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Goswami D, Patel H, Betz W, Armstrong J, Camargo N, Patil A, Chakravarty S, Murphy SC, Sim BKL, Vaughan AM, Hoffman SL, Kappe SH. A replication competent Plasmodium falciparum parasite completely attenuated by dual gene deletion. EMBO Mol Med 2024; 16:723-754. [PMID: 38514791 PMCID: PMC11018819 DOI: 10.1038/s44321-024-00057-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2023] [Revised: 03/06/2024] [Accepted: 03/07/2024] [Indexed: 03/23/2024] Open
Abstract
Vaccination with infectious Plasmodium falciparum (Pf) sporozoites (SPZ) administered with antimalarial drugs (PfSPZ-CVac), confers superior sterilizing protection against infection when compared to vaccination with replication-deficient, radiation-attenuated PfSPZ. However, the requirement for drug administration constitutes a major limitation for PfSPZ-CVac. To obviate this limitation, we generated late liver stage-arresting replication competent (LARC) parasites by deletion of the Mei2 and LINUP genes (mei2-/linup- or LARC2). We show that Plasmodium yoelii (Py) LARC2 sporozoites did not cause breakthrough blood stage infections and engendered durable sterilizing immunity against various infectious sporozoite challenges in diverse strains of mice. We next genetically engineered a PfLARC2 parasite strain that was devoid of extraneous DNA and produced cryopreserved PfSPZ-LARC2. PfSPZ-LARC2 liver stages replicated robustly in liver-humanized mice but displayed severe defects in late liver stage differentiation and did not form liver stage merozoites. This resulted in complete abrogation of parasite transition to viable blood stage infection. Therefore, PfSPZ-LARC2 is the next-generation vaccine strain expected to unite the safety profile of radiation-attenuated PfSPZ with the superior protective efficacy of PfSPZ-CVac.
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Affiliation(s)
- Debashree Goswami
- Center for Global Infectious Disease Research, Seattle Children's Research Institute, 307 Westlake Avenue North, Suite 500, Seattle, WA, 98109, USA
| | - Hardik Patel
- Center for Global Infectious Disease Research, Seattle Children's Research Institute, 307 Westlake Avenue North, Suite 500, Seattle, WA, 98109, USA
| | - William Betz
- Center for Global Infectious Disease Research, Seattle Children's Research Institute, 307 Westlake Avenue North, Suite 500, Seattle, WA, 98109, USA
| | - Janna Armstrong
- Center for Global Infectious Disease Research, Seattle Children's Research Institute, 307 Westlake Avenue North, Suite 500, Seattle, WA, 98109, USA
| | - Nelly Camargo
- Center for Global Infectious Disease Research, Seattle Children's Research Institute, 307 Westlake Avenue North, Suite 500, Seattle, WA, 98109, USA
| | - Asha Patil
- Sanaria Inc., 9800 Medical Center Dr., Rockville, MD, 20850, USA
| | | | - Sean C Murphy
- Department of Laboratory Medicine and Pathology, University of Washington, Seattle, WA, USA
| | - B Kim Lee Sim
- Sanaria Inc., 9800 Medical Center Dr., Rockville, MD, 20850, USA
| | - Ashley M Vaughan
- Center for Global Infectious Disease Research, Seattle Children's Research Institute, 307 Westlake Avenue North, Suite 500, Seattle, WA, 98109, USA
- Department of Pediatrics, University of Washington, Seattle, WA, USA
| | | | - Stefan Hi Kappe
- Center for Global Infectious Disease Research, Seattle Children's Research Institute, 307 Westlake Avenue North, Suite 500, Seattle, WA, 98109, USA.
- Department of Pediatrics, University of Washington, Seattle, WA, USA.
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2
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Richie TL, Church LWP, Murshedkar T, Billingsley PF, James ER, Chen MC, Abebe Y, KC N, Chakravarty S, Dolberg D, Healy SA, Diawara H, Sissoko MS, Sagara I, Cook DM, Epstein JE, Mordmüller B, Kapulu M, Kreidenweiss A, Franke-Fayard B, Agnandji ST, López Mikue MSA, McCall MBB, Steinhardt L, Oneko M, Olotu A, Vaughan AM, Kublin JG, Murphy SC, Jongo S, Tanner M, Sirima SB, Laurens MB, Daubenberger C, Silva JC, Lyke KE, Janse CJ, Roestenberg M, Sauerwein RW, Abdulla S, Dicko A, Kappe SHI, Lee Sim BK, Duffy PE, Kremsner PG, Hoffman SL. Sporozoite immunization: innovative translational science to support the fight against malaria. Expert Rev Vaccines 2023; 22:964-1007. [PMID: 37571809 PMCID: PMC10949369 DOI: 10.1080/14760584.2023.2245890] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2022] [Accepted: 08/04/2023] [Indexed: 08/13/2023]
Abstract
INTRODUCTION Malaria, a devastating febrile illness caused by protozoan parasites, sickened 247,000,000 people in 2021 and killed 619,000, mostly children and pregnant women in sub-Saharan Africa. A highly effective vaccine is urgently needed, especially for Plasmodium falciparum (Pf), the deadliest human malaria parasite. AREAS COVERED Sporozoites (SPZ), the parasite stage transmitted by Anopheles mosquitoes to humans, are the only vaccine immunogen achieving >90% efficacy against Pf infection. This review describes >30 clinical trials of PfSPZ vaccines in the U.S.A., Europe, Africa, and Asia, based on first-hand knowledge of the trials and PubMed searches of 'sporozoites,' 'malaria,' and 'vaccines.' EXPERT OPINION First generation (radiation-attenuated) PfSPZ vaccines are safe, well tolerated, 80-100% efficacious against homologous controlled human malaria infection (CHMI) and provide 18-19 months protection without boosting in Africa. Second generation chemo-attenuated PfSPZ are more potent, 100% efficacious against stringent heterologous (variant strain) CHMI, but require a co-administered drug, raising safety concerns. Third generation, late liver stage-arresting, replication competent (LARC), genetically-attenuated PfSPZ are expected to be both safe and highly efficacious. Overall, PfSPZ vaccines meet safety, tolerability, and efficacy requirements for protecting pregnant women and travelers exposed to Pf in Africa, with licensure for these populations possible within 5 years. Protecting children and mass vaccination programs to block transmission and eliminate malaria are long-term objectives.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | | | - Sara A. Healy
- Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Halimatou Diawara
- Malaria Research and Training Center, Mali-NIAID ICER, University of Science, Techniques and Technologies of Bamako, Bamako, Mali
| | - Mahamadou S. Sissoko
- Malaria Research and Training Center, Mali-NIAID ICER, University of Science, Techniques and Technologies of Bamako, Bamako, Mali
| | - Issaka Sagara
- Malaria Research and Training Center, Mali-NIAID ICER, University of Science, Techniques and Technologies of Bamako, Bamako, Mali
| | - David M. Cook
- Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Judith E. Epstein
- Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Benjamin Mordmüller
- Department of Medical Microbiology, Radboud University Medical Center, Nijmegen, The Netherlands
- Institut für Tropenmedizin, Universitätsklinikum Tübingen, Tübingen, Germany
| | - Melissa Kapulu
- Biosciences Department, Kenya Medical Research Institute KEMRI-Wellcome Research Programme, Kilifi, Kenya
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK
| | - Andrea Kreidenweiss
- Institut für Tropenmedizin, Universitätsklinikum Tübingen, Tübingen, Germany
- German Center for Infection Research (DZIF), partner site Tübingen, Tübingen, Germany
| | | | - Selidji T. Agnandji
- Department of Parasitology, Leiden University Medical Center, Leiden, The Netherlands
- Centre de Recherches Médicales de Lambaréné, Lambaréné, Gabon
| | | | - Matthew B. B. McCall
- Department of Medical Microbiology, Radboud University Medical Center, Nijmegen, The Netherlands
- Institut für Tropenmedizin, Universitätsklinikum Tübingen, Tübingen, Germany
- Centre de Recherches Médicales de Lambaréné, Lambaréné, Gabon
| | - Laura Steinhardt
- Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA, USA
| | - Martina Oneko
- Kenya Medical Research Institute, Centre for Global Health Research, Kisumu, Kenya
| | - Ally Olotu
- Bagamoyo Research and Training Center, Ifakara Health Institute, Bagamoyo, Tanzania
| | - Ashley M. Vaughan
- Center for Global Infectious Disease Research, Seattle Children’s Research Institute, Seattle, WA, USA
- Department of Pediatrics, University of Washington, Seattle, WA, USA
| | - James G. Kublin
- Department of Global Health, University of Washington, Seattle, WA, USA
- Vaccine and Infectious Disease Division, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
| | - Sean C. Murphy
- Department of Laboratory Medicine and Pathology, University of Washington, Seattle, WA, USA
- Center for Emerging and Re-emerging Infectious Diseases and Department of Microbiology, University of Washington, Seattle, WA, USA
| | - Said Jongo
- Bagamoyo Research and Training Center, Ifakara Health Institute, Bagamoyo, Tanzania
| | - Marcel Tanner
- Medical Parasitology and Infection Biology, Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
| | | | - Matthew B. Laurens
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Claudia Daubenberger
- Medical Parasitology and Infection Biology, Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
| | - Joana C. Silva
- Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, MD, USA
- Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Kirsten E. Lyke
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Chris J. Janse
- Department of Parasitology, Leiden University Medical Center, Leiden, The Netherlands
| | - Meta Roestenberg
- Department of Parasitology, Leiden University Medical Center, Leiden, The Netherlands
- Department of Infectious Diseases, Leiden University Medical Center, Leiden, The Netherlands
| | - Robert W. Sauerwein
- Department of Medical Microbiology, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Salim Abdulla
- Bagamoyo Research and Training Center, Ifakara Health Institute, Bagamoyo, Tanzania
| | - Alassane Dicko
- Malaria Research and Training Center, Mali-NIAID ICER, University of Science, Techniques and Technologies of Bamako, Bamako, Mali
| | - Stefan H. I. Kappe
- Center for Global Infectious Disease Research, Seattle Children’s Research Institute, Seattle, WA, USA
- Department of Pediatrics, University of Washington, Seattle, WA, USA
| | | | - Patrick E. Duffy
- Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Peter G. Kremsner
- Institut für Tropenmedizin, Universitätsklinikum Tübingen, Tübingen, Germany
- German Center for Infection Research (DZIF), partner site Tübingen, Tübingen, Germany
- Centre de Recherches Médicales de Lambaréné, Lambaréné, Gabon
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3
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Moita D, Maia TG, Duarte M, Andrade CM, Albuquerque IS, Dwivedi A, Silva JC, González-Céron L, Janse CJ, Mendes AM, Prudêncio M. A genetically modified Plasmodium berghei parasite as a surrogate for whole-sporozoite vaccination against P. vivax malaria. NPJ Vaccines 2022; 7:163. [PMID: 36526627 PMCID: PMC9755804 DOI: 10.1038/s41541-022-00585-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2022] [Accepted: 11/25/2022] [Indexed: 12/23/2022] Open
Abstract
Two malaria parasite species, Plasmodium falciparum (Pf) and P. vivax (Pv) are responsible for most of the disease burden caused by malaria. Vaccine development against this disease has focused mainly on Pf. Whole-sporozoite (WSp) vaccination, targeting pre-erythrocytic (PE) parasite stages, is a promising strategy for immunization against malaria and several PfWSp-based vaccine candidates are currently undergoing clinical evaluation. In contrast, no WSp candidates have been developed for Pv, mainly due to constraints in the production of Pv sporozoites in the laboratory. Recently, we developed a novel approach for WSp vaccination against Pf based on the use of transgenic rodent P. berghei (Pb) sporozoites expressing immunogens of this human-infective parasite. We showed that this platform can be used to deliver PE Pf antigens, eliciting both targeted humoral responses and cross-species cellular immune responses against Pf. Here we explored this WSp platform for the delivery of Pv antigens. As the Pv circumsporozoite protein (CSP) is a leading vaccine candidate antigen, we generated a transgenic Pb parasite, PbviVac, that, in addition to its endogenous PbCSP, expresses PvCSP under the control of a strictly PE promoter. Immunofluorescence microscopy analyses confirmed that both the PbCSP and the PvCSP antigens are expressed in PbviVac sporozoites and liver stages and that PbviVac sporozoite infectivity of hepatic cells is similar to that of its wild-type Pb counterpart. Immunization of mice with PbviVac sporozoites elicits the production of anti-PvCSP antibodies that efficiently recognize and bind to Pv sporozoites. Our results warrant further development and evaluation of PbviVac as a surrogate for WSp vaccination against Pv malaria.
