101
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Preerythrocytic, live-attenuated Plasmodium falciparum vaccine candidates by design. Proc Natl Acad Sci U S A 2009; 106:13004-9. [PMID: 19625622 DOI: 10.1073/pnas.0906387106] [Citation(s) in RCA: 128] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Falciparum malaria is initiated when Anopheles mosquitoes transmit the Plasmodium sporozoite stage during a blood meal. Irradiated sporozoites confer sterile protection against subsequent malaria infection in animal models and humans. This level of protection is unmatched by current recombinant malaria vaccines. However, the live-attenuated vaccine approach faces formidable obstacles, including development of accurate, reproducible attenuation techniques. We tested whether Plasmodium falciparum could be attenuated at the early liver stage by genetic engineering. The P. falciparum genetically attenuated parasites (GAPs) harbor individual deletions or simultaneous deletions of the sporozoite-expressed genes P52 and P36. Gene deletions were done by double-cross-over recombination to avoid genetic reversion of the knockout parasites. The gene deletions did not affect parasite replication throughout the erythrocytic cycle, gametocyte production, mosquito infections, and sporozoite production rates. However, the deletions caused parasite developmental arrest during hepatocyte infection. The double-gene deletion line exhibited a more severe intrahepatocytic growth defect compared with the single-gene deletion lines, and it did not persist. This defect was assessed in an in vitro liver-stage growth assay and in a chimeric mouse model harboring human hepatocytes. The strong phenotype of the double knockout GAP justifies its human testing as a whole-organism vaccine candidate using the established sporozoite challenge model. GAPs might provide a safe and reproducible platform to develop an efficacious whole-cell malaria vaccine that prevents infection at the preerythrocytic stage.
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102
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Good MF. The hope but challenge for developing a vaccine that might control malaria. Eur J Immunol 2009; 39:939-43. [DOI: 10.1002/eji.200939390] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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103
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Chattopadhyay R, Conteh S, Li M, James ER, Epstein JE, Hoffman SL. The Effects of radiation on the safety and protective efficacy of an attenuated Plasmodium yoelii sporozoite malaria vaccine. Vaccine 2008; 27:3675-80. [PMID: 19071177 DOI: 10.1016/j.vaccine.2008.11.073] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2008] [Revised: 11/05/2008] [Accepted: 11/17/2008] [Indexed: 11/25/2022]
Abstract
We are developing a radiation attenuated Plasmodium falciparum sporozoite (PfSPZ) malaria vaccine. An important step was to determine the minimum dose of irradiation required to adequately attenuate each sporozoite. This was studied in the Plasmodium yoelii rodent model system. Exposure to 100 Gy completely attenuated P. yoelii sporozoites (PySPZ). Next we demonstrated that immunization of mice intravenously with 3 doses of 750 PySPZ that had received 200 Gy, double the radiation dose required for attenuation, resulted in 100% protection. These results support the contention that a radiation attenuated sporozoite vaccine for malaria will be safe and effective at a range of radiation doses.
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Affiliation(s)
- Rana Chattopadhyay
- Sanaria Inc., 9800 Medical Center Drive, Rockville, MD 20850, United States
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104
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Malaria vaccines: into a mirror, darkly? Trends Parasitol 2008; 24:532-6. [DOI: 10.1016/j.pt.2008.09.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2008] [Revised: 09/08/2008] [Accepted: 09/10/2008] [Indexed: 12/25/2022]
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105
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Enhanced immunogenicity of Plasmodium falciparum peptide vaccines using a topical adjuvant containing a potent synthetic Toll-like receptor 7 agonist, imiquimod. Infect Immun 2008; 77:739-48. [PMID: 19047411 DOI: 10.1128/iai.00974-08] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Plasmodium sporozoites injected into the skin by malaria-infected mosquitoes can be effectively targeted by antibodies that block parasite invasion of host hepatocytes and thus prevent the subsequent development of blood stage infections responsible for clinical disease. Malaria subunit vaccines require potent adjuvants, as they lack known pathogen-associated molecular patterns found in attenuated viral or bacterial vaccines that function as Toll-like receptor (TLR) agonists to stimulate dendritic cells and initiate strong adaptive immune responses. A synthetic TLR7 agonist, imiquimod, which is FDA approved for topical treatment of various skin conditions, can function as a potent adjuvant for eliciting T-cell responses to intracellular pathogens and model protein antigens. In the current studies, the topical application of imiquimod at the site of subcutaneously injected Plasmodium falciparum circumsporozoite (CS) peptides elicited strong parasite-specific humoral immunity that protected against challenge with transgenic rodent parasites that express P. falciparum CS repeats. In addition, injection of a simple linear peptide followed by topical imiquimod elicited strong Th1 CD4(+) T-cell responses, as well as high antibody titers. The correlation of high anti-repeat antibody titers with resistance to sporozoite challenge in vivo and in vitro supports use of this topical TLR7 agonist adjuvant to elicit protective humoral immunity. The safety, simplicity, and economic advantages of a topical synthetic TLR7 agonist adjuvant also apply to other vaccines requiring high antibody titers, such as malaria asexual or sexual blood stage antigens to prevent red blood cell invasion and block transmission to the mosquito vector, and to vaccines to other extracellular pathogens.
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106
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Abstract
As dendritic cells (DCs) initiate all adaptive and some innate immune responses, it is not surprising that DC function during malaria is the subject of intensive investigations. However, the results of these investigations have so far been controversial. Here, we discuss various aspects of these studies, including the influence of the species and strain of Plasmodium on DC function, the effects of Plasmodium infection on the activation of CD8(+) T cells by DCs, the effects of haemozoin and the effects of Plasmodium infections on DC Toll-like-receptor signalling.
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Affiliation(s)
- Michelle N Wykes
- The Queensland Institute of Medical Research, The Bancroft Centre, 300 Herston Road, Brisbane, Queensland 4006, Australia.
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107
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van Schaijk BCL, Janse CJ, van Gemert GJ, van Dijk MR, Gego A, Franetich JF, van de Vegte-Bolmer M, Yalaoui S, Silvie O, Hoffman SL, Waters AP, Mazier D, Sauerwein RW, Khan SM. Gene disruption of Plasmodium falciparum p52 results in attenuation of malaria liver stage development in cultured primary human hepatocytes. PLoS One 2008; 3:e3549. [PMID: 18958160 PMCID: PMC2568858 DOI: 10.1371/journal.pone.0003549] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2008] [Accepted: 10/07/2008] [Indexed: 11/19/2022] Open
Abstract
Difficulties with inducing sterile and long lasting protective immunity against malaria with subunit vaccines has renewed interest in vaccinations with attenuated Plasmodium parasites. Immunizations with sporozoites that are attenuated by radiation (RAS) can induce strong protective immunity both in humans and rodent models of malaria. Recently, in rodent parasites it has been shown that through the deletion of a single gene, sporozoites can also become attenuated in liver stage development and, importantly, immunization with these sporozoites results in immune responses identical to RAS. The promise of vaccination using these genetically attenuated sporozoites (GAS) depends on translating the results in rodent malaria models to human malaria. In this study, we perform the first essential step in this transition by disrupting, p52, in P. falciparum an ortholog of the rodent parasite gene, p36p, which we had previously shown can confer long lasting protective immunity in mice. These P. falciparum P52 deficient sporozoites demonstrate gliding motility, cell traversal and an invasion rate into primary human hepatocytes in vitro that is comparable to wild type sporozoites. However, inside the host hepatocyte development is arrested very soon after invasion. This study reveals, for the first time, that disrupting the equivalent gene in both P. falciparum and rodent malaria Plasmodium species generates parasites that become similarly arrested during liver stage development and these results pave the way for further development of GAS for human use.
