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Thomson-Luque R, Stabler TC, Fürle K, Silva JC, Daubenberger C. Plasmodium falciparum merozoite surface protein 1 as asexual blood stage malaria vaccine candidate. Expert Rev Vaccines 2024; 23:160-173. [PMID: 38100310 DOI: 10.1080/14760584.2023.2295430] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2023] [Accepted: 12/12/2023] [Indexed: 12/17/2023]
Abstract
INTRODUCTION Malaria represents a public health challenge in tropical and subtropical regions, and currently deployed control strategies are likely insufficient to drive elimination of malaria. Development and improvement of malaria vaccines might be key to reduce disease burden. Vaccines targeting asexual blood stages of the parasite have shown limited efficacy when studied in human trials conducted over the past decades. AREAS COVERED Vaccine candidates based on the merozoite surface protein 1 (MSP1) were initially envisioned as one of the most promising approaches to provide immune protection against asexual blood-stage malaria. Successful immunization studies in monkey involved the use of the full-length MSP1 (MSP1FL) as vaccine construct. Vaccines using MSP1FL for immunization have the potential benefit of including numerous conserved B-cell and T-cell epitopes. This could result in improved parasite strain-transcending, protective immunity in the field. We review outcomes of clinical trials that utilized a variety of MSP1 constructs and formulations, including MSP1FL, either alone or in combination with other antigens, in both animal models and humans. EXPERT OPINION Novel approaches to analyze breadth and magnitude of effector functions of MSP1-targeting antibodies in volunteers undergoing experimental vaccination and controlled human malaria infection will help to define correlates of protective immunity.
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Affiliation(s)
- Richard Thomson-Luque
- Centre for Infectious Diseases-Parasitology, Heidelberg University Hospital, Heidelberg, Germany
- Sumaya-Biotech GmbH & Co. KG Heidelberg, Germany
| | - Thomas C Stabler
- Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, MD, USA
- University of Basel Basel, Switzerland
- Swiss Tropical and Public Health Institute Allschwil, Switzerland
| | - Kristin Fürle
- Centre for Infectious Diseases-Parasitology, Heidelberg University Hospital, Heidelberg, Germany
| | - Joana C Silva
- Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, MD, USA
- Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, MD, USA
- Global Health and Tropical Medicine, Instituto de Higiene e Medicina Tropical, Universidade NOVA de Lisboa (GHTM IHMT, UNL), Lisbon, Portugal
| | - Claudia Daubenberger
- University of Basel Basel, Switzerland
- Swiss Tropical and Public Health Institute Allschwil, Switzerland
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Antonelli LR, Junqueira C, Vinetz JM, Golenbock DT, Ferreira MU, Gazzinelli RT. The immunology of Plasmodium vivax malaria. Immunol Rev 2019; 293:163-189. [PMID: 31642531 DOI: 10.1111/imr.12816] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2019] [Accepted: 09/10/2019] [Indexed: 12/13/2022]
Abstract
Plasmodium vivax infection, the predominant cause of malaria in Asia and Latin America, affects ~14 million individuals annually, with considerable adverse effects on wellbeing and socioeconomic development. A clinical hallmark of Plasmodium infection, the paroxysm, is driven by pyrogenic cytokines produced during the immune response. Here, we review studies on the role of specific immune cell types, cognate innate immune receptors, and inflammatory cytokines on parasite control and disease symptoms. This review also summarizes studies on recurrent infections in individuals living in endemic regions as well as asymptomatic infections, a serious barrier to eliminating this disease. We propose potential mechanisms behind these repeated and subclinical infections, such as poor induction of immunological memory cells and inefficient T effector cells. We address the role of antibody-mediated resistance to P. vivax infection and discuss current progress in vaccine development. Finally, we review immunoregulatory mechanisms, such as inhibitory receptors, T regulatory cells, and the anti-inflammatory cytokine, IL-10, that antagonizes both innate and acquired immune responses, interfering with the development of protective immunity and parasite clearance. These studies provide new insights for the clinical management of symptomatic as well as asymptomatic individuals and the development of an efficacious vaccine for vivax malaria.
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Affiliation(s)
- Lis R Antonelli
- Instituto de Pesquisas Rene Rachou, Fundação Oswaldo Cruz, Belo Horizonte, Brazil
| | - Caroline Junqueira
- Instituto de Pesquisas Rene Rachou, Fundação Oswaldo Cruz, Belo Horizonte, Brazil
| | - Joseph M Vinetz
- Section of Infectious Diseases, Department of Internal Medicine, Yale School of Medicine, New Haven, CT, USA
| | - Douglas T Golenbock
- Division of Infectious Disease and immunology, Department of Medicine, University of Massachusetts Medical School, Worcester, MA, USA
| | - Marcelo U Ferreira
- Departamento de Parasitologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, Brazil
| | - Ricardo T Gazzinelli
- Instituto de Pesquisas Rene Rachou, Fundação Oswaldo Cruz, Belo Horizonte, Brazil.,Division of Infectious Disease and immunology, Department of Medicine, University of Massachusetts Medical School, Worcester, MA, USA.,Plataforma de Medicina Translacional, Fundação Oswaldo Cruz, Ribeirão Preto, Brazil
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3
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Punde N, Kooken J, Leary D, Legler PM, Angov E. Codon harmonization reduces amino acid misincorporation in bacterially expressed P. falciparum proteins and improves their immunogenicity. AMB Express 2019; 9:167. [PMID: 31630257 PMCID: PMC6800875 DOI: 10.1186/s13568-019-0890-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2019] [Accepted: 10/01/2019] [Indexed: 11/25/2022] Open
Abstract
Codon usage frequency influences protein structure and function. The frequency with which codons are used potentially impacts primary, secondary and tertiary protein structure. Poor expression, loss of function, insolubility, or truncation can result from species-specific differences in codon usage. “Codon harmonization” more closely aligns native codon usage frequencies with those of the expression host particularly within putative inter-domain segments where slower rates of translation may play a role in protein folding. Heterologous expression of Plasmodium falciparum genes in Escherichia coli has been a challenge due to their AT-rich codon bias and the highly repetitive DNA sequences. Here, codon harmonization was applied to the malarial antigen, CelTOS (Cell-traversal protein for ookinetes and sporozoites). CelTOS is a highly conserved P. falciparum protein involved in cellular traversal through mosquito and vertebrate host cells. It reversibly refolds after thermal denaturation making it a desirable malarial vaccine candidate. Protein expressed in E. coli from a codon harmonized sequence of P. falciparum CelTOS (CH-PfCelTOS) was compared with protein expressed from the native codon sequence (N-PfCelTOS) to assess the impact of codon usage on protein expression levels, solubility, yield, stability, structural integrity, recognition with CelTOS-specific mAbs and immunogenicity in mice. While the translated proteins were expected to be identical, the translated products produced from the codon-harmonized sequence differed in helical content and showed a smaller distribution of polypeptides in mass spectra indicating lower heterogeneity of the codon harmonized version and fewer amino acid misincorporations. Substitutions of hydrophobic-to-hydrophobic amino acid were observed more commonly than any other. CH-PfCelTOS induced significantly higher antibody levels compared with N-PfCelTOS; however, no significant differences in either IFN-γ or IL-4 cellular responses were detected between the two antigens.