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Affiliation(s)
- Diana Moita
- Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina da Universidade de Lisboa, Lisboa, Portugal
| | - Teresa G Maia
- Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina da Universidade de Lisboa, Lisboa, Portugal
| | - Miguel Duarte
- Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina da Universidade de Lisboa, Lisboa, Portugal
| | - Carolina M Andrade
- Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina da Universidade de Lisboa, Lisboa, Portugal
| | - Inês S Albuquerque
- Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina da Universidade de Lisboa, Lisboa, Portugal
| | - Ankit Dwivedi
- Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Joana C Silva
- Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Lilia González-Céron
- Centro Regional de Investigación en Salud Pública, Instituto Nacional de Salud Pública, Tapachula, Chiapas, México
| | - Chris J Janse
- Department of Parasitology, Leiden University Medical Center, Leiden, Netherlands
| | - António M Mendes
- Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina da Universidade de Lisboa, Lisboa, Portugal
| | - Miguel Prudêncio
- Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina da Universidade de Lisboa, Lisboa, Portugal.
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4
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Imai T, Ngo-Thanh H, Suzue K, Shimo A, Nakamura A, Horiuchi Y, Hisaeda H, Murakami T. Live Vaccination with Blood-Stage Plasmodium yoelii 17XNL Prevents the Development of Experimental Cerebral Malaria. Vaccines (Basel) 2022; 10:vaccines10050762. [PMID: 35632518 PMCID: PMC9145751 DOI: 10.3390/vaccines10050762] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Revised: 05/09/2022] [Accepted: 05/09/2022] [Indexed: 01/27/2023] Open
Abstract
In our work, we aim to develop a malaria vaccine with cross-strain (-species) protection. C57BL/6 mice infected with the P. berghei ANKA strain (PbA) develop experimental cerebral malaria (ECM). In contrast, ECM development is inhibited in infected mice depleted of T cells. The clinical applications of immune-cell depletion are limited due to the benefits of host defense against infectious diseases. Therefore, in the present study we attempted to develop a new method for preventing ECM without immune cell depletion. We demonstrated that mice inoculated with a heterologous live-vaccine of P. yoelii 17XNL were able to prevent both ECM and lung pathology and survived longer than control mice when challenged with PbA. Live vaccination protected blood–organ barriers from PbA infection. Meanwhile, live vaccination conferred sterile protection against homologous challenge with the P. yoelii 17XL virulent strain for the long-term. Analysis of the immune response induced by live vaccination showed that cross-reactive antibodies against PbA antigens were generated. IL-10, which has an immunosuppressive effect, was strongly induced in mice challenged with PbA, unlike the pro-inflammatory cytokine IFNγ. These results suggest that the protective effect of heterologous live vaccination against ECM development results from IL-10-mediated host protection.
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Affiliation(s)
- Takashi Imai
- Department of Infectious Diseases and Host Defense, Graduate School of Medicine, Gunma University, Maebashi 371-8511, Japan; (H.N.-T.); (K.S.)
- Department of Microbiology, Saitama Medical University, Moroyama-machi, Iruma-gun, Saitama 350-0495, Japan; (A.S.); (A.N.); (Y.H.); (T.M.)
- Correspondence: ; Tel.: +81-49-276-1166
| | - Ha Ngo-Thanh
- Department of Infectious Diseases and Host Defense, Graduate School of Medicine, Gunma University, Maebashi 371-8511, Japan; (H.N.-T.); (K.S.)
- National Hospital for Tropical Disease, 78 Giai Phong, Dong Da, Hanoi 10000, Vietnam
| | - Kazutomo Suzue
- Department of Infectious Diseases and Host Defense, Graduate School of Medicine, Gunma University, Maebashi 371-8511, Japan; (H.N.-T.); (K.S.)
| | - Aoi Shimo
- Department of Microbiology, Saitama Medical University, Moroyama-machi, Iruma-gun, Saitama 350-0495, Japan; (A.S.); (A.N.); (Y.H.); (T.M.)
| | - Akihiro Nakamura
- Department of Microbiology, Saitama Medical University, Moroyama-machi, Iruma-gun, Saitama 350-0495, Japan; (A.S.); (A.N.); (Y.H.); (T.M.)
| | - Yutaka Horiuchi
- Department of Microbiology, Saitama Medical University, Moroyama-machi, Iruma-gun, Saitama 350-0495, Japan; (A.S.); (A.N.); (Y.H.); (T.M.)
| | - Hajime Hisaeda
- Department of Parasitology, National Institute of Infectious Diseases, Tokyo 162-0052, Japan;
| | - Takashi Murakami
- Department of Microbiology, Saitama Medical University, Moroyama-machi, Iruma-gun, Saitama 350-0495, Japan; (A.S.); (A.N.); (Y.H.); (T.M.)
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Reuling IJ, Mendes AM, de Jong GM, Fabra-García A, Nunes-Cabaço H, van Gemert GJ, Graumans W, Coffeng LE, de Vlas SJ, Yang ASP, Lee C, Wu Y, Birkett AJ, Ockenhouse CF, Koelewijn R, van Hellemond JJ, van Genderen PJJ, Sauerwein RW, Prudêncio M. An open-label phase 1/2a trial of a genetically modified rodent malaria parasite for immunization against Plasmodium falciparum malaria. Sci Transl Med 2021; 12:12/544/eaay2578. [PMID: 32434846 DOI: 10.1126/scitranslmed.aay2578] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Accepted: 04/22/2020] [Indexed: 12/14/2022]
Abstract
For some diseases, successful vaccines have been developed using a nonpathogenic counterpart of the causative microorganism of choice. The nonpathogenicity of the rodent Plasmodium berghei (Pb) parasite in humans prompted us to evaluate its potential as a platform for vaccination against human infection by Plasmodium falciparum (Pf), a causative agent of malaria. We hypothesized that the genetic insertion of a leading protein target for clinical development of a malaria vaccine, Pf circumsporozoite protein (CSP), in its natural pre-erythrocytic environment, would enhance Pb's capacity to induce protective immunity against Pf infection. Hence, we recently generated a transgenic Pb sporozoite immunization platform expressing PfCSP (PbVac), and we now report the clinical evaluation of its biological activity against controlled human malaria infection (CHMI). This first-in-human trial shows that PbVac is safe and well tolerated, when administered by a total of ~300 PbVac-infected mosquitoes per volunteer. Although protective efficacy evaluated by CHMI showed no sterile protection at the tested dose, significant delays in patency (2.2 days, P = 0.03) and decreased parasite density were observed after immunization, corresponding to an estimated 95% reduction in Pf liver parasite burden (confidence interval, 56 to 99%; P = 0.010). PbVac elicits dose-dependent cross-species cellular immune responses and functional PfCSP-dependent antibody responses that efficiently block Pf sporozoite invasion of liver cells in vitro. This study demonstrates that PbVac immunization elicits a marked biological effect, inhibiting a subsequent infection by the human Pf parasite, and establishes the clinical validation of a new paradigm in malaria vaccination.
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Affiliation(s)
- Isaie J Reuling
- Radboud Center for Infectious Diseases, Department of Medical Microbiology, Radboud University Medical Center, 6525 GA Nijmegen, Netherlands
| | - António M Mendes
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Avenida Professor Egas Moniz, 1649-028 Lisboa, Portugal
| | - Gerdie M de Jong
- Department of Medical Microbiology and Infectious Diseases, Erasmus MC, 3015 GD Rotterdam, Netherlands
| | - Amanda Fabra-García
- Radboud Center for Infectious Diseases, Department of Medical Microbiology, Radboud University Medical Center, 6525 GA Nijmegen, Netherlands
| | - Helena Nunes-Cabaço
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Avenida Professor Egas Moniz, 1649-028 Lisboa, Portugal
| | - Geert-Jan van Gemert
- Radboud Center for Infectious Diseases, Department of Medical Microbiology, Radboud University Medical Center, 6525 GA Nijmegen, Netherlands
| | - Wouter Graumans
- Radboud Center for Infectious Diseases, Department of Medical Microbiology, Radboud University Medical Center, 6525 GA Nijmegen, Netherlands
| | - Luc E Coffeng
- Department of Public Health, Erasmus MC, University Medical Center Rotterdam, 3015 GD Rotterdam, Netherlands
| | - Sake J de Vlas
- Department of Public Health, Erasmus MC, University Medical Center Rotterdam, 3015 GD Rotterdam, Netherlands
| | - Annie S P Yang
- Radboud Center for Infectious Diseases, Department of Medical Microbiology, Radboud University Medical Center, 6525 GA Nijmegen, Netherlands
| | - Cynthia Lee
- PATH's Malaria Vaccine Initiative, Washington, DC 20001, USA
| | - Yimin Wu
- PATH's Malaria Vaccine Initiative, Washington, DC 20001, USA
| | | | | | - Rob Koelewijn
- Department of Medical Microbiology and Infectious Diseases, Erasmus MC, 3015 GD Rotterdam, Netherlands
| | - Jaap J van Hellemond
- Department of Medical Microbiology and Infectious Diseases, Erasmus MC, 3015 GD Rotterdam, Netherlands
| | - Perry J J van Genderen
- Department of Medical Microbiology and Infectious Diseases, Erasmus MC, 3015 GD Rotterdam, Netherlands. .,Corporate Travel Clinic Erasmus MC, 3015 CP Rotterdam, Netherlands
| | - Robert W Sauerwein
- Radboud Center for Infectious Diseases, Department of Medical Microbiology, Radboud University Medical Center, 6525 GA Nijmegen, Netherlands.
| | - Miguel Prudêncio
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Avenida Professor Egas Moniz, 1649-028 Lisboa, Portugal.
