels of gamma interferon (IFN-gamma) and diminished IL-4 levels by spleen cells stimulated in vitro with parasite antigen compared to mice immunized with antigen alone, antigen in alum, or antigen plus IL-12. Mice immunized with malaria antigen plus recombinant IL-12 in alum had high levels of total malaria-specific antibody and immunoglobulin G2a. Compared to unimmunized mice, immunization with antigen plus IL-12 in alum induced the highest level of protective immunity against challenge infection with P. chabaudi AS, which was evident as a significantly decreased peak parasitemia level and 100% survival. Protective immunity was dependent on CD4(+) T cells, IFN-gamma, and B cells and was long-lasting. Replacement of IL-12 as an adjuvant by synthetic oligodeoxynucleotides (ODN) containing CpG motifs induced a similar level of vaccine-induced protection against challenge infection with P. chabaudi AS. These results illustrate that it is possible to enhance the potency of a crude malaria antigen preparation delivered in alum by inclusion of immunostimulatory molecules, such as IL-12 or CpG-ODN.
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Affiliation(s)
- Zhong Su
- Centre for the Study of Host Resistance, McGill University Health Centre Research Institute, McGill University, Montreal, Quebec, Canada
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43
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Rainczuk A, Scorza T, Smooker PM, Spithill TW. Induction of specific T-cell responses, opsonizing antibodies, and protection against Plasmodium chabaudi adami infection in mice vaccinated with genomic expression libraries expressed in targeted and secretory DNA vectors. Infect Immun 2003; 71:4506-15. [PMID: 12874330 PMCID: PMC166036 DOI: 10.1128/iai.71.8.4506-4515.2003] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
It has been proposed that a multivalent malaria vaccine is necessary to mimic the naturally acquired resistance to this disease observed in humans. A major experimental challenge is to identify the optimal components to be used in such a multivalent vaccine. Expression library immunization (ELI) is a method for screening genomes of a pathogen to identify novel combinations of vaccine sequences. Here we describe immune responses associated with, and the protective efficacy of, genomic Plasmodium chabaudi adami DS expression libraries constructed in VR1020 (secretory), monocyte chemotactic protein-3 (chemoattractant), and cytotoxic T lymphocyte antigen 4 (lymph node-targeting) DNA vaccine vectors. With splenocytes from vaccinated mice, specific T-cell responses, as well as gamma interferon and interleukin-4 production, were observed after stimulation with P. chabaudi adami-infected erythrocytes, demonstrating the specificity of genomic library vaccination for two of the three libraries constructed. Sera obtained from mice vaccinated with genomic libraries promoted the opsonization of P. chabaudi adami-infected erythrocytes by murine macrophages in vitro, further demonstrating the induction of malaria-specific immune responses following ELI. Over three vaccine trials using biolistic delivery of the three libraries, protection after lethal challenge with P. chabaudi adami DS ranged from 33 to 50%. These results show that protective epitopes or antigens are expressed within the libraries and that ELI induces responses specific to P. chabaudi adami malaria. This study further demonstrates that ELI is a suitable approach for screening the malaria genome to identify the components of multivalent vaccines.
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MESH Headings
- Abatacept
- Animals
- Antibodies, Protozoan/biosynthesis
- Antigens, CD
- Antigens, Differentiation/genetics
- Antigens, Protozoan/genetics
- Base Sequence
- CTLA-4 Antigen
- Chemokine CCL7
- Cytokines
- DNA, Protozoan/genetics
- Female
- Gene Library
- Genetic Vectors
- Genome, Protozoan
- Humans
- Immunity, Cellular
- Immunoconjugates
- In Vitro Techniques
- Macrophages/immunology
- Malaria/immunology
- Malaria/prevention & control
- Malaria Vaccines/genetics
- Malaria Vaccines/pharmacology
- Mice
- Mice, Inbred BALB C
- Monocyte Chemoattractant Proteins/genetics
- Opsonin Proteins/biosynthesis
- Phagocytosis
- Plasmodium chabaudi/genetics
- Plasmodium chabaudi/immunology
- Plasmodium chabaudi/pathogenicity
- T-Lymphocytes/immunology
- Vaccines, DNA/genetics
- Vaccines, DNA/pharmacology
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Affiliation(s)
- A Rainczuk
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia
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44
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Rivero A, Ferguson HM. The energetic budget of Anopheles stephensi infected with Plasmodium chabaudi: is energy depletion a mechanism for virulence? Proc Biol Sci 2003; 270:1365-71. [PMID: 12965027 PMCID: PMC1691381 DOI: 10.1098/rspb.2003.2389] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Evidence continues to accumulate showing that the malaria parasites (Plasmodium spp.) reduce the survival and fecundity of their mosquito vectors (Anopheles spp.). Our ability to identify the possible epidemiological and evolutionary consequences of these parasite-induced fitness reductions has been hampered by a poor understanding of the physiological basis of these shifts. Here, we explore whether the reductions in fecundity and longevity are the result of a parasite-mediated depletion or reallocation of the energetic resources of the mosquito. Mosquitoes infected with Plasmodium chabaudi were expected to have less energetic resources than uninfected mosquitoes, and energy levels were predicted to be lowest in mosquitoes infected with the most virulent parasite genotypes. Not only was there no evidence of a parasite-mediated reduction in the overall energetic budget of mosquitoes, but Plasmodium was actually associated with increased levels of glucose, a key insect nutritional and energetic resource. The data strongly suggest the existence of an increase in sugar feeding in mosquitoes infected with Plasmodium. We suggest different adaptive explanations for an enhanced sugar uptake in infected mosquitoes and call for more studies to investigate the physiological role of glucose in the Plasmodium-mosquito interaction.