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Chen Q, Liang W, Qian F, Qian B, Cao J, Zhang D, Xu Y, Tang L. Rice-produced MSP142ofPlasmodium falciparumelicits antibodies that inhibit parasite growth in vitro. Parasite Immunol 2016; 38:635-41. [DOI: 10.1111/pim.12352] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2016] [Accepted: 08/01/2016] [Indexed: 11/30/2022]
Affiliation(s)
- Q. Chen
- National Institute of Parasitic Diseases; Chinese Center for Disease Control and Prevention; WHO Collaborating Centre for Tropical Diseases; Key Laboratory of Parasite and Vector Biology; Ministry of Health; Shanghai China
| | - W. Liang
- State Key Laboratory of Hybrid Rice; School of Life Sciences and Biotechnology; Shanghai Jiao Tong University; Shanghai China
| | - F. Qian
- Department of Rheumatology and Immunology; Changzheng Hospital; Second Military Medical University; Shanghai China
| | - B. Qian
- State Key Laboratory of Hybrid Rice; School of Life Sciences and Biotechnology; Shanghai Jiao Tong University; Shanghai China
| | - J. Cao
- National Institute of Parasitic Diseases; Chinese Center for Disease Control and Prevention; WHO Collaborating Centre for Tropical Diseases; Key Laboratory of Parasite and Vector Biology; Ministry of Health; Shanghai China
| | - D. Zhang
- State Key Laboratory of Hybrid Rice; School of Life Sciences and Biotechnology; Shanghai Jiao Tong University; Shanghai China
| | - Y. Xu
- National Institute of Parasitic Diseases; Chinese Center for Disease Control and Prevention; WHO Collaborating Centre for Tropical Diseases; Key Laboratory of Parasite and Vector Biology; Ministry of Health; Shanghai China
| | - L. Tang
- National Institute of Parasitic Diseases; Chinese Center for Disease Control and Prevention; WHO Collaborating Centre for Tropical Diseases; Key Laboratory of Parasite and Vector Biology; Ministry of Health; Shanghai China
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5
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Plasmodium falciparum infection and age influence parasite growth inhibition mediated by IgG in Beninese infants. Acta Trop 2016; 159:111-9. [PMID: 27001144 DOI: 10.1016/j.actatropica.2016.03.020] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2015] [Revised: 02/10/2016] [Accepted: 03/17/2016] [Indexed: 11/22/2022]
Abstract
Antibodies that impede the invasion of Plasmodium falciparum (P. falciparum) merozoites into erythrocytes play a critical role in anti-malarial immunity. The Growth Inhibition Assay (GIA) is an in vitro measure of the functional capacity of such antibodies to limit erythrocyte invasion and/or parasite growth. Up to now, it is unclear whether growth-inhibitory activity correlates with protection from clinical disease and there are inconsistent results from studies performed with GIA. Studies that have focused on the relationship between IgGs and their in vitro parasite Growth Inhibition Activity (GIAc) in infants aged less than two years old are rare. Here, we used clinical and parasitological data to precisely define symptomatic or asymptomatic infection with P. falciparum in groups of infants followed-up actively for 18 months post-natally. We quantified the levels of IgG1 and IgG3 directed to a panel of candidate P. falciparum vaccine antigens (AMA-1, MSP1, 2, 3 and GLURP) using ELISA and the functional activity of IgG was quantified using GIA. Data were then correlated with individuals' infection status. At 18 months of age, infants harbouring infections at the time of blood sampling had an average 19% less GIAc than those not infected (p=0.004, multivariate linear regression). GIAc decreased from 12 to 18 months of age (p=0.003, Wilcoxon matched pairs test). Antibody levels quantified at 18 months in infants were strongly correlated with their exposure to malarial infection, however GIAc was not correlated with malaria infectious status (asymptomatic and symptomatic groups). In conclusion, both infection status at blood draw and age influence parasite growth inhibition mediated by IgG in the GIA. Both factors must be taken into account when correlations between GIAc and anti-malarial protection or vaccine efficacy have to be made.
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Biryukov S, Angov E, Landmesser ME, Spring MD, Ockenhouse CF, Stoute JA. Complement and Antibody-mediated Enhancement of Red Blood Cell Invasion and Growth of Malaria Parasites. EBioMedicine 2016; 9:207-216. [PMID: 27333049 PMCID: PMC4972486 DOI: 10.1016/j.ebiom.2016.05.015] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2016] [Revised: 05/03/2016] [Accepted: 05/12/2016] [Indexed: 11/02/2022] Open
Abstract
Plasmodium falciparum malaria is a deadly pathogen. The invasion of red blood cells (RBCs) by merozoites is a target for vaccine development. Although anti-merozoite antibodies can block invasion in vitro, there is no efficacy in vivo. To explain this discrepancy we hypothesized that complement activation could enhance RBC invasion by binding to the complement receptor 1 (CR1). Here we show that a monoclonal antibody directed against the merozoite and human polyclonal IgG from merozoite vaccine recipients enhanced RBC invasion in a complement-dependent manner and that soluble CR1 inhibited this enhancement. Sialic acid-independent strains, that presumably are able to bind to CR1 via a native ligand, showed less complement-dependent enhancement of RBC invasion than sialic acid-dependent strains that do not utilize native CR1 ligands. Confocal fluorescent microscopy revealed that complement-dependent invasion resulted in aggregation of CR1 at the RBC surface in contact with the merozoite. Finally, total anti-P. berghei IgG enhanced parasite growth and C3 deficiency decreased parasite growth in mice. These results demonstrate, contrary to current views, that complement activation in conjunction with antibodies can paradoxically aid parasites invade RBCs and should be considered in future design and testing of merozoite vaccines.
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Affiliation(s)
- Sergei Biryukov
- Department of Microbiology and Immunology, Pennsylvania State University, College of Medicine, 500 University Drive, Hershey, PA 17033, United States
| | - Evelina Angov
- Walter Reed Army Institute of Research, Division of Malaria Vaccine Development, Silver Spring, MD 20910, United States
| | - Mary E Landmesser
- Department of Microbiology and Immunology, Pennsylvania State University, College of Medicine, 500 University Drive, Hershey, PA 17033, United States; Department of Medicine, Division of Infectious Diseases and Epidemiology, Pennsylvania State University, College of Medicine, 500 University Drive, Hershey, PA 17033, United States
| | - Michele D Spring
- Walter Reed Army Institute of Research, Division of Malaria Vaccine Development, Silver Spring, MD 20910, United States
| | | | - José A Stoute
- Department of Microbiology and Immunology, Pennsylvania State University, College of Medicine, 500 University Drive, Hershey, PA 17033, United States; Department of Medicine, Division of Infectious Diseases and Epidemiology, Pennsylvania State University, College of Medicine, 500 University Drive, Hershey, PA 17033, United States.
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Abstract
There have been significant decreases in malaria mortality and morbidity in the last 10-15 years, and the most advanced pre-erythrocytic malaria vaccine, RTS,S, received a positive opinion from European regulators in July 2015. However, no blood-stage vaccine has reached a phase III trial. The first part of this review summarizes the pros and cons of various assays and models that have been and will be used to predict the efficacy of blood-stage vaccines. In the second part, blood-stage vaccine candidates that showed some efficacy in human clinical trials or controlled human malaria infection models are discussed. Then, candidates under clinical investigation are described in the third part, and other novel candidates and strategies are reviewed in the last part.