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6
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Jongo SA, Church LWP, Mtoro AT, Schindler T, Chakravarty S, Ruben AJ, Swanson PA, Kassim KR, Mpina M, Tumbo AM, Milando FA, Qassim M, Juma OA, Bakari BM, Simon B, James ER, Abebe Y, Kc N, Saverino E, Fink M, Cosi G, Gondwe L, Studer F, Styers D, Seder RA, Schindler T, Billingsley PF, Daubenberger C, Sim BKL, Tanner M, Richie TL, Abdulla S, Hoffman SL. Increase of Dose Associated With Decrease in Protection Against Controlled Human Malaria Infection by PfSPZ Vaccine in Tanzanian Adults. Clin Infect Dis 2021; 71:2849-2857. [PMID: 31782768 DOI: 10.1093/cid/ciz1152] [Citation(s) in RCA: 36] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2019] [Accepted: 11/28/2019] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND A vaccine would be an ideal tool for reducing malaria's impact. PfSPZ Vaccine (radiation attenuated, aseptic, purified, cryopreserved Plasmodium falciparum [Pf] sporozoites [SPZ]) has been well tolerated and safe in >1526 malaria-naive and experienced 6-month to 65-year-olds in the United States, Europe, and Africa. When vaccine efficacy (VE) of 5 doses of 2.7 × 105 PfSPZ of PfSPZ Vaccine was assessed in adults against controlled human malaria infection (CHMI) in the United States and Tanzania and intense field transmission of heterogeneous Pf in Mali, Tanzanians had the lowest VE (20%). METHODS To increase VE in Tanzania, we increased PfSPZ/dose (9 × 105 or 1.8 × 106) and decreased numbers of doses to 3 at 8-week intervals in a double blind, placebo-controlled trial. RESULTS All 22 CHMIs in controls resulted in parasitemia by quantitative polymerase chain reaction. For the 9 × 105 PfSPZ group, VE was 100% (5/5) at 3 or 11 weeks (P < .000l, Barnard test, 2-tailed). For 1.8 × 106 PfSPZ, VE was 33% (2/6) at 7.5 weeks (P = .028). VE of dosage groups (100% vs 33%) was significantly different (P = .022). Volunteers underwent repeat CHMI at 37-40 weeks after last dose. 6/6 and 5/6 volunteers developed parasitemia, but time to first parasitemia was significantly longer than controls in the 9 × 105 PfSPZ group (10.89 vs 7.80 days) (P = .039), indicating a significant reduction in parasites in the liver. Antibody and T-cell responses were higher in the 1.8 × 106 PfSPZ group. CONCLUSIONS In Tanzania, increasing the dose from 2.7 × 105 to 9 × 105 PfSPZ increased VE from 20% to 100%, but increasing to 1.8 × 106 PfSPZ significantly reduced VE. CLINICAL TRIALS REGISTRATION NCT02613520.
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Affiliation(s)
- Said A Jongo
- Ifakara Health Institute, Bagamoyo Research and Training Centre, Bagamoyo, Tanzania
| | | | - Ali T Mtoro
- Ifakara Health Institute, Bagamoyo Research and Training Centre, Bagamoyo, Tanzania
| | - Tobias Schindler
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Switzerland
| | | | | | - Phillip A Swanson
- Vaccine Research Center (VRC), National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - Kamaka R Kassim
- Ifakara Health Institute, Bagamoyo Research and Training Centre, Bagamoyo, Tanzania
| | - Maximillian Mpina
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Switzerland
| | - Anneth-Mwasi Tumbo
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Switzerland
| | - Florence A Milando
- Ifakara Health Institute, Bagamoyo Research and Training Centre, Bagamoyo, Tanzania
| | - Munira Qassim
- Ifakara Health Institute, Bagamoyo Research and Training Centre, Bagamoyo, Tanzania
| | - Omar A Juma
- Ifakara Health Institute, Bagamoyo Research and Training Centre, Bagamoyo, Tanzania
| | - Bakari M Bakari
- Ifakara Health Institute, Bagamoyo Research and Training Centre, Bagamoyo, Tanzania
| | - Beatus Simon
- Ifakara Health Institute, Bagamoyo Research and Training Centre, Bagamoyo, Tanzania
| | | | | | | | | | - Martina Fink
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Switzerland
| | - Glenda Cosi
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Switzerland
| | - Linda Gondwe
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Switzerland
| | - Fabian Studer
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Switzerland
| | | | - Robert A Seder
- Vaccine Research Center (VRC), National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - Tobias Schindler
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Switzerland
| | | | - Claudia Daubenberger
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Switzerland
| | - B Kim Lee Sim
- Sanaria Inc., Rockville, Maryland, USA.,Protein Potential LLC, Rockville, Maryland, USA
| | - Marcel Tanner
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Switzerland
| | | | - Salim Abdulla
- Ifakara Health Institute, Bagamoyo Research and Training Centre, Bagamoyo, Tanzania
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7
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Hobbs CV, Sahu T, Neal J, Conteh S, Voza T, Borkowsky W, Langhorne J, Duffy PE. Determinants of Malaria Protective Immunity in Mice Immunized with Live Sporozoites during Trimethoprim-Sulfamethoxazole Prophylaxis. Am J Trop Med Hyg 2020; 104:666-670. [PMID: 33350377 PMCID: PMC7866335 DOI: 10.4269/ajtmh.20-0749] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Accepted: 10/09/2020] [Indexed: 11/21/2022] Open
Abstract
HIV and malaria geographically overlap. Trimethoprim–sulfamethoxazole (TMP-SMX) is a drug widely used in HIV-exposed uninfected and infected children in malaria-endemic areas, and is known to have antimalarial effects. Further study in terms of antimalarial impact and effect on development of malaria-specific immunity is therefore essential. Using rodent malaria models, we previously showed that repeated Plasmodium exposure during TMP-SMX administration, or chemoprophylaxis vaccination (CVac), induces CD8 T-cell–dependent preerythrocytic immunity. However, humoral immune responses have been shown to be important in models of preerythrocytic immunity. Herein, we demonstrate that antibody-mediated responses contribute to protective immunity induced by CVac immune sera using TMP-SMX in models of homologous, but not heterologous, parasite species. Clinical studies must account for potential anti-Plasmodium antibody induced during TMP-SMX prophylaxis.
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Affiliation(s)
- Charlotte V Hobbs
- Department of Microbiology, Batson Children's Hospital, University of Mississippi Medical Center, Jackson, Mississippi.,Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland.,Division of Infectious Diseases, Department of Pediatrics, Batson Children's Hospital, University of Mississippi Medical Center, Jackson, Mississippi
| | - Tejram Sahu
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Malaria Research Institute, Johns Hopkins University Bloomberg School of Public Health, Baltimore, Maryland.,Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland
| | - Jillian Neal
- Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland
| | - Solomon Conteh
- Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland
| | - Tatiana Voza
- Biological Sciences Department, New York City College of Technology, CUNY, New York, New York
| | - William Borkowsky
- Division of Infectious Disease and Immunology, Department of Pediatrics, New York University School of Medicine, New York, New York
| | | | - Patrick E Duffy
- Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland
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8
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Mitran CJ, Yanow SK. The Case for Exploiting Cross-Species Epitopes in Malaria Vaccine Design. Front Immunol 2020; 11:335. [PMID: 32174924 PMCID: PMC7056716 DOI: 10.3389/fimmu.2020.00335] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2019] [Accepted: 02/10/2020] [Indexed: 12/21/2022] Open
Abstract
The infection dynamics between different species of Plasmodium that infect the same human host can both suppress and exacerbate disease. This could arise from inter-parasite interactions, such as competition, from immune regulation, or both. The occurrence of protective, cross-species (heterologous) immunity is an unlikely event, especially considering that strain-transcending immunity within a species is only partial despite lifelong exposure to that species. Here we review the literature in humans and animal models to identify the contexts where heterologous immunity can arise, and which antigens may be involved. From the perspective of vaccine design, understanding the mechanisms by which exposure to an antigen from one species can elicit a protective response to another species offers an alternative strategy to conventional approaches that focus on immunodominant antigens within a single species. The underlying hypothesis is that certain epitopes are conserved across evolution, in sequence or in structure, and shared in antigens from different species. Vaccines that focus on conserved epitopes may overcome the challenges posed by polymorphic immunodominant antigens; but to uncover these epitopes requires approaches that consider the evolutionary history of protein families across species. The key question for vaccinologists will be whether vaccines that express these epitopes can elicit immune responses that are functional and contribute to protection against Plasmodium parasites.
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Affiliation(s)
| | - Stephanie K. Yanow
- School of Public Health, University of Alberta, Edmonton, AB, Canada
- Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, AB, Canada
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9
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Sears KP, Kappmeyer LS, Wise LN, Silva M, Ueti MW, White S, Reif KE, Knowles DP. Infection dynamics of Theileria equi and Theileria haneyi, a newly discovered apicomplexan of the horse. Vet Parasitol 2019; 271:68-75. [PMID: 31303207 DOI: 10.1016/j.vetpar.2019.06.009] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2018] [Revised: 06/10/2019] [Accepted: 06/11/2019] [Indexed: 11/15/2022]
Abstract
Theileria equi infection, exotic to the United States has reemerged through intravenous (iatrogenic) and tick-borne transmission. Surveillance at the US-Mexico border identified a new species, Theileria haneyi, (T. haneyiEP) (EP = Eagle Pass, Texas) which warranted additional investigation due to inability to detect by PCR targeting of T. equi ema-1 and EMA-1-cELISA validated for T. equi. Infection dynamics of T. haneyiEP were evaluated, including ability to superinfect in the presence of T. equi-Texas (T. equiTX), the isolate responsible for the reemergence of T. equi in the U S. Experimental infection with T. equiTX or T. haneyiEP revealed minimal clinical disease however, T. equiTX infection led to significantly greater neutropenia. Comparison of time to antibody detection following inoculation revealed significantly greater time to detectable anti-T. haneyiEP antibody (26.67 days post-inoculation (DPI)) than T. equiTX (11.67 DPI). Regardless of initial infection with either T. equiTX or T. haneyiEP, superinfection was established. Comparative analysis of antibody responses from a splenectomized horse infected with T. haneyiEP to that of a spleen intact horse infected with T. equiFL revealed a different antibody binding profile to T. haneyiEP, T. equiTX and T. equiFL merozoite antigen and limited shared antigen/cross-reactive antibody(s). Affinity purified T. equi EMA-1 and EMA-2 from T. equiFL were shown as targets for horse antibodies against T. haneyi. Data presented here show (1) T. haneyiEP can superinfect in the presence of T. equiTX infection and co-persists for minimally 25 months, (2) intravenous challenge with T. haneyi is subclinical, and (3) limited cross-reactive antibody between T. haneyiEP and T. equi includes reactivity to EMA-1 and EMA-2.
