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A probabilistic model of pre-erythrocytic malaria vaccine combination in mice. PLoS One 2019; 14:e0209028. [PMID: 30625136 PMCID: PMC6326473 DOI: 10.1371/journal.pone.0209028] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2018] [Accepted: 11/27/2018] [Indexed: 11/19/2022] Open
Abstract
Malaria remains one the world’s most deadly infectious diseases, with almost half a million deaths and over 150 million clinical cases each year. An effective vaccine would contribute enormously to malaria control and will almost certainly be required for eventual eradication of the disease. However, the leading malaria vaccine candidate, RTS,S, shows only 30–50% efficacy under field conditions, making it less cost-effective than long-lasting insecticide treated bed nets. Other subunit malaria vaccine candidates, including TRAP-based vaccines, show no better protective efficacy. This has led to increased interest in combining subunit malaria vaccines as a means of enhancing protective efficacy. Mathematical models of the effect of combining such vaccines on protective efficacy can help inform optimal vaccine strategies and decision-making at all stages of the clinical process. So far, however, no such model has been developed for pre-clinical murine studies, the stage at which all candidate antigens and combinations begin evaluation. To address this gap, this paper develops a mathematical model of vaccine combination adapted to murine malaria studies. The model is based on simple probabilistic assumptions which put the model on a firmer theoretical footing than previous clinical models, which rather than deriving a relationship between immune responses and protective efficacy posit the relationship to be either exponential or Hill curves. Data from pre-clinical murine malaria studies are used to derive values for unknowns in the model which in turn allows simulations of vaccine combination efficacy and suggests optimal strategies to pursue. Finally, the ability of the model to shed light on fundamental biological variables of murine malaria such as the blood stage growth rate and sporozoite infectivity is explored.
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Tailoring a Plasmodium vivax Vaccine To Enhance Efficacy through a Combination of a CSP Virus-Like Particle and TRAP Viral Vectors. Infect Immun 2018; 86:IAI.00114-18. [PMID: 29986894 PMCID: PMC6105880 DOI: 10.1128/iai.00114-18] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2018] [Accepted: 06/22/2018] [Indexed: 12/15/2022] Open
Abstract
Vivax malaria remains one of the most serious and neglected tropical diseases, with 132 to 391 million clinical cases per year and 2.5 billion people at risk of infection. A vaccine against Plasmodium vivax could have more impact than any other intervention, and the use of a vaccine targeting multiple antigens may result in higher efficacy against sporozoite infection than targeting a single antigen. Vivax malaria remains one of the most serious and neglected tropical diseases, with 132 to 391 million clinical cases per year and 2.5 billion people at risk of infection. A vaccine against Plasmodium vivax could have more impact than any other intervention, and the use of a vaccine targeting multiple antigens may result in higher efficacy against sporozoite infection than targeting a single antigen. Here, two leading P. vivax preerythrocytic vaccine candidate antigens, the P. vivax circumsporozoite protein (PvCSP) and the thrombospondin-related adhesion protein (PvTRAP) were delivered as a combined vaccine. This strategy provided a dose-sparing effect, with 100% sterile protection in mice using doses that individually conferred low or no protection, as with the unadjuvanted antigens PvTRAP (0%) and PvCSP (50%), and reached protection similar to that of adjuvanted components. Efficacy against malaria infection was assessed using a new mouse challenge model consisting of a double-transgenic Plasmodium berghei parasite simultaneously expressing PvCSP and PvTRAP used in mice immunized with the virus-like particle (VLP) Rv21 previously reported to induce high efficacy in mice using Matrix-M adjuvant, while PvTRAP was concomitantly administered in chimpanzee adenovirus and modified vaccinia virus Ankara (MVA) vectors (viral-vectored TRAP, or vvTRAP) to support effective induction of T cells. We examined immunity elicited by these vaccines in the context of two adjuvants approved for human use (AddaVax and Matrix-M). Matrix-M supported the highest anti-PvCSP antibody titers when combined with Rv21, and, interestingly, mixing PvCSP Rv21 and PvTRAP viral vectors enhanced immunity to malaria over levels provided by single vaccines.