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Affiliation(s)
- Ben C. L. van Schaijk
- Department of Medical Microbiology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Chris J. Janse
- Department of Parasitology, Leiden University Medical Centre, Leiden, The Netherlands
| | - Geert-Jan van Gemert
- Department of Medical Microbiology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Melissa R. van Dijk
- Department of Parasitology, Leiden University Medical Centre, Leiden, The Netherlands
| | - Audrey Gego
- INSERM, U511, Paris, France
- Université Pierre et Marie Curie-Paris6, UMR S511 Paris, France
| | | | - Marga van de Vegte-Bolmer
- Department of Medical Microbiology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Samir Yalaoui
- INSERM, U511, Paris, France
- Université Pierre et Marie Curie-Paris6, UMR S511 Paris, France
| | - Olivier Silvie
- INSERM, U511, Paris, France
- Université Pierre et Marie Curie-Paris6, UMR S511 Paris, France
| | | | - Andrew P. Waters
- Department of Parasitology, Leiden University Medical Centre, Leiden, The Netherlands
| | - Dominique Mazier
- INSERM, U511, Paris, France
- Université Pierre et Marie Curie-Paris6, UMR S511 Paris, France
- AP-HP, Groupe hospitalier Pitié-Salpêtrière, Service Parasitologie-Mycologie, Paris, France
| | - Robert W. Sauerwein
- Department of Medical Microbiology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Shahid M. Khan
- Department of Parasitology, Leiden University Medical Centre, Leiden, The Netherlands
- * E-mail:
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108
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Vanderberg JP. Reflections on early malaria vaccine studies, the first successful human malaria vaccination, and beyond. Vaccine 2008; 27:2-9. [PMID: 18973784 DOI: 10.1016/j.vaccine.2008.10.028] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2008] [Revised: 10/10/2008] [Accepted: 10/12/2008] [Indexed: 10/21/2022]
Abstract
Advances towards protective vaccines against malaria were made feasible by the development of a rodent model of mammalian malaria that allowed production of all stages of the malaria parasite for study. Investigations with sporozoites (the stage transmitted by mosquitoes in their saliva) demonstrated that immunization with radiation-attenuated sporozoites could produce a solid, sterile immunity, first shown in studies with mice and later with human volunteers. Protective immune mechanisms involve anti-sporozoite antibodies that immobilize sporozoites injected into the skin by mosquitoes, followed by CD4+ and CD8+ T-cells acting against liver stage parasites produced by sporozoites that have escaped antibody-based immunity and invaded hepatocytes. Two alternative approaches now being used in human trials are immunization with intact, attenuated sporozoites vs. immunization with "sub-unit" vaccines based on immunogenic components of sporozoites or liver stage parasites. In addition to immunization against these pre-erythrocytic stages, encouraging progress is being made on immunization against blood stage parasites and on immunization for production of transmission-blocking antibodies. There is reason to be optimistic that one or more of the approaches will work on a large scale, and that a multi-stage vaccine may be able to combine several of these approaches in a sequential immunological assault against the malaria parasite as it progresses through its stages.
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Affiliation(s)
- Jerome P Vanderberg
- Department of Medical Parasitology, New York University School of Medicine, 341 East 25th Street, New York, NY 10010, USA.
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109
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Ting LM, Gissot M, Coppi A, Sinnis P, Kim K. Attenuated Plasmodium yoelii lacking purine nucleoside phosphorylase confer protective immunity. Nat Med 2008; 14:954-8. [PMID: 18758447 DOI: 10.1038/nm.1867] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2008] [Accepted: 07/14/2008] [Indexed: 11/09/2022]
Abstract
Malaria continues to devastate sub-Saharan Africa owing to the emergence of drug resistance to established antimalarials and to the lack of an efficacious vaccine. Plasmodium species have a unique streamlined purine pathway in which the dual specificity enzyme purine nucleoside phosphorylase (PNP) functions in both purine recycling and purine salvage. To evaluate the importance of PNP in an in vivo model of malaria, we disrupted PyPNP, the gene encoding PNP in the lethal Plasmodium yoelii YM strain. P. yoelii parasites lacking PNP were attenuated and cleared in mice. Although able to form gametocytes, PNP-deficient parasites did not form oocysts in mosquito midguts and were not transmitted from mosquitoes to mice. Mice given PNP-deficient parasites were immune to subsequent challenge to a lethal inoculum of P. yoelii YM and to challenge from P. yoelii 17XNL, another strain. These in vivo studies with PNP-deficient parasites support purine salvage as a target for antimalarials. They also suggest a strategy for the development of attenuated nontransmissible metabolic mutants as blood-stage malaria vaccine strains.
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Affiliation(s)
- Li-Min Ting
- Department of Medicine and Microbiology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, New York 10461, USA
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110
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Ménard R, Heussler V, Yuda M, Nussenzweig V. Plasmodium pre-erythrocytic stages: what's new? Trends Parasitol 2008; 24:564-9. [PMID: 18929511 DOI: 10.1016/j.pt.2008.08.009] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2008] [Revised: 08/14/2008] [Accepted: 08/20/2008] [Indexed: 10/21/2022]
Abstract
The pre-erythrocytic (PE) phase of malaria infection, which extends from injection of sporozoites into the skin to the release of the first generation of merozoites, has traditionally been the 'black box' of the Plasmodium life cycle. However, since the advent of parasite transfection technology 13 years ago, our understanding of the PE phase in cellular and molecular terms has dramatically improved. Here, we review and comment on the major developments in the field in the past five years. Progress has been made in many diverse areas, including identifying and characterizing new proteins of interest, imaging parasites in vivo, understanding better the cell biology of hepatocyte infection and developing new vaccines against PE stages of the parasite.
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Affiliation(s)
- Robert Ménard
- Institut Pasteur, Unité de Biologie et Génétique du Paludisme, 75724 Paris cedex 15, France.
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111
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112
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Abstract
The demonstration of efficacy of two candidate malaria vaccines in children living in malaria-endemic areas, namely RTS,S from the circumsporozoite protein that reduced infection and clinical malaria in Mozambique, and an asexual blood-stage vaccine combining MSP1/MSP2/RESA that reduced parasite density in Papua New Guinea, allows one to believe that a malaria vaccine will be available for the fight against malaria in the next decade. Even if long-lasting impregnated bednets and indoor residual spraying have proven to be effective in reducing malaria transmission, these interventions may not be sufficient in the long-run since they rely on too few compounds and are, thus, vulnerable to the emergence of resistance. New tools, such as malaria vaccines, may, therefore, provide an added value to achieve the goal of local elimination and subsequent eradication of malaria. A promising candidate for that purpose would be a highly efficacious multicomponent vaccine that includes at least a sexual-stage antigen, the appropriate initial setting would be an area with low endemicity and limited population exchange, and the most suitable mode of delivery would be mass vaccination. For nonimmune populations, such as travelers visiting malaria-endemic areas, the usefulness of the first generation of malaria vaccine(s) will be limited, since the level of protection that is foreseen is unlikely to achieve that of malaria chemoprophylaxis. Only long-term travelers, expatriates and soldiers might realistically benefit from a pre-erythrocytic and/or blood-stage vaccine with an intermediate level of efficacy.
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113
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Vaughan A, Chiu SY, Ramasamy G, Li L, Gardner MJ, Tarun AS, Kappe SHI, Peng X. Assessment and improvement of the Plasmodium yoelii yoelii genome annotation through comparative analysis. ACTA ACUST UNITED AC 2008; 24:i383-9. [PMID: 18586738 PMCID: PMC2718618 DOI: 10.1093/bioinformatics/btn140] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Motivation: The sequencing of the Plasmodium yoelii genome, a model rodent malaria parasite, has greatly facilitated research for the development of new drug and vaccine candidates against malaria. Unfortunately, only preliminary gene models were annotated on the partially sequenced genome, mostly by in silico gene prediction, and there has been no major improvement of the annotation since 2002. Results: Here we report on a systematic assessment of the accuracy of the genome annotation based on a detailed analysis of a comprehensive set of cDNA sequences and proteomics data. We found that the coverage of the current annotation tends to be biased toward genes expressed in the blood stages of the parasite life cycle. Based on our proteomic analysis, we estimate that about 15% of the liver stage proteome data we have generated is absent from the current annotation. Through comparative analysis we identified and manually curated a further 510 P. yoelii genes which have clear orthologs in the P. falciparum genome, but were not present or incorrectly annotated in the current annotation. This study suggests that improvements of the current P. yoelii genome annotation should focus on genes expressed in stages other than blood stages. Comparative analysis will be critically helpful for this re-annotation. The addition of newly annotated genes will facilitate the use of P. yoelii as a model system for studying human malaria. Contact:xinxia.peng@sbri.org; stefan.kappe@sbri.org Supplementary information:Supplementary data are available at Bioinformatics online.
