151
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Alaro JR, Partridge A, Miura K, Diouf A, Lopez AM, Angov E, Long CA, Burns JM. A chimeric Plasmodium falciparum merozoite surface protein vaccine induces high titers of parasite growth inhibitory antibodies. Infect Immun 2013; 81:3843-54. [PMID: 23897613 PMCID: PMC3811772 DOI: 10.1128/iai.00522-13] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2013] [Accepted: 07/23/2013] [Indexed: 01/20/2023] Open
Abstract
The C-terminal 19-kDa domain of Plasmodium falciparum merozoite surface protein 1 (PfMSP119) is an established target of protective antibodies. However, clinical trials of PfMSP142, a leading blood-stage vaccine candidate which contains the protective epitopes of PfMSP119, revealed suboptimal immunogenicity and efficacy. Based on proof-of-concept studies in the Plasmodium yoelii murine model, we produced a chimeric vaccine antigen containing recombinant PfMSP119 (rPfMSP119) fused to the N terminus of P. falciparum merozoite surface protein 8 that lacked its low-complexity Asn/Asp-rich domain, rPfMSP8 (ΔAsn/Asp). Immunization of mice with the chimeric rPfMSP1/8 vaccine elicited strong T cell responses to conserved epitopes associated with the rPfMSP8 (ΔAsn/Asp) fusion partner. While specific for PfMSP8, this T cell response was adequate to provide help for the production of high titers of antibodies to both PfMSP119 and rPfMSP8 (ΔAsn/Asp) components. This occurred with formulations adjuvanted with either Quil A or with Montanide ISA 720 plus CpG oligodeoxynucleotide (ODN) and was observed in both inbred and outbred strains of mice. PfMSP1/8-induced antibodies were highly reactive with two major alleles of PfMSP119 (FVO and 3D7). Of particular interest, immunization with PfMSP1/8 elicited higher titers of PfMSP119-specific antibodies than a combined formulation of rPfMSP142 and rPfMSP8 (ΔAsn/Asp). As a measure of functionality, PfMSP1/8-specific rabbit IgG was shown to potently inhibit the in vitro growth of blood-stage parasites of the FVO and 3D7 strains of P. falciparum. These data support the further testing and evaluation of this chimeric PfMSP1/8 antigen as a component of a multivalent vaccine for P. falciparum malaria.
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Affiliation(s)
- James R. Alaro
- Center for Molecular Parasitology, Department of Microbiology and Immunology, Drexel University College of Medicine, Philadelphia, Pennsylvania, USA
- Malaria Immunology Section, Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, USA
| | - Andrea Partridge
- Center for Molecular Parasitology, Department of Microbiology and Immunology, Drexel University College of Medicine, Philadelphia, Pennsylvania, USA
| | - Kazutoyo Miura
- Malaria Immunology Section, Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, USA
| | - Ababacar Diouf
- Malaria Immunology Section, Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, USA
| | - Ana M. Lopez
- Center for Molecular Parasitology, Department of Microbiology and Immunology, Drexel University College of Medicine, Philadelphia, Pennsylvania, USA
| | - Evelina Angov
- U.S. Military Malaria Research Program, Malaria Vaccine Branch, Walter Reed Army Institute of Research, Silver Spring, Maryland, USA
| | - Carole A. Long
- Center for Molecular Parasitology, Department of Microbiology and Immunology, Drexel University College of Medicine, Philadelphia, Pennsylvania, USA
- Malaria Immunology Section, Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, USA
| | - James M. Burns
- Center for Molecular Parasitology, Department of Microbiology and Immunology, Drexel University College of Medicine, Philadelphia, Pennsylvania, USA
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152
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Functional comparison of Plasmodium falciparum transmission-blocking vaccine candidates by the standard membrane-feeding assay. Infect Immun 2013; 81:4377-82. [PMID: 24042109 DOI: 10.1128/iai.01056-13] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Recently, there has been a renewed interest in the development of transmission-blocking vaccines (TBV) against Plasmodium falciparum malaria. While several candidate TBVs have been reported, studies directly comparing them in functional assays are limited. To this end, recombinant proteins of TBV candidates Pfs25, Pfs230, and PfHAP2 were expressed in the wheat germ cell-free expression system. Outbred CD-1 mice were immunized twice with the antigens. Two weeks after the second immunization, IgG levels were measured by enzyme-linked immunosorbent assay (ELISA), and IgG functionality was assessed by the standard membrane-feeding assay (SMFA) using cultured P. falciparum NF54 gametocytes and Anopheles stephensi mosquitoes. All three recombinant proteins elicited similar levels of antigen-specific IgG judged by ELISA. When IgGs purified from pools of immune serum were tested at 0.75 mg/ml in the SMFA, all three IgGs showed 97 to 100% inhibition in oocyst intensity compared to control IgG. In two additional independent SMFA evaluations, anti-Pfs25, anti-Pfs230, and anti-PfHAP2 IgGs inhibited oocyst intensity in a dose-dependent manner. When all three data sets were analyzed, anti-Pfs25 antibody showed significantly higher inhibition than the other two antibodies (P < 0.001 for both), while there was no significant difference between the other two (P = 0.15). A proportion of plasma samples collected from adults living in an area of malaria endemicity in Mali recognized Pfs230 and PfHAP2. This is the first study showing that the HAP2 protein of P. falciparum can induce transmission-blocking antibody. The current study supports the possibility of using this system for a comparative study with multiple TBV candidates.
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153
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Hill DL, Eriksson EM, Li Wai Suen CSN, Chiu CY, Ryg-Cornejo V, Robinson LJ, Siba PM, Mueller I, Hansen DS, Schofield L. Opsonising antibodies to P. falciparum merozoites associated with immunity to clinical malaria. PLoS One 2013; 8:e74627. [PMID: 24040299 PMCID: PMC3767630 DOI: 10.1371/journal.pone.0074627] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2013] [Accepted: 08/04/2013] [Indexed: 11/19/2022] Open
Abstract
Naturally acquired humoral immunity to the malarial parasite Plasmodium falciparum can protect against disease, although the precise mechanisms remain unclear. Although antibody levels can be measured by ELISA, few studies have investigated functional antibody assays in relation to clinical outcomes. In this study we applied a recently developed functional assay of antibody-mediated opsonisation of merozoites, to plasma samples from a longitudinal cohort study conducted in a malaria endemic region of Papua New Guinea (PNG). Phagocytic activity was quantified by flow cytometry using a standardized and high-throughput protocol, and was subsequently evaluated for association with protection from clinical malaria and high-density parasitemia. Opsonising antibody responses were found to: i) increase with age, ii) be enhanced by concurrent infection, and iii) correlate with protection from clinical episodes and high-density parasitemia. Stronger protective associations were observed in individuals with no detectable parasitemia at baseline. This study presents the first evidence for merozoite phagocytosis as a correlate of acquired immunity and clinical protection against P. falciparum malaria.
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Affiliation(s)
- Danika L. Hill
- Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
- Department of Medical Biology, University of Melbourne, Parkville, Victoria, Australia
| | - Emily M. Eriksson
- Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
- Department of Medical Biology, University of Melbourne, Parkville, Victoria, Australia
| | - Connie S. N. Li Wai Suen
- Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
- Department of Medical Biology, University of Melbourne, Parkville, Victoria, Australia
| | - Chris Y. Chiu
- Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
- Department of Medical Biology, University of Melbourne, Parkville, Victoria, Australia
| | - Victoria Ryg-Cornejo
- Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
- Department of Medical Biology, University of Melbourne, Parkville, Victoria, Australia
| | - Leanne J. Robinson
- Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
- Vector Borne Disease Unit, Papua New Guinea Institute of Medical Research, Goroka, Eastern Highlands Province, Papua, New Guinea
| | - Peter M. Siba
- Vector Borne Disease Unit, Papua New Guinea Institute of Medical Research, Goroka, Eastern Highlands Province, Papua, New Guinea
| | - Ivo Mueller
- Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
- Department of Medical Biology, University of Melbourne, Parkville, Victoria, Australia
- Barcelona Center for International Health, University of Barcelona, Barcelona, Spain
| | - Diana S. Hansen
- Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
| | - Louis Schofield
- Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
- Department of Medical Biology, University of Melbourne, Parkville, Victoria, Australia
- * E-mail:
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154
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Reyes-Sandoval A, Bachmann MF. Plasmodium vivax malaria vaccines: why are we where we are? Hum Vaccin Immunother 2013; 9:2558-65. [PMID: 23978931 PMCID: PMC4162059 DOI: 10.4161/hv.26157] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Malaria is one of the few diseases in which morbidity is still measured in hundreds of millions of cases every year. Plasmodium vivax and Plasmodium falciparum are responsible for nearly all the malaria cases in the world and despite difficulties in obtaining an exact number, estimates indicate an astonishing 349-552 million clinical cases of malaria due to P. falciparum in 2007 and between 132-391 million clinical episodes due to P. vivax in 2009. It is becoming evident that eradication of malaria will be an arduous task and P. vivax will be one of the most difficult species to eliminate and perhaps become the last standing malaria parasite. Indeed, in countries that succeed in decreasing the disease burden, nearly all the remaining malaria cases are caused by P. vivax. Such resilience is mainly due to the sophisticated mechanism that the parasite has evolved to remain dormant for months or years forming hypnozoites, a small structure in the liver that will be a major hurdle in the efforts toward malaria eradication. Furthermore, while clinical trials of vaccines against P. falciparum are making fast progress, a very different picture is seen with P. vivax, where only few candidates are currently active in clinical trials.
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Affiliation(s)
| | - Martin F Bachmann
- The Jenner Institute; University of Oxford; Oxford, UK; Dermatology; University Hospital Zurich; Zurich, Switzerland
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155
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Seder RA, Chang LJ, Enama ME, Zephir KL, Sarwar UN, Gordon IJ, Holman LA, James ER, Billingsley PF, Gunasekera A, Richman A, Chakravarty S, Manoj A, Velmurugan S, Li M, Ruben AJ, Li T, Eappen AG, Stafford RE, Plummer SH, Hendel CS, Novik L, Costner PJM, Mendoza FH, Saunders JG, Nason MC, Richardson JH, Murphy J, Davidson SA, Richie TL, Sedegah M, Sutamihardja A, Fahle GA, Lyke KE, Laurens MB, Roederer M, Tewari K, Epstein JE, Sim BKL, Ledgerwood JE, Graham BS, Hoffman SL. Protection against malaria by intravenous immunization with a nonreplicating sporozoite vaccine. Science 2013; 341:1359-65. [PMID: 23929949 DOI: 10.1126/science.1241800] [Citation(s) in RCA: 579] [Impact Index Per Article: 52.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Consistent, high-level, vaccine-induced protection against human malaria has only been achieved by inoculation of Plasmodium falciparum (Pf) sporozoites (SPZ) by mosquito bites. We report that the PfSPZ Vaccine--composed of attenuated, aseptic, purified, cryopreserved PfSPZ--was safe and well tolerated when administered four to six times intravenously (IV) to 40 adults. Zero of six subjects receiving five doses and three of nine subjects receiving four doses of 1.35 × 10(5) PfSPZ Vaccine and five of six nonvaccinated controls developed malaria after controlled human malaria infection (P = 0.015 in the five-dose group and P = 0.028 for overall, both versus controls). PfSPZ-specific antibody and T cell responses were dose-dependent. These data indicate that there is a dose-dependent immunological threshold for establishing high-level protection against malaria that can be achieved with IV administration of a vaccine that is safe and meets regulatory standards.