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Affiliation(s)
- Kelly P Sears
- Veterinary Clinical Sciences, Washington State University, Pullman, WA, USA.
| | - Lowell S Kappmeyer
- Animal Disease Research Unit, Agricultural Research Service, United States Department of Agriculture, Pullman, WA, USA
| | - Lauren N Wise
- Animal Disease Research Unit, Agricultural Research Service, United States Department of Agriculture, Pullman, WA, USA; St. George's University, School of Veterinary Medicine True Blue Campus, St. George's, Grenada West Indies, Grenada
| | - Marta Silva
- Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, WA, USA
| | - Massaro W Ueti
- Animal Disease Research Unit, Agricultural Research Service, United States Department of Agriculture, Pullman, WA, USA
| | - Stephen White
- Animal Disease Research Unit, Agricultural Research Service, United States Department of Agriculture, Pullman, WA, USA; Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, WA, USA
| | - Kathryn E Reif
- Animal Disease Research Unit, Agricultural Research Service, United States Department of Agriculture, Pullman, WA, USA; Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, WA, USA
| | - Donald P Knowles
- Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, WA, USA
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10
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Mendes AM, Machado M, Gonçalves-Rosa N, Reuling IJ, Foquet L, Marques C, Salman AM, Yang ASP, Moser KA, Dwivedi A, Hermsen CC, Jiménez-Díaz B, Viera S, Santos JM, Albuquerque I, Bhatia SN, Bial J, Angulo-Barturen I, Silva JC, Leroux-Roels G, Janse CJ, Khan SM, Mota MM, Sauerwein RW, Prudêncio M. A Plasmodium berghei sporozoite-based vaccination platform against human malaria. NPJ Vaccines 2018; 3:33. [PMID: 30155278 PMCID: PMC6109154 DOI: 10.1038/s41541-018-0068-2] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2018] [Revised: 05/21/2018] [Accepted: 05/31/2018] [Indexed: 12/15/2022] Open
Abstract
There is a pressing need for safe and highly effective Plasmodium falciparum (Pf) malaria vaccines. The circumsporozoite protein (CS), expressed on sporozoites and during early hepatic stages, is a leading target vaccine candidate, but clinical efficacy has been modest so far. Conversely, whole-sporozoite (WSp) vaccines have consistently shown high levels of sterilizing immunity and constitute a promising approach to effective immunization against malaria. Here, we describe a novel WSp malaria vaccine that employs transgenic sporozoites of rodent P. berghei (Pb) parasites as cross-species immunizing agents and as platforms for expression and delivery of PfCS (PbVac). We show that both wild-type Pb and PbVac sporozoites unabatedly infect and develop in human hepatocytes while unable to establish an infection in human red blood cells. In a rabbit model, similarly susceptible to Pb hepatic but not blood infection, we show that PbVac elicits cross-species cellular immune responses, as well as PfCS-specific antibodies that efficiently inhibit Pf sporozoite liver invasion in human hepatocytes and in mice with humanized livers. Thus, PbVac is safe and induces functional immune responses in preclinical studies, warranting clinical testing and development. A genetically engineered parasite, related to malaria-causing Plasmodium falciparum, excels as a vaccine in preclinical tests. A team led by Miguel Prudêncio, of the University of Lisbon, Portugal, developed a genetically altered vaccine candidate based on Plasmodium berghei, which is pathogenic to rodents but, in humans, fails to progress from a harmless, transient liver infection to causing full, blood-borne malaria. The candidate expresses a human form of ‘circumsporozoite protein,’ a known antigen, and is designed to provoke a more comprehensive immune response as it presents a whole pathogen to the host. In preclinical tests, the candidate generated antibodies able to neutralize infection in human hepatocytes and also provoked a cellular immune response in rabbits. The team’s candidate proved safe and efficacious, warranting further trials and clinical testing.
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Affiliation(s)
- António M Mendes
- 1Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Avenida Professor Egas Moniz, 1649-028 Lisboa, Portugal
| | - Marta Machado
- 1Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Avenida Professor Egas Moniz, 1649-028 Lisboa, Portugal
| | - Nataniel Gonçalves-Rosa
- 1Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Avenida Professor Egas Moniz, 1649-028 Lisboa, Portugal
| | - Isaie J Reuling
- 2Department of Medical Microbiology, Radboud University Medical Center, Geert Grooteplein 28, Microbiology 268, 6500 HB Nijmegen, The Netherlands
| | - Lander Foquet
- 3Center for Vaccinology, Ghent University and Ghent University Hospital, De Pintelaan 185, 9000 Ghent, Belgium.,Departments of Clinical Chemistry, Microbiology and Immunology, Ghent University, Ghent University Hospital, Ghent, Belgium
| | - Cláudia Marques
- 1Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Avenida Professor Egas Moniz, 1649-028 Lisboa, Portugal
| | - Ahmed M Salman
- 5Leiden Malaria Research Group, Parasitology, Center of Infectious Diseases, Leiden University Medical Center, Leiden, The Netherlands.,6The Jenner Institute, Nuffield Department of Medicine, University of Oxford, ORCRB, Roosevelt Drive, Oxford, OX3 7DQ UK
| | - Annie S P Yang
- 2Department of Medical Microbiology, Radboud University Medical Center, Geert Grooteplein 28, Microbiology 268, 6500 HB Nijmegen, The Netherlands
| | - Kara A Moser
- 7Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, MD 21201 USA
| | - Ankit Dwivedi
- 7Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, MD 21201 USA
| | - Cornelus C Hermsen
- 2Department of Medical Microbiology, Radboud University Medical Center, Geert Grooteplein 28, Microbiology 268, 6500 HB Nijmegen, The Netherlands
| | - Belén Jiménez-Díaz
- 8Diseases of the Developing World, GlaxoSmithKline, Severo Ochoa, 2, 28760 Tres Cantos, Madrid Spain
| | - Sara Viera
- 8Diseases of the Developing World, GlaxoSmithKline, Severo Ochoa, 2, 28760 Tres Cantos, Madrid Spain
| | - Jorge M Santos
- 1Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Avenida Professor Egas Moniz, 1649-028 Lisboa, Portugal.,12Present Address: Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, 665 Huntington Avenue, 02115 Boston, MA USA
| | - Inês Albuquerque
- 1Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Avenida Professor Egas Moniz, 1649-028 Lisboa, Portugal
| | - Sangeeta N Bhatia
- 9Health Sciences and Technology/Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, MA 02139 USA
| | - John Bial
- 10Yecuris Corporation, PO Box 4645, Tualatin, OR 97062 USA
| | - Iñigo Angulo-Barturen
- 8Diseases of the Developing World, GlaxoSmithKline, Severo Ochoa, 2, 28760 Tres Cantos, Madrid Spain
| | - Joana C Silva
- 7Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, MD 21201 USA.,11Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, MD 21201 USA
| | - Geert Leroux-Roels
- 3Center for Vaccinology, Ghent University and Ghent University Hospital, De Pintelaan 185, 9000 Ghent, Belgium
| | - Chris J Janse
- 5Leiden Malaria Research Group, Parasitology, Center of Infectious Diseases, Leiden University Medical Center, Leiden, The Netherlands
| | - Shahid M Khan
- 5Leiden Malaria Research Group, Parasitology, Center of Infectious Diseases, Leiden University Medical Center, Leiden, The Netherlands
| | - Maria M Mota
- 1Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Avenida Professor Egas Moniz, 1649-028 Lisboa, Portugal
| | - Robert W Sauerwein
- 2Department of Medical Microbiology, Radboud University Medical Center, Geert Grooteplein 28, Microbiology 268, 6500 HB Nijmegen, The Netherlands
| | - Miguel Prudêncio
- 1Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Avenida Professor Egas Moniz, 1649-028 Lisboa, Portugal
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11
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Muh F, Ahmed MA, Han JH, Nyunt MH, Lee SK, Lau YL, Kaneko O, Han ET. Cross-species analysis of apical asparagine-rich protein of Plasmodium vivax and Plasmodium knowlesi. Sci Rep 2018; 8:5781. [PMID: 29636493 PMCID: PMC5893618 DOI: 10.1038/s41598-018-23728-1] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2017] [Accepted: 03/01/2018] [Indexed: 11/09/2022] Open
Abstract
The Plasmodium falciparum apical asparagine (Asn)-rich protein (AARP) is one of malarial proteins, and it has been studied as a candidate of malaria subunit vaccine. Basic characterization of PvAARP has been performed with a focus on its immunogenicity and localization. In this study, we further analyzed the immunogenicity of PvAARP, focusing on the longevity of the antibody response, cross-species immunity and invasion inhibitory activity by using the primate malaria parasite Plasmodium knowlesi. We found that vivax malaria patient sera retained anti-PvAARP antibodies for at least one year without re-infection. Recombinant PvAARP protein was strongly recognized by knowlesi malaria patients. Antibody raised against the P. vivax and P. knowlesi AARP N-termini reacted with the apical side of the P. knowlesi merozoites and inhibited erythrocyte invasion by P. knowlesi in a concentration-dependent manner, thereby suggesting a cross-species nature of anti-PvAARP antibody against PkAARP. These results can be explained by B cell epitopes predicted in conserved surface-exposed regions of the AARP N-terminus in both species. The long-lived anti-PvAARP antibody response, cross-reactivity, and invasion inhibitory activity of anti-PvAARP support a critical role of AARP during the erythrocyte invasion and suggest that PvAARP induces long-lived cross-species protective immunity against P. vivax and P. knowlesi.