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Cabral-Miranda G, Heath MD, Gomes AC, Mohsen MO, Montoya-Diaz E, Salman AM, Atcheson E, Skinner MA, Kramer MF, Reyes-Sandoval A, Bachmann MF. Microcrystalline Tyrosine (MCT ®): A Depot Adjuvant in Licensed Allergy Immunotherapy Offers New Opportunities in Malaria. Vaccines (Basel) 2017; 5:vaccines5040032. [PMID: 28953265 PMCID: PMC5748599 DOI: 10.3390/vaccines5040032] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Revised: 08/25/2017] [Accepted: 09/20/2017] [Indexed: 02/07/2023] Open
Abstract
Microcrystalline Tyrosine (MCT®) is a widely used proprietary depot excipient in specific immunotherapy for allergy. In the current study we assessed the potential of MCT to serve as an adjuvant in the development of a vaccine against malaria. To this end, we formulated the circumsporozoite protein (CSP) of P. vivax in MCT and compared the induced immune responses to CSP formulated in PBS or Alum. Both MCT and Alum strongly increased immunogenicity of CSP compared to PBS in both C57BL/6 and BALB/c mice. Challenge studies in mice using a chimeric P. bergei expressing CSP of P. vivax demonstrated clinically improved symptoms of malaria with CSP formulated in both MCT and Alum; protection was, however, more pronounced if CSP was formulated in MCT. Hence, MCT may be an attractive biodegradable adjuvant useful for the development of novel prophylactic vaccines.
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Affiliation(s)
- Gustavo Cabral-Miranda
- Nuffield Department of Medicine, Centre for Cellular and Molecular Physiology (CCMP), The Jenner Institute, University of Oxford, Oxford OX3 7BN, UK.
| | - Matthew D Heath
- Allergy Therapeutics (UK) Ltd. Dominion Way, Worthing BN14 8SA, UK.
| | - Ariane C Gomes
- Nuffield Department of Medicine, Centre for Cellular and Molecular Physiology (CCMP), The Jenner Institute, University of Oxford, Oxford OX3 7BN, UK.
| | - Mona O Mohsen
- Nuffield Department of Medicine, Centre for Cellular and Molecular Physiology (CCMP), The Jenner Institute, University of Oxford, Oxford OX3 7BN, UK.
| | - Eduardo Montoya-Diaz
- Nuffield Department of Medicine, Centre for Cellular and Molecular Physiology (CCMP), The Jenner Institute, University of Oxford, Oxford OX3 7BN, UK.
| | - Ahmed M Salman
- Nuffield Department of Medicine, Centre for Cellular and Molecular Physiology (CCMP), The Jenner Institute, University of Oxford, Oxford OX3 7BN, UK.
| | - Erwan Atcheson
- Nuffield Department of Medicine, Centre for Cellular and Molecular Physiology (CCMP), The Jenner Institute, University of Oxford, Oxford OX3 7BN, UK.
| | - Murray A Skinner
- Allergy Therapeutics (UK) Ltd. Dominion Way, Worthing BN14 8SA, UK.
| | | | - Arturo Reyes-Sandoval
- Nuffield Department of Medicine, Centre for Cellular and Molecular Physiology (CCMP), The Jenner Institute, University of Oxford, Oxford OX3 7BN, UK.
| | - Martin F Bachmann
- Nuffield Department of Medicine, Centre for Cellular and Molecular Physiology (CCMP), The Jenner Institute, University of Oxford, Oxford OX3 7BN, UK.
- Immunology, RIA, Inselspital, University of Bern, 3010 Bern ,Switzerland.
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Spencer AJ, Longley RJ, Gola A, Ulaszewska M, Lambe T, Hill AVS. The Threshold of Protection from Liver-Stage Malaria Relies on a Fine Balance between the Number of Infected Hepatocytes and Effector CD8 + T Cells Present in the Liver. THE JOURNAL OF IMMUNOLOGY 2017; 198:2006-2016. [PMID: 28087668 PMCID: PMC5318841 DOI: 10.4049/jimmunol.1601209] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Accepted: 12/16/2016] [Indexed: 12/20/2022]
Abstract
Since the demonstration of sterile protection afforded by injection of irradiated sporozoites, CD8+ T cells have been shown to play a significant role in protection from liver-stage malaria. This is, however, dependent on the presence of an extremely high number of circulating effector cells, thought to be necessary to scan, locate, and kill infected hepatocytes in the short time that parasites are present in the liver. We used an adoptive transfer model to elucidate the kinetics of the effector CD8+ T cell response in the liver following Plasmodium berghei sporozoite challenge. Although effector CD8+ T cells require <24 h to find, locate, and kill infected hepatocytes, active migration of Ag-specific CD8+ T cells into the liver was not observed during the 2-d liver stage of infection, as divided cells were only detected from day 3 postchallenge. However, the percentage of donor cells recruited into division was shown to indicate the level of Ag presentation from infected hepatocytes. By titrating the number of transferred Ag-specific effector CD8+ T cells and sporozoites, we demonstrate that achieving protection toward liver-stage malaria is reliant on CD8+ T cells being able to locate infected hepatocytes, resulting in a protection threshold dependent on a fine balance between the number of infected hepatocytes and CD8+ T cells present in the liver. With such a fine balance determining protection, achieving a high number of CD8+ T cells will be critical to the success of a cell-mediated vaccine against liver-stage malaria.