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Affiliation(s)
- Robert A Seder
- Vaccine Research Center, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20852, USA.
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156
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Sreenivasamurthy SK, Dey G, Ramu M, Kumar M, Gupta MK, Mohanty AK, Harsha HC, Sharma P, Kumar N, Pandey A, Kumar A, Prasad TSK. A compendium of molecules involved in vector-pathogen interactions pertaining to malaria. Malar J 2013; 12:216. [PMID: 23802619 PMCID: PMC3734095 DOI: 10.1186/1475-2875-12-216] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2013] [Accepted: 06/24/2013] [Indexed: 02/06/2023] Open
Abstract
Malaria is a vector-borne disease causing extensive morbidity, debility and mortality. Development of resistance to drugs among parasites and to conventional insecticides among vector-mosquitoes necessitates innovative measures to combat this disease. Identification of molecules involved in the maintenance of complex developmental cycles of the parasites within the vector and the host can provide attractive targets to intervene in the disease transmission. In the last decade, several efforts have been made in identifying such molecules involved in mosquito-parasite interactions and, subsequently, validating their role in the development of parasites within the vector. In this study, a list of mosquito proteins, which facilitate or inhibit the development of malaria parasites in the midgut, haemolymph and salivary glands of mosquitoes, is compiled. A total of 94 molecules have been reported and validated for their role in the development of malaria parasites inside the vector. This compendium of molecules will serve as a centralized resource to biomedical researchers investigating vector-pathogen interactions and malaria transmission.
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157
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Shimp RL, Rowe C, Reiter K, Chen B, Nguyen V, Aebig J, Rausch KM, Kumar K, Wu Y, Jin AJ, Jones DS, Narum DL. Development of a Pfs25-EPA malaria transmission blocking vaccine as a chemically conjugated nanoparticle. Vaccine 2013; 31:2954-62. [PMID: 23623858 PMCID: PMC3683851 DOI: 10.1016/j.vaccine.2013.04.034] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2012] [Revised: 02/28/2013] [Accepted: 04/11/2013] [Indexed: 11/16/2022]
Abstract
Successful efforts to control infectious diseases have often required the use of effective vaccines. The current global strategy for control of malaria, including elimination and eradication will also benefit from the development of an effective vaccine that interrupts malaria transmission. To this end, a vaccine that disrupts malaria transmission within the mosquito host has been investigated for several decades targeting a 25 kDa ookinete specific surface protein, identified as Pfs25. Phase 1 human trial results using a recombinant Pfs25H/Montanide ISA51 formulation demonstrated that human Pfs25 specific antibodies block parasite infectivity to mosquitoes; however, the extent of blocking was likely insufficient for an effective transmission blocking vaccine. To overcome the poor immunogenicity, processes to produce and characterize recombinant Pfs25H conjugated to a detoxified form of Pseudomonas aeruginosa exoprotein A (EPA) have been developed and used to manufacture a cGMP pilot lot for use in human clinical trials. The Pfs25-EPA conjugate appears as a nanoparticle with an average molar mass in solution of approximately 600 kDa by static light scattering with an average diameter 20 nm (range 10-40 nm) by dynamic light scattering. The molar ratio of Pfs25H to EPA is about 3 to 1 by amino acid analysis, respectively. Outbred mice immunized with the Pfs25-EPA conjugated nanoparticle formulated on Alhydrogel(®) had a 75-110 fold increase in Pfs25H specific antibodies when compared to an unconjugated Pfs25H/Alhydrogel(®) formulation. A phase 1 human trial using the Pfs25-EPA/Alhydrogel(®) formulation is ongoing in the United States.
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Affiliation(s)
- Richard L. Shimp
- Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Disease, National Institutes of Health, Rockville, MD 20852, USA
| | - Christopher Rowe
- Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Disease, National Institutes of Health, Rockville, MD 20852, USA
| | - Karine Reiter
- Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Disease, National Institutes of Health, Rockville, MD 20852, USA
| | - Beth Chen
- Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Disease, National Institutes of Health, Rockville, MD 20852, USA
| | - Vu Nguyen
- Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Disease, National Institutes of Health, Rockville, MD 20852, USA
| | - Joan Aebig
- Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Disease, National Institutes of Health, Rockville, MD 20852, USA
| | - Kelly M. Rausch
- Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Disease, National Institutes of Health, Rockville, MD 20852, USA
| | - Krishan Kumar
- Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Disease, National Institutes of Health, Rockville, MD 20852, USA
| | - Yimin Wu
- Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Disease, National Institutes of Health, Rockville, MD 20852, USA
| | - Albert J. Jin
- Laboratory of Cellular Imaging and Macromolecular Biophysics, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD 20892, USA
| | - David S. Jones
- Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Disease, National Institutes of Health, Rockville, MD 20852, USA
| | - David L. Narum
- Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Disease, National Institutes of Health, Rockville, MD 20852, USA
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158
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Burrows JN, van Huijsduijnen RH, Möhrle JJ, Oeuvray C, Wells TNC. Designing the next generation of medicines for malaria control and eradication. Malar J 2013; 12:187. [PMID: 23742293 PMCID: PMC3685552 DOI: 10.1186/1475-2875-12-187] [Citation(s) in RCA: 207] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2013] [Accepted: 05/29/2013] [Indexed: 11/10/2022] Open
Abstract
In the fight against malaria new medicines are an essential weapon. For the parts of the world where the current gold standard artemisinin combination therapies are active, significant improvements can still be made: for example combination medicines which allow for single dose regimens, cheaper, safer and more effective medicines, or improved stability under field conditions. For those parts of the world where the existing combinations show less than optimal activity, the priority is to have activity against emerging resistant strains, and other criteria take a secondary role. For new medicines to be optimal in malaria control they must also be able to reduce transmission and prevent relapse of dormant forms: additional constraints on a combination medicine. In the absence of a highly effective vaccine, new medicines are also needed to protect patient populations. In this paper, an outline definition of the ideal and minimally acceptable characteristics of the types of clinical candidate molecule which are needed (target candidate profiles) is suggested. In addition, the optimal and minimally acceptable characteristics of combination medicines are outlined (target product profiles). MMV presents now a suggested framework for combining the new candidates to produce the new medicines. Sustained investment over the next decade in discovery and development of new molecules is essential to enable the long-term delivery of the medicines needed to combat malaria.
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Affiliation(s)
- Jeremy N Burrows
- Medicines for Malaria Venture-MMV, PO Box 1826, Route de Pré-Bois 20, Geneva 151215, Switzerland
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159
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Bridges DJ, Winters AM, Hamer DH. Malaria elimination: surveillance and response. Pathog Glob Health 2013; 106:224-31. [PMID: 23265423 DOI: 10.1179/2047773212y.0000000035] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
In the last decade, substantial progress has been made in reducing malaria-associated morbidity and mortality across the globe. Nevertheless, sustained malaria control is essential to continue this downward trend. In some countries, where aggressive malaria control has reduced malaria to a low burden level, elimination, either nationally or subnationally, is now the aim. As countries or areas with a low malaria burden move towards elimination, there is a transition away from programs of universal coverage towards a strategy of localized detection and response to individual malaria cases. To do so and succeed, it is imperative that a strong surveillance and response system is supported, that community cadres are trained to provide appropriate diagnostics and treatment, and that field diagnostics are further developed such that their sensitivity allows for the detection and subsequent treatment of malaria reservoirs in low prevalence environments. To be certain, there are big challenges on the road to elimination, notably the development of drug and insecticide resistance. Nevertheless, countries like Zambia are making great strides towards implementing systems that support malaria elimination in target areas. Continued development of new diagnostics and antimalarial therapies is needed to support progress in malaria control and elimination.