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Affiliation(s)
- Ashley Vaughan
- Seattle Biomedical Research Institute, Seattle, WA 98109, USA
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114
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Abstract
Advances in our understanding of the molecular and cell biology of the malaria parasite have led to new vaccine development efforts resulting in a pipeline of over 40 candidates undergoing clinical phase I-III trials. Vaccine-induced CD4+ and CD8+ T cells specific for pre-erythrocytic stage antigens have been found to express cytolytic and multi-cytokine effector functions that support a key role for these T cells within the hepatic environment. However, little is known of the cellular interactions that occur during the effector phase in which the intracellular hepatic stage of the parasite is targeted and destroyed. This review focuses on cell biological aspects of the interaction between malaria-specific effector cells and the various antigen-presenting cells that are known to exist within the liver, including hepatocytes, dendritic cells, Kupffer cells, stellate cells and sinusoidal endothelia. Considering the unique immune properties of the liver, it is conceivable that these different hepatic antigen-presenting cells fulfil distinct but complementary roles during the effector phase against Plasmodium liver stages.
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Affiliation(s)
- Ute Frevert
- Department of Medical Parasitology, New York University School of Medicine, 341 E 25 St, New York, NY 10010, USA.
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115
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Klotz C, Frevert U. Plasmodium yoelii sporozoites modulate cytokine profile and induce apoptosis in murine Kupffer cells. Int J Parasitol 2008; 38:1639-50. [PMID: 18656478 DOI: 10.1016/j.ijpara.2008.05.018] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2008] [Revised: 05/29/2008] [Accepted: 05/29/2008] [Indexed: 01/13/2023]
Abstract
Plasmodium sporozoites traverse Kupffer cells on their way into the liver. Sporozoite contact does not elicit a respiratory burst in these hepatic macrophages and blocks the formation of reactive oxygen species in response to secondary stimuli via elevation of the intracellular cAMP concentration. Here we show that increasing the cAMP level with dibutyryl cyclic adenosine monophosphate (db-cAMP) or isobutylmethylxanthine (IBMX) also modulates cytokine secretion in murine Kupffer cells towards an overall anti-inflammatory profile. Stimulation of Plasmodium yoelii sporozoite-exposed Kupffer cells with lipopolysaccharide or IFN-gamma reveals down-modulation of TNF-alpha, IL-6 and MCP-1, and up-regulation of IL-10. Prerequisite for this shift of the cytokine profile are parasite viability and contact with Kupffer cells, but not invasion. Whilst sporozoite-exposed Kupffer cells become TUNEL-positive and exhibit other signs of apoptotic death such as membrane blebbing, nuclear condensation and fragmentation, sporozoites remain intact and appear to transform to early exo-erythrocytic forms in Kupffer cell cultures. Together, the in vitro data indicate that Plasmodium possesses mechanisms to render Kupffer cells insensitive to pro-inflammatory stimuli and eventually eliminates these macrophages by forcing them into programmed cell death.
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Affiliation(s)
- Christian Klotz
- Department of Medical Parasitology, New York University School of Medicine, 341 E 25 Street, New York, NY 10010, USA.
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116
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Waters AP. Genome-informed contributions to malaria therapies: feeding somewhere down the (pipe)line. Cell Host Microbe 2008; 3:280-3. [PMID: 18474354 DOI: 10.1016/j.chom.2008.04.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Whole-genome sequences of Plasmodium spp. have helped redefine malaria research, including initiatives that seek to develop drugs, vaccines, and other antimalarial therapies. The problems caused by malaria were brought to the public's attention once more on World Malaria Day (April 25). Unfortunately, the current impact of genome-informed research is not as great as might have been hoped, and the reasons for this and continuing challenges are discussed.
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Affiliation(s)
- Andrew P Waters
- Division of Infection and Immunity, Institute of Biomedical Life Sciences, University of Glasgow, 120 University Place, Glasgow G12 8TA, Scotland, UK.
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117
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Thompson J, Millington OR, Garside P, Brewer JM. What can transgenic parasites tell us about the development of Plasmodium-specific immune responses? Parasite Immunol 2008; 30:223-33. [PMID: 18324925 DOI: 10.1111/j.1365-3024.2007.01011.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Malaria infects 500 million people and kills an estimated 2.7 million annually, representing one of the most significant diseases in the world. However, efforts to develop effective vaccines have met with limited success. One reason is our lack of basic knowledge of how and where the immune system responds to parasite antigens. This is important as the early events during induction of an immune response influence the acquisition of effector function and development of memory responses. Our knowledge of the interactions of Plasmodia with the host immune system has largely been derived through in vitro study. This is a significant issue as the component parts of the immune system do not work in isolation and their interactions occur in distinct and specialized micro- and macro-anatomical locations that can only be assessed in the physiological context, in vivo. In this context, the availability of transgenic malaria parasites over the last 10 years has greatly enhanced our ability to understand and evaluate factors involved in host-parasite interactions in vivo. In this article, we review the current status of this area and speculate on what parasite transgenesis approaches will tell us about the development of Plasmodium-specific immune responses in the future.
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Affiliation(s)
- J Thompson
- Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, King's Buildings, Edinburgh, UK
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118
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Abstract
The development and implementation of a malaria vaccine would constitute a major breakthrough for global health. Recently, numerous new candidates have entered clinical testing, following strategies that are as diverse as the malaria cycle is complex. While promising results have been obtained, some candidate vaccines have not fulfilled expectations. The challenges are not merely scientific; further progresses will require the development of competent investigator networks, partnerships between academics, industry and funding agencies, and continuous political commitment. In this review, we present the developmental status of all malaria vaccine candidates that are currently in human clinical testing against Plasmodium falciparum, as well as selected malaria vaccine candidates at preclinical development stage, and discuss the main challenges facing the field of malaria vaccine development.
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Affiliation(s)
- Johan Vekemans
- GlaxoSmithKline Biologicals, Emerging Diseases, Global Clinical Research and Development Vaccines, Rixensart, Belgium.
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119
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Pinzon-Charry A, Good MF. Malaria vaccines: the case for a whole-organism approach. Expert Opin Biol Ther 2008; 8:441-8. [DOI: 10.1517/14712598.8.4.441] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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120
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Purcell LA, Yanow SK, Lee M, Spithill TW, Rodriguez A. Chemical attenuation of Plasmodium berghei sporozoites induces sterile immunity in mice. Infect Immun 2008; 76:1193-9. [PMID: 18174336 PMCID: PMC2258828 DOI: 10.1128/iai.01399-07] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2007] [Revised: 11/16/2007] [Accepted: 12/19/2007] [Indexed: 11/20/2022] Open
Abstract
Radiation and genetic attenuation of Plasmodium sporozoites are two approaches for whole-organism vaccines that protect against malaria. We evaluated chemical attenuation of sporozoites as an alternative vaccine strategy. Sporozoites were treated with the DNA sequence-specific alkylating agent centanamycin, a compound that significantly affects blood stage parasitemia and transmission of murine malaria and also inhibits Plasmodium falciparum growth in vitro. Here we show that treatment of Plasmodium berghei sporozoites with centanamycin impaired parasite function both in vitro and in vivo. The infection of hepatocytes by sporozoites in vitro was significantly reduced, and treated parasites showed arrested liver stage development. Inoculation of mice with sporozoites that were treated in vitro with centanamycin failed to produce blood stage infections. Furthermore, BALB/c and C57BL/6 mice vaccinated with treated sporozoites were protected against subsequent challenge with wild-type sporozoites. Our findings demonstrate that chemically attenuated sporozoites could be a viable alternative for the production of an effective liver stage vaccine for malaria.