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Affiliation(s)
- Kazutoyo Miura
- a Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases , National Institutes of Health , Rockville , MD , USA
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8
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Contrasting Patterns of Serologic and Functional Antibody Dynamics to Plasmodium falciparum Antigens in a Kenyan Birth Cohort. CLINICAL AND VACCINE IMMUNOLOGY : CVI 2015; 23:104-16. [PMID: 26656119 PMCID: PMC4744923 DOI: 10.1128/cvi.00452-15] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Accepted: 11/20/2015] [Indexed: 11/20/2022]
Abstract
IgG antibodies to Plasmodium falciparum are transferred from the maternal to fetal circulation during pregnancy, wane after birth, and are subsequently acquired in response to natural infection. We examined the dynamics of malaria antibody responses of 84 Kenyan infants from birth to 36 months of age by (i) serology, (ii) variant surface antigen (VSA) assay, (iii) growth inhibitory activity (GIA), and (iv) invasion inhibition assays (IIA) specific for merozoite surface protein 1 (MSP1) and sialic acid-dependent invasion pathway. Maternal antibodies in each of these four categories were detected in cord blood and decreased to their lowest level by approximately 6 months of age. Serologic antibodies to 3 preerythrocytic and 10 blood-stage antigens subsequently increased, reaching peak prevalence by 36 months. In contrast, antibodies measured by VSA, GIA, and IIA remained low even up to 36 months. Infants sensitized to P. falciparum in utero, defined by cord blood lymphocyte recall responses to malaria antigens, acquired antimalarial antibodies at the same rate as those who were not sensitized in utero, indicating that fetal exposure to malaria antigens did not affect subsequent infant antimalarial responses. Infants with detectable serologic antibodies at 12 months of age had an increased risk of P. falciparum infection during the subsequent 24 months. We conclude that serologic measures of antimalarial antibodies in children 36 months of age or younger represent biomarkers of malaria exposure rather than protection and that functional antibodies develop after 36 months of age in this population.
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Khan F, Porter M, Schwenk R, DeBot M, Saudan P, Dutta S. Head-to-Head Comparison of Soluble vs. Qβ VLP Circumsporozoite Protein Vaccines Reveals Selective Enhancement of NANP Repeat Responses. PLoS One 2015; 10:e0142035. [PMID: 26571021 PMCID: PMC4646581 DOI: 10.1371/journal.pone.0142035] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2015] [Accepted: 10/17/2015] [Indexed: 11/23/2022] Open
Abstract
Circumsporozoite protein (CSP) of Plasmodium falciparum is a promising malaria vaccine target. RTS,S, the most advanced malaria vaccine candidate consists of the central NANP repeat and carboxy-terminal region of CSP displayed on a hepatitis B virus-like particle (VLP). To build upon the success of RTS,S, we produced a near full-length Plasmodium falciparum CSP that also includes the conserved amino-terminal region of CSP. We recently showed that this soluble CSP, combined with a synthetic Toll-like-receptor-4 (TLR4) agonist in stable oil-in-water emulsion (GLA/SE), induces a potent and protective immune response in mice against transgenic parasite challenge. Here we have investigated whether the immunogenicity of soluble CSP could be further augmented by presentation on a VLP. Bacteriophage Qβ VLPs can be readily produced in E.coli, they have a diameter of 25 nm and contain packaged E. coli RNA which serves as a built in adjuvant through the activation of TLR7/8. CSP was chemically conjugated to Qβ and the CSP-Qβ vaccine immunogenicity and efficacy were compared to adjuvanted soluble CSP in the C57Bl/6 mouse model. When formulated with adjuvants lacking a TLR4 agonist (Alum, SE and Montanide) the Qβ-CSP induced higher anti-NANP repeat titers, higher levels of cytophilic IgG2b/c antibodies and a trend towards higher protection against transgenic parasite challenge as compared to soluble CSP formulated in the same adjuvant. The VLP and soluble CSP immunogenicity difference was most pronounced at low antigen dose, and within the CSP molecule, the titers against the NANP repeats were preferentially enhanced by Qβ presentation. While a TLR4 agonist enhanced the immunogenicity of soluble CSP to levels comparable to the VLP vaccine, the TLR4 agonist did not further improve the immunogenicity of the Qβ-CSP vaccine. The data presented here pave the way for further improvement in the Qβ conjugation chemistry and evaluation of both the Qβ-CSP and soluble CSP vaccines in the non-human primate model.
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Affiliation(s)
- Farhat Khan
- Structural Vaccinology Laboratory, Malaria Vaccine Branch, Walter Reed Army Institute of Research, Silver Spring, MD 20910, United States of America
| | - Mike Porter
- Structural Vaccinology Laboratory, Malaria Vaccine Branch, Walter Reed Army Institute of Research, Silver Spring, MD 20910, United States of America
| | - Robert Schwenk
- Structural Vaccinology Laboratory, Malaria Vaccine Branch, Walter Reed Army Institute of Research, Silver Spring, MD 20910, United States of America
| | - Margot DeBot
- Structural Vaccinology Laboratory, Malaria Vaccine Branch, Walter Reed Army Institute of Research, Silver Spring, MD 20910, United States of America
| | - Philippe Saudan
- Cytos Biotechnology, Wagistrasse 25, 8952 Schlieren, Switzerland
| | - Sheetij Dutta
- Structural Vaccinology Laboratory, Malaria Vaccine Branch, Walter Reed Army Institute of Research, Silver Spring, MD 20910, United States of America
- * E-mail:
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Douglas AD, Baldeviano GC, Lucas CM, Lugo-Roman LA, Crosnier C, Bartholdson SJ, Diouf A, Miura K, Lambert LE, Ventocilla JA, Leiva KP, Milne KH, Illingworth JJ, Spencer AJ, Hjerrild KA, Alanine DGW, Turner AV, Moorhead JT, Edgel KA, Wu Y, Long CA, Wright GJ, Lescano AG, Draper SJ. A PfRH5-based vaccine is efficacious against heterologous strain blood-stage Plasmodium falciparum infection in aotus monkeys. Cell Host Microbe 2015; 17:130-9. [PMID: 25590760 PMCID: PMC4297294 DOI: 10.1016/j.chom.2014.11.017] [Citation(s) in RCA: 145] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2014] [Revised: 09/11/2014] [Accepted: 11/13/2014] [Indexed: 12/22/2022]
Abstract
Antigenic diversity has posed a critical barrier to vaccine development against the pathogenic blood-stage infection of the human malaria parasite Plasmodium falciparum. To date, only strain-specific protection has been reported by trials of such vaccines in nonhuman primates. We recently showed that P. falciparum reticulocyte binding protein homolog 5 (PfRH5), a merozoite adhesin required for erythrocyte invasion, is highly susceptible to vaccine-inducible strain-transcending parasite-neutralizing antibody. In vivo efficacy of PfRH5-based vaccines has not previously been evaluated. Here, we demonstrate that PfRH5-based vaccines can protect Aotus monkeys against a virulent vaccine-heterologous P. falciparum challenge and show that such protection can be achieved by a human-compatible vaccine formulation. Protection was associated with anti-PfRH5 antibody concentration and in vitro parasite-neutralizing activity, supporting the use of this in vitro assay to predict the in vivo efficacy of future vaccine candidates. These data suggest that PfRH5-based vaccines have potential to achieve strain-transcending efficacy in humans. Vaccines based on the P. falciparum merozoite antigen PfRH5 were tested in Aotus monkeys PfRH5-based vaccines afforded protection against heterologous strains of P. falciparum Protection correlated with anti-PfRH5 IgG concentration and in vivo neutralization
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Affiliation(s)
| | | | - Carmen M Lucas
- US Naval Medical Research Unit No. 6 (NAMRU-6), Lima, Peru
| | | | | | | | - Ababacar Diouf
- Laboratory of Malaria and Vector Research, NIAID/NIH, Rockville, MD 20852, USA
| | - Kazutoyo Miura
- Laboratory of Malaria and Vector Research, NIAID/NIH, Rockville, MD 20852, USA
| | - Lynn E Lambert
- Laboratory of Malaria Immunology and Vaccinology, NIAID/NIH, Rockville, MD 20852, USA
| | | | - Karina P Leiva
- US Naval Medical Research Unit No. 6 (NAMRU-6), Lima, Peru
| | | | | | | | | | | | | | | | | | - Yimin Wu
- Laboratory of Malaria Immunology and Vaccinology, NIAID/NIH, Rockville, MD 20852, USA
| | - Carole A Long
- Laboratory of Malaria and Vector Research, NIAID/NIH, Rockville, MD 20852, USA
| | | | | | - Simon J Draper
- Jenner Institute, University of Oxford, Oxford OX3 7DQ, UK