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160
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Palacpac NMQ, Ntege E, Yeka A, Balikagala B, Suzuki N, Shirai H, Yagi M, Ito K, Fukushima W, Hirota Y, Nsereko C, Okada T, Kanoi BN, Tetsutani K, Arisue N, Itagaki S, Tougan T, Ishii KJ, Ueda S, Egwang TG, Horii T. Phase 1b randomized trial and follow-up study in Uganda of the blood-stage malaria vaccine candidate BK-SE36. PLoS One 2013; 8:e64073. [PMID: 23724021 PMCID: PMC3665850 DOI: 10.1371/journal.pone.0064073] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2013] [Accepted: 04/05/2013] [Indexed: 01/31/2023] Open
Abstract
Background Up to now a malaria vaccine remains elusive. The Plasmodium falciparum serine repeat antigen-5 formulated with aluminum hydroxyl gel (BK-SE36) is a blood-stage malaria vaccine candidate that has undergone phase 1a trial in malaria-naive Japanese adults. We have now assessed the safety and immunogenicity of BK-SE36 in a malaria endemic area in Northern Uganda. Methods We performed a two-stage, randomized, single-blinded, placebo-controlled phase 1b trial (Current Controlled trials ISRCTN71619711). A computer-generated sequence randomized healthy subjects for 2 subcutaneous injections at 21-day intervals in Stage1 (21–40 year-olds) to 1-mL BK-SE36 (BKSE1.0) (n = 36) or saline (n = 20) and in Stage2 (6–20 year-olds) to BKSE1.0 (n = 33), 0.5-mL BK-SE36 (BKSE0.5) (n = 33), or saline (n = 18). Subjects and laboratory personnel were blinded. Safety and antibody responses 21-days post-second vaccination (Day42) were assessed. Post-trial, to compare the risk of malaria episodes 130–365 days post-second vaccination, Stage2 subjects were age-matched to 50 control individuals. Results Nearly all subjects who received BK-SE36 had induration (Stage1, n = 33, 92%; Stage2, n = 63, 96%) as a local adverse event. No serious adverse event related to BK-SE36 was reported. Pre-existing anti-SE36 antibody titers negatively correlated with vaccination-induced antibody response. At Day42, change in antibody titers was significant for seronegative adults (1.95-fold higher than baseline [95% CI, 1.56–2.43], p = 0.004) and 6–10 year-olds (5.71-fold [95% CI, 2.38–13.72], p = 0.002) vaccinated with BKSE1.0. Immunogenicity response to BKSE0.5 was low and not significant (1.55-fold [95% CI, 1.24–1.94], p = 0.75). In the ancillary analysis, cumulative incidence of first malaria episodes with ≥5000 parasites/µL was 7 cases/33 subjects in BKSE1.0 and 10 cases/33 subjects in BKSE0.5 vs. 29 cases/66 subjects in the control group. Risk ratio for BKSE1.0 was 0.48 (95% CI, 0.24–0.98; p = 0.04). Conclusion BK-SE36 is safe and immunogenic. The promising potential of BK-SE36, observed in the follow-up study, warrants a double-blind phase 1/2b trial in children under 5 years. Trial Registration Controlled-Trials.com ISRCTN71619711 ISRCTN71619711
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Affiliation(s)
- Nirianne Marie Q. Palacpac
- Department of Molecular Protozoology, Research Institute for Microbial Diseases, Osaka University, Suita, Osaka, Japan
- The Research Foundation for Microbial Diseases of Osaka University, Suita, Osaka, Japan
| | | | - Adoke Yeka
- Med Biotech Laboratories, Kampala, Uganda
- Makerere University School of Public Health, Kampala, Uganda
| | | | - Nahoko Suzuki
- The Research Foundation for Microbial Diseases of Osaka University, Kanonji, Kagawa, Japan
| | - Hiroki Shirai
- The Research Foundation for Microbial Diseases of Osaka University, Kanonji, Kagawa, Japan
| | - Masanori Yagi
- Department of Molecular Protozoology, Research Institute for Microbial Diseases, Osaka University, Suita, Osaka, Japan
| | - Kazuya Ito
- Department of Public Health, Faculty of Medicine, Osaka City University, Osaka, Japan
- Sumida Hospital, Medical Co. Living Together Association (LTA) Clinical Pharmacology Center, Tokyo, Japan
| | - Wakaba Fukushima
- Department of Public Health, Faculty of Medicine, Osaka City University, Osaka, Japan
| | - Yoshio Hirota
- Department of Public Health, Faculty of Medicine, Osaka City University, Osaka, Japan
| | | | - Takuya Okada
- The Research Foundation for Microbial Diseases of Osaka University, Kanonji, Kagawa, Japan
| | | | - Kohhei Tetsutani
- The Research Foundation for Microbial Diseases of Osaka University, Suita, Osaka, Japan
- Laboratory of Adjuvant Innovation, National Institute of Biomedical Innovation, Ibaraki City, Osaka, Japan
| | - Nobuko Arisue
- Department of Molecular Protozoology, Research Institute for Microbial Diseases, Osaka University, Suita, Osaka, Japan
| | - Sawako Itagaki
- Department of Molecular Protozoology, Research Institute for Microbial Diseases, Osaka University, Suita, Osaka, Japan
| | - Takahiro Tougan
- Department of Molecular Protozoology, Research Institute for Microbial Diseases, Osaka University, Suita, Osaka, Japan
| | - Ken J. Ishii
- Laboratory of Adjuvant Innovation, National Institute of Biomedical Innovation, Ibaraki City, Osaka, Japan
- Laboratory of Vaccine Science, Immunology Frontier Research Center, World Premier Institute for Immunology, Osaka University, Suita, Osaka, Japan
| | - Shigeharu Ueda
- The Research Foundation for Microbial Diseases of Osaka University, Suita, Osaka, Japan
| | | | - Toshihiro Horii
- Department of Molecular Protozoology, Research Institute for Microbial Diseases, Osaka University, Suita, Osaka, Japan
- * E-mail:
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161
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Grant AJ, Muskavitch MAT, O’Connell RJ. Malaria infection does not affect the sensitivity of peripheral receptor neurons in Anopheles stephensi. Parasit Vectors 2013; 6:134. [PMID: 23642231 PMCID: PMC3659000 DOI: 10.1186/1756-3305-6-134] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Accepted: 04/23/2013] [Indexed: 02/04/2023] Open
Abstract
BACKGROUND Mosquitoes transmit many important diseases including malaria, dengue and yellow fever. Disease transmission from one vertebrate host to another depends on repeated blood feedings by single mosquitoes. In order for the mosquito to acquire the blood that it needs to complete oogenesis, the insect must locate a suitable host. Olfactory cues (including carbon dioxide) released by the host and detected by the mosquito are the primary signals that vector insects use for host location. Previous studies have suggested that the physiological status - including bacterial, fungal, viral and Plasmodium infections - can modulate aspects of behavior in haematophagous insects. METHODS Standard electrophysiological techniques were used to record extracellular responses from the receptor neurons located in sensilla found on the maxillary palps of the insects. The recording microelectrode was inserted through the cuticle at the base of an individual sensillum and the extracellular electrical signals obtained from the three neurons within the sensillum were recorded. Stimulations consisted of 2 s pulses of the desired concentrations of CO(2) or dosages of 1-octen-3-ol. RESULTS Accordingly, we were interested in determining whether Plasmodium infection affects the sensitivity of those peripheral olfactory sensors that are involved in host-seeking in mosquitoes. Our studies indicate that infection of female Anopheles stephensi with Plasmodium berghei does not alter the response characteristics of the neurons innervating the maxillary palp sensilla that respond to the attractants carbon dioxide and 1-octen-3-ol. Although the response characteristics of the peripheral sensory neurons are not affected by infection status, we found that the age of the mosquito alone does affect the threshold of sensitivity of these neurons to carbon dioxide. The proportion of older insects (21-30 d post-emergence) that responds to 150 ppm carbon dioxide is higher than the proportion that responds among younger insects (1-10 d post-emergence). CONCLUSIONS Anopheles stephensi infected with Plasmodium berghei exhibit sensitivities to stimulation with carbon dioxide and 1-octen-3-ol similar to those of uninfected mosquitoes. However, the age of the infected or uninfected mosquito does affect the threshold of sensitivity of these neurons to carbon dioxide.
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Affiliation(s)
- Alan J Grant
- Department of Immunology and Infectious Diseases, Harvard School of Public Health, Harvard University, 665 Huntington Avenue, Boston, Massachusetts 02115, USA
| | - Marc A T Muskavitch
- Department of Immunology and Infectious Diseases, Harvard School of Public Health, Harvard University, 665 Huntington Avenue, Boston, Massachusetts 02115, USA
- Biology Department, Boston College, 140 Commonwealth Avenue, Chestnut Hill, Massachusetts, 02467, USA
| | - Robert J O’Connell
- University of Massachusetts Medical School, Worcester, Massachusetts, 01505, USA
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162
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Soares IS, Françoso KS, Jampaulo VO, Rodrigues MM. CD8(+) T-cell-mediated immunity against malaria: a novel heterologous prime-boost strategy. Expert Rev Vaccines 2013; 11:1039-41. [PMID: 23151162 DOI: 10.1586/erv.12.82] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Recently, a vaccine against malaria was successfully tested in a human Phase III trial. The efficacy of this vaccine formulation, based on the Plasmodium falciparum circumsporozoite protein, was approximately 50% and correlated with the presence of antibodies specific to the infective stages of the malaria parasites. Different strategies are being pursued to improve vaccine efficacy levels. One such strategy is the induction of specific cytotoxic T cells that can destroy the intracellular hepatocyte stages of the malaria parasite. In this study, a novel vaccination protocol was developed to elicit strong immune responses mediated by CD8(+) cytotoxic cells specific to the circumsporozoite protein. As proof-of-concept, the authors used the rodent malaria Plasmodium yoelii parasite. The vaccination strategy consisted of a heterologous prime-boost vaccination regimen involving porcine parvovirus-like particles for priming and the modified vaccinia virus Ankara for the booster immunization, both of which expressed the immunodominant CD8 epitope of the P. yoelii circumsporozoite protein. Results from this experimental model were extremely meaningful. This vaccination strategy led to a significant T-cell immune response mediated by CD8(+) multifunctional T effector and effector-memory cells. However, most importantly for the malaria vaccine development was the fact that following a sporozoite challenge, immunized mice eliminated more than 97% of the malaria parasites during the hepatocyte stages. These results confirm and extend a vast body of knowledge showing that a heterologous prime-boost vaccination strategy can elicit strong CD8(+) T-cell-mediated protective immunity and may increase the efficacy of malaria vaccines.
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Affiliation(s)
- Irene S Soares
- Departamento de Análises Clínicas e Toxicológicas, Faculdade de Ciências Farmacêuticas, Universidade de São Paulo, Av. Prof. Lineu Prestes 580, São Paulo, 05508-900, Brazil.
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Molecular characterization of the carboxypeptidase B1 of Anopheles stephensi and its evaluation as a target for transmission-blocking vaccines. Infect Immun 2013; 81:2206-16. [PMID: 23569111 DOI: 10.1128/iai.01331-12] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Malaria is one of the most important infectious diseases in the world, and it has many economic and social impacts on populations, especially in poor countries. Transmission-blocking vaccines (TBVs) are valuable tools for malaria eradication. A study on Anopheles gambiae revealed that polyclonal antibodies to carboxypeptidase B1 of A. gambiae can block sexual parasite development in the mosquito midgut. Hence, it was introduced as a TBV target in regions where A. gambiae is the main malaria vector. However, in Iran and neighboring countries as far as China, the main malaria vector is Anopheles stephensi. Also, the genome of this organism has not been sequenced yet. Therefore, in this study, carboxypeptidase B1 of A. stephensi was characterized by genomic and proteomic approaches. Furthermore, its expression pattern after ingestion of Plasmodium falciparum gametocytes and the effect of anti-CPBAs1 antibodies on sexual parasite development were evaluated. Our results revealed that the cpbAs1 expression level was increased after ingestion of the mature gametocytes of P. falciparum and that anti-CPBAs1 directed antibodies could significantly reduce the mosquito infection rate in the test group compared with the control group. Therefore, according to our findings and with respect to the high similarity of carboxypeptidase enzymes between the two main malaria vectors in Africa (A. gambiae) and Asia (A. stephensi) and the presence of other sympatric vectors, CPBAs1 could be introduced as a TBV candidate in regions where A. stephensi is the main malaria vector, and this will broaden the scope for the potential wider application of CPBAs1 antigen homologs/orthologs.