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Affiliation(s)
- Lisa A Purcell
- Institute of Parasitology and Centre for Host-Parasite Interactions, McGill University, 21111 Lakeshore Road, Sainte-Anne-de-Bellevue, Quebec H9X3V9, Canada
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121
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Chen Q, Wang H. Implications of imaging malaria sporozoites. Trends Parasitol 2008; 24:106-9. [PMID: 18280209 DOI: 10.1016/j.pt.2007.11.009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2007] [Revised: 12/11/2007] [Accepted: 11/15/2007] [Indexed: 11/26/2022]
Abstract
The sporozoites of Plasmodium parasites undergo several transmigrations before their establishment in the hepatocytes of a vertebrate host. Techniques that illustrate parasite intra-vital migration and their interaction with host cells will advance the understanding of parasite biology. In a recent publication, Amino et al. provided a detailed protocol for in vivo imaging of Plasmodium berghei sporozoites in the dermis. The report has important implications in the dissection of malaria parasite biology.
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Affiliation(s)
- Qijun Chen
- Key Laboratory of Zoonosis, Ministry of Education, Changchun 130062, China. [corrected]
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122
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Release of hepatic Plasmodium yoelii merozoites into the pulmonary microvasculature. PLoS Pathog 2008; 3:e171. [PMID: 17997605 PMCID: PMC2065874 DOI: 10.1371/journal.ppat.0030171] [Citation(s) in RCA: 148] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2007] [Accepted: 09/26/2007] [Indexed: 11/19/2022] Open
Abstract
Plasmodium undergoes one round of multiplication in the liver prior to invading erythrocytes and initiating the symptomatic blood phase of the malaria infection. Productive hepatocyte infection by sporozoites leads to the generation of thousands of merozoites capable of erythrocyte invasion. Merozoites are released from infected hepatocytes as merosomes, packets of hundreds of parasites surrounded by host cell membrane. Intravital microscopy of green fluorescent protein-expressing P. yoelii parasites showed that the majority of merosomes exit the liver intact, adapt a relatively uniform size of 12-18 microm, and contain 100-200 merozoites. Merosomes survived the subsequent passage through the right heart undamaged and accumulated in the lungs. Merosomes were absent from blood harvested from the left ventricle and from tail vein blood, indicating that the lungs effectively cleared the blood from all large parasite aggregates. Accordingly, merosomes were not detectable in major organs such as brain, kidney, and spleen. The failure of annexin V to label merosomes collected from hepatic effluent indicates that phosphatidylserine is not exposed on the surface of the merosome membrane suggesting the infected hepatocyte did not undergo apoptosis prior to merosome release. Merosomal merozoites continued to express green fluorescent protein and did not incorporate propidium iodide or YO-PRO-1 indicating parasite viability and an intact merosome membrane. Evidence of merosomal merozoite infectivity was provided by hepatic effluent containing merosomes being significantly more infective than blood with an identical low-level parasitemia. Ex vivo analysis showed that merosomes eventually disintegrate inside pulmonary capillaries, thus liberating merozoites into the bloodstream. We conclude that merosome packaging protects hepatic merozoites from phagocytic attack by sinusoidal Kupffer cells, and that release into the lung microvasculature enhances the chance of successful erythrocyte invasion. We believe this previously unknown part of the plasmodial life cycle ensures an effective transition from the liver to the blood phase of the malaria infection.
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Safety and immunogenicity of an AMA-1 malaria vaccine in Malian adults: results of a phase 1 randomized controlled trial. PLoS One 2008; 3:e1465. [PMID: 18213374 PMCID: PMC2186380 DOI: 10.1371/journal.pone.0001465] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2007] [Accepted: 12/17/2007] [Indexed: 11/19/2022] Open
Abstract
Background The objective was to evaluate the safety, reactogenicity and immunogenicity of the AMA-1-based blood-stage malaria vaccine FMP2.1/AS02A in adults exposed to seasonal malaria. Methodology/Principal Findings A phase 1 double blind randomized controlled dose escalation trial was conducted in Bandiagara, Mali, West Africa, a rural town with intense seasonal transmission of Plasmodium falciparum malaria. The malaria vaccine FMP2.1/AS02A is a recombinant protein (FMP2.1) based on apical membrane antigen-1 (AMA-1) from the 3D7 clone of P. falciparum, adjuvanted with AS02A. The comparator vaccine was a cell-culture rabies virus vaccine (RabAvert). Sixty healthy, malaria-experienced adults aged 18–55 y were recruited into 2 cohorts and randomized to receive either a half dose or full dose of the malaria vaccine (FMP2.1 25 µg/AS02A 0.25 mL or FMP2.1 50 µg/AS02A 0.5 mL) or rabies vaccine given in 3 doses at 0, 1 and 2 mo, and were followed for 1 y. Solicited symptoms were assessed for 7 d and unsolicited symptoms for 30 d after each vaccination. Serious adverse events were assessed throughout the study. Titers of anti-AMA-1 antibodies were measured by ELISA and P. falciparum growth inhibition assays were performed on sera collected at pre- and post-vaccination time points. Transient local pain and swelling were common and more frequent in both malaria vaccine dosage groups than in the comparator group. Anti-AMA-1 antibodies increased significantly in both malaria vaccine groups, peaking at nearly 5-fold and more than 6-fold higher than baseline in the half-dose and full-dose groups, respectively. Conclusion/Significance The FMP2.1/AS02A vaccine had a good safety profile, was well-tolerated, and was highly immunogenic in malaria-exposed adults. This malaria vaccine is being evaluated in Phase 1 and 2 trials in children at this site. Trial Registration ClinicalTrials.gov NCT00308061
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Sedegah M, Weiss WW, Hoffman SL. Cross-protection between attenuated Plasmodium berghei and P. yoelii sporozoites. Parasite Immunol 2008; 29:559-65. [PMID: 17944745 PMCID: PMC2955969 DOI: 10.1111/j.1365-3024.2007.00976.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
An attenuatedPlasmodium falciparum sporozoite (PfSPZ) vaccine is under development, in part, based on studies in mice withP. berghei. We usedP. berghei andP. yoelii to study vaccine-induced protection against challenge with a species of parasite different from the immunizing parasite in BALB/c mice. One-hundred percent of mice were protected against homologous challenge. Seventy-nine percent immunized with attenuatedP. berghei sporozoite (PbSPZ)(six experiments) were protected against challenge withP. yoelii sporozoite (PySPZ), and 63% immunized with attenuatedPySPZ(three experiments) were protected against challenge withPbSPZ. Antibodies in sera of immunized mice only recognized homologous sporozoites and could not have mediated protection against heterologous challenge. Immunization with attenuatedPySPZ orPbSPZ induced CD8+ T cell-dependent protection against heterologous challenge. Immunization with attenuatedPySPZ induced CD8+ T cell-dependent protection against homologous challenge. However, homologous protection induced by attenuatedPbSPZ was not dependent on CD8+ or CD4+ T cells, and depletion of both populations only reduced protection by 36%. Immunization of C57BL/10 mice withPbSPZ induced CD8+ T cell-dependent protection againstP. berghei, but no protection againstP. yoelii. The cross-protection data in BALB/c mice support testing a human vaccine based on attenuatedPfSPZ for its efficacy againstP. vivax.
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Affiliation(s)
- M Sedegah
- Malaria Program, Naval Medical Research Center, Silver Spring, MD, USA
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125
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A combined transcriptome and proteome survey of malaria parasite liver stages. Proc Natl Acad Sci U S A 2008; 105:305-10. [PMID: 18172196 DOI: 10.1073/pnas.0710780104] [Citation(s) in RCA: 290] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
For 50 years since their discovery, the malaria parasite liver stages (LS) have been difficult to analyze, impeding their utilization as a critical target for antiinfection vaccines and drugs. We have undertaken a comprehensive transcriptome analysis in combination with a proteomic survey of LS. Green fluorescent protein-tagged Plasmodium yoelii (PyGFP) was used to efficiently isolate LS-infected hepatocytes from the rodent host. Genome-wide LS gene expression was profiled and compared with other parasite life cycle stages. The analysis revealed approximately 2,000 genes active during LS development, and proteomic analysis identified 816 proteins. A subset of proteins appeared to be expressed in LS only. The data revealed exported parasite proteins and LS metabolic pathways including expression of FASII pathway enzymes. The FASII inhibitor hexachlorophene and the antibiotics, tetracycline and rifampicin, that target the apicoplast inhibited LS development, identifying FASII and other pathways localized in the apicoplast as potential drug targets to prevent malaria infection.