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Schwenk R, DeBot M, Porter M, Nikki J, Rein L, Spaccapelo R, Crisanti A, Wightman PD, Ockenhouse CF, Dutta S. IgG2 antibodies against a clinical grade Plasmodium falciparum CSP vaccine antigen associate with protection against transgenic sporozoite challenge in mice. PLoS One 2014; 9:e111020. [PMID: 25343487 PMCID: PMC4208815 DOI: 10.1371/journal.pone.0111020] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2014] [Accepted: 09/19/2014] [Indexed: 12/26/2022] Open
Abstract
The availability of a highly purified and well characterized circumsporozoite protein (CSP) is essential to improve upon the partial success of recombinant CSP-based malaria vaccine candidates. Soluble, near full-length, Plasmodium falciparum CSP vaccine antigen (CS/D) was produced in E. coli under bio-production conditions that comply with current Good Manufacturing Practices (cGMP). A mouse immunogenicity study was conducted using a stable oil-in-water emulsion (SE) of CS/D in combination with the Toll-Like Receptor 4 (TLR4) agonist Glucopyranosyl Lipid A (GLA/SE), or one of two TLR7/8 agonists: R848 (un-conjugated) or 3M-051 (covalently conjugated). Compared to Alum and SE, GLA/SE induced higher CS/D specific antibody response in Balb/c mice. Subclass analysis showed higher IgG2:IgG1 ratio of GLA/SE induced antibodies as compared to Alum and SE. TLR synergy was not observed when soluble R848 was mixed with GLA/SE. Antibody response of 3M051 formulations in Balb/c was similar to GLA/SE, except for the higher IgG2:IgG1 ratio and a trend towards higher T cell responses in 3M051 containing groups. However, no synergistic enhancement of antibody and T cell response was evident when 3M051 conjugate was mixed with GLA/SE. In C57Bl/6 mice, CS/D adjuvanted with 3M051/SE or GLA/SE induced higher CSP repeat specific titers compared to SE. While, 3M051 induced antibodies had high IgG2c:IgG1 ratio, GLA/SE promoted high levels of both IgG1 and IgG2c. GLA/SE also induced more potent T-cell responses compared to SE in two independent C57/BL6 vaccination studies, suggesting a balanced and productive TH1/TH2 response. GLA and 3M-051 similarly enhanced the protective efficacy of CS/D against challenge with a transgenic P. berghei parasite and most importantly, high levels of cytophilic IgG2 antibodies were associated with protection in this model. Our data indicated that the cGMP-grade, soluble CS/D antigen combined with the TLR4-containing adjuvant GLA/SE warrants further evaluation for protective responses in humans.
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Affiliation(s)
- Robert Schwenk
- Malaria Vaccine Branch, Walter Reed Army Institute of Research, Silver Spring, MD, United States of America
| | - Margot DeBot
- Malaria Vaccine Branch, Walter Reed Army Institute of Research, Silver Spring, MD, United States of America
| | - Michael Porter
- Malaria Vaccine Branch, Walter Reed Army Institute of Research, Silver Spring, MD, United States of America
| | - Jennifer Nikki
- Malaria Vaccine Branch, Walter Reed Army Institute of Research, Silver Spring, MD, United States of America
| | - Lisa Rein
- Malaria Vaccine Branch, Walter Reed Army Institute of Research, Silver Spring, MD, United States of America
| | - Roberta Spaccapelo
- Department of Experimental Medicine, University of Perugia, Perugia, Italy
| | | | - Paul D. Wightman
- 3M Drug Delivery Systems, St. Paul, MN, United States of America
| | - Christian F. Ockenhouse
- Malaria Vaccine Branch, Walter Reed Army Institute of Research, Silver Spring, MD, United States of America
| | - Sheetij Dutta
- Malaria Vaccine Branch, Walter Reed Army Institute of Research, Silver Spring, MD, United States of America
- * E-mail:
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12
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Sheikh IH, Kaushal DC, Singh V, Kumar N, Chandra D, Kaushal NA. Cloning, overexpression and characterization of soluble 42kDa fragment of merozoite surface protein-1 of Plasmodium vivax. Protein Expr Purif 2014; 103:64-74. [PMID: 25195175 DOI: 10.1016/j.pep.2014.08.015] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2014] [Revised: 08/19/2014] [Accepted: 08/25/2014] [Indexed: 11/24/2022]
Abstract
Plasmodium vivax represents the second most prevalent malaria species of major public health importance and the global eradication of malaria requires the development of vaccines to prevent infection. The lack of in vitro culture and a suitable animal model for P. vivax malaria are the major problems for the delay in developing a functional vivax vaccine. A number of antigens have been identified for P. vivax as potential malaria vaccine candidates and among these 42kDa fragment of merozoite surface protein-1 (MSP-142) is one of most promising antigen of asexual blood stage. In most of the earlier studies, the MSP-142 of malaria parasites was expressed as insoluble protein in inclusion bodies and it is difficult to get purified protein in conformation form. In the present study, we have cloned, overexpressed and characterized the 42kDa fragment of P. vivax MSP-1 as soluble protein in Escherichiacoli. The 42kDa gene fragment of P. vivax MSP-1 was PCR amplified using specific primers, sequenced and subcloned into pTriEx-4 expression vector. The optimum expression of recombinant P. vivax protein was obtained in SOC growth medium by inducing with 0.2mM IPTG at 37°C for 4h. The SDS-PAGE analysis showed a fusion protein of 55kDa and about 80% was present in soluble form. The purified P. vivax MSP-142 was characterized and found to be correctly folded and in conformation form as evident by CD spectroscopy, presence of 1 free -SH group and the reactivity with reduction sensitive conformational monoclonals against P. vivax MSP-142.
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Affiliation(s)
- Inayat Hussain Sheikh
- Division of Parasitology, CSIR-Central Drug Research Institute, Lucknow 226031, India; Department of Biochemistry, Lucknow University, Lucknow, India
| | - Deep C Kaushal
- Amity University Uttar Pradesh, Lucknow Campus, Lucknow 226010, India
| | - Vandana Singh
- Division of Parasitology, CSIR-Central Drug Research Institute, Lucknow 226031, India
| | - Niraj Kumar
- Division of Parasitology, CSIR-Central Drug Research Institute, Lucknow 226031, India
| | - Deepak Chandra
- Department of Biochemistry, Lucknow University, Lucknow, India
| | - Nuzhat A Kaushal
- Division of Parasitology, CSIR-Central Drug Research Institute, Lucknow 226031, India.
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Barry AE, Arnott A. Strategies for designing and monitoring malaria vaccines targeting diverse antigens. Front Immunol 2014; 5:359. [PMID: 25120545 PMCID: PMC4112938 DOI: 10.3389/fimmu.2014.00359] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2014] [Accepted: 07/13/2014] [Indexed: 01/28/2023] Open
Abstract
After more than 50 years of intensive research and development, only one malaria vaccine candidate, “RTS,S,” has progressed to Phase 3 clinical trials. Despite only partial efficacy, this candidate is now forecast to become the first licensed malaria vaccine. Hence, more efficacious second-generation malaria vaccines that can significantly reduce transmission are urgently needed. This review will focus on a major obstacle hindering development of effective malaria vaccines: parasite antigenic diversity. Despite extensive genetic diversity in leading candidate antigens, vaccines have been and continue to be formulated using recombinant antigens representing only one or two strains. These vaccine strains represent only a small fraction of the diversity circulating in natural parasite populations, leading to escape of non-vaccine strains and challenging investigators’ abilities to measure strain-specific efficacy in vaccine trials. Novel strategies are needed to overcome antigenic diversity in order for vaccine development to succeed. Many studies have now cataloged the global diversity of leading Plasmodium falciparum and Plasmodium vivax vaccine antigens. In this review, we describe how population genetic approaches can be applied to this rich data source to predict the alleles that best represent antigenic diversity, polymorphisms that contribute to it, and to identify key polymorphisms associated with antigenic escape. We also suggest an approach to summarize the known global diversity of a given antigen to predict antigenic diversity, how to select variants that best represent the strains circulating in natural parasite populations and how to investigate the strain-specific efficacy of vaccine trials. Use of these strategies in the design and monitoring of vaccine trials will not only shed light on the contribution of genetic diversity to the antigenic diversity of malaria, but will also maximize the potential of future malaria vaccine candidates.