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164
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Mehrizi AA, Sepehri M, Karimi F, Djadid ND, Zakeri S. Population genetics, sequence diversity and selection in the gene encoding the Plasmodium falciparum apical membrane antigen 1 in clinical isolates from the south-east of Iran. INFECTION GENETICS AND EVOLUTION 2013; 17:51-61. [PMID: 23557839 DOI: 10.1016/j.meegid.2013.03.042] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2013] [Revised: 03/17/2013] [Accepted: 03/23/2013] [Indexed: 12/26/2022]
Abstract
The Plasmodium falciparum apical membrane antigen1 (AMA1) is a leading malaria vaccine candidate antigen. In the present investigation, for the first time, the almost full length of the ama1 gene covering domain I (DI), DII and DIII was PCR amplified and sequenced in 21 P. falciparum isolates collected from the southeastern parts of Iran. The result showed the low genetic diversity of Iranian PfAMA1 with 11 PfAMA1 haplotypes in which nine out of 11 haplotypes are novel and have been reported for the first time. The Iranian P. falciparum population indicated a moderate level of genetic differentiation. The difference among the rates of non-synonymous and synonymous mutations, Tajima's D and McDonald-Kreitman tests suggested that the diversity at DI is due to positive natural selection. In addition, recombination contributes to the diversity of Iranian PfAMA1 and this is supported by the decline of the linkage disequilibrium index R(2) with increasing the nucleotide distance. The highly polymorphic residues (positions: 187, 197, 200, 230 and 243) were polymorphic; however, most of the SNPs in non-polymorphic residues were conserved except the residue at position 395. Nevertheless, no mutation was found in the DII loop of the Iranian PfAMA1, indicating that it is subjected to purifying selection. In conclusion, the low genetic diversity in PfAMA1 among Iranian isolates supports and provides valuable information for the development of a PfAMA1-based malaria vaccine.
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MESH Headings
- Amino Acid Sequence
- Antigens, Protozoan/chemistry
- Antigens, Protozoan/genetics
- Antigens, Protozoan/immunology
- Epitopes, B-Lymphocyte/chemistry
- Epitopes, B-Lymphocyte/immunology
- Evolution, Molecular
- Gene Frequency
- Genetic Variation
- Haplotypes
- Humans
- Iran
- Malaria Vaccines/genetics
- Malaria Vaccines/immunology
- Malaria, Falciparum/immunology
- Malaria, Falciparum/prevention & control
- Membrane Proteins/chemistry
- Membrane Proteins/genetics
- Membrane Proteins/immunology
- Molecular Sequence Data
- Mutation
- Phylogeny
- Plasmodium falciparum/genetics
- Plasmodium falciparum/immunology
- Plasmodium falciparum/isolation & purification
- Polymorphism, Genetic
- Protozoan Proteins/chemistry
- Protozoan Proteins/genetics
- Protozoan Proteins/immunology
- Recombination, Genetic
- Selection, Genetic
- Sequence Analysis, DNA
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Affiliation(s)
- Akram Abouie Mehrizi
- Malaria and Vector Research Group, Biotechnology Research Center, Pasteur Institute of Iran, Tehran 1316943551, Iran
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165
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Actualités en matière de recherche vaccinale. Compte-rendu de la 15e conférence annuelle sur la recherche vaccinale organisée par la National Foundation for Infectious Diseases. Arch Pediatr 2013; 20:449-58. [DOI: 10.1016/j.arcped.2013.01.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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166
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Miura K, Deng B, Tullo G, Diouf A, Moretz SE, Locke E, Morin M, Fay MP, Long CA. Qualification of standard membrane-feeding assay with Plasmodium falciparum malaria and potential improvements for future assays. PLoS One 2013; 8:e57909. [PMID: 23483940 PMCID: PMC3590281 DOI: 10.1371/journal.pone.0057909] [Citation(s) in RCA: 108] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2012] [Accepted: 01/29/2013] [Indexed: 11/18/2022] Open
Abstract
Vaccines that interrupt malaria transmission are of increasing interest and a robust functional assay to measure this activity would promote their development by providing a biologically relevant means of evaluating potential vaccine candidates. Therefore, we aimed to qualify the standard membrane-feeding assay (SMFA). The assay measures the transmission-blocking activity of antibodies by feeding cultured P. falciparum gametocytes to Anopheles mosquitoes in the presence of the test antibodies and measuring subsequent mosquito infection. The International Conference on Harmonisation (ICH) Harmonised Tripartite Guideline Q2(R1) details characteristics considered in assay validation. Of these characteristics, we decided to qualify the SMFA for Precision, Linearity, Range and Specificity. The transmission-blocking 4B7 monoclonal antibody was tested over 6 feeding experiments at several concentrations to determine four suitable concentrations that were tested in triplicate in the qualification experiments (3 additional feeds) to evaluate Precision, Linearity and Range. For Specificity, 4B7 was tested in the presence of normal mouse IgG. We determined intra- and inter-assay variability of % inhibition of mean oocyst intensity at each concentration of 4B7 (lower concentrations showed higher variability). We also showed that % inhibition was dependent on 4B7 concentration and the activity is specific to 4B7. Since obtaining empirical data is time-consuming, we generated a model using data from all 9 feeds and simulated the effects of different parameters on final readouts to improve the assay procedure and analytical methods for future studies. For example, we estimated the effect of number of mosquitoes dissected on variability of % inhibition, and simulated the relationship between % inhibition in oocyst intensity and % inhibition of prevalence of infected mosquitos at different mean oocysts in the control. SMFA is one of the few biological assays used in preclinical and early clinical development of transmission-blocking vaccines, and this study strongly supports its further development and application.
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Affiliation(s)
- Kazutoyo Miura
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Disease, National Institutes of Health, Rockville, MD, USA.
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167
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Mwangoka G, Ogutu B, Msambichaka B, Mzee T, Salim N, Kafuruki S, Mpina M, Shekalaghe S, Tanner M, Abdulla S. Experience and challenges from clinical trials with malaria vaccines in Africa. Malar J 2013; 12:86. [PMID: 23496910 PMCID: PMC3599886 DOI: 10.1186/1475-2875-12-86] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2012] [Accepted: 02/28/2013] [Indexed: 11/10/2022] Open
Abstract
Malaria vaccines are considered amongst the most important modalities for potential elimination of malaria disease and transmission. Research and development in this field has been an area of intense effort by many groups over the last few decades. Despite this, there is currently no licensed malaria vaccine. Researchers, clinical trialists and vaccine developers have been working on many approached to make malaria vaccine available.African research institutions have developed and demonstrated a great capacity to undertake clinical trials in accordance to the International Conference on Harmonization-Good Clinical Practice (ICH-GCP) standards in the last decade; particularly in the field of malaria vaccines and anti-malarial drugs. This capacity is a result of networking among African scientists in collaboration with other partners; this has traversed both clinical trials and malaria control programmes as part of the Global Malaria Action Plan (GMAP). GMAP outlined and support global strategies toward the elimination and eradication of malaria in many areas, translating in reduction in public health burden, especially for African children. In the sub-Saharan region the capacity to undertake more clinical trials remains small in comparison to the actual need.However, sustainability of the already developed capacity is essential and crucial for the evaluation of different interventions and diagnostic tools/strategies for other diseases like TB, HIV, neglected tropical diseases and non-communicable diseases. There is urgent need for innovative mechanisms for the sustainability and expansion of the capacity in clinical trials in sub-Saharan Africa as the catalyst for health improvement and maintained.
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Affiliation(s)
| | - Bernhards Ogutu
- Malaria Clinical Trials Alliance (MCTA), INDEPTH Network, Accra, Ghana
| | | | - Tutu Mzee
- Ifakara Health Institute, Ifakara, Tanzania
| | | | | | | | | | - Marcel Tanner
- Swiss Tropical and Public Health Institute, Basel, Switzerland
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168
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Heppner DG. The malaria vaccine--status quo 2013. Travel Med Infect Dis 2013; 11:2-7. [PMID: 23454205 DOI: 10.1016/j.tmaid.2013.01.006] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2012] [Revised: 01/24/2013] [Accepted: 01/24/2013] [Indexed: 01/23/2023]
Abstract
It has been 40 years since David Clyde's landmark induction of sterile immunity against deadly falciparum malaria through immunization by exposure to 1000 irradiated mosquitoes, and the first recombinant Plasmodium falciparum vaccine, RTS,S/AS01, is now in Phase III testing. Interim reports from this largest ever Phase III pediatric trial in Africa show the malaria vaccine decreased clinical and severe disease by 56% and 47% respectively in 5-17 month olds, and by 31% and 26% respectively in infants participating in the Expanded Programme on Immunization. Final data in 2014 will more fully describe the efficacy of RTS,S/AS01 over time against all falciparum malaria cases under a variety of transmission conditions, results essential for decisions on licensure and deployment. Meanwhile, candidate components of a second-generation malaria vaccine are emerging. A field trial of the polymorphic blood stage vaccine AMA-1/AS02 demonstrated no overall efficacy (ve = 17%, P = 0.18), yet a sieve analysis revealed allele-specific efficacy (ve = 64%, P = 0.03) against the vaccine strain, suggesting AMA-1 antigens could be part of a multicomponent vaccine. Initial trials of new antigens include the highly conserved pre-erythrocytic candidate PfCelTOS, a synthetic Plasmodium vivax circumsporozoite antigen VMP-001, and sexual stage vaccines containing antigens from both P. falciparum (Pfs25) and P. vivax (Pvs25) intended to interrupt transmission. Targets for a vaccine to protect against placental malaria, the leading remediable cause of low birth weight infants in Africa, have been identified. Lastly, renewed efforts are underway to develop a practical attenuated-sporozoite vaccine to recapture the promise of David Clyde's experiment.
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Affiliation(s)
- D Gray Heppner
- Heppner Associates, LLC, 9441 Brenner Court, Vienna, VA 22180-3402, USA.