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126
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Dubovsky F, Malkin E. Malaria vaccines. Vaccines (Basel) 2008. [DOI: 10.1016/b978-1-4160-3611-1.50056-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
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127
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Renom Llonch M, Lafuente van der Sluis S, Alonso Fernández PL. Vacuna frente a la malaria: el gran reto para los países en vías de desarrollo. Enferm Infecc Microbiol Clin 2008. [DOI: 10.1016/s0213-005x(08)76228-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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128
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Grüner AC, Mauduit M, Tewari R, Romero JF, Depinay N, Kayibanda M, Lallemand E, Chavatte JM, Crisanti A, Sinnis P, Mazier D, Corradin G, Snounou G, Rénia L. Sterile protection against malaria is independent of immune responses to the circumsporozoite protein. PLoS One 2007; 2:e1371. [PMID: 18159254 PMCID: PMC2147056 DOI: 10.1371/journal.pone.0001371] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2007] [Accepted: 12/05/2007] [Indexed: 11/24/2022] Open
Abstract
Background Research aimed at developing vaccines against infectious diseases generally seeks to induce robust immune responses to immunodominant antigens. This approach has led to a number of efficient bacterial and viral vaccines, but it has yet to do so for parasitic pathogens. For malaria, a disease of global importance due to infection by Plasmodium protozoa, immunization with radiation-attenuated sporozoites uniquely leads to long lasting sterile immunity against infection. The circumsporozoite protein (CSP), an important component of the sporozoite's surface, remains the leading candidate antigen for vaccines targeting the parasite's pre-erythrocytic stages. Difficulties in developing CSP-based vaccines that reproduce the levels of protection afforded by radiation-attenuated sporozoites have led us to question the role of CSP in the acquisition of sterile immunity. We have used a parasite transgenic for the CSP because it allowed us to test whether a major immunodominant Plasmodium antigen is indeed needed for the induction of sterile protective immunity against infection. Methodology/Main Findings We employed a P. berghei parasite line that expresses a heterologous CSP from P. falciparum in order to assess the role of the CSP in the protection conferred by vaccination with radiation-attenuated P. berghei parasites. Our data demonstrated that sterile immunity could be obtained despite the absence of immune responses specific to the CSP expressed by the parasite used for challenge. Conclusions We conclude that other pre-erythrocytic parasite antigens, possibly hitherto uncharacterised, can be targeted to induce sterile immunity against malaria. From a broader perspective, our results raise the question as to whether immunodominant parasite antigens should be the favoured targets for vaccine development.
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Affiliation(s)
- Anne Charlotte Grüner
- Institut Cochin, Department of Immunology, Université Paris Descartes, Centre National de la Recherche Scientifique (CNRS) UMR 8104, Paris, France
- Inserm, U567, Paris, France
| | - Marjorie Mauduit
- Institut Cochin, Department of Immunology, Université Paris Descartes, Centre National de la Recherche Scientifique (CNRS) UMR 8104, Paris, France
- Inserm, U567, Paris, France
| | - Rita Tewari
- Division of Cell and Molecular Biology, Faculty of Natural Sciences, Imperial College London, London, United Kingdom
| | - Jackeline F. Romero
- Institut de Biochimie, Université de Lausanne, Epalinges, Lausanne, Switzerland
| | - Nadya Depinay
- Institut Cochin, Department of Immunology, Université Paris Descartes, Centre National de la Recherche Scientifique (CNRS) UMR 8104, Paris, France
- Inserm, U567, Paris, France
| | - Michèle Kayibanda
- Institut Cochin, Department of Immunology, Université Paris Descartes, Centre National de la Recherche Scientifique (CNRS) UMR 8104, Paris, France
- Inserm, U567, Paris, France
| | - Eliette Lallemand
- Institut Cochin, Department of Immunology, Université Paris Descartes, Centre National de la Recherche Scientifique (CNRS) UMR 8104, Paris, France
- Inserm, U567, Paris, France
| | - Jean-Marc Chavatte
- Equipe Parasitologie Comparée et Modèles Expérimentaux USM0307, Centre National de la Recherche Scientifique (CNRS) IFR101, Muséum National d'Histoire Naturelle, Paris, France
| | - Andrea Crisanti
- Division of Cell and Molecular Biology, Faculty of Natural Sciences, Imperial College London, London, United Kingdom
| | - Photini Sinnis
- Department of Medical Parasitology, New York University School of Medicine, New York, New York, United States of America
| | - Dominique Mazier
- Université Pierre et Marie Curie-Paris 6, UMR S511 Paris, France
- INSERM, U511, Paris, France
- Assistance Publique - Hôpitaux de Paris (AP-HP), Groupe hospitalier Pitié-Salpêtrière, Service Parasitologie-Mycologie, Paris, France
| | - Giampietro Corradin
- Institut de Biochimie, Université de Lausanne, Epalinges, Lausanne, Switzerland
| | - Georges Snounou
- Equipe Parasitologie Comparée et Modèles Expérimentaux USM0307, Centre National de la Recherche Scientifique (CNRS) IFR101, Muséum National d'Histoire Naturelle, Paris, France
| | - Laurent Rénia
- Institut Cochin, Department of Immunology, Université Paris Descartes, Centre National de la Recherche Scientifique (CNRS) UMR 8104, Paris, France
- Inserm, U567, Paris, France
- Singapore Immunology Network, Agency for Science, Technology and Research (A*STAR), Biopolis, Singapore
- * To whom correspondence should be addressed. E-mail:
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Abstract
PURPOSE OF REVIEW This review examines the potential of current preerythrocytic stage malaria vaccine approaches to reduce the global burden of malaria. RECENT FINDINGS Radiation-attenuated parasite vaccines induce lasting sterile protection in all models tested. Inherent safety concerns in conjunction with challenges to produce and deliver a radiation-attenuated parasite vaccine have prevented its mass production and application. Recent advances in genetic engineering and initiatives in production process development of live attenuated malaria vaccines, however, will overcome roadblocks that currently prevent their large-scale application. Development of preerythrocytic subunit vaccines has focused on the circumsporozoite protein and the thrombospondin related anonymous protein, yet the most advanced circumsporozoite protein-based vaccine confers limited protection against infection in malaria endemic areas. Work in rodent malaria models demonstrated that circumsporozoite protein-based immunity is not required for to achieve sterile protection. SUMMARY We conclude that preerythrocytic malaria vaccine efforts should focus on two major areas: development of a safe live attenuated sporozoite vaccine with its accelerated testing in malaria endemic areas and identification of as yet unknown antigens that reproduce sterilizing immune responses induced by vaccination with whole parasites. The sporozoite challenge model provides a unique opportunity to rapidly test preerythrocytic vaccine candidates.
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130
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Cross-species immunity in malaria vaccine development: two, three, or even four for the price of one? Infect Immun 2007; 76:873-8. [PMID: 18056479 DOI: 10.1128/iai.00431-07] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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131
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Affiliation(s)
- Judith E Epstein
- US Military Malaria Vaccine Program, Naval Medical Research Center, Silver Spring, MD 20910, USA.