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Affiliation(s)
- Alyssa E Barry
- Division of Infection and Immunity, Walter and Eliza Hall Institute of Medical Research , Parkville, VIC , Australia ; Department of Medical Biology, The University of Melbourne , Parkville, VIC , Australia
| | - Alicia Arnott
- Division of Infection and Immunity, Walter and Eliza Hall Institute of Medical Research , Parkville, VIC , Australia ; Department of Medical Biology, The University of Melbourne , Parkville, VIC , Australia
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Elias SC, Choudhary P, de Cassan SC, Biswas S, Collins KA, Halstead FD, Bliss CM, Ewer KJ, Hodgson SH, Duncan CJA, Hill AVS, Draper SJ. Analysis of human B-cell responses following ChAd63-MVA MSP1 and AMA1 immunization and controlled malaria infection. Immunology 2014; 141:628-44. [PMID: 24303947 PMCID: PMC3956436 DOI: 10.1111/imm.12226] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2013] [Revised: 11/25/2013] [Accepted: 11/26/2013] [Indexed: 02/07/2023] Open
Abstract
Acquisition of non-sterilizing natural immunity to Plasmodium falciparum malaria has been shown in low transmission areas following multiple exposures. However, conflicting data from endemic areas suggest that the parasite may interfere with the induction of effective B-cell responses. To date, the impact of blood-stage parasite exposure on antigen-specific B cells has not been reported following controlled human malaria infection (CHMI). Here we analysed human B-cell responses in a series of Phase I/IIa clinical trials, which include CHMI, using candidate virus-vectored vaccines encoding two blood-stage antigens: merozoite surface protein 1 (MSP1) and apical membrane antigen 1 (AMA1). Previously vaccinated volunteers show boosting of pre-existing antigen-specific memory B-cell (mBC) responses following CHMI. In contrast, unvaccinated malaria-naive control volunteers developed an mBC response against MSP1 but not AMA1. Serum IgG correlated with the mBC response after booster vaccination but this relationship was less well maintained following CHMI. A significant reduction in peripheral MSP1-specific mBC was observed at the point of diagnosis of blood-stage infection. This was coincident with a reduction in peripheral blood B-cell subsets expressing CXCR3 and elevated serum levels of interferon-γ and CXCL9, suggesting migration away from the periphery. These CHMI data confirm that mBC and antibody responses can be induced and boosted by blood-stage parasite exposure, in support of epidemiological studies on low-level parasite exposure.
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Affiliation(s)
- Sean C Elias
- The Jenner Institute, University of Oxford, Oxford, UK
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Successful vaccines for naturally occurring protozoal diseases of animals should guide human vaccine research. A review of protozoal vaccines and their designs. Parasitology 2014; 141:624-40. [PMID: 24476952 PMCID: PMC3961066 DOI: 10.1017/s0031182013002060] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Effective vaccines are available for many protozoal diseases of animals, including vaccines for zoonotic pathogens and for several species of vector-transmitted apicomplexan haemoparasites. In comparison with human diseases, vaccine development for animals has practical advantages such as the ability to perform experiments in the natural host, the option to manufacture some vaccines in vivo, and lower safety requirements. Although it is proper for human vaccines to be held to higher standards, the enduring lack of vaccines for human protozoal diseases is difficult to reconcile with the comparatively immense amount of research funding. Common tactical problems of human protozoal vaccine research include reliance upon adapted rather than natural animal disease models, and an overwhelming emphasis on novel approaches that are usually attempted in replacement of rather than for improvement upon the types of designs used in effective veterinary vaccines. Currently, all effective protozoal vaccines for animals are predicated upon the ability to grow protozoal organisms. Because human protozoal vaccines need to be as effective as animal vaccines, researchers should benefit from a comparison of existing veterinary products and leading experimental vaccine designs. With this in mind, protozoal vaccines are here reviewed.
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Cheong FW, Fong MY, Lau YL, Mahmud R. Immunogenicity of bacterial-expressed recombinant Plasmodium knowlesi merozoite surface protein-142 (MSP-142). Malar J 2013; 12:454. [PMID: 24354660 PMCID: PMC3878241 DOI: 10.1186/1475-2875-12-454] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2013] [Accepted: 12/17/2013] [Indexed: 11/10/2022] Open
Abstract
Background Plasmodium knowlesi is the fifth Plasmodium species that can infect humans. The Plasmodium merozoite surface protein-142 (MSP-142) is a potential candidate for malaria vaccine. However, limited studies have focused on P. knowlesi MSP-142. Methods A ~42 kDa recombinant P. knowlesi MSP-142 (pkMSP-142) was expressed using an Escherichia coli system. The purified pkMSP-142 was evaluated with malaria and non-malaria human patient sera (n = 189) using Western blots and ELISA. The immunogenicity of pkMSP-142 was evaluated in mouse model. Results The purified pkMSP-142 had a sensitivity of 91.0% for detection of human malaria in both assays. Specificity was 97.5 and 92.6% in Western blots and ELISA, respectively. Levels of cytokine interferon-gamma, interleukin-2, interleukin-4, and interleukin-10 significantly increased in pkMSP-142-immunized mice as compared to the negative control mice. pkMSP-142-raised antibody had high endpoint titres, and the IgG isotype distribution was IgG1 > IgG2b > IgG3 > IgG2a. Conclusions pkMSP-142 was highly immunogenic and able to detect human malaria. Hence, pkMSP-142 would be a useful candidate for malaria vaccine development and seroprevalence studies.
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Affiliation(s)
| | - Mun Yik Fong
- Department of Parasitology, Faculty of Medicine, University of Malaya, 50603, Kuala Lumpur, Malaysia.
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Saraswat M, Musante L, Ravidá A, Shortt B, Byrne B, Holthofer H. Preparative purification of recombinant proteins: current status and future trends. BIOMED RESEARCH INTERNATIONAL 2013; 2013:312709. [PMID: 24455685 PMCID: PMC3877584 DOI: 10.1155/2013/312709] [Citation(s) in RCA: 93] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/23/2013] [Accepted: 11/17/2013] [Indexed: 12/18/2022]
Abstract
Advances in fermentation technologies have resulted in the production of increased yields of proteins of economic, biopharmaceutical, and medicinal importance. Consequently, there is an absolute requirement for the development of rapid, cost-effective methodologies which facilitate the purification of such products in the absence of contaminants, such as superfluous proteins and endotoxins. Here, we provide a comprehensive overview of a selection of key purification methodologies currently being applied in both academic and industrial settings and discuss how innovative and effective protocols such as aqueous two-phase partitioning, membrane chromatography, and high-performance tangential flow filtration may be applied independently of or in conjunction with more traditional protocols for downstream processing applications.