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169
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Antigenicity and immunogenicity of Plasmodium vivax merozoite surface protein-3. PLoS One 2013; 8:e56061. [PMID: 23457498 PMCID: PMC3573074 DOI: 10.1371/journal.pone.0056061] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2012] [Accepted: 01/04/2013] [Indexed: 11/19/2022] Open
Abstract
A recent clinical trial in African children demonstrated the potential utility of merozoite surface protein (MSP)-3 as a vaccine against Plasmodium falciparum malaria. The present study evaluated the use of Plasmodium vivax MSP-3 (PvMSP-3) as a target antigen in vaccine formulations against malaria caused by P. vivax. Recombinant proteins representing MSP-3α and MSP-3β of P. vivax were expressed as soluble histidine-tagged bacterial fusions. Antigenicity during natural infection was evaluated by detecting specific antibodies using sera from individuals living in endemic areas of Brazil. A large proportion of infected individuals presented IgG antibodies to PvMSP-3α (68.2%) and at least 1 recombinant protein representing PvMSP-3β (79.1%). In spite of the large responder frequency, reactivity to both antigens was significantly lower than was observed for the immunodominant epitope present on the 19-kDa C-terminal region of PvMSP-1. Immunogenicity of the recombinant proteins was studied in mice in the absence or presence of different adjuvant formulations. PvMSP-3β, but not PvMSP-3α, induced a TLR4-independent humoral immune response in the absence of any adjuvant formulation. The immunogenicity of the recombinant antigens were also tested in formulations containing different adjuvants (Alum, Salmonella enterica flagellin, CpG, Quil A,TiterMax® and incomplete Freunds adjuvant) and combinations of two adjuvants (Alum plus flagellin, and CpG plus flagellin). Recombinant PvMSP-3α and PvMSP-3β elicited higher antibody titers capable of recognizing P. vivax-infected erythrocytes harvested from malaria patients. Our results confirm that P. vivax MSP-3 antigens are immunogenic during natural infection, and the corresponding recombinant proteins may be useful in elucidating their vaccine potential.
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170
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Battle KE, Gething PW, Elyazar IRF, Moyes CL, Sinka ME, Howes RE, Guerra CA, Price RN, Baird KJ, Hay SI. The global public health significance of Plasmodium vivax. ADVANCES IN PARASITOLOGY 2013. [PMID: 23199486 DOI: 10.1016/b978-0-12-397900-1.00001-3] [Citation(s) in RCA: 94] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Plasmodium vivax occurs globally and thrives in both temperate and tropical climates. Here, we review the evidence of the biological limits of its contemporary distribution and the global population at risk (PAR) of the disease within endemic countries. We also review the most recent evidence for the endemic level of transmission within its range and discuss the implications for burden of disease assessments. Finally, the evidence-base for defining the contemporary distribution and PAR of P. vivax are discussed alongside a description of the vectors of human malaria within the limits of risk. This information along with recent data documenting the severe morbid and fatal consequences of P. vivax infection indicates that the public health significance of P. vivax is likely to have been seriously underestimated.
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Affiliation(s)
- Katherine E Battle
- Department of Zoology, University of Oxford, South Parks Road, Oxford, UK
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171
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Riley EM, Stewart VA. Immune mechanisms in malaria: new insights in vaccine development. Nat Med 2013; 19:168-78. [DOI: 10.1038/nm.3083] [Citation(s) in RCA: 144] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2012] [Accepted: 01/07/2013] [Indexed: 02/07/2023]
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172
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Plowe CV. Malaria Vaccines. Infect Dis (Lond) 2013. [DOI: 10.1007/978-1-4614-5719-0_8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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173
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Bousema T, Churcher TS, Morlais I, Dinglasan RR. Can field-based mosquito feeding assays be used for evaluating transmission-blocking interventions? Trends Parasitol 2012; 29:53-9. [PMID: 23273727 DOI: 10.1016/j.pt.2012.11.004] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2012] [Revised: 11/21/2012] [Accepted: 11/27/2012] [Indexed: 11/18/2022]
Abstract
A recent meta-analysis of mosquito feeding assays to determine the Plasmodium falciparum transmission potential of naturally infected gametocyte carriers highlighted considerable variation in transmission efficiency between assay methodologies and between laboratories. This begs the question as to whether mosquito feeding assays should be used for the evaluation of transmission-reducing interventions in the field and whether these field-based mosquito assays are currently standardized sufficiently to enable accurate evaluations. Here, we address biological and methodological reasons for the observed variations, discuss whether these preclude the use of field-based mosquito feeding assays in field evaluations of transmission-blocking interventions, and propose how we can maximize the precision of estimates. Altogether, we underscore the significant advantages of field-based mosquito feeding assays in basic malaria research and field trials.
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Affiliation(s)
- Teun Bousema
- Department of Immunology and Infection, London School of Hygiene and Tropical Medicine, London, UK.
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174
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Birkholtz LM, Bornman R, Focke W, Mutero C, de Jager C. Sustainable malaria control: transdisciplinary approaches for translational applications. Malar J 2012; 11:431. [PMID: 23268712 PMCID: PMC3548719 DOI: 10.1186/1475-2875-11-431] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2012] [Accepted: 12/14/2012] [Indexed: 01/05/2023] Open
Abstract
With the adoption of the Global Malaria Action Plan, several countries are moving from malaria control towards elimination and eradication. However, the sustainability of some of the approaches taken may be questionable. Here, an overview of malaria control and elimination strategies is provided and the sustainability of each in context of vector- and parasite control is assessed. From this, it can be concluded that transdisciplinary approaches are essential for sustained malaria control and elimination in malaria-endemic communities.
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Affiliation(s)
- Lyn-Marie Birkholtz
- Department of Biochemistry, University of Pretoria, Private Bag x20, Pretoria, Gauteng, South Africa, 0028
| | - Riana Bornman
- University of Pretoria Centre for Sustainable Malaria Control (UP CSMC), University of Pretoria, Private Bag x323, Pretoria, Gauteng, South Africa, 0001
| | - Walter Focke
- Department of Chemical Engineering, University of Pretoria, Private Bag x20, Pretoria, Gauteng, South Africa, 0028
| | - Clifford Mutero
- University of Pretoria Centre for Sustainable Malaria Control (UP CSMC), University of Pretoria, Private Bag x323, Pretoria, Gauteng, South Africa, 0001
- International Centre of Insect Physiology and Ecology, P.O. Box 30772, Nairobi, Kenya, 00100
| | - Christiaan de Jager
- University of Pretoria Centre for Sustainable Malaria Control (UP CSMC), University of Pretoria, Private Bag x323, Pretoria, Gauteng, South Africa, 0001
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175
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Chew CH, Lim YAL, Lee PC, Mahmud R, Chua KH. Hexaplex PCR detection system for identification of five human Plasmodium species with an internal control. J Clin Microbiol 2012; 50:4012-9. [PMID: 23035191 PMCID: PMC3502955 DOI: 10.1128/jcm.06454-11] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2011] [Accepted: 09/24/2012] [Indexed: 11/20/2022] Open
Abstract
Malaria remains one of the major killers of humankind and persists to threaten the lives of more than one-third of the world's population. Given that human malaria can now be caused by five species of Plasmodium, i.e., Plasmodium falciparum, Plasmodium vivax, Plasmodium malariae, Plasmodium ovale, and the recently included Plasmodium knowlesi, there is a critical need not only to augment global health efforts in malaria control but also, more importantly, to develop a rapid, accurate, species-sensitive/species-specific, and economically effective diagnostic method for malaria caused by these five species. Therefore, in the present study, a straightforward single-step hexaplex PCR system targeting five human Plasmodium 18S small-subunit rRNAs (ssu rRNAs) was designed, and the system successfully detected all five human malaria parasites. In addition, this system enables the differentiation of single infection as well as mixed infections up to the two-species level. This assay was validated with 50 randomly blinded test and 184 clinical samples suspected to indicate malaria. This hexaplex PCR system is not only an ideal alternative for routine malaria diagnosis in laboratories with conventional PCR machines but also adds value to diagnoses when there is a lack of an experienced microscopist or/and when the parasite morphology is confusing. Indeed, this system will definitely enhance the accuracy and accelerate the speed in the diagnosis of malaria, as well as improve the efficacy of malaria treatment and control, in addition to providing reliable data from epidemiological surveillance studies.
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Affiliation(s)
- Ching Hoong Chew
- Department of Molecular Medicine, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia
| | - Yvonne Ai Lian Lim
- Department of Parasitology, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia
| | - Ping Chin Lee
- School of Science and Technology, Universiti Malaysia Sabah, Kota Kinabalu, Sabah, Malaysia
| | - Rohela Mahmud
- Department of Parasitology, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia
| | - Kek Heng Chua
- Department of Molecular Medicine, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia
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176
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Improving N-terminal protein annotation of Plasmodium species based on signal peptide prediction of orthologous proteins. Malar J 2012; 11:375. [PMID: 23153225 PMCID: PMC3529677 DOI: 10.1186/1475-2875-11-375] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2012] [Accepted: 10/31/2012] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Signal peptide is one of the most important motifs involved in protein trafficking and it ultimately influences protein function. Considering the expected functional conservation among orthologs it was hypothesized that divergence in signal peptides within orthologous groups is mainly due to N-terminal protein sequence misannotation. Thus, discrepancies in signal peptide prediction of orthologous proteins were used to identify misannotated proteins in five Plasmodium species. METHODS Signal peptide (SignalP) and orthology (OrthoMCL) were combined in an innovative strategy to identify orthologous groups showing discrepancies in signal peptide prediction among their protein members (Mixed groups). In a comparative analysis, multiple alignments for each of these groups and gene models were visually inspected in search of misannotated proteins and, whenever possible, alternative gene models were proposed. Thresholds for signal peptide prediction parameters were also modified to reduce their impact as a possible source of discrepancy among orthologs. Validation of new gene models was based on RT-PCR (few examples) or on experimental evidence already published (ApiLoc). RESULTS The rate of misannotated proteins was significantly higher in Mixed groups than in Positive or Negative groups, corroborating the proposed hypothesis. A total of 478 proteins were reannotated and change of signal peptide prediction from negative to positive was the most common. Reannotations triggered the conversion of almost 50% of all Mixed groups, which were further reduced by optimization of signal peptide prediction parameters. CONCLUSIONS The methodological novelty proposed here combining orthology and signal peptide prediction proved to be an effective strategy for the identification of proteins showing wrongly N-terminal annotated sequences, and it might have an important impact in the available data for genome-wide searching of potential vaccine and drug targets and proteins involved in host/parasite interactions, as demonstrated for five Plasmodium species.
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Vannice KS, Brown GV, Akanmori BD, Moorthy VS. MALVAC 2012 scientific forum: accelerating development of second-generation malaria vaccines. Malar J 2012; 11:372. [PMID: 23140365 PMCID: PMC3519521 DOI: 10.1186/1475-2875-11-372] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2012] [Accepted: 10/18/2012] [Indexed: 11/25/2022] Open
Abstract
The World Health Organization (WHO) convened a malaria vaccines committee (MALVAC) scientific forum from 20 to 21 February 2012 in Geneva, Switzerland, to review the global malaria vaccine portfolio, to gain consensus on approaches to accelerate second-generation malaria vaccine development, and to discuss the need to update the vision and strategic goal of the Malaria Vaccine Technology Roadmap. This article summarizes the forum, which included reviews of leading Plasmodium falciparum vaccine candidates for pre-erythrocytic vaccines, blood-stage vaccines, and transmission-blocking vaccines. Other major topics included vaccine candidates against Plasmodium vivax, clinical trial site capacity development in Africa, trial design considerations for a second-generation malaria vaccine, adjuvant selection, and regulatory oversight functions including vaccine licensure.