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Affiliation(s)
- Fauzi Muh
- Department of Medical Environmental Biology and Tropical Medicine, School of Medicine, Kangwon National University, Chuncheon, Gangwon-do, Republic of Korea
| | - Md Atique Ahmed
- Department of Medical Environmental Biology and Tropical Medicine, School of Medicine, Kangwon National University, Chuncheon, Gangwon-do, Republic of Korea
| | - Jin-Hee Han
- Department of Medical Environmental Biology and Tropical Medicine, School of Medicine, Kangwon National University, Chuncheon, Gangwon-do, Republic of Korea
| | - Myat Htut Nyunt
- Department of Medical Environmental Biology and Tropical Medicine, School of Medicine, Kangwon National University, Chuncheon, Gangwon-do, Republic of Korea
- Department of Medical Research, Yangon, Myanmar
| | - Seong-Kyun Lee
- Department of Medical Environmental Biology and Tropical Medicine, School of Medicine, Kangwon National University, Chuncheon, Gangwon-do, Republic of Korea
| | - Yee Ling Lau
- Department of Parasitology, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia
| | - Osamu Kaneko
- Department of Protozoology, Institute of Tropical Medicine (NEKKEN), Nagasaki University, Sakamoto, Nagasaki, Japan
| | - Eun-Taek Han
- Department of Medical Environmental Biology and Tropical Medicine, School of Medicine, Kangwon National University, Chuncheon, Gangwon-do, Republic of Korea.
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12
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Baird JK. Asia-Pacific malaria is singular, pervasive, diverse and invisible. Int J Parasitol 2016; 47:371-377. [PMID: 27836630 PMCID: PMC5482320 DOI: 10.1016/j.ijpara.2016.06.006] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2016] [Revised: 05/29/2016] [Accepted: 06/01/2016] [Indexed: 12/27/2022]
Abstract
Malaria in the Asia-Pacific region has been targeted for elimination by the year 2030. This article asks the question, "by what means?" in the context of proven technical strategies and tools against key challenges imposed by the distinct character of the Asia-Pacific malaria problem. The misperception of malaria in the Asia-Pacific region as a less serious but otherwise essentially similar problem to African malaria lulls us into rote application of the same tools and strategies. Those now mitigating the harm done by malaria in Africa will not suffice to eliminate malaria in the Asia-Pacific region - these tasks and the problems are fundamentally distinct. This article describes the singular characteristics of Asia-Pacific malaria and the bearing of those upon the technical strategy of malaria elimination. Most of the tools needed for that endeavour do not yet exist and spirited calls for elimination within the next 14years may discourage the patience and investments needed to conceive, optimise and validate them.
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Affiliation(s)
- J Kevin Baird
- Eijkman Oxford Clinical Research Unit, Jakarta, Indonesia; Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom.
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13
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Billman ZP, Kas A, Stone BC, Murphy SC. Defining rules of CD8(+) T cell expansion against pre-erythrocytic Plasmodium antigens in sporozoite-immunized mice. Malar J 2016; 15:238. [PMID: 27113469 PMCID: PMC4845300 DOI: 10.1186/s12936-016-1295-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2016] [Accepted: 04/14/2016] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Whole Plasmodium sporozoites serve as both experimental tools and potentially as deployable vaccines in the fight against malaria infection. Live sporozoites infect hepatocytes and induce a diverse repertoire of CD8(+) T cell responses, some of which are capable of killing Plasmodium-infected hepatocytes. Previous studies in Plasmodium yoelii-immunized BALB/c mice showed that some CD8(+) T cell responses expanded with repeated parasite exposure, whereas other responses did not. RESULTS Here, similar outcomes were observed using known Plasmodium berghei epitopes in C57BL/6 mice. With the exception of the response to PbTRAP, IFNγ-producing T cell responses to most studied antigens, such as PbGAP50, failed to re-expand in mice immunized with two doses of irradiated P. berghei sporozoites. In an effort to boost secondary CD8(+) T cell responses, heterologous cross-species immunizations were performed. Alignment of P. yoelii 17XNL and P. berghei ANKA proteins revealed that >60 % of the amino acids in syntenic orthologous proteins are continuously homologous in fragments ≥8-amino acids long, suggesting that cross-species immunization could potentially trigger responses to a large number of common Class I epitopes. Heterologous immunization resulted in a larger liver burden than homologous immunization. Amongst seven tested antigen-specific responses, only CSP- and TRAP-specific CD8(+) T cell responses were expanded by secondary homologous sporozoite immunization and only those to the L3 ribosomal protein and S20 could be re-expanded by heterologous immunization. In general, heterologous late-arresting, genetically attenuated sporozoites were better at secondarily expanding L3-specific responses than were irradiated sporozoites. GAP50 and several other antigens shared between P. berghei and P. yoelii induced a large number of IFNγ-positive T cells during primary immunization, yet these responses could not be re-expanded by either homologous or heterologous secondary immunization. CONCLUSIONS These studies highlight how responses to different sporozoite antigens can markedly differ in recall following repeated sporozoite vaccinations. Cross-species immunization broadens the secondary response to sporozoites and may represent a novel strategy for candidate antigen discovery.
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Affiliation(s)
- Zachary P Billman
- Department of Laboratory Medicine, University of Washington, Seattle, WA, USA.,Center for Emerging and Re-emerging Infectious Diseases, University of Washington, Seattle, WA, USA
| | - Arnold Kas
- Department of Laboratory Medicine, University of Washington, Seattle, WA, USA.,Center for Emerging and Re-emerging Infectious Diseases, University of Washington, Seattle, WA, USA
| | - Brad C Stone
- Department of Laboratory Medicine, University of Washington, Seattle, WA, USA.,Center for Emerging and Re-emerging Infectious Diseases, University of Washington, Seattle, WA, USA
| | - Sean C Murphy
- Department of Laboratory Medicine, University of Washington, Seattle, WA, USA. .,Department of Microbiology, University of Washington, Seattle, WA, USA. .,Center for Emerging and Re-emerging Infectious Diseases, University of Washington, Seattle, WA, USA.
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14
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Bijker EM, Nganou-Makamdop K, van Gemert GJ, Zavala F, Cockburn I, Sauerwein RW. Studying the effect of chloroquine on sporozoite-induced protection and immune responses in Plasmodium berghei malaria. Malar J 2015; 14:130. [PMID: 25889324 PMCID: PMC4389414 DOI: 10.1186/s12936-015-0626-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2014] [Accepted: 02/20/2015] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Sporozoite immunization of animals and humans under a chemo-prophylactic cover of chloroquine (CPS-CQ) efficiently induces sterile protection against malaria. In humans, CPS-CQ is strikingly more efficient than immunization with radiation attenuated sporozoites (RAS), raising the hypothesis that this might be partially due to CQ. Chloroquine, an established anti-malarial drug, is also well known for its immune modulating properties including improvement of cross-presentation. The aim of this study was to investigate whether co-administration of CQ during sporozoite immunization improves cellular responses and protective efficacy in Plasmodium berghei models. METHODS A number of experiments in selected complimentary P. berghei murine models in Balb/cByJ and C57BL/6j mice was performed. First, the effect of CQ administration on the induction of protection and immune responses by RAS immunization was studied. Next, the effect of CQ on the induction of circumsporozoite (CS) protein-specific CD8(+) T cells by immunization with P. berghei parasites expressing a mutant CS protein was investigated. Finally, a direct comparison of CPS-CQ to CPS with mefloquine (MQ), an anti-malarial with little known immune modulating effects, was performed. RESULTS When CQ was co-administered during immunization with graded numbers of RAS, this did not lead to an increase in frequencies of total memory CD8(+) T cells or CS protein-specific CD8(+) T cells. Also parasite-specific cytokine production and protection remained unaltered. Replacement of CQ by MQ for CPS immunization resulted in significantly reduced percentages of IFNγ producing memory T cells in the liver (p = 0.01), but similar protection. CONCLUSIONS This study does not provide evidence for a direct beneficial effect of CQ on the induction of sporozoite-induced immune responses and protection in P. berghei malaria models. Alternatively, the higher efficiency of CPS compared to RAS might be explained by an indirect effect of CQ through limiting blood-stage exposure after immunization or to increased antigen exposure and, therefore, improved breadth of the immune response.
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Affiliation(s)
- Else M Bijker
- Department of Medical Microbiology, Radboud University Medical Center, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands.
| | - Krystelle Nganou-Makamdop
- Department of Medical Microbiology, Radboud University Medical Center, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands. .,Current address: Vaccine Research Centre; National Institutes of Health, 40 Convent drive, Bethesda, MD, 20892, USA.
| | - Geert-Jan van Gemert
- Department of Medical Microbiology, Radboud University Medical Center, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands.
| | - Fidel Zavala
- Johns Hopkins Malaria Research Institute and Department of Molecular Microbiology and Immunology, John Hopkins Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD, 21205, USA.
| | - Ian Cockburn
- Johns Hopkins Malaria Research Institute and Department of Molecular Microbiology and Immunology, John Hopkins Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD, 21205, USA. .,Current address: John Curtin School of Medical Research, Australian National University, GPO Box 334, Canberra City, ACT 2600, Australia.
| | - Robert W Sauerwein
- Department of Medical Microbiology, Radboud University Medical Center, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands.
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15
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Van Braeckel-Budimir N, Harty JT. CD8 T-cell-mediated protection against liver-stage malaria: lessons from a mouse model. Front Microbiol 2014; 5:272. [PMID: 24936199 PMCID: PMC4047659 DOI: 10.3389/fmicb.2014.00272] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2014] [Accepted: 05/19/2014] [Indexed: 01/08/2023] Open
Abstract
Malaria is a major global health problem, with severe mortality in children living in sub-Saharan Africa, and there is currently no licensed, effective vaccine. However, vaccine-induced protection from Plasmodium infection, the causative agent of malaria, was established for humans in small clinical trials and for rodents in the 1960s. Soon after, a critical role for memory CD8 T cells in vaccine-induced protection against Plasmodium liver-stage infection was established in rodent models and is assumed to apply to humans. However, these seminal early studies have led to only modest advances over the ensuing years in our understanding the basic features of memory CD8 T cells required for protection against liver-stage Plasmodium infection, an issue which has likely impeded the development of effective vaccines for humans. Given the ethical and practical limitations in gaining mechanistic insight from human vaccine and challenge studies, animal models still have an important role in dissecting the basic parameters underlying memory CD8 T-cell immunity to Plasmodium. Here, we will highlight recent data from our own work in the mouse model of Plasmodium infection that identify quantitative and qualitative features of protective memory CD8 T-cell responses. Finally, these lessons will be discussed in the context of recent findings from clinical trials of vaccine-induced protection in controlled human challenge models.