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Affiliation(s)
- Mayank Saraswat
- Centre for Bioanalytical Sciences (CBAS), Dublin City University (DCU), Dublin 9, Ireland
| | - Luca Musante
- Centre for Bioanalytical Sciences (CBAS), Dublin City University (DCU), Dublin 9, Ireland
| | - Alessandra Ravidá
- Centre for Bioanalytical Sciences (CBAS), Dublin City University (DCU), Dublin 9, Ireland
| | - Brian Shortt
- Centre for Bioanalytical Sciences (CBAS), Dublin City University (DCU), Dublin 9, Ireland
| | - Barry Byrne
- Centre for Bioanalytical Sciences (CBAS), Dublin City University (DCU), Dublin 9, Ireland
| | - Harry Holthofer
- Centre for Bioanalytical Sciences (CBAS), Dublin City University (DCU), Dublin 9, Ireland
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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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Wilson PT, Malhotra I, Mungai P, King CL, Dent AE. Transplacentally transferred functional antibodies against Plasmodium falciparum decrease with age. Acta Trop 2013; 128:149-53. [PMID: 23911334 DOI: 10.1016/j.actatropica.2013.07.018] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2013] [Revised: 07/17/2013] [Accepted: 07/21/2013] [Indexed: 11/16/2022]
Abstract
Transplacental transfer of antibodies from clinically malaria immune pregnant women to their fetuses is thought to provide passive protection against malaria during infancy. However, the presences and duration of functional antibodies against Plasmodium falciparum (Pf) in newborns has not been described. We used growth inhibition assays (GIA) to measure total anti-malaria functional antibodies present at birth and over the following year. Samples were drawn from cord blood (n=86) and in infants at six and 12 months of life (n=86 and 65 respectively). Three laboratory Pf strains (D10, W2mef, 3D7) and a field isolate (Msambweni 2006) were used in the assays. Median (ranges) GIA levels for cord plasma differed between laboratory parasite strains: D10, 0% (0-81); W2mef, 6% (0-80); 3D7, 18% (0-88); Msambweni 2006, 6% (0-43) (P<0.001, Wilcoxon signed-rank test). GIA levels against all Pf strains were found to decline in infants from birth to six months (P<0.01, Wilcoxon, signed-rank test). Functional antibodies as measured by GIA are transferred to the fetus and wane in the infants over time. Infant protection from clinical malaria disease may in part be mediated by these functional anti-malaria antibodies.
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Affiliation(s)
- Patrick T Wilson
- Center for Global Health and Diseases, Case Western Reserve University, Cleveland, OH, USA.
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20
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Kwon KC, Verma D, Singh ND, Herzog R, Daniell H. Oral delivery of human biopharmaceuticals, autoantigens and vaccine antigens bioencapsulated in plant cells. Adv Drug Deliv Rev 2013; 65:782-99. [PMID: 23099275 PMCID: PMC3582797 DOI: 10.1016/j.addr.2012.10.005] [Citation(s) in RCA: 94] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2012] [Revised: 09/26/2012] [Accepted: 10/17/2012] [Indexed: 12/19/2022]
Abstract
Among 12billion injections administered annually, unsafe delivery leads to >20million infections and >100million reactions. In an emerging new concept, freeze-dried plant cells (lettuce) expressing vaccine antigens/biopharmaceuticals are protected in the stomach from acids/enzymes but are released to the immune or blood circulatory system when plant cell walls are digested by microbes that colonize the gut. Vaccine antigens bioencapsulated in plant cells upon oral delivery after priming, conferred both mucosal and systemic immunity and protection against bacterial, viral or protozoan pathogens or toxin challenge. Oral delivery of autoantigens was effective against complications of type 1 diabetes and hemophilia, by developing tolerance. Oral delivery of proinsulin or exendin-4 expressed in plant cells regulated blood glucose levels similar to injections. Therefore, this new platform offers a low cost alternative to deliver different therapeutic proteins to combat infectious or inherited diseases by eliminating inactivated pathogens, expensive purification, cold storage/transportation and sterile injections.
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Affiliation(s)
- Kwang-Chul Kwon
- Department of Molecular Biology and Microbiology, College of Medicine, University of Central Florida, Biomolecular Science Building, Orlando, FL 32816-2364, USA
| | - Dheeraj Verma
- Department of Molecular Biology and Microbiology, College of Medicine, University of Central Florida, Biomolecular Science Building, Orlando, FL 32816-2364, USA
| | - Nameirakpam D. Singh
- Department of Molecular Biology and Microbiology, College of Medicine, University of Central Florida, Biomolecular Science Building, Orlando, FL 32816-2364, USA
| | - Roland Herzog
- Department of Pediatrics, College of Medicine, University of Florida, Cancer and Genetics Research Complex, 2033 Mowry Road, Gainesville, FL 32610, USA
| | - Henry Daniell
- Department of Molecular Biology and Microbiology, College of Medicine, University of Central Florida, Biomolecular Science Building, Orlando, FL 32816-2364, USA
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Elias SC, Collins KA, Halstead FD, Choudhary P, Bliss CM, Ewer KJ, Sheehy SH, Duncan CJA, Biswas S, Hill AVS, Draper SJ. Assessment of immune interference, antagonism, and diversion following human immunization with biallelic blood-stage malaria viral-vectored vaccines and controlled malaria infection. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2013; 190:1135-47. [PMID: 23293353 PMCID: PMC3672846 DOI: 10.4049/jimmunol.1201455] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Overcoming antigenic variation is one of the major challenges in the development of an effective vaccine against Plasmodium falciparum, a causative agent of human malaria. Inclusion of multiple Ag variants in subunit vaccine candidates is one strategy that has aimed to overcome this problem for the leading blood-stage malaria vaccine targets, that is, merozoite surface protein 1 (MSP1) and apical membrane Ag 1 (AMA1). However, previous studies, utilizing malaria Ags, have concluded that inclusion of multiple allelic variants, encoding altered peptide ligands, in such a vaccine may be detrimental to both the priming and in vivo restimulation of Ag-experienced T cells. In this study, we analyze the T cell responses to two alleles of MSP1 and AMA1 induced by vaccination of malaria-naive adult volunteers with bivalent viral-vectored vaccine candidates. We show a significant bias to the 3D7/MAD20 allele compared with the Wellcome allele for the 33 kDa region of MSP1, but not for the 19 kDa fragment or the AMA1 Ag. Although this bias could be caused by "immune interference" at priming, the data do not support a significant role for "immune antagonism" during memory T cell restimulation, despite observation of the latter at a minimal epitope level in vitro. A lack of class I HLA epitopes in the Wellcome allele that are recognized by vaccinated volunteers may in fact contribute to the observed bias. We also show that controlled infection with 3D7 strain P. falciparum parasites neither boosts existing 3D7-specific T cell responses nor appears to "immune divert" cellular responses toward the Wellcome allele.
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Affiliation(s)
- Sean C Elias
- The Jenner Institute, University of Oxford, Oxford OX3 7DQ, United Kingdom.