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Affiliation(s)
- Kirsten S Vannice
- Johns Hopkins Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland, USA
| | - Graham V Brown
- Nossal Institute for Global Health, University of Melbourne, Carlton, Victoria, 3010, Australia
| | - Bartholomew D Akanmori
- Immunization and Vaccines Development Programme, Division for Prevention and Control of Communicable Diseases, WHO Regional Office for Africa, Brazzaville, Congo
| | - Vasee S Moorthy
- Initiative for Vaccine Research, Department of Immunization, Vaccines & Biologicals, World Health Organization, Avenue Appia 20, Geneva, 1211-CH 27, Switzerland
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178
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Bousema T, Dinglasan RR, Morlais I, Gouagna LC, van Warmerdam T, Awono-Ambene PH, Bonnet S, Diallo M, Coulibaly M, Tchuinkam T, Mulder B, Targett G, Drakeley C, Sutherland C, Robert V, Doumbo O, Touré Y, Graves PM, Roeffen W, Sauerwein R, Birkett A, Locke E, Morin M, Wu Y, Churcher TS. Mosquito feeding assays to determine the infectiousness of naturally infected Plasmodium falciparum gametocyte carriers. PLoS One 2012; 7:e42821. [PMID: 22936993 PMCID: PMC3425579 DOI: 10.1371/journal.pone.0042821] [Citation(s) in RCA: 143] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2012] [Accepted: 07/11/2012] [Indexed: 12/27/2022] Open
Abstract
Introduction In the era of malaria elimination and eradication, drug-based and vaccine-based approaches to reduce malaria transmission are receiving greater attention. Such interventions require assays that reliably measure the transmission of Plasmodium from humans to Anopheles mosquitoes. Methods We compared two commonly used mosquito feeding assay procedures: direct skin feeding assays and membrane feeding assays. Three conditions under which membrane feeding assays are performed were examined: assays with i) whole blood, ii) blood pellets resuspended with autologous plasma of the gametocyte carrier, and iii) blood pellets resuspended with heterologous control serum. Results 930 transmission experiments from Cameroon, The Gambia, Mali and Senegal were included in the analyses. Direct skin feeding assays resulted in higher mosquito infection rates compared to membrane feeding assays (odds ratio 2.39, 95% confidence interval 1.94–2.95) with evident heterogeneity between studies. Mosquito infection rates in membrane feeding assays and direct skin feeding assays were strongly correlated (p<0.0001). Replacing the plasma of the gametocyte donor with malaria naïve control serum resulted in higher mosquito infection rates compared to own plasma (OR 1.92, 95% CI 1.68–2.19) while the infectiousness of gametocytes may be reduced during the replacement procedure (OR 0.60, 95% CI 0.52–0.70). Conclusions Despite a higher efficiency of direct skin feeding assays, membrane feeding assays appear suitable tools to compare the infectiousness between individuals and to evaluate transmission-reducing interventions. Several aspects of membrane feeding procedures currently lack standardization; this variability makes comparisons between laboratories challenging and should be addressed to facilitate future testing of transmission-reducing interventions.
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Affiliation(s)
- Teun Bousema
- Department of Immunity and Infection, London School of Hygiene & Tropical Medicine, London, United Kingdom.
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179
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Brooks A, Smith TA, de Savigny D, Lengeler C. Implementing new health interventions in developing countries: why do we lose a decade or more? BMC Public Health 2012; 12:683. [PMID: 22908877 PMCID: PMC3495221 DOI: 10.1186/1471-2458-12-683] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2012] [Accepted: 08/06/2012] [Indexed: 11/23/2022] Open
Abstract
BACKGROUND It is unclear how long it takes for health interventions to transition from research and development (R&D) to being used against diseases prevalent in resource-poor countries. We undertook an analysis of the time required to begin implementation of four vaccines and three malaria interventions. We evaluated five milestones for each intervention, and assessed if the milestones were associated with beginning implementation. METHODS The authors screened World Health Organization (WHO) databases to determine the number of years between first regulatory approval of interventions, and countries beginning implementation. Descriptive analyses of temporal patterns and statistical analyses using logistic regression and Cox proportional hazard models were used to evaluate associations between five milestones and the beginning of implementation for each intervention. The milestones were: (A) presence of a coordinating group focused on the intervention; (B) availability of an intervention tailored to developing country health systems; (C) international financing commitment, and; (D) initial and (E) comprehensive WHO recommendations. Countries were categorized by World Bank income criteria. RESULTS Five years after regulatory approval, no low-income countries (LICs) had begun implementing any of the vaccines, increasing to an average of only 4% of LICs after 10 years. Each malaria intervention was used by an average of 7% of LICs after five years and 37% after 10 years. Four of the interventions had similar implementation rates to hepatitis B vaccine (HepB), while one was slower and one was faster than HepB. A financing commitment and initial WHO recommendation appeared to be temporally associated with the beginning of implementation. The initial recommendation from WHO was the only milestone associated in all statistical analyses with countries beginning implementation (relative rate = 1.97, P < 0.001). CONCLUSIONS Although possible that four milestones were not associated with countries beginning implementation, we propose an alternative interpretation; that the milestones were not realized early enough in each intervention's development to shorten the time to beginning implementation. We discuss a framework built upon existing literature for consideration during the development of future interventions. Identifying critical milestones and their timing relative to R&D, promises to help new interventions realize their intended public health impact more rapidly.
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Affiliation(s)
- Alan Brooks
- Swiss Tropical and Public Health Institute, Socinstrasse 57, Basel, CH-4002, Switzerland
- University of Basel, Petersplatz 1, Basel, CH-4003, Switzerland
| | - Thomas A Smith
- Swiss Tropical and Public Health Institute, Socinstrasse 57, Basel, CH-4002, Switzerland
- University of Basel, Petersplatz 1, Basel, CH-4003, Switzerland
| | - Don de Savigny
- Swiss Tropical and Public Health Institute, Socinstrasse 57, Basel, CH-4002, Switzerland
- University of Basel, Petersplatz 1, Basel, CH-4003, Switzerland
| | - Christian Lengeler
- Swiss Tropical and Public Health Institute, Socinstrasse 57, Basel, CH-4002, Switzerland
- University of Basel, Petersplatz 1, Basel, CH-4003, Switzerland
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180
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Jones S, Sutherland CJ, Hermsen C, Arens T, Teelen K, Hallett R, Corran P, van der Vegte-Bolmer M, Sauerwein R, Drakeley CJ, Bousema T. Filter paper collection of Plasmodium falciparum mRNA for detecting low-density gametocytes. Malar J 2012; 11:266. [PMID: 22873569 PMCID: PMC3441243 DOI: 10.1186/1475-2875-11-266] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2012] [Accepted: 08/02/2012] [Indexed: 01/01/2023] Open
Abstract
BACKGROUND Accurate sampling of sub-microscopic gametocytes is necessary for epidemiological studies to identify the infectious reservoir of Plasmodium falciparum. Detection of gametocyte mRNA achieves sensitive detection, but requires careful handling of samples. Filter papers can be used for collecting RNA samples, but rigorous testing of their capacity to withstand adverse storage conditions has not been fully explored. METHODS Three gametocyte dilutions: 10/μL, 1.0/μL and 0.1/μL were spotted onto Whatman™ 903 Protein Saver Cards, FTA Classic Cards and 3MM filter papers that were stored under frozen, cold chain or tropical conditions for up to 13 weeks . RNA was extracted, then detected by quantitative nucleic acid sequence-based amplification (QT-NASBA) and reverse-transcriptase PCR (RT-PCR). RESULTS Successful gametocyte detection was more frequently observed from the Whatman 903 Protein Saver Card compared to the Whatman FTA Classic Card, by both techniques (p<0.0001). When papers were stored at higher temperatures, a loss in sensitivity was experienced for the FTA Classic Card but not the 903 Protein Saver Card or Whatman 3MM filter paper. The sensitivity of gametocyte detection was decreased when papers were stored at high humidity. CONCLUSIONS This study indicates the Whatman 903 Protein Saver Card is better for Pfs25 mRNA sampling compared to the Whatman FTA Classic Card, and that the Whatman 3MM filter paper may prove to be a satisfactory cheaper option for Pfs25 mRNA sampling. When appropriately dried, filter papers provide a useful approach to Pfs25 mRNA sampling, especially in settings where storage in RNA-protecting buffer is not possible.
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Affiliation(s)
- Sophie Jones
- Department of Immunology & Infection; Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, UK
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181
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Pluschke G, Tamborrini M. Development of a virosomal malaria vaccine candidate: from synthetic peptide design to clinical concept validation. Future Virol 2012. [DOI: 10.2217/fvl.12.74] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
An ideal malaria vaccine would prevent disease and reduce transmission by targeting several developmental stages of human malaria parasites. To be cost-effective, a modular antigen delivery technology is required for the development of such a multivalent subunit vaccine. In this review, we summarize and discuss a strategy to develop synthetic peptidomimetics of key malaria target antigens for inclusion in a multivalent malaria subunit vaccine based on immunopotentiating reconstituted influenza virosomes. Clinical testing of a bivalent virosomal formulation incorporating two structurally optimized peptidomimetics has demonstrated safety, immunogenicity and pilot efficacy. While this clinical validation supports the concept of using peptide-loaded virosomes for vaccination in humans, it is assumed that additional antigens will have to be added to the bivalent formulation to generate a highly effective malaria vaccine.