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Affiliation(s)
| | - John T Harty
- Department of Microbiology, University of Iowa Iowa, IA, USA
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Doll KL, Butler NS, Harty JT. CD8 T cell independent immunity after single dose infection-treatment-vaccination (ITV) against Plasmodium yoelii. Vaccine 2013; 32:483-91. [PMID: 24321740 DOI: 10.1016/j.vaccine.2013.11.058] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2013] [Revised: 09/30/2013] [Accepted: 11/15/2013] [Indexed: 10/25/2022]
Abstract
Sporozoite vaccination of both humans and rodents elicits potent anti-malarial immunity, but the dose of sporozoites and the number of immunizations required varies with vaccination approach. Here we examine the immunological basis for superior protection afforded from single-dose vaccination with virulent sporozoites administered under prophylatic chloroquine-cover, referred to as infection-treatment-vaccination (ITV), compared to the well-studied approach of administering radiation-attenuated Plasmodium sporozoites (RAS). Earlier rodent studies utilizing ITV and RAS vaccination suggested a major role of CD8 T cells in reducing liver parasite burden after sporozoite challenge in a BALB/c mouse model. Consistent with this, we find that in C57Bl/6 mice ITV elicits substantially higher parasite-specific CD8 T cell responses than RAS vaccination and enhances immunity against P. yoelii infection. However, we show ITV-induced CD8 T cells are not necessary for protection following liver-stage sporozoite or blood-stage parasite challenge. Mechanistically, we found protection afforded from single-dose ITV is associated with low grade, transient parasitemia shortly following cessation of chloroquine treatment and generation of potent antibody responses to blood-stage parasites. Collectively, our data show the mechanistic basis for enhanced protective immunity against P. yoelli elicited by ITV in highly susceptible C57Bl/6 mice is independent of CD8 T cells. These studies may be relevant in understanding the potent immunity observed with ITV in humans.
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Affiliation(s)
- Katherine L Doll
- Department of Microbiology, University of Iowa, Iowa City, IA, USA
| | - Noah S Butler
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
| | - John T Harty
- Department of Microbiology, University of Iowa, Iowa City, IA, USA; Department of Pathology, University of Iowa, Iowa City, IA, USA; Interdisciplinary Program in Immunology, University of Iowa, Iowa City, IA, USA.
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In vivo CD8+ T cell dynamics in the liver of Plasmodium yoelii immunized and infected mice. PLoS One 2013; 8:e70842. [PMID: 23967119 PMCID: PMC3743839 DOI: 10.1371/journal.pone.0070842] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2013] [Accepted: 06/21/2013] [Indexed: 12/28/2022] Open
Abstract
Plasmodium falciparum malaria remains one of the most serious health problems globally and a protective malaria vaccine is desperately needed. Vaccination with attenuated parasites elicits multiple cellular effector mechanisms that lead to Plasmodium liver stage elimination. While granule-mediated cytotoxicity requires contact between CD8+ effector T cells and infected hepatocytes, cytokine secretion should allow parasite killing over longer distances. To better understand the mechanism of parasite elimination in vivo, we monitored the dynamics of CD8+ T cells in the livers of naïve, immunized and sporozoite-infected mice by intravital microscopy. We found that immunization of BALB/c mice with attenuated P. yoelii 17XNL sporozoites significantly increases the velocity of CD8+ T cells patrolling the hepatic microvasculature from 2.69±0.34 μm/min in naïve mice to 5.74±0.66 μm/min, 9.26±0.92 μm/min, and 7.11±0.73 μm/min in mice immunized with irradiated, early genetically attenuated (Pyuis4-deficient), and late genetically attenuated (Pyfabb/f-deficient) parasites, respectively. Sporozoite infection of immunized mice revealed a 97% and 63% reduction in liver stage density and volume, respectively, compared to naïve controls. To examine cellular mechanisms of immunity in situ, naïve mice were passively immunized with hepatic or splenic CD8+ T cells. Unexpectedly, adoptive transfer rendered the motile CD8+ T cells from immunized mice immotile in the liver of P. yoelii infected mice. Similarly, when mice were simultaneously inoculated with viable sporozoites and CD8+ T cells, velocities 18 h later were also significantly reduced to 0.68±0.10 μm/min, 1.53±0.22 μm/min, and 1.06±0.26 μm/min for CD8+ T cells from mice immunized with irradiated wild type sporozoites, Pyfabb/f-deficient parasites, and P. yoelii CS280–288 peptide, respectively. Because immobilized CD8+ T cells are unable to make contact with infected hepatocytes, soluble mediators could potentially play a key role in parasite elimination under these experimental conditions.
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The species specificity of immunity generated by live whole organism immunisation with erythrocytic and pre-erythrocytic stages of rodent malaria parasites and implications for vaccine development. Int J Parasitol 2012; 42:859-70. [DOI: 10.1016/j.ijpara.2012.07.001] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2012] [Revised: 06/29/2012] [Accepted: 07/03/2012] [Indexed: 11/20/2022]
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Nganou-Makamdop K, van Gemert GJ, Arens T, Hermsen CC, Sauerwein RW. Long term protection after immunization with P. berghei sporozoites correlates with sustained IFNγ responses of hepatic CD8+ memory T cells. PLoS One 2012; 7:e36508. [PMID: 22563506 PMCID: PMC3341355 DOI: 10.1371/journal.pone.0036508] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2012] [Accepted: 04/02/2012] [Indexed: 11/18/2022] Open
Abstract
Protection against P. berghei malaria can successfully be induced in mice by immunization with both radiation attenuated sporozoites (RAS) arresting early during liver stage development, or sporozoites combined with chloroquine chemoprophylaxis (CPS), resulting in complete intra-hepatic parasite development before killing of blood-stages by chloroquine takes place. We assessed the longevity of protective cellular immune responses by RAS and CPS P. berghei immunization of C57BL/6j mice. Strong effector and memory (TEM) CD8+ T cell responses were induced predominantly in the liver of both RAS and CPS immunized mice while CD4+ T cells with memory phenotype remained at base line levels. Compared to unprotected naïve mice, we found high sporozoite-specific IFNγ ex vivo responses that associated with induced levels of in vivo CD8+ TEM cells in the liver but not spleen. Long term evaluation over a period of 9 months showed a decline of malaria-specific IFNγ responses in RAS and CPS mice that significantly correlated with loss of protection (r2 = 0.60, p<0.0001). The reducing IFNγ response by hepatic memory CD8+ T cells could be boosted by re-exposure to wild-type sporozoites. Our data show that sustainable protection against malaria associates with distinct intra-hepatic immune responses characterized by strong IFNγ producing CD8+ memory T cells.
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Affiliation(s)
- Krystelle Nganou-Makamdop
- Department of Medical Microbiology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
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Butler NS, Schmidt NW, Vaughan AM, Aly AS, Kappe SHI, Harty JT. Superior antimalarial immunity after vaccination with late liver stage-arresting genetically attenuated parasites. Cell Host Microbe 2011; 9:451-62. [PMID: 21669394 DOI: 10.1016/j.chom.2011.05.008] [Citation(s) in RCA: 182] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2011] [Revised: 04/20/2011] [Accepted: 05/31/2011] [Indexed: 10/18/2022]
Abstract
While subunit vaccines have shown partial efficacy in clinical trials, radiation-attenuated sporozoites (RAS) remain the "gold standard" for sterilizing protection against Plasmodium infection in human vaccinees. The variability in immunogenicity and replication introduced by the extensive, random DNA damage necessary to generate RAS could be overcome by genetically attenuated parasites (GAP) designed via gene deletion to arrest at defined points during liver-stage development. Here, we demonstrate the principle that late liver stage-arresting GAP induce larger and broader CD8 T cell responses that provide superior protection in inbred and outbred mice compared to RAS or early-arresting GAP immunizations. Late liver stage-arresting GAP also engender high levels of cross-stage and cross-species protection and complete protection when administered by translationally relevant intradermal or subcutaneous routes. Collectively, our results underscore the potential utility of late liver stage-arresting GAP as broadly protective next-generation live-attenuated malaria vaccines and support their potential as a powerful model for identifying antigens to generate cross-stage protection.
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Affiliation(s)
- Noah S Butler
- Department of Microbiology, University of Iowa, 3-512 Bowen Science Building, Iowa City, IA 52242, USA
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Harnessing immune responses against Plasmodium for rational vaccine design. Trends Parasitol 2011; 27:274-83. [PMID: 21531627 DOI: 10.1016/j.pt.2011.01.002] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2010] [Revised: 01/11/2011] [Accepted: 01/12/2011] [Indexed: 01/06/2023]
Abstract
In recent years, groundbreaking advances have been made in understanding the biology of and immune mechanisms against the Plasmodium spp. parasite, the causative agent of malaria. Novel features of the Plasmodium life cycle have been unravelled and immune mechanisms, which take place during both infection and immunization, have been dissected. We have undoubtedly enhanced our knowledge, but the question now is how to use this information to manipulate immune responses against Plasmodium and to develop an efficacious malaria vaccine. In this review, we discuss the latest developments in the field and speculate on how immune responses against Plasmodium could be harnessed for rational vaccine design and application.
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Schmidt NW, Butler NS, Harty JT. Plasmodium-host interactions directly influence the threshold of memory CD8 T cells required for protective immunity. THE JOURNAL OF IMMUNOLOGY 2011; 186:5873-84. [PMID: 21460205 DOI: 10.4049/jimmunol.1100194] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Plasmodium infections are responsible for millions of cases of malaria and ∼1 million deaths annually. Recently, we showed that sterile protection (95%) in BALB/c mice required Plasmodium berghei circumsporozoite protein (CS(252-260))-specific memory CD8 T cells exceeding a threshold of 1% of all PBLs. Importantly, it is not known if Plasmodium species affect the threshold of CS-specific memory CD8 T cells required for protection. Furthermore, C57BL/6 mice immunized with radiation-attenuated parasites are more difficult to protect against Plasmodium sporozoite challenge than similarly immunized BALB/c mice; however, it is not known whether this is the result of different CD8 T cell specificity, functional attributes of CD8 T cells, or mouse strain-specific factors expressed in nonhematopoietic cells. In this article, we show that more CS-specific memory CD8 T cells are required for protection against P. yoelii sporozoite challenge than for protection against P. berghei sporozoite challenge. Furthermore, P. berghei CS(252)-specific CD8 T cells exhibit reduced protection against P. berghei sporozoite challenge in the context of C57BL/6 and C57BL/10 non-MHC-linked genes in CB6F1 and B10.D2 mice, respectively. Generation and immunization of reciprocal chimeric mice between BALB/c and B10.D2 strains revealed that B10 background factors expressed by nonhematopoietic cells increased the threshold required for protection through a CD8 T cell-extrinsic mechanism. Finally, reduced CS-specific memory CD8 T cell protection in P. yoelii-infected BALB/c or P. berghei-infected B10.D2 mice correlated with increased rates of Plasmodium amplification in the liver. Thus, both Plasmodium species and strain-specific background genes in nonhematopoietic cells determine the threshold of memory CD8 T cells required for protection.