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Affiliation(s)
| | - Rhea J Longley
- The Jenner Institute, University of Oxford, Oxford OX3 7DQ, United Kingdom
| | - Anita Gola
- The Jenner Institute, University of Oxford, Oxford OX3 7DQ, United Kingdom
| | - Marta Ulaszewska
- The Jenner Institute, University of Oxford, Oxford OX3 7DQ, United Kingdom
| | - Teresa Lambe
- The Jenner Institute, University of Oxford, Oxford OX3 7DQ, United Kingdom
| | - Adrian V S Hill
- The Jenner Institute, University of Oxford, Oxford OX3 7DQ, United Kingdom
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Rampling T, Ewer KJ, Bowyer G, Bliss CM, Edwards NJ, Wright D, Payne RO, Venkatraman N, de Barra E, Snudden CM, Poulton ID, de Graaf H, Sukhtankar P, Roberts R, Ivinson K, Weltzin R, Rajkumar BY, Wille-Reece U, Lee CK, Ockenhouse CF, Sinden RE, Gerry S, Lawrie AM, Vekemans J, Morelle D, Lievens M, Ballou RW, Cooke GS, Faust SN, Gilbert S, Hill AVS. Safety and High Level Efficacy of the Combination Malaria Vaccine Regimen of RTS,S/AS01B With Chimpanzee Adenovirus 63 and Modified Vaccinia Ankara Vectored Vaccines Expressing ME-TRAP. J Infect Dis 2016; 214:772-81. [PMID: 27307573 PMCID: PMC4978377 DOI: 10.1093/infdis/jiw244] [Citation(s) in RCA: 71] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2016] [Accepted: 06/06/2016] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND The need for a highly efficacious vaccine against Plasmodium falciparum remains pressing. In this controlled human malaria infection (CHMI) study, we assessed the safety, efficacy and immunogenicity of a schedule combining 2 distinct vaccine types in a staggered immunization regimen: one inducing high-titer antibodies to circumsporozoite protein (RTS,S/AS01B) and the other inducing potent T-cell responses to thrombospondin-related adhesion protein (TRAP) by using a viral vector. METHOD Thirty-seven healthy malaria-naive adults were vaccinated with either a chimpanzee adenovirus 63 and modified vaccinia virus Ankara-vectored vaccine expressing a multiepitope string fused to TRAP and 3 doses of RTS,S/AS01B (group 1; n = 20) or 3 doses of RTS,S/AS01B alone (group 2; n = 17). CHMI was delivered by mosquito bites to 33 vaccinated subjects at week 12 after the first vaccination and to 6 unvaccinated controls. RESULTS No suspected unexpected serious adverse reactions or severe adverse events related to vaccination were reported. Protective vaccine efficacy was observed in 14 of 17 subjects (82.4%) in group 1 and 12 of 16 subjects (75%) in group 2. All control subjects received a diagnosis of blood-stage malaria parasite infection. Both vaccination regimens were immunogenic. Fourteen protected subjects underwent repeat CHMI 6 months after initial CHMI; 7 of 8 (87.5%) in group 1 and 5 of 6 (83.3%) in group 2 remained protected. CONCLUSIONS The high level of sterile efficacy observed in this trial is encouraging for further evaluation of combination approaches using these vaccine types. CLINICAL TRIALS REGISTRATION NCT01883609.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | | | | | - Hans de Graaf
- NIHR Wellcome Trust Clinical Research Facility, University of Southampton and University Hospital Southampton NHS Foundation Trust, United Kingdom
| | - Priya Sukhtankar
- NIHR Wellcome Trust Clinical Research Facility, University of Southampton and University Hospital Southampton NHS Foundation Trust, United Kingdom
| | | | - Karen Ivinson
- PATH Malaria Vaccine Initiative, Seattle, Washington
| | - Rich Weltzin
- PATH Malaria Vaccine Initiative, Seattle, Washington
| | | | | | - Cynthia K Lee
- PATH Malaria Vaccine Initiative, Seattle, Washington
| | | | | | - Stephen Gerry
- Centre for Statistics in Medicine, University of Oxford
| | | | | | | | | | | | - Graham S Cooke
- Infectious Diseases Section, Faculty of Medicine, Department of Medicine, Imperial College London
| | - Saul N Faust
- NIHR Wellcome Trust Clinical Research Facility, University of Southampton and University Hospital Southampton NHS Foundation Trust, United Kingdom
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