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Affiliation(s)
- Gerd Pluschke
- Swiss Tropical & Public Health Institute, Socinstr. 57, 4002 Basel, Switzerland
| | - Marco Tamborrini
- Swiss Tropical & Public Health Institute, Socinstr. 57, 4002 Basel, Switzerland
- University of Basel, Petersplatz 1, 4003 Basel, Switzerland
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182
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Smith T, Tediosi F. Simulating the impact of malaria vaccination: what has been learnt? Expert Rev Vaccines 2012; 11:751-3. [DOI: 10.1586/erv.12.51] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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183
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Preparation and antiprotozoal evaluation of promising β-carboline alkaloids. Biomed Pharmacother 2012; 66:339-47. [DOI: 10.1016/j.biopha.2011.12.006] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2011] [Accepted: 12/15/2011] [Indexed: 11/18/2022] Open
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184
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Gregory JA, Li F, Tomosada LM, Cox CJ, Topol AB, Vinetz JM, Mayfield S. Algae-produced Pfs25 elicits antibodies that inhibit malaria transmission. PLoS One 2012; 7:e37179. [PMID: 22615931 PMCID: PMC3353897 DOI: 10.1371/journal.pone.0037179] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2012] [Accepted: 04/17/2012] [Indexed: 12/21/2022] Open
Abstract
Subunit vaccines are significantly more expensive to produce than traditional vaccines because they are based primarily on recombinant proteins that must be purified from the expression system. Despite the increased cost, subunit vaccines are being developed because they are safe, effective, and can elicit antibodies that confer protection against diseases that are not currently vaccine-preventable. Algae are an attractive platform for producing subunit vaccines because they are relatively inexpensive to grow, genetically tractable, easily scaled to large volumes, have a short generation time, and are devoid of inflammatory, viral, or prion contaminants often present in other systems. We tested whether algal chloroplasts can produce malaria transmission blocking vaccine candidates, Plasmodium falciparum surface protein 25 (Pfs25) and 28 (Pfs28). Antibodies that recognize Pfs25 and Pfs28 disrupt the sexual development of parasites within the mosquito midgut, thus preventing transmission of malaria from one human host to the next. These proteins have been difficult to produce in traditional recombinant systems because they contain tandem repeats of structurally complex epidermal growth factor-like domains, which cannot be produced in bacterial systems, and because they are not glycosylated, so they must be modified for production in eukaryotic systems. Production in algal chloroplasts avoids these issues because chloroplasts can fold complex eukaryotic proteins and do not glycosylate proteins. Here we demonstrate that algae are the first recombinant system to successfully produce an unmodified and aglycosylated version of Pfs25 or Pfs28. These antigens are structurally similar to the native proteins and antibodies raised to these recombinant proteins recognize Pfs25 and Pfs28 from P. falciparum. Furthermore, antibodies to algae-produced Pfs25 bind the surface of in-vitro cultured P. falciparum sexual stage parasites and exhibit transmission blocking activity. Thus, algae are promising organisms for producing cysteine-disulfide-containing malaria transmission blocking vaccine candidate proteins.
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Affiliation(s)
- James A. Gregory
- Division of Biological Sciences, and the San Diego Center for Algae Biotechnology, University of California San Diego, California, United States of America
| | - Fengwu Li
- Division of Infectious Disease, Department of Medicine, University of California San Diego, La Jolla, California, United States of America
| | - Lauren M. Tomosada
- Division of Biological Sciences, and the San Diego Center for Algae Biotechnology, University of California San Diego, California, United States of America
| | - Chesa J. Cox
- Division of Biological Sciences, and the San Diego Center for Algae Biotechnology, University of California San Diego, California, United States of America
| | - Aaron B. Topol
- Division of Biological Sciences, and the San Diego Center for Algae Biotechnology, University of California San Diego, California, United States of America
| | - Joseph M. Vinetz
- Division of Infectious Disease, Department of Medicine, University of California San Diego, La Jolla, California, United States of America
| | - Stephen Mayfield
- Division of Biological Sciences, and the San Diego Center for Algae Biotechnology, University of California San Diego, California, United States of America
- * E-mail:
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185
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Khan SM, Janse CJ, Kappe SHI, Mikolajczak SA. Genetic engineering of attenuated malaria parasites for vaccination. Curr Opin Biotechnol 2012; 23:908-16. [PMID: 22560204 DOI: 10.1016/j.copbio.2012.04.003] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2012] [Revised: 04/06/2012] [Accepted: 04/12/2012] [Indexed: 01/28/2023]
Abstract
Vaccination with live-attenuated Plasmodium sporozoites that arrest in the liver can completely protect against a malaria infection both in animal models and in humans; this has provided the conceptual basis for the most promising, but also challenging, approach to develop an efficacious malaria vaccine. Advances in genetic manipulation of Plasmodium in conjunction with improved genomic and biological information has enabled new approaches to design genetically attenuated parasites (GAPs). In this review we discuss the principles in discovery and development of GAPs in preclinical models that are important in selecting GAP parasites for first-in-human clinical studies. Finally, we highlight the challenges in manufacture, formulation and delivery of a live-attenuated whole parasite malaria vaccine, as well as the further refinements that may be implemented in the next generation GAP vaccines.
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Affiliation(s)
- Shahid M Khan
- Leiden Malaria Research Group, Department of Parasitology, Leiden University Medical Center, 2333 ZA Leiden, The Netherlands.
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186
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Affiliation(s)
- Jürg Utzinger
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
- * E-mail:
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187
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Approaching the target: the path towards an effective malaria vaccine. Mediterr J Hematol Infect Dis 2012; 4:e2012015. [PMID: 22550560 PMCID: PMC3340989 DOI: 10.4084/mjhid.2012.015] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2012] [Accepted: 02/07/2012] [Indexed: 11/08/2022] Open
Abstract
Developing an effective malaria vaccine has been the goal of the scientific community for many years. A malaria vaccine, added to existing tools and strategies, would further prevent infection and decrease the unacceptable malaria morbidity and mortality burden. Great progress has been made over the last decade and a number of vaccine candidates are in the clinical phases of development. The RTS,S malaria vaccine candidate, based on a recombinant P. falciparum protein, is the most advanced of such candidates, currently undergoing a large phase III trial. RTS,S has consistently shown around 50% efficacy protecting against the first clinical episode of malaria, in some cases extending up to 4 years. It is hoped that RTS,S will eventually become the first licensed malaria vaccine. This first vaccine against a human parasite is a groundbreaking achievement, but improved malaria vaccines conferring higher protection will be needed if the aspiration of malaria eradication is to be achieved.
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188
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Wilson ML, Walker ED, Mzilahowa T, Mathanga DP, Taylor TE. Malaria elimination in Malawi: research needs in highly endemic, poverty-stricken contexts. Acta Trop 2012; 121:218-26. [PMID: 22100546 PMCID: PMC3294061 DOI: 10.1016/j.actatropica.2011.11.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2011] [Revised: 11/02/2011] [Accepted: 11/04/2011] [Indexed: 11/18/2022]
Abstract
Malaria control in the impoverished, highly endemic settings of sub-Saharan Africa remains a major public health challenge. Successes have been achieved only where sustained, concerted, multi-pronged interventions have been instituted. As one of the world's poorest countries, Malawi experiences malaria incidence rates that have remained high despite a decade of gradually expanding and more intensive prevention efforts. The Malawi International Center for Excellence in Malaria Research (ICEMR) is beginning work to augment the knowledge base for reducing Plasmodium transmission and malaria morbidity and mortality. Among ICEMR goals, we intend to better assess patterns of infection and disease, and analyze transmission by Anopheles vector species in both urban and rural ecological settings. We will evaluate parasite population genetics and dynamics, transmission intensities and vector ecologies, social and environmental determinants of disease patterns and risk, and human-vector-parasite dynamics. Such context-specific information will help to focus appropriate prevention and treatment activities on efforts to control malaria in Malawi. In zones of intense and stable transmission, like Malawi, elimination poses particularly thorny challenges - and these challengers are different from those of traditional control and prevention activities. Working toward elimination will require knowledge of how various interventions impact on transmission as it approaches very low levels. At present, Malawi is faced with immediate, context-specific problems of scaling-up prevention and control activities simply to begin reducing infection and disease to tolerable levels. The research required to support these objectives is critically evaluated here.
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Affiliation(s)
- Mark L Wilson
- Department of Epidemiology, School of Public Health, University of Michigan, Ann Arbor, USA.
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189
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Expression, immunogenicity, histopathology, and potency of a mosquito-based malaria transmission-blocking recombinant vaccine. Infect Immun 2012; 80:1606-14. [PMID: 22311924 DOI: 10.1128/iai.06212-11] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Vaccines have been at the forefront of global research efforts to combat malaria, yet despite several vaccine candidates, this goal has yet to be realized. A potentially effective approach to disrupting the spread of malaria is the use of transmission-blocking vaccines (TBV), which prevent the development of malarial parasites within their mosquito vector, thereby abrogating the cascade of secondary infections in humans. Since malaria is transmitted to human hosts by the bite of an obligate insect vector, mosquito species in the genus Anopheles, targeting mosquito midgut antigens that serve as ligands for Plasmodium parasites represents a promising approach to breaking the transmission cycle. The midgut-specific anopheline alanyl aminopeptidase N (AnAPN1) is highly conserved across Anopheles vectors and is a putative ligand for Plasmodium ookinete invasion. We have developed a scalable, high-yield Escherichia coli expression and purification platform for the recombinant AnAPN1 TBV antigen and report on its marked vaccine potency and immunogenicity, its capacity for eliciting transmission-blocking antibodies, and its apparent lack of immunization-associated histopathologies in a small-animal model.
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190
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Breman JG, Brandling-Bennett AD. The challenge of malaria eradication in the twenty-first century: research linked to operations is the key. Vaccine 2012; 29 Suppl 4:D97-103. [PMID: 22284402 DOI: 10.1016/j.vaccine.2011.12.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2011] [Revised: 11/24/2011] [Accepted: 12/01/2011] [Indexed: 10/14/2022]
Abstract
Interest and support for malaria control, eradication, and research has increased greatly over the past decade. This has resulted from appreciation of the huge medical, social, and economic burden that malaria exacts from endemic populations. Recent breakthroughs in drug development (artemisinin-based combination treatments), preventive interventions (long-lasting, insecticide-treated bed nets), improved diagnosis (rapid diagnostic tests), and community mobilization have resulted in deployment of new antimalarial tools. National programs supported by the Global Fund to Fight AIDS, Tuberculosis and Malaria, the U.S. President's Malaria Initiative, and other donors have resulted in substantial reductions in malaria morbidity and mortality. Bill and Melinda Gates have given great impetus to eradication with support for the development of key research strategies and direct funding of innovative research projects, including malaria vaccine and drug discovery, that could decrease disease and transmission. Linking research to field operations is a strategy that succeeded for smallpox eradication and will be required for the demise of malaria.
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Affiliation(s)
- Joel G Breman
- Fogarty International Center, National Institutes of Health, 16 Center Drive, Bethesda, MD 20892, USA.