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Affiliation(s)
- A Rivero
- Institute of Cell, Animal and Population Biology, University of Edinburgh, West Mains Road, Edinburgh EH9 3JT, UK.
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45
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Abstract
Studies of invertebrate-parasite interactions frequently report that infection reduces host fecundity. The extent of the reduction is likely to be determined by a wide range of host and parasite factors. We conducted a laboratory experiment to evaluate the role of parasite genetics and infection genetic diversity on the fecundity of mosquitoes carrying malaria parasites. The malaria vector Anopheles stephensi was infected with either of 2 different genotypes of the rodent malaria parasite Plasmodium chabaudi, or by a mixture of both. Mixed genotype infections reduced mosquito fecundity by 20%, significantly more than either of the 2 single genotype infections. Mixed genotype infections were associated with high gametocyte densities and anaemia in mice, both of which were correlated with reduced bloodmeal size in mosquitoes. Bloodmeal size was the most important predictor of mosquito fecundity; the presence and number of parasites had no direct effect. Parasite density influenced the propensity of mosquitoes to feed on infected mice, with a higher percentage of mosquitoes taking a meal as asexual parasite and gametocyte density increased. Thus mosquitoes may preferentially feed on hosts who will most impair their fecundity.
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Affiliation(s)
- H M Ferguson
- Institute of Cell, Animal and Population Biology, University of Edinburgh, West Mains Road, Edinburgh EH9 3JT, UK.
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46
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Abstract
Here we examined the impact of host immunity on relationships between parasite virulence, transmission rate, intrinsic growth rate and host recovery rate in the rodent malaria parasite, Plasmodium chabaudi. Groups of naïve and immunized mice were infected with 1 of 10 cloned lines of parasites and their infection dynamics were monitored for 19 days. We found that (1) host immunity reduced the growth rate, virulence, transmission rate and infection length, with a consequent 3-fold reduction in life-time transmission potential, (2) clone means for these traits ranked similarly across naïve and immunized mice, (3) regression slopes of transmission potential on growth rate, virulence and infection length were similar in naive and immunized mice, (4) virulence and infection length were positively correlated in immunized but not naïve mice, and (5) for a similar level of parasite growth rate and virulence, transmission potential and infection length were lower in immunized than naïve mice. Thus host immunity reduced all these fitness traits in a manner consistent with direct parasite-driven biological links among them. These results support the basic assumption underlying our theory that predicts that anti-disease vaccines will select for higher virulence in those microparasites for which virulence is integrally linked to transmission.
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Affiliation(s)
- M J Mackinnon
- Institute of Cell, Animal and Population Biology, University of Edinburgh, West Mains Road, Edinburgh EH9 3JT, Scotland.
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47
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Smith EC, Taylor-Robinson AW. Parasite-specific immunoglobulin isotypes during lethal and non-lethal murine malaria infections. Parasitol Res 2003; 89:26-33. [PMID: 12474040 DOI: 10.1007/s00436-002-0687-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2002] [Accepted: 05/13/2002] [Indexed: 11/29/2022]
Abstract
Production of parasite-specific antibodies is an important component of immunity to blood stage malaria infection, as shown by several previous studies in rodent models. However, no study has addressed the induction of humoral immunity by different parasites in a genetically homogeneous host population. Here, levels of parasite-specific immunoglobulin isotypes were measured during primary infections of Plasmodium chabaudi and of Plasmodium yoelii in inbred NIH mice inoculated with cloned lines of either avirulent or virulent erythrocytic parasites. Non-lethal infections were characterized by early and late significant upregulation of IgG2a and IgG1, respectively. In contrast, for lethal infections, a slower, reduced IgG2a response correlated with a rapidly fatal outcome prior to any significant synthesis of IgG1. It is proposed that the sequential upregulated synthesis of parasite-specific IgG2a (cytophilic) and IgG1 (non-cytophilic) is associated with protective immunity to blood stage malaria infections in mice. This may provide an immunological framework for examining humoral immunity to malaria in humans.