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Otsyula N, Angov E, Bergmann-Leitner E, Koech M, Khan F, Bennett J, Otieno L, Cummings J, Andagalu B, Tosh D, Waitumbi J, Richie N, Shi M, Miller L, Otieno W, Otieno GA, Ware L, House B, Godeaux O, Dubois MC, Ogutu B, Ballou WR, Soisson L, Diggs C, Cohen J, Polhemus M, Heppner DG, Ockenhouse CF, Spring MD. Results from tandem Phase 1 studies evaluating the safety, reactogenicity and immunogenicity of the vaccine candidate antigen Plasmodium falciparum FVO merozoite surface protein-1 (MSP1(42)) administered intramuscularly with adjuvant system AS01. Malar J 2013; 12:29. [PMID: 23342996 PMCID: PMC3582548 DOI: 10.1186/1475-2875-12-29] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2012] [Accepted: 01/14/2013] [Indexed: 01/06/2023] Open
Abstract
Background The development of an asexual blood stage vaccine against Plasmodium falciparum malaria based on the major merozoite surface protein-1 (MSP1) antigen is founded on the protective efficacy observed in preclinical studies and induction of invasion and growth inhibitory antibody responses. The 42 kDa C-terminus of MSP1 has been developed as the recombinant protein vaccine antigen, and the 3D7 allotype, formulated with the Adjuvant System AS02A, has been evaluated extensively in human clinical trials. In preclinical rabbit studies, the FVO allele of MSP142 has been shown to have improved immunogenicity over the 3D7 allele, in terms of antibody titres as well as growth inhibitory activity of antibodies against both the heterologous 3D7 and homologous FVO parasites. Methods Two Phase 1 clinical studies were conducted to examine the safety, reactogenicity and immunogenicity of the FVO allele of MSP142 in the adjuvant system AS01 administered intramuscularly at 0-, 1-, and 2-months: one in the USA and, after evaluation of safety data results, one in Western Kenya. The US study was an open-label, dose escalation study of 10 and 50 μg doses of MSP142 in 26 adults, while the Kenya study, evaluating 30 volunteers, was a double-blind, randomized study of only the 50 μg dose with a rabies vaccine comparator. Results In these studies it was demonstrated that this vaccine formulation has an acceptable safety profile and is immunogenic in malaria-naïve and malaria-experienced populations. High titres of anti-MSP1 antibodies were induced in both study populations, although there was a limited number of volunteers whose serum demonstrated significant inhibition of blood-stage parasites as measured by growth inhibition assay. In the US volunteers, the antibodies generated exhibited better cross-reactivity to heterologous MSP1 alleles than a MSP1-based vaccine (3D7 allele) previously tested at both study sites. Conclusions Given that the primary effector mechanism for blood stage vaccine targets is humoral, the antibody responses demonstrated to this vaccine candidate, both quantitative (total antibody titres) and qualitative (functional antibodies inhibiting parasite growth) warrant further consideration of its application in endemic settings. Trial registrations Clinical Trials NCT00666380
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Affiliation(s)
- Nekoye Otsyula
- Walter Reed Project, Kenya Medical Research Institute, Kisumu, Kenya
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Badu K, Siangla J, Larbi J, Lawson BW, Afrane Y, Ong'echa J, Remoue F, Zhou G, Githeko AK, Yan G. Variation in exposure to Anopheles gambiae salivary gland peptide (gSG6-P1) across different malaria transmission settings in the western Kenya highlands. Malar J 2012; 11:318. [PMID: 22963464 PMCID: PMC3541077 DOI: 10.1186/1475-2875-11-318] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2012] [Accepted: 09/06/2012] [Indexed: 11/21/2022] Open
Abstract
Background The existing metrics of malaria transmission are limited in sensitivity under low transmission intensity. Robust surveillance systems are needed as interventions to monitor reduced transmission and prevention of rapid reintroduction. Serological tools based on antibody responses to parasite and vector antigens are potential tools for transmission measurements. The current study sought to evaluate antibody responses to Anopheles gambiae salivary gland peptide (gSG6- P1), as a biomarker of human exposure to Anopheles bites, in different transmission settings and seasons. The comparison between anti-MSP-119 IgG immune responders and non-responders allowed exploring the robustness of the gSG6-P1 peptide as a surveillance tool in an area of decreasing malaria transmission. Methods Total IgG levels to gSG6-P1 were measured in an age-stratified cohort (< 5, 5–14 and ≥ 15 years) in a total of 1,366 participants from three localities in western Kenya [Kisii (hypoendemic), Kakamega (mesoendemic), and Kombewa (hyperendemic)] including 607 sera that were additionally tested for MSP-119 specific responses during a low and a high malaria transmission seasons. Antibody prevalence and levels were compared between localities with different transmission intensities. Regression analysis was performed to examine the association between gSG6-P1 and MSP-119 seroprevalence and parasite prevalence. Result Seroprevalence of gSG6-P1 in the uphill population was 36% while it was 50% valley bottom (χ2 = 13.2, df = 1, p < 0.001). Median gSG6-P1 antibody levels in the Valley bottom were twice as high as that observed in the uphill population [4.50 vs. 2.05, p < 0.001] and showed seasonal variation. The odds of gSG6-P1 seropositives having MSP-119 antibodies were almost three times higher than the odds of seronegatives (OR = 2.87, 95% CI [1.977, 4.176]). The observed parasite prevalence for Kisii, Kakamega and Kombewa were 4%, 19.7% and 44.6% whilst the equivalent gSG6-P1 seroprevalence were 28%, 34% and 54%, respectively. Conclusion The seroprevalence of IgG to gSG6-P1 was sensitive and robust in distinguishing between hypo, meso and hyper transmission settings and seasonal fluctuations.
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Affiliation(s)
- Kingsley Badu
- Department of Theoretical and Applied Biology, College of Sciences, Kwame Nkrumah, University of Science & Technology, Kumasi, Ghana.
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Bergmann-Leitner ES, Duncan EH, Mease RM, Angov E. Impact of pre-existing MSP1(42)-allele specific immunity on potency of an erythrocytic Plasmodium falciparum vaccine. Malar J 2012; 11:315. [PMID: 22958482 PMCID: PMC3502560 DOI: 10.1186/1475-2875-11-315] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2012] [Accepted: 08/30/2012] [Indexed: 01/03/2023] Open
Abstract
Background MSP1 is the major surface protein on merozoites and a prime candidate for a blood stage malaria vaccine. Preclinical and seroepidemiological studies have implicated antibodies to MSP1 in protection against blood stage parasitaemia and/or reduced parasite densities, respectively. Malaria endemic areas have multiple strains of Plasmodium falciparum circulating at any given time, giving rise to complex immune responses, an issue which is generally not addressed in clinical trials conducted in non-endemic areas. A lack of understanding of the effect of pre-existing immunity to heterologous parasite strains may significantly contribute to vaccine failure in the field. The purpose of this study was to model the effect of pre-existing immunity to MSP142 on the immunogenicity of blood-stage malaria vaccines based on alternative MSP1 alleles. Methods Inbred and outbred mice were immunized with various recombinant P. falciparum MSP142 proteins that represent the two major alleles of MSP142, MAD20 (3D7) and Wellcome (K1, FVO). Humoral immune responses were analysed by ELISA and LuminexTM, and functional activity of induced MSP142-specific antibodies was assessed by growth inhibition assays. T-cell responses were characterized using ex vivo ELISpot assays. Results Analysis of the immune responses induced by various immunization regimens demonstrated a strong allele-specific response at the T cell level in both inbred and outbred mice. The success of heterologous regimens depended on the degree of homology of the N-terminal p33 portion of the MSP142, likely due to the fact that most T cell epitopes reside in this part of the molecule. Analysis of humoral immune responses revealed a marked cross-reactivity between the alleles. Functional analyses showed that some of the heterologous regimens induced antibodies with improved growth inhibitory activities. Conclusion The development of a more broadly efficacious MSP1 based vaccine may be hindered by clonally imprinted p33 responses mainly restricted at the T cell level. In this study, the homology of the p33 sequence between the clonally imprinted response and the vaccine allele determines the magnitude of vaccine induced responses.
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Affiliation(s)
- Elke S Bergmann-Leitner
- Malaria Vaccine Branch, US Military Malaria Vaccine Program, Walter Reed Army Institute of Research, Silver Spring, MD 20910, USA.