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132
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A randomized placebo-controlled phase Ia malaria vaccine trial of two virosome-formulated synthetic peptides in healthy adult volunteers. PLoS One 2007; 2:e1018. [PMID: 17925866 PMCID: PMC2001290 DOI: 10.1371/journal.pone.0001018] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2007] [Accepted: 09/25/2007] [Indexed: 11/19/2022] Open
Abstract
Background and Objectives Influenza virosomes represent an innovative human-compatible antigen delivery system that has already proven its suitability for subunit vaccine design. The aim of the study was to proof the concept that virosomes can also be used to elicit high titers of antibodies against synthetic peptides. The specific objective was to demonstrate the safety and immunogenicity of two virosome-formulated P. falciparum protein derived synthetic peptide antigens given in two different doses alone or in combination. Methodology/Principal Findings The design was a single blind, randomized, placebo controlled, dose-escalating study involving 46 healthy Caucasian volunteers aged 18–45 years. Five groups of 8 subjects received virosomal formulations containing 10 µg or 50 µg of AMA 49-CPE, an apical membrane antigen-1 (AMA-1) derived synthetic phospatidylethanolamine (PE)-peptide conjugate or 10 ug or 50 ug of UK39, a circumsporozoite protein (CSP) derived synthetic PE-peptide conjugate or 50 ug of both antigens each. A control group of 6 subjects received unmodified virosomes. Virosomal formulations of the antigens (designated PEV301 and PEV302 for the AMA-1 and the CSP virosomal vaccine, respectively) or unmodified virosomes were injected i. m. on days 0, 60 and 180. In terms of safety, no serious or severe adverse events (AEs) related to the vaccine were observed. 11/46 study participants reported 16 vaccine related local AEs. Of these 16 events, all being pain, 4 occurred after the 1st, 7 after the 2nd and 5 after the 3rd vaccination. 6 systemic AEs probably related to the study vaccine were reported after the 1st injection, 10 after the 2nd and 6 after the 3rd. Generally, no difference in the distribution of the systemic AEs between either the doses applied (10 respectively 50 µg) or the synthetic antigen vaccines (PEV301 and PEV302) used for immunization was found. In terms of immunogenicity, both PEV301 and PEV302 elicited already after two injections a synthetic peptide-specific antibody response in all volunteers immunized with the appropriate dose. In the case of PEV301 the 50 µg antigen dose was associated with a higher mean antibody titer and seroconversion rate than the 10 µg dose. In contrast, for PEV302 mean titer and seroconversion rate were higher with the lower dose. Combined delivery of PEV301 and PEV302 did not interfere with the development of an antibody response to either of the two antigens. No relevant antibody responses against the two malaria antigens were observed in the control group receiving unmodified virosomes. Conclusions The present study demonstrates that three immunizations with the virosomal malaria vaccine components PEV301 or/and PEV302 (containing 10 µg or 50 µg of antigen) are safe and well tolerated. At appropriate antigen doses seroconversion rates of 100% were achieved. Two injections may be sufficient for eliciting an appropriate immune response, at least in individuals with pre-existing anti-malarial immunity. These results justify further development of a final multi-stage virosomal vaccine formulation incorporating additional malaria antigens. Trial Registration ClinicalTrials.gov NCT00400101
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133
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Hoffman BU, Chattopadhyay R. Plasmodium falciparum: effect of radiation on levels of gene transcripts in sporozoites. Exp Parasitol 2007; 118:247-52. [PMID: 17935717 DOI: 10.1016/j.exppara.2007.08.014] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2007] [Revised: 08/13/2007] [Accepted: 08/28/2007] [Indexed: 10/22/2022]
Abstract
Humans immunized by the bites of irradiated Plasmodium falciparum (Pf) sporozoite-infected mosquitoes are protected against malaria. Radiation attenuates the sporozoites preventing them from fully developing and replicating in hepatocytes, but the effects of radiation on gene expression in sporozoites are unknown. We used RT-PCR (35 cycles of PCR followed by densitometry) to assess the expression of ten genes in Pf sporozoites, and in sporozoites irradiated with 15,000cGy. Irradiation reduced expression substantially (>60%) of two DNA repair genes; moderately (30-60%) of PfUIS3, the Pf orthologue of PbUIS3, a gene up-regulated in Plasmodium berghei sporozoites and of a third DNA repair gene; and minimally (<30%) of the Pf18S ribosomal RNA, PfCSP, PfSSP2/TRAP, and PfCELTOS genes. Irradiation increased expression of PfSPATR minimally. PfLSA1 RNA was not detectable in sporozoites. These results establish that radiation of sporozoites affects gene expression levels and provide the foundation for studies to identify specific genes involved in attenuation and protective immunity.
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Affiliation(s)
- Benjamin U Hoffman
- Protein Potential LLC, 9800 Medical Center Drive, Rockville, MD 20850, USA.
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135
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Abstract
Malaria vaccine discovery and development follow two principal strategies. Most subunit vaccines are designed to mimic naturally acquired immunity that develops over years upon continuous exposure to Plasmodium transmission. Experimental model vaccines, such as attenuated live parasites and transmission-blocking antigens, induce immune responses superior to naturally acquired immunity. The promises and hurdles of the different tracks towards an effective and affordable vaccine against malaria are discussed.
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Affiliation(s)
- Kai Matuschewski
- Department of Parasitology, Heidelberg University School of Medicine, Germany.
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136
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Okitsu SL, Kienzl U, Moehle K, Silvie O, Peduzzi E, Mueller MS, Sauerwein RW, Matile H, Zurbriggen R, Mazier D, Robinson JA, Pluschke G. Structure-activity-based design of a synthetic malaria peptide eliciting sporozoite inhibitory antibodies in a virosomal formulation. ACTA ACUST UNITED AC 2007; 14:577-87. [PMID: 17524988 DOI: 10.1016/j.chembiol.2007.04.008] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2006] [Revised: 03/13/2007] [Accepted: 04/02/2007] [Indexed: 10/23/2022]
Abstract
The circumsporozoite protein (CSP) of Plasmodium falciparum is a leading candidate antigen for inclusion in a malaria subunit vaccine. We describe here the design of a conformationally constrained synthetic peptide, designated UK-39, which has structural and antigenic similarity to the NPNA-repeat region of native CSP. NMR studies on the antigen support the presence of helical turn-like structures within consecutive NPNA motifs in aqueous solution. Intramuscular delivery of UK-39 to mice and rabbits on the surface of reconstituted influenza virosomes elicited high titers of sporozoite crossreactive antibodies. Influenza virus proteins were crucially important for the immunostimulatory activity of the virosome-based antigen delivery system, as a liposomal formulation of UK-39 was not immunogenic. IgG antibodies elicited by UK-39 inhibited invasion of hepatocytes by P. falciparum sporozoites, but not by antigenically distinct P. yoelii sporozoites. Our approach to optimized virosome-formulated synthetic peptide vaccines should be generally applicable for other infectious and noninfectious diseases.
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Affiliation(s)
- Shinji L Okitsu
- Molecular Immunology, Swiss Tropical Institute, CH-4002 Basel, Switzerland
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137
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Abstract
The observation that individuals living in malaria endemic areas fail to develop sterilizing immunity to malaria infection has led to the assumption that malaria-specific immune responses are sub-optimal. Recently, T cell receptor (TCR) transgenic mice specific for the sporozoite and blood stages of the malaria parasite have been developed. Studies using these models have found that, unexpectedly, T cell memory in malaria is not noticeably defective. However, if T cell memory is 'normal' why are people not better protected? We suggest this is because protective immunity and T cell memory do not always correlate; moreover, T cells alone may simply not be able to provide the type of antibody-mediated sterilizing immunity induced by traditional vaccines.
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Affiliation(s)
- Ian A Cockburn
- Department of Molecular Microbiology and Immunology, Johns Hopkins Malaria Research Institute, Bloomberg School of Public Health, 615 N. Wolfe Street, Baltimore, MD 21205, USA.