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Affiliation(s)
- Elizabeth C Smith
- School of Biology, University of Leeds, Clarendon Way, Leeds LS2 9JT, UK
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48
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Su Z, Fortin A, Gros P, Stevenson MM. Opsonin-independent phagocytosis: an effector mechanism against acute blood-stage Plasmodium chabaudi AS infection. J Infect Dis 2002; 186:1321-9. [PMID: 12402202 DOI: 10.1086/344576] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2002] [Revised: 07/09/2002] [Indexed: 11/03/2022] Open
Abstract
Opsonin-independent macrophage phagocytosis was investigated as a possible mechanism of controlling early blood-stage Plasmodium chabaudi AS infection. Early during infection, peritoneal macrophages from resistant C57BL/6 (B6) mice exhibited increased phagocytosis of parasitized red blood cells (pRBCs) and free merozoites, which was absent in mice with deficient interferon (IFN)-gamma production during infection, including susceptible A/J, interleukin (IL)-12 p40, and IFN-gamma gene knockout mice. IFN-gamma treatment of macrophages collected from B6 and A/J mice early during infection enhanced phagocytosis of pRBCs, but IL-10 treatment inhibited this function. In vitro and in vivo studies in which type I and II class A scavenger receptor-deficient mice and inhibitors of scavenger and mannose receptors were used revealed that scavenger receptors other than class A type I and II and mannose receptors may play a role in malaria parasite uptake. These results indicate that opsonin-independent phagocytosis contributes to the IFN-gamma-dependent control of acute blood-stage malaria infection.
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Affiliation(s)
- Zhong Su
- Centre for the Study of Host Resistance, Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, Quebec, Canada.
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49
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Nahrevanian H, Dascombe MJ. Expression of inducible nitric oxide synthase (iNOS) mRNA in target organs of lethal and non-lethal strains of murine malaria. Parasite Immunol 2002; 24:471-8. [PMID: 12654089 DOI: 10.1046/j.1365-3024.2002.00490.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Nitric oxide (NO) is a putative mediator of the immunological and/or pathological responses to malaria, consequently it is a potential target for novel drug therapy. Numerous cell types increase expression of inducible nitric oxide synthase (iNOS) under inflammatory conditions, the most relevant stimuli being cytokines and endotoxins. In this study the expression of iNOS mRNA in several target organs (brain, liver, spleen) of malaria have been investigated in MF1 mice during lethal Plasmodium (P.) berghei and non-lethal P. c. chabaudi infection. In P. berghei malaria, iNOS mRNA decreased in liver and was unchanged in spleen during the period of rising parasitaemia, but increased in both organs late in the infection, when parasitaemia was high and death imminent. In mice infected with P. c. chabaudi, spleen iNOS mRNA increased progressively throughout the early, peak and recovery periods of parasitaemia, but decreased in liver. Brain iNOS mRNA decreased in samples collected throughout the time courses of both infections. Hence it is evident that changes in iNOS mRNA in murine malaria depend upon the tissue, day of infection, degree of parasitaemia and strain of Plasmodium. These data indicate induction of iNOS mRNA in the spleen has a role in combating these strains of Plasmodium in MF1 mice. Failure to clear lethal P. berghei parasitaemia was associated with increased iNOS mRNA expression in the liver, which may contribute to the pathology of this malaria.
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50
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Abstract
In an effort to understand what limits the virulence of malaria parasites, we infected inbred mice of three genotypes (C57Bl/6J, CBA/Ca and DBA/2) with one of two parasite lines of the rodent malaria Plasmodium chabaudi. One of these parasite lines had been serially passaged through C57Bl/6J mice and had evolved higher asexual growth rate, virulence and transmission in the process. The other parasite line was the unadapted ancestral line which had low virulence. In all three host genotypes, the C57Bl/6J-adapted parasite line was more virulent than the ancestral line thus indicating that trade-offs in virulence between alternative host genotypes had not placed strong constraints on the evolution of high virulence in this system. By examining the infection dynamics for fitness-related components-asexual parasite population growth, transmission and virulence-we revealed alternative possible explanations for what sets the upper limit to virulence in nature. The total number of transmission forms (gametocytes) produced during the infection, a measure of parasite Darwinian fitness, was four-fold higher in mice that survived the infection than those which died. Among mice that survived, total gametocyte production was greatest in the host genotype that suffered intermediate levels of morbidity (anaemia and weight loss). Thus, there were transmission costs of high virulence that were partly due to host death (as most theoretical models of virulence evolution assume), but perhaps partly due to some factor related to high morbidity. Both mortality and morbidity-related factors might therefore influence the upper limit on virulence of malaria parasites.
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Affiliation(s)
- M J Mackinnon
- Institute of Cell, Animal and Population Biology, University of Edinburgh, West Mains Road, Edinburgh, Scotland EH9 3JT, UK.
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