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Affiliation(s)
- Nathan W Schmidt
- Department of Microbiology, University of Iowa, Iowa City, IA 52242, USA
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Douradinha B, Augustijn KD, Moore SG, Ramesar J, Mota MM, Waters AP, Janse CJ, Thompson J. Plasmodium Cysteine Repeat Modular Proteins 3 and 4 are essential for malaria parasite transmission from the mosquito to the host. Malar J 2011; 10:71. [PMID: 21453484 PMCID: PMC3083381 DOI: 10.1186/1475-2875-10-71] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2010] [Accepted: 03/31/2011] [Indexed: 02/23/2023] Open
Abstract
BACKGROUND The Plasmodium Cysteine Repeat Modular Proteins (PCRMP) are a family of four conserved proteins of malaria parasites, that contain a number of motifs implicated in host-parasite interactions. Analysis of mutants of the rodent parasite Plasmodium berghei lacking expression of PCRMP1 or 2 showed that these proteins are essential for targeting of P. berghei sporozoites to the mosquito salivary gland and, hence, for transmission from the mosquito to the mouse. METHODS In this work, the role of the remaining PCRMP family members, PCRMP3 and 4, has been investigated throughout the Plasmodium life cycle by generation and analysis of P. berghei gene deletion mutants, Δpcrmp3 and Δpcrmp4. The role of PCRMP members during the transmission and hepatic stages of the Plasmodium lifecycle has been evaluated by light- and electron microscopy and by analysis of liver stage development in HEPG2 cells in vitro and by infecting mice with mutant sporozoites. In addition, mice were immunized with live Δpcrmp3 and Δpcrmp4 sporozoites to evaluate their immunization potential as a genetically-attenuated parasite-based vaccine. RESULTS Disruption of pcrmp3 and pcrmp4 in P. berghei revealed that they are also essential for transmission of the parasite through the mosquito vector, although acting in a distinct way to pbcrmp1 and 2. Mutants lacking expression of PCRMP3 or PCRMP4 show normal blood stage development and oocyst formation in the mosquito and develop into morphologically normal sporozoites, but these have a defect in egress from oocysts and do not enter the salivary glands. Sporozoites extracted from oocysts perform gliding motility and invade and infect hepatocytes but do not undergo further development and proliferation. Furthermore, the study shows that immunization with Δcrmp3 and Δcrmp4 sporozoites does not confer protective immunity upon subsequent challenge. CONCLUSIONS PCRMP3 and 4 play multiple roles during the Plasmodium life cycle; they are essential for the establishment of sporozoite infection in the mosquito salivary gland, and subsequently for development in hepatocytes. However, although Δpcrmp3 and Δpcrmp4 parasites are completely growth-impaired in the liver, immunization with live sporozoites does not induce the protective immune responses that have been shown for other genetically-attenuated parasites.
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Affiliation(s)
- Bruno Douradinha
- Malaria Unit, Instituto de Medicina Molecular, Faculdade de Medicina de Lisboa, Av. Prof. Egas Moniz, 1649-028 Lisbon, Portugal
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Jordán-Villegas A, Perdomo AB, Epstein JE, López J, Castellanos A, Manzano MR, Hernández MA, Soto L, Méndez F, Richie TL, Hoffman SL, Arévalo-Herrera M, Herrera S. Immune responses and protection of Aotus monkeys immunized with irradiated Plasmodium vivax sporozoites. Am J Trop Med Hyg 2011; 84:43-50. [PMID: 21292877 DOI: 10.4269/ajtmh.2011.09-0759] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
A non-human primate model for the induction of protective immunity against the pre-erythrocytic stages of Plasmodium vivax malaria using radiation-attenuated P. vivax sporozoites may help to characterize protective immune mechanisms and identify novel malaria vaccine candidates. Immune responses and protective efficacy induced by vaccination with irradiated P. vivax sporozoites were evaluated in malaria-naive Aotus monkeys. Three groups of six monkeys received two, five, or ten intravenous inoculations, respectively, of 100,000 irradiated P. vivax sporozoites; control groups received either 10 doses of uninfected salivary gland extract or no inoculations. Immunization resulted in the production low levels of antibodies that specifically recognized P. vivax sporozoites and the circumsporozoite protein. Additionally, immunization induced low levels of antigen-specific IFN-γ responses. Intravenous challenge with viable sporozoites resulted in partial protection in a dose-dependent manner. These findings suggest that the Aotus monkey model may be able to play a role in preclinical development of P. vivax pre-erythrocytic stage vaccines.
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CULLETON RL, INOUE M, REECE SE, CHEESMAN S, CARTER R. Strain-specific immunity induced by immunization with pre-erythrocytic stages of Plasmodium chabaudi. Parasite Immunol 2010; 33:73-8. [DOI: 10.1111/j.1365-3024.2010.01251.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Extreme CD8 T cell requirements for anti-malarial liver-stage immunity following immunization with radiation attenuated sporozoites. PLoS Pathog 2010; 6:e1000998. [PMID: 20657824 PMCID: PMC2904779 DOI: 10.1371/journal.ppat.1000998] [Citation(s) in RCA: 147] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2010] [Accepted: 06/11/2010] [Indexed: 12/02/2022] Open
Abstract
Radiation-attenuated Plasmodium sporozoites (RAS) are the only vaccine shown to induce sterilizing protection against malaria in both humans and rodents. Importantly, these “whole-parasite” vaccines are currently under evaluation in human clinical trials. Studies with inbred mice reveal that RAS-induced CD8 T cells targeting liver-stage parasites are critical for protection. However, the paucity of defined T cell epitopes for these parasites has precluded precise understanding of the specific characteristics of RAS-induced protective CD8 T cell responses. Thus, it is not known whether quantitative or qualitative differences in RAS-induced CD8 T cell responses underlie the relative resistance or susceptibility of immune inbred mice to sporozoite challenge. Moreover, whether extraordinarily large CD8 T cell responses are generated and required for protection following RAS immunization, as has been described for CD8 T cell responses following single-antigen subunit vaccination, remains unknown. Here, we used surrogate T cell activation markers to identify and track whole-parasite, RAS-vaccine-induced effector and memory CD8 T cell responses. Our data show that the differential susceptibility of RAS-immune inbred mouse strains to Plasmodium berghei or P. yoelii sporozoite challenge does not result from host- or parasite-specific decreases in the CD8 T cell response. Moreover, the surrogate activation marker approach allowed us for the first time to evaluate CD8 T cell responses and protective immunity following RAS-immunization in outbred hosts. Importantly, we show that compared to a protective subunit vaccine that elicits a CD8 T cell response to a single epitope, diversifying the targeted antigens through whole-parasite RAS immunization only minimally, if at all, reduced the numerical requirements for memory CD8 T cell-mediated protection. Thus, our studies reveal that extremely high frequencies of RAS-induced memory CD8 T cells are required, but may not suffice, for sterilizing anti-Plasmodial immunity. These data provide new insights into protective CD8 T cell responses elicited by RAS-immunization in genetically diverse hosts, information with relevance to developing attenuated whole-parasite vaccines. Plasmodium infections are a global health crisis resulting in ∼300 million cases of malaria each year and ∼1 million deaths. Radiation-attenuated Plasmodium sporozoites (RAS) are the only vaccines that induce sterilizing anti-malarial immunity in humans. Importantly, “whole parasite” anti-malarial RAS vaccines are currently under evaluation in clinical trials. In rodents, RAS-induced protection is largely mediated by CD8 T cells. However, the quantitative and qualitative characteristics of RAS-induced protective CD8 T cell responses are unknown. Here, we used surrogate markers of T cell activation to reveal the magnitude and kinetics of Plasmodium-specific CD8 T cell responses following RAS-immunization in both inbred and outbred mice. Our data show that, independent of host genetic background, extremely large memory CD8 T cell responses were required, but not always sufficient for sterilizing protection. These data have broad implications for evaluating total T cell responses to attenuated pathogen-vaccines and direct relevance for efforts to translate attenuated whole-Plasmodium vaccines to humans.
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Guilbride DL, Gawlinski P, Guilbride PDL. Why functional pre-erythrocytic and bloodstage malaria vaccines fail: a meta-analysis of fully protective immunizations and novel immunological model. PLoS One 2010; 5:e10685. [PMID: 20502667 PMCID: PMC2873430 DOI: 10.1371/journal.pone.0010685] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2009] [Accepted: 04/16/2010] [Indexed: 12/26/2022] Open
Abstract
BACKGROUND Clinically protective malaria vaccines consistently fail to protect adults and children in endemic settings, and at best only partially protect infants. METHODOLOGY/PRINCIPAL FINDINGS We identify and evaluate 1916 immunization studies between 1965-February 2010, and exclude partially or nonprotective results to find 177 completely protective immunization experiments. Detailed reexamination reveals an unexpectedly mundane basis for selective vaccine failure: live malaria parasites in the skin inhibit vaccine function. We next show published molecular and cellular data support a testable, novel model where parasite-host interactions in the skin induce malaria-specific regulatory T cells, and subvert early antigen-specific immunity to parasite-specific immunotolerance. This ensures infection and tolerance to reinfection. Exposure to Plasmodium-infected mosquito bites therefore systematically triggers immunosuppression of endemic vaccine-elicited responses. The extensive vaccine trial data solidly substantiate this model experimentally. CONCLUSIONS/SIGNIFICANCE We conclude skinstage-initiated immunosuppression, unassociated with bloodstage parasites, systematically blocks vaccine function in the field. Our model exposes novel molecular and procedural strategies to significantly and quickly increase protective efficacy in both pipeline and currently ineffective malaria vaccines, and forces fundamental reassessment of central precepts determining vaccine development. This has major implications for accelerated local eliminations of malaria, and significantly increases potential for eradication.