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138
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Abstract
PURPOSE OF REVIEW To focus on recent novel concepts in the development of malaria vaccines. RECENT FINDINGS There is a renewed interest in whole attenuated sporozoite vaccines, either as irradiated or genetically modified sporozoites, because they consistently elicit solid protection against challenge infections. Enthusiasm about these vaccines is, however, tempered by technical, logistical, safety and even cultural hurdles that might need to be surmounted. Less than a score of Plasmodium falciparum proteins are currently in the development pipeline as malaria vaccines. There is an urgent need to ratchet up the process of candidate vaccine discovery, and reverse vaccinology and genome-wide surveys remain promising strategies. The development of malaria vaccines for placental malaria is an active area and chondroitin sulfate A-binding epitopes of the variant PfEMP1 have been identified. Live bacteria and viral vectors hold special promise for vaccine delivery. SUMMARY Attenuated sporozoite vaccines have made a resurgence to center stage in malaria vaccine development. There is an urgent need to identify more subunit vaccine candidates that can enter into the development pipeline, identify surrogate markers of immunity and design vaccines which induce long-lasting immunity.
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139
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Douradinha B, van Dijk MR, Ataide R, van Gemert GJ, Thompson J, Franetich JF, Mazier D, Luty AJF, Sauerwein R, Janse CJ, Waters AP, Mota MM. Genetically attenuated P36p-deficient Plasmodium berghei sporozoites confer long-lasting and partial cross-species protection. Int J Parasitol 2007; 37:1511-9. [PMID: 17604034 DOI: 10.1016/j.ijpara.2007.05.005] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2007] [Revised: 04/18/2007] [Accepted: 05/08/2007] [Indexed: 11/30/2022]
Abstract
Immunisation with live, radiation-attenuated sporozoites (RAS) or genetically attenuated sporozoites (GAS) of rodent plasmodial parasites protects against subsequent challenge infections. We recently showed that immunisation with Plasmodium berghei GAS that lack the microneme protein P36p protects mice for a period of up to 4 months. Here, we show that the period of full protection induced by p36p(-)-sporozoites lasts 12 and 18 months in C57Bl6 and BALB/c mice, respectively. Full protection is also achieved with three doses of only 1000 p36p(-) (but not RAS) sporozoites. Subcutaneous, intradermal or intramuscular routes of administration also lead to partial protection. In addition, immunisation with either P. berghei RAS- or, to a lesser extent, p36p(-)-sporozoites inhibits parasite intrahepatic development in mice challenged with Plasmodium yoelii sporozoites. Since naturally acquired malaria infections or subunit-based vaccines only induce short-term immune responses, the protection conferred by immunisation with p36p(-)-sporozoites described here further emphasises the potential of GAS as a vaccination strategy for malaria.
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Affiliation(s)
- Bruno Douradinha
- Unidade Malaria, Instituto de Medicina Molecular, Faculdade de Medicina da Universidade de Lisboa, 1649-028, Lisboa, Portugal
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Richie T. High road, low road? Choices and challenges on the pathway to a malaria vaccine. Parasitology 2007; 133 Suppl:S113-44. [PMID: 17274843 DOI: 10.1017/s0031182006001843] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Malaria causes much physical and economic hardship in endemic countries with billions of people at risk. A vaccine would clearly benefit these countries, reducing the requirement for hospital care and the economic impact of infection. Successful immunization with irradiated sporozoites and the fact that repeated exposure to malaria induces partial immunity to infection and high levels of protection against the clinical manifestations, suggest that a vaccine is feasible. Numerous candidate antigens have been identified but the vaccine, which has been promised to be 'just round the corner' for many years, remains elusive. The factors contributing to this frustratingly slow progress are discussed including gaps in the knowledge of host/parasite biology, methods to induce potent cell-mediated immune responses, the difficulties associated with defining immune correlates of protection and antigen production and delivery. Finally, the use of attenuated organism vaccines is discussed.
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Affiliation(s)
- T Richie
- Malaria Program, Naval Medical Research Center, 503 Robert Grant Avenue, Silver Spring, Maryland 20910-7500, USA.
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141
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Bano N, Romano JD, Jayabalasingham B, Coppens I. Cellular interactions of Plasmodium liver stage with its host mammalian cell. Int J Parasitol 2007; 37:1329-41. [PMID: 17537443 DOI: 10.1016/j.ijpara.2007.04.005] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2007] [Revised: 03/10/2007] [Accepted: 04/03/2007] [Indexed: 01/08/2023]
Abstract
The Plasmodium liver forms are bridgehead stages between the mosquito sporozoite stages and mammalian blood stages that instigate the malaria disease. In hepatocytes, Plasmodium achieves one of the fastest growth rates among eukaryotic cells. However, nothing is known about host hepatic cell interactions, e.g. nutrient scavenging and/or subversion of cellular functions necessary for Plasmodium development and replication. Plasmodium usually invades hepatocytes by establishing a parasitophorous vacuole wherein it undergoes multiple nuclear division cycles. We show that Plasmodium preferentially develops in the host juxtanuclear region. By comparison with the parasitophorous vacuole of other apicomplexan parasites which associate with diverse host organelles, the Plasmodium parasitophorous vacuole only forms an association with the host endoplasmic reticulum. Intrahepatic Plasmodium actively modifies the permeability of its vacuole to allow the transfer of a large variety of molecules from the host cytosol to the vacuolar space through open channels. In contrast with malaria blood stages, the pores within the parasitophorous vacuole membrane of the liver stage display a smaller size as they restrict the passage of solutes to less than 855Da. These pores are stably maintained during parasite karyokinesis until complete cellularisation. Host-derived cholesterol accumulated at the parasitophorous vacuole membrane may modulate the channel activity. These observations define the parasitophorous vacuole of the Plasmodium liver stage as a dynamic and highly permeable compartment that can ensure the sustained supply of host molecules to support parasite growth in the nutrient-rich environment of liver cells.
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Affiliation(s)
- Nazneen Bano
- Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, The Malaria Research Institute, 615 N. Wolfe Street, Baltimore, MD 21205, USA
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142
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Sturm A, Heussler V. Live and let die: manipulation of host hepatocytes by exoerythrocytic Plasmodium parasites. Med Microbiol Immunol 2007; 196:127-33. [PMID: 17410380 DOI: 10.1007/s00430-007-0044-3] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2007] [Indexed: 10/23/2022]
Abstract
The generation of rodent Plasmodium strains expressing fluorescent proteins in all life cycle stages has had a big impact on malaria research. With this tool in hand, for the first time it was possible to follow in real time by in vivo microscopy the infection route of Plasmodium sporozoites transmitted to the mammalian host by Anopheles mosquitoes. Recently, this work has been extended to the analysis of both hepatocyte infection by Plasmodium sporozoites, as well as liver merozoite transport into blood vessels. The stunning results of these studies have considerably changed our understanding of hepatocyte invasion and parasite liberation. Here, we describe the most important findings of the last years and in addition, we elaborate on the molecular events during the intracellular development of Plasmodium exoerythrocytic forms that give rise to erythrocyte infecting merozoites.
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Affiliation(s)
- Angelika Sturm
- Bernhard Nocht Institute for Tropical Medicine, Bernhard-Nocht-Str. 74, 20359 Hamburg, Germany
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143
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Snounou G, Rénia L. The vaccine is dead – long live the vaccine. Trends Parasitol 2007; 23:129-32. [PMID: 17300988 DOI: 10.1016/j.pt.2007.02.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2006] [Revised: 01/11/2007] [Accepted: 02/01/2007] [Indexed: 10/23/2022]
Abstract
An important chapter in the search for a vaccine against malaria, that of the anti-Plasmodium falciparum vaccine candidate SPf66, has been effectively closed. A Cochrane review of ten major efficacy trials in endemic areas concluded it 'has little or no effect on preventing malaria'. This provides an appropriate opportunity to reflect on the perspectives for current and future vaccine formulations against Plasmodium.
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Affiliation(s)
- Georges Snounou
- Parasitologie Comparée et Modèles Expérimentaux, Centre National de la Recherche Scientifique IFR101, Muséum National d'Histoire Naturelle, 75231 Paris Cedex 05, France.