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191
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Schwartz L, Brown GV, Genton B, Moorthy VS. A review of malaria vaccine clinical projects based on the WHO rainbow table. Malar J 2012; 11:11. [PMID: 22230255 PMCID: PMC3286401 DOI: 10.1186/1475-2875-11-11] [Citation(s) in RCA: 172] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2011] [Accepted: 01/09/2012] [Indexed: 12/14/2022] Open
Abstract
Development and Phase 3 testing of the most advanced malaria vaccine, RTS,S/AS01, indicates that malaria vaccine R&D is moving into a new phase. Field trials of several research malaria vaccines have also confirmed that it is possible to impact the host-parasite relationship through vaccine-induced immune responses to multiple antigenic targets using different platforms. Other approaches have been appropriately tested but turned out to be disappointing after clinical evaluation. As the malaria community considers the potential role of a first-generation malaria vaccine in malaria control efforts, it is an apposite time to carefully document terminated and ongoing malaria vaccine research projects so that lessons learned can be applied to increase the chances of success for second-generation malaria vaccines over the next 10 years. The most comprehensive resource of malaria vaccine projects is a spreadsheet compiled by WHO thanks to the input from funding agencies, sponsors and investigators worldwide. This spreadsheet, available from WHO's website, is known as "the rainbow table". By summarizing the published and some unpublished information available for each project on the rainbow table, the most comprehensive review of malaria vaccine projects to be published in the last several years is provided below.
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Affiliation(s)
- Lauren Schwartz
- Initiative for Vaccine Research, Department of Immunization, Vaccines & Biologicals, World Health Organization, Avenue Appia 20, 1211-CH 27, Geneva, Switzerland
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192
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Bousema T, Griffin JT, Sauerwein RW, Smith DL, Churcher TS, Takken W, Ghani A, Drakeley C, Gosling R. Hitting hotspots: spatial targeting of malaria for control and elimination. PLoS Med 2012; 9:e1001165. [PMID: 22303287 PMCID: PMC3269430 DOI: 10.1371/journal.pmed.1001165] [Citation(s) in RCA: 400] [Impact Index Per Article: 33.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Teun Bousema and colleagues argue that targeting malaria “hotspots” is a highly efficient way to reduce malaria transmission at all levels of transmission intensity.
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Affiliation(s)
- Teun Bousema
- Department of Immunity and Infection, London School of Hygiene & Tropical Medicine, London, United Kingdom.
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193
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Greenwood B, Salisbury D, Hill AVS. Vaccines and global health. Philos Trans R Soc Lond B Biol Sci 2011; 366:2733-42. [PMID: 21893534 DOI: 10.1098/rstb.2011.0076] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Vaccines have made a major contribution to global health in recent decades but they could do much more. In November 2011, a Royal Society discussion meeting, 'New vaccines for global health', was held in London to discuss the past contribution of vaccines to global health and to consider what more could be expected in the future. Papers presented at the meeting reviewed recent successes in the deployment of vaccines against major infections of childhood and the challenges faced in developing vaccines against some of the world's remaining major infectious diseases such as human immunodeficiency virus (HIV), malaria and tuberculosis. The important contribution that development of more effective veterinary vaccines could make to global health was also addressed. Some of the social and financial challenges to the development and deployment of new vaccines were reviewed. The latter issues were also discussed at a subsequent satellite meeting, 'Accelerating vaccine development', held at the Kavli Royal Society International Centre. Delegates at this meeting considered challenges to the more rapid development and deployment of both human and veterinary vaccines and how these might be addressed. Papers based on presentations at the discussion meeting and a summary of the main conclusions of the satellite meeting are included in this issue of Philosophical Transactions of the Royal Society B.
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Affiliation(s)
- Brian Greenwood
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, UK.
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194
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Abstract
There is no licenced vaccine against any human parasitic disease and Plasmodium falciparum malaria, a major cause of infectious mortality, presents a great challenge to vaccine developers. This has led to the assessment of a wide variety of approaches to malaria vaccine design and development, assisted by the availability of a safe challenge model for small-scale efficacy testing of vaccine candidates. Malaria vaccine development has been at the forefront of assessing many new vaccine technologies including novel adjuvants, vectored prime-boost regimes and the concept of community vaccination to block malaria transmission. Most current vaccine candidates target a single stage of the parasite's life cycle and vaccines against the early pre-erythrocytic stages have shown most success. A protein in adjuvant vaccine, working through antibodies against sporozoites, and viral vector vaccines targeting the intracellular liver-stage parasite with cellular immunity show partial efficacy in humans, and the anti-sporozoite vaccine is currently in phase III trials. However, a more effective malaria vaccine suitable for widespread cost-effective deployment is likely to require a multi-component vaccine targeting more than one life cycle stage. The most attractive near-term approach to develop such a product is to combine existing partially effective pre-erythrocytic vaccine candidates.
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Affiliation(s)
- Adrian V S Hill
- The Jenner Institute, University of Oxford, Old Road Campus Research Building, Oxford OX37DQ, UK.
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195
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Markus MB. Dormancy in mammalian malaria. Trends Parasitol 2011; 28:39-45. [PMID: 22118814 DOI: 10.1016/j.pt.2011.10.005] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2011] [Revised: 10/15/2011] [Accepted: 10/18/2011] [Indexed: 11/26/2022]
Abstract
This analysis principally concerns biological aspects of dormancy in mammalian malaria, with particular reference to the hypnozoite. Research is needed to reveal what happens to sporozoites of Plasmodium cynomolgi between the time of inoculation and when hypnozoites are first seen in the liver 36-40 h later. It is likely that hypnozoites of relapsing malarial parasites will prove to be directly sporozoite-derived rather than merozoite-derived. There is indirect evidence that, contrary to what is generally assumed, activation of hypnozoites might not be the only cause of recurrent Plasmodium vivax malaria. Latent stages pose a threat to success in eradicating malaria; some suggestions are therefore made for demystifying work on hypnozoites and quiescent merozoites.
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Affiliation(s)
- Miles B Markus
- School of Animal, Plant and Environmental Sciences, University of Witwatersrand, Johannesburg, South Africa.
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Abstract
Vaccines are the most powerful public health tools mankind has created, but malaria parasites are bigger, more complicated, and wilier than the viruses and bacteria that have been conquered or controlled with vaccines. Despite decades of research toward a vaccine for malaria, this goal has remained elusive. Nevertheless, recent advances justify optimism that a licensed malaria vaccine is within reach. A subunit recombinant protein vaccine that affords in the neighborhood of 50% protective efficacy against clinical malaria is in the late stages of clinical evaluation in Africa. Incremental improvements on this successful vaccine are possible and worth pursuing, but the best hope for a highly efficacious malaria vaccine that would improve prospects for malaria eradication may lie with the use of attenuated whole parasites and powerful immune-boosting adjuvants.
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Affiliation(s)
- Mahamadou A Thera
- Malaria Research and Training Center, Faculty of Medicine, University of Bamako, Bamako, Mali, West Africa.
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Thera MA, Doumbo OK, Coulibaly D, Laurens MB, Ouattara A, Kone AK, Guindo AB, Traore K, Traore I, Kouriba B, Diallo DA, Diarra I, Daou M, Dolo A, Tolo Y, Sissoko MS, Niangaly A, Sissoko M, Takala-Harrison S, Lyke KE, Wu Y, Blackwelder WC, Godeaux O, Vekemans J, Dubois MC, Ballou WR, Cohen J, Thompson D, Dube T, Soisson L, Diggs CL, House B, Lanar DE, Dutta S, Heppner DG, Plowe CV. A field trial to assess a blood-stage malaria vaccine. N Engl J Med 2011; 365:1004-13. [PMID: 21916638 PMCID: PMC3242358 DOI: 10.1056/nejmoa1008115] [Citation(s) in RCA: 275] [Impact Index Per Article: 21.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
BACKGROUND Blood-stage malaria vaccines are intended to prevent clinical disease. The malaria vaccine FMP2.1/AS02(A), a recombinant protein based on apical membrane antigen 1 (AMA1) from the 3D7 strain of Plasmodium falciparum, has previously been shown to have immunogenicity and acceptable safety in Malian adults and children. METHODS In a double-blind, randomized trial, we immunized 400 Malian children with either the malaria vaccine or a control (rabies) vaccine and followed them for 6 months. The primary end point was clinical malaria, defined as fever and at least 2500 parasites per cubic millimeter of blood. A secondary end point was clinical malaria caused by parasites with the AMA1 DNA sequence found in the vaccine strain. RESULTS The cumulative incidence of the primary end point was 48.4% in the malaria-vaccine group and 54.4% in the control group; efficacy against the primary end point was 17.4% (hazard ratio for the primary end point, 0.83; 95% confidence interval [CI], 0.63 to 1.09; P=0.18). Efficacy against the first and subsequent episodes of clinical malaria, as defined on the basis of various parasite-density thresholds, was approximately 20%. Efficacy against clinical malaria caused by parasites with AMA1 corresponding to that of the vaccine strain was 64.3% (hazard ratio, 0.36; 95% CI, 0.08 to 0.86; P=0.03). Local reactions and fever after vaccination were more frequent with the malaria vaccine. CONCLUSIONS On the basis of the primary end point, the malaria vaccine did not provide significant protection against clinical malaria, but on the basis of secondary results, it may have strain-specific efficacy. If this finding is confirmed, AMA1 might be useful in a multicomponent malaria vaccine. (Funded by the National Institute of Allergy and Infectious Diseases and others; ClinicalTrials.gov number, NCT00460525.).
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Affiliation(s)
- Mahamadou A Thera
- Malaria Research and Training Center, University of Bamako, Bamako, Mali
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Epstein JE, Tewari K, Lyke KE, Sim BKL, Billingsley PF, Laurens MB, Gunasekera A, Chakravarty S, James ER, Sedegah M, Richman A, Velmurugan S, Reyes S, Li M, Tucker K, Ahumada A, Ruben AJ, Li T, Stafford R, Eappen AG, Tamminga C, Bennett JW, Ockenhouse CF, Murphy JR, Komisar J, Thomas N, Loyevsky M, Birkett A, Plowe CV, Loucq C, Edelman R, Richie TL, Seder RA, Hoffman SL. Live Attenuated Malaria Vaccine Designed to Protect Through Hepatic CD8+ T Cell Immunity. Science 2011; 334:475-80. [PMID: 21903775 DOI: 10.1126/science.1211548] [Citation(s) in RCA: 392] [Impact Index Per Article: 30.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Affiliation(s)
- J E Epstein
- U.S. Military Malaria Vaccine Program, Naval Medical Research Center, Silver Spring, MD 20910, USA
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Plasmodium falciparum serine repeat antigen 5 (SE36) as a malaria vaccine candidate. Vaccine 2011; 29:5837-45. [DOI: 10.1016/j.vaccine.2011.06.052] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2011] [Revised: 05/31/2011] [Accepted: 06/14/2011] [Indexed: 12/29/2022]
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