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Steenkeste N, Rogers WO, Okell L, Jeanne I, Incardona S, Duval L, Chy S, Hewitt S, Chou M, Socheat D, Babin FX, Ariey F, Rogier C. Sub-microscopic malaria cases and mixed malaria infection in a remote area of high malaria endemicity in Rattanakiri province, Cambodia: implication for malaria elimination. Malar J 2010; 9:108. [PMID: 20409349 PMCID: PMC2868861 DOI: 10.1186/1475-2875-9-108] [Citation(s) in RCA: 103] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2009] [Accepted: 04/22/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Malaria microscopy and rapid diagnostic tests are insensitive for very low-density parasitaemia. This insensitivity may lead to missed asymptomatic sub-microscopic parasitaemia, a potential reservoir for infection. Similarly, mixed infections and interactions between Plasmodium species may be missed. The objectives were first to develop a rapid and sensitive PCR-based diagnostic method to detect low parasitaemia and mixed infections, and then to investigate the epidemiological importance of sub-microscopic and mixed infections in Rattanakiri Province, Cambodia. METHODS A new malaria diagnostic method, using restriction fragment length polymorphism analysis of the cytochrome b genes of the four human Plasmodium species and denaturing high performance liquid chromatography, has been developed. The results of this RFLP-dHPLC method have been compared to 1) traditional nested PCR amplification of the 18S rRNA gene, 2) sequencing of the amplified fragments of the cytochrome b gene and 3) microscopy. Blood spots on filter paper and Giemsa-stained blood thick smears collected in 2001 from 1,356 inhabitants of eight villages of Rattanakiri Province have been analysed by the RFLP-dHPLC method and microscopy to assess the prevalence of sub-microscopic and mixed infections. RESULTS The sensitivity and specificity of the new RFLP-dHPLC was similar to that of the other molecular methods. The RFLP-dHPLC method was more sensitive and specific than microscopy, particularly for detecting low-level parasitaemia and mixed infections. In Rattanakiri Province, the prevalences of Plasmodium falciparum and Plasmodium vivax were approximately two-fold and three-fold higher, respectively, by RFLP-dHPLC (59% and 15%, respectively) than by microscopy (28% and 5%, respectively). In addition, Plasmodium ovale and Plasmodium malariae were never detected by microscopy, while they were detected by RFLP-dHPLC, in 11.2% and 1.3% of the blood samples, respectively. Moreover, the proportion of mixed infections detected by RFLP-dHPLC was higher (23%) than with microscopy (8%). CONCLUSIONS The rapid and sensitive molecular diagnosis method developed here could be considered for mass screening and ACT treatment of inhabitants of low-endemicity areas of Southeast Asia.
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Affiliation(s)
- Nicolas Steenkeste
- Unité d'Epidémiologie Moléculaire, Institut Pasteur du Cambodge, Phnom Penh, Cambodia.
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Minimal role for the circumsporozoite protein in the induction of sterile immunity by vaccination with live rodent malaria sporozoites. Infect Immun 2010; 78:2182-8. [PMID: 20194600 DOI: 10.1128/iai.01415-09] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Immunization with live Plasmodium sporozoites under chloroquine prophylaxis (Spz plus CQ) induces sterile immunity against sporozoite challenge in rodents and, more importantly, in humans. Full protection is obtained with substantially fewer parasites than with the classic immunization with radiation-attenuated sporozoites. The sterile protection observed comprised a massive reduction in the hepatic parasite load and an additional effect at the blood stage level. Differences in the immune responses induced by the two protocols occur but are as yet little characterized. We have previously demonstrated that in mice immunized with irradiated sporozoites, immune responses against the circumsporozoite protein (CSP), the major component of the sporozoite's surface and the leading malaria vaccine candidate, were not essential for sterile protection. Here, we have employed transgenic Plasmodium berghei parasites in which the endogenous CSP was replaced by that of Plasmodium yoelii, another rodent malaria species, to assess the role of CSP in the sterile protection induced by the Spz-plus-CQ protocol. The data demonstrated that this role was minor because sterile immunity was obtained irrespective of the origin of CSP expressed by the parasites in this model of protection. The immunity was obtained through a single transient exposure of the host to the immunizing parasites (preerythrocytic and erythrocytic), a dose much smaller than that required for immunization with radiation-attenuated sporozoites.
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Vaughan AM, Wang R, Kappe SHI. Genetically engineered, attenuated whole-cell vaccine approaches for malaria. HUMAN VACCINES 2010; 6:107-13. [PMID: 19838068 DOI: 10.4161/hv.6.1.9654] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Malaria remains one of the most significant infectious diseases affecting human populations in developing countries. The quest for an efficacious malaria vaccine has been ongoing for nearly a century with limited success. The identification of malaria parasite antigens focused efforts on the development of subunit vaccines but has so far yielded only one partially efficacious vaccine candidate, RTS/S. The lack of high vaccine efficacy observed to date with subunit vaccine candidates raises doubts that the development of a single antigen or even a multi-antigen malaria subunit vaccine is possible. Fortunately, it has been demonstrated in animal studies and experimental clinical studies that immunizations with live-attenuated sporozoite stages of the malaria parasite confer long lasting, sterile protection against infection, providing a benchmark for vaccine development. These early successful vaccinations with live-attenuated malaria parasites did not however, promote a developmental path forward for such a vaccine approach. The discovery of genetically engineered parasite strains that are fully attenuated during the early asymptomatic liver infection and confer complete sterile protection in animal malaria models support the development of a live attenuated sporozoite vaccine for Plasmodium falciparum and its accelerated safety and efficacy testing in malaria challenge models and in malaria endemic areas.
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Mauduit M, Grüner AC, Tewari R, Depinay N, Kayibanda M, Chavatte JM, Franetich JF, Crisanti A, Mazier D, Snounou G, Rénia L. A role for immune responses against non-CS components in the cross-species protection induced by immunization with irradiated malaria sporozoites. PLoS One 2009; 4:e7717. [PMID: 19890387 PMCID: PMC2766644 DOI: 10.1371/journal.pone.0007717] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2009] [Accepted: 10/09/2009] [Indexed: 12/02/2022] Open
Abstract
Immunization with irradiated Plasmodium sporozoites induces sterile immunity in rodents, monkeys and humans. The major surface component of the sporozoite the circumsporozoite protein (CS) long considered as the antigen predominantly responsible for this immunity, thus remains the leading candidate antigen for vaccines targeting the parasite's pre-erythrocytic (PE) stages. However, this role for CS was questioned when we recently showed that immunization with irradiated sporozoites (IrrSpz) of a P. berghei line whose endogenous CS was replaced by that of P. falciparum still conferred sterile protection against challenge with wild type P. berghei sporozoites. In order to investigate the involvement of CS in the cross-species protection recently observed between the two rodent parasites P. berghei and P. yoelii, we adopted our gene replacement approach for the P. yoelii CS and exploited the ability to conduct reciprocal challenges. Overall, we found that immunization led to sterile immunity irrespective of the origin of the CS in the immunizing or challenge sporozoites. However, for some combinations, immune responses to CS contributed to the acquisition of protective immunity and were dependent on the immunizing IrrSpz dose. Nonetheless, when data from all the cross-species immunization/challenges were considered, the immune responses directed against non-CS parasite antigens shared by the two parasite species played a major role in the sterile protection induced by immunization with IrrSpz. This opens the perspective to develop a single vaccine formulation that could protect against multiple parasite species.
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Affiliation(s)
- Marjorie Mauduit
- Singapore Immunology Network (SIgN), Agency for Science, Technology and Research (A*STAR), Biopolis, Singapore
- Department of Immunology, Institut Cochin, Université Paris Descartes, CNRS (UMR 8104), Paris, France
- INSERM, U567, Paris, France
| | - Anne Charlotte Grüner
- Singapore Immunology Network (SIgN), Agency for Science, Technology and Research (A*STAR), Biopolis, Singapore
- Department of Immunology, Institut Cochin, Université Paris Descartes, CNRS (UMR 8104), Paris, France
- INSERM, U567, Paris, France
| | - Rita Tewari
- Division of Cell and Molecular Biology, Faculty of Natural Sciences, Imperial College, London, United Kingdom
- Institute of Genetics, School of Biology, University of Nottingham, Nottingham, United Kingdom
| | - Nadya Depinay
- Department of Immunology, Institut Cochin, Université Paris Descartes, CNRS (UMR 8104), Paris, France
- INSERM, U567, Paris, France
| | - Michèle Kayibanda
- Department of Immunology, Institut Cochin, Université Paris Descartes, CNRS (UMR 8104), Paris, France
- INSERM, U567, Paris, France
| | - Jean-Marc Chavatte
- Parasitologie Comparée et Modèles Expérimentaux USM0307, CNRS IFR101, Muséum National d'Histoire Naturelle, Paris, France
| | | | - Andrea Crisanti
- Division of Cell and Molecular Biology, Faculty of Natural Sciences, Imperial College, London, United Kingdom
| | - Dominique Mazier
- INSERM U945, Paris, France
- Université Pierre et Marie Curie-Paris6, UMR S945, Paris, France
- Assistance Publique Hopitaux de Paris (AP HP), Groupe Hospitalier Pitié-Salpêtrière, Service parasito-Mycologie, Paris, France
| | - Georges Snounou
- Parasitologie Comparée et Modèles Expérimentaux USM0307, CNRS IFR101, Muséum National d'Histoire Naturelle, Paris, France
- INSERM U945, Paris, France
- Université Pierre et Marie Curie-Paris6, UMR S945, Paris, France
| | - Laurent Rénia
- Singapore Immunology Network (SIgN), Agency for Science, Technology and Research (A*STAR), Biopolis, Singapore
- Department of Immunology, Institut Cochin, Université Paris Descartes, CNRS (UMR 8104), Paris, France
- INSERM, U567, Paris, France
- * E-mail:
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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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Purcell LA, Wong KA, Yanow SK, Lee M, Spithill TW, Rodriguez A. Chemically attenuated Plasmodium sporozoites induce specific immune responses, sterile immunity and cross-protection against heterologous challenge. Vaccine 2008; 26:4880-4. [PMID: 18672017 DOI: 10.1016/j.vaccine.2008.07.017] [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: 02/08/2008] [Revised: 07/09/2008] [Accepted: 07/09/2008] [Indexed: 11/19/2022]
Abstract
Vaccination with Plasmodium sporozoites attenuated by irradiation or genetic manipulation induces a protective immune response in rodent malaria models. Recently, vaccination with chemically attenuated P. berghei sporozoites (CAS) has also been shown to elicit sterile immunity in mice. Here we show that vaccination with CAS of P. yoelii also protects against homologous infection and that a P. berghei CAS vaccine cross protects against heterologous challenge with P. yoelii sporozoites. Vaccination with P. yoelii or P. berghei CAS induced parasite-specific antibodies and IFN-gamma-producing CD8(+) T cells at levels not significantly different from radiation-attenuated sporozoites. Our findings provide an initial characterization of the immune response generated by CAS vaccination and suggest that this attenuation process could be used in the production of an effective cross-protective liver stage vaccine for malaria.
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Affiliation(s)
- Lisa A Purcell
- McGill University, Institute of Parasitology and Centre for Host-Parasite Interactions, Sainte-Anne-de-Bellevue, QC, Canada
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