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144
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Donovan MJ, Messmore AS, Scrafford DA, Sacks DL, Kamhawi S, McDowell MA. Uninfected mosquito bites confer protection against infection with malaria parasites. Infect Immun 2007; 75:2523-30. [PMID: 17339356 PMCID: PMC1865743 DOI: 10.1128/iai.01928-06] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Despite decades of research and multiple initiatives, malaria continues to be one of the world's most debilitating infectious diseases. New insights for malaria control and vaccine development will be essential to thwart the staggering worldwide impact of this disease (A. Bjorkman and A. Bhattarai, Acta Trop. 94:163-169, 2005); ultimately successful vaccine strategies will undoubtedly be multifactorial, incorporating multiple antigens and targeting diverse aspects of the malaria parasites' biology (M. F. Good et al., Immunol. Rev. 201:254-267, 2004). Using a murine model of malaria infection, we show here that exposure to bites from uninfected mosquitoes prior to Plasmodium yoelii infection influences the local and systemic immune responses and limits parasite development within the host. In hosts preexposed to bites from uninfected mosquitoes, reduced parasite burdens in the livers were detected early, and during the blood-stage of the life cycle, these burdens remained lower than those in hosts that received mosquito bites only at the time of infection. Repeated exposure to bites from uninfected mosquitoes skewed the immune response towards a T-helper 1 (Th1) phenotype as indicated by increased levels of interleukin-12, gamma interferon, and inducible nitric oxide synthase. These data suggest that the addition of mosquito salivary components to antimalaria vaccines may be a viable strategy for creating a Th1-biased environment known to be effective against malaria infection. Furthermore, this strategy may be important for the development of vaccines to combat other mosquito-transmitted pathogens.
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Affiliation(s)
- Michael J Donovan
- Center for Global Health and Infectious Diseases, Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46656, USA
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145
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Wykes M, Good MF. A case for whole-parasite malaria vaccines. Int J Parasitol 2007; 37:705-12. [PMID: 17408673 DOI: 10.1016/j.ijpara.2007.02.007] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2006] [Revised: 02/13/2007] [Accepted: 02/15/2007] [Indexed: 10/23/2022]
Abstract
Malaria causes morbidity in 300-500 million people each year and claims 2-3 millions lives annually, mostly children in sub-Saharan Africa. In 1983, the cloning of malaria antigens offered great promise for developing a viable subunit vaccine. However, an efficacious human vaccine is still not available. Immunological studies on how the host's immune system interacts with the parasite and studies on the pathogenic aspect of Plasmodium have found that several factors can impede protection by current vaccines. These findings suggest a novel approach needs to be considered.
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Affiliation(s)
- Michelle Wykes
- The Queensland Institute of Medical Research, The Bancroft Centre, Brisbane, Qld, Australia.
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146
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147
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Abstract
Plasmodium sporozoites make a remarkable journey from the skin, where they are deposited by an infected Anopheline mosquito, to the liver, where they invade hepatocytes and develop into exoerythrocytic stages. Although much work has been done to elucidate the molecular mechanisms by which sporozoites invade hepatocytes, little is known about the interactions between host and parasite before the sporozoite enters the blood circulation. It has always been assumed that sporozoites rapidly exit the injection site, making their interactions with the host at this site, brief and difficult to study. Using quantitative PCR, we determined the kinetics with which sporozoites leave the injection site and arrive in the liver and found that the majority of infective sporozoites remain in the skin for hours. We then performed sub-inoculation experiments which confirmed these findings and showed that the pattern of sporozoite exit from the injection site resembles a slow trickle. Last, we found that drainage of approximately 20% of the sporozoite inoculum to the lymphatics is associated with a significant enlargement of the draining lymph node, a response not observed after intravenous inoculation. These findings indicate that there is ample time for host and parasite to interact at the inoculation site and are of relevance to the pre-erythrocytic stage malaria vaccine effort.
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Affiliation(s)
- Lucy Megumi Yamauchi
- Department of Medical Parasitology, New York University School of Medicine341 East 25th Street, New York, NY 10010, USA.
| | - Alida Coppi
- Department of Medical Parasitology, New York University School of Medicine341 East 25th Street, New York, NY 10010, USA.
| | - Georges Snounou
- Parasitolgie Comparée et Modèle Expérimentaux, USM 0307, CNRS IFR101, Muséum National d'Histoire NaturelleCP52, 61 Rue Buffon, 75231 Paris Cedex 05, France.
| | - Photini Sinnis
- Department of Medical Parasitology, New York University School of Medicine341 East 25th Street, New York, NY 10010, USA.
- *For correspondence. E-mail ; Tel. (+1) 212 263 6818; Fax (+1) 212 263 8116
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148
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Loukas A, Tran M, Pearson MS. Schistosome membrane proteins as vaccines. Int J Parasitol 2006; 37:257-63. [PMID: 17222846 DOI: 10.1016/j.ijpara.2006.12.001] [Citation(s) in RCA: 121] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2006] [Revised: 11/28/2006] [Accepted: 12/03/2006] [Indexed: 01/08/2023]
Abstract
Schistosomes are parasitic blood flukes that infect approximately 200 million people and are arguably the most important human helminth in terms of mortality. The outermost surface of intra-mammalian stages of the parasite, the tegument, is the key to the parasite's success, but it is also generally viewed as the most susceptible target for vaccines and drugs. Over the past 2 years the proteome of the Schistosoma mansoni tegument has been investigated and these studies revealed surprisingly few proteins that are predicted to be accessible to the host immune response, namely proteins with at least one membrane-spanning domain. However, of this handful of proteins, some are showing great promise as recombinant vaccines against schistosomiasis at a pre-clinical level. In particular, the tetraspanin family of integral membrane proteins appears to be abundantly represented in the tegument, and convergent data using the mouse vaccine model and correlates of protective immunity in naturally exposed people suggests that this family of membrane proteins offer great promise for schistosomiasis vaccines. With the recent advances in schistosome genomics and proteomics, a new suite of potential vaccine antigens are presented and these warrant detailed investigation and appropriate funding over the next few years.
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Affiliation(s)
- Alex Loukas
- Helminth Biology Laboratory, Division of Infectious Diseases and Immunology, Queensland Institute of Medical Research Brisbane, Qld 4006, Australia.
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149
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Yadava A, Sattabongkot J, Washington MA, Ware LA, Majam V, Zheng H, Kumar S, Ockenhouse CF. A novel chimeric Plasmodium vivax circumsporozoite protein induces biologically functional antibodies that recognize both VK210 and VK247 sporozoites. Infect Immun 2006; 75:1177-85. [PMID: 17158893 PMCID: PMC1828583 DOI: 10.1128/iai.01667-06] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A successful vaccine against Plasmodium vivax malaria would significantly improve the health and quality of the lives of more than 1 billion people around the world. A subunit vaccine is the only option in the absence of long-term culture of P. vivax parasites. The circumsporozoite protein that covers the surface of Plasmodium sporozoites is one of the best-studied malarial antigens and the most promising vaccine in clinical trials. We report here the development of a novel "immunologically optimal" recombinant vaccine expressed in Escherichia coli that encodes a chimeric CS protein encompassing repeats from the two major alleles, VK210 and VK247. This molecule is widely recognized by sera from patients naturally exposed to P. vivax infection and induces a highly potent immune response in genetically disparate strains of mice. Antibodies from immunized animals recognize both VK210 and VK247 sporozoites. Furthermore, these antibodies appear to be protective in nature since they cause the agglutination of live sporozoites, an in vitro surrogate of sporozoite infectivity. These results strongly suggest that recombinant CS is biologically active and highly immunogenic across major histocompatibility complex strains and raises the prospect that in humans this vaccine may induce protective immune responses.
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Affiliation(s)
- Anjali Yadava
- Division of Malaria Vaccine Development, Walter Reed Army Institute of Research, Silver Spring, MD 20910, USA.
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150
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Ménard R. [Malaria: a new life for Plasmodium]. Med Sci (Paris) 2006; 22:921-3. [PMID: 17101089 DOI: 10.1051/medsci/20062211921] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Robert Ménard
- Unité de Biologie et Génétique du Paludisme, Institut Pasteur, 28, Rue du Docteur Roux, 75724 Paris Cedex 15, France.
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