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Overview of plant-made vaccine antigens against malaria. J Biomed Biotechnol 2012; 2012:206918. [PMID: 22911156 PMCID: PMC3403509 DOI: 10.1155/2012/206918] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2012] [Revised: 05/22/2012] [Accepted: 05/23/2012] [Indexed: 11/18/2022] Open
Abstract
This paper is an overview of vaccine antigens against malaria produced in plants. Plant-based expression systems represent an interesting production platform due to their reduced manufacturing costs and high scalability. At present, different Plasmodium antigens and expression strategies have been optimized in plants. Furthermore, malaria antigens are one of the few examples of eukaryotic proteins with vaccine value expressed in plants, making plant-derived malaria antigens an interesting model to analyze. Up to now, malaria antigen expression in plants has allowed the complete synthesis of these vaccine antigens, which have been able to induce an active immune response in mice. Therefore, plant production platforms offer wonderful prospects for improving the access to malaria vaccines.
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Qian F, Reiter K, Zhang Y, Shimp RL, Nguyen V, Aebig JA, Rausch KM, Zhu D, Lambert L, Mullen GED, Martin LB, Long CA, Miller LH, Narum DL. Immunogenicity of self-associated aggregates and chemically cross-linked conjugates of the 42 kDa Plasmodium falciparum merozoite surface protein-1. PLoS One 2012; 7:e36996. [PMID: 22675476 PMCID: PMC3366955 DOI: 10.1371/journal.pone.0036996] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2012] [Accepted: 04/11/2012] [Indexed: 12/04/2022] Open
Abstract
Self-associated protein aggregates or cross-linked protein conjugates are, in general, more immunogenic than oligomeric or monomeric forms. In particular, the immunogenicity in mice of a recombinant malaria transmission blocking vaccine candidate, the ookinete specific Plasmodium falciparum 25 kDa protein (Pfs25), was increased more than 1000-fold when evaluated as a chemical cross-linked protein-protein conjugate as compared to a formulated monomer. Whether alternative approaches using protein complexes improve the immunogenicity of other recombinant malaria vaccine candidates is worth assessing. In this work, the immunogenicity of the recombinant 42 kDa processed form of the P. falciparum merozoite surface protein 1 (MSP142) was evaluated as a self-associated, non-covalent aggregate and as a chemical cross-linked protein-protein conjugate to ExoProtein A, which is a recombinant detoxified form of Pseudomonas aeruginosa exotoxin A. MSP142 conjugates were prepared and characterized biochemically and biophysically to determine their molar mass in solution and stoichiometry, when relevant. The immunogenicity of the MSP142 self-associated aggregates, cross-linked chemical conjugates and monomers were compared in BALB/c mice after adsorption to aluminum hydroxide adjuvant, and in one instance in association with the TLR9 agonist CPG7909 with an aluminum hydroxide formulation. Antibody titers were assessed by ELISA. Unlike observations made for Pfs25, no significant enhancement in MSP142 specific antibody titers was observed for any conjugate as compared to the formulated monomer or dimer, except for the addition of the TLR9 agonist CPG7909. Clearly, enhancing the immunogenicity of a recombinant protein vaccine candidate by the formation of protein complexes must be established on an empirical basis.
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Affiliation(s)
- Feng Qian
- Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, United States of America
- Department of Rheumatology and Immunology, Changzheng Hospital, Second Military Medical University, Shanghai, People's Republic of China
| | - Karine Reiter
- Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, United States of America
| | - Yanling Zhang
- Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, United States of America
| | - Richard L. Shimp
- Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, United States of America
| | - Vu Nguyen
- Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, United States of America
| | - Joan A. Aebig
- Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, United States of America
| | - Kelly M. Rausch
- Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, United States of America
| | - Daming Zhu
- Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, United States of America
| | - Lynn Lambert
- Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, United States of America
| | - Gregory E. D. Mullen
- Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, United States of America
- Division of Imaging Sciences, School of Medicine, King’s College London, London, United Kingdom
| | - Laura B. Martin
- Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, United States of America
- Novartis Vaccines Institute for Global Health S.r.l. (NVGH), Siena, Italy
| | - Carole A. Long
- Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, United States of America
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, United States of America
| | - Louis H. Miller
- Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, United States of America
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, United States of America
| | - David L. Narum
- Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, United States of America
- * E-mail:
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Badu K, Afrane YA, Larbi J, Stewart VA, Waitumbi J, Angov E, Ong'echa JM, Perkins DJ, Zhou G, Githeko A, Yan G. Marked variation in MSP-119 antibody responses to malaria in western Kenyan highlands. BMC Infect Dis 2012; 12:50. [PMID: 22380785 PMCID: PMC3306741 DOI: 10.1186/1471-2334-12-50] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2011] [Accepted: 03/01/2012] [Indexed: 11/25/2022] Open
Abstract
Background Assessment of malaria endemicity at different altitudes and transmission intensities, in the era of dwindling vector densities in the highlands, will provide valuable information for malaria control and surveillance. Measurement of serum anti-malarial antibodies is a useful marker of malaria exposure that indicates long-term transmission potential. We studied the serologic evidence of malaria endemicity at two highland sites along a transmission intensity cline. An improved understanding of the micro-geographic variation in malaria exposure in the highland ecosystems will be relevant in planning effective malaria control. Methods Total IgG levels to Plasmodium falciparum MSP-119 were measured in an age-stratified cohort (< 5, 5-14 and ≥ 15 years) in 795 participants from an uphill and valley bottom residents during low and high malaria transmission seasons. Antibody prevalence and level was compared between different localities. Regression analysis was performed to examine the association between antibody prevalence and parasite prevalence. Age-specific MSP-119 seroprevalence data was fitted to a simple reversible catalytic model to investigate the relationship between parasite exposure and age. Results Higher MSP-119 seroprevalence and density were observed in the valley residents than in the uphill dwellers. Adults (> 15 years) recorded high and stable immune response in spite of changing seasons. Lower responses were observed in children (≤ 15 years), which, fluctuated with changing seasons particularly in the valley residents. In the uphill population, annual seroconversion rate (SCR) was 8.3% and reversion rate was 3.0%, with seroprevalence reaching a plateau of 73.3% by age of 20. Contrary, in the valley bottom population, the annual SCR was 35.8% and the annual seroreversion rate was 3.5%, and seroprevalence in the population had reached 91.2% by age 10. Conclusion The study reveals the micro-geographic variation in malaria endemicity in the highland eco-system; this validates the usefulness of sero-epidemiological tools in assessing malaria endemicity in the era of decreasing sensitivity of conventional tools.
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Affiliation(s)
- Kingsley Badu
- Center for Global Health Research, Kenya Medical Research Institute, Kisumu, Kenya.
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Mehrizi AA, Zakeri S, Rafati S, Salmanian AH, Djadid ND. Immune responses elicited by co-immunization of Plasmodium vivax and P. falciparum MSP-1 using prime-boost immunization strategies. Parasite Immunol 2012; 33:594-608. [PMID: 21883290 DOI: 10.1111/j.1365-3024.2011.01331.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Carboxy-terminus of merozoite surface protein-1 (MSP-1(19) ) is the major protein on the surface of the plasmodial merozoite that acts as one of the most important blood-stage vaccine candidates. The present investigation was designed to evaluate the immune responses when either two recombinant antigens (rPvMSP-1(19) + rPfMSP-1(19)) or two plasmid constructs (pcDNA3.1 hygro-PvMSP-1(19) + pcDNA3.1 hygro-PfMSP-1(19)) were administered in combination at a single site in mice by using different immunization strategies (protein/protein, DNA/DNA and DNA/protein) at weeks 0, 5 and 8. All mice were monitored for the level of MSP-1(19) -specific antibody for up to 40 weeks. The inclusion of both recombinant antigens in a vaccine mixture could not inhibit induction of antibodies to the other antigen when the two recombinant antigens were combined in immunization formulation. Interestingly, antisera from immunized mice with either recombinant antigen failed to cross-react with heterologous antigen. Moreover, the results of this study showed that co-immunization with both antigens at a single site generated a substantial PvMSP-1(19) - and PfMSP-1(19) -specific antibody responses and also IFN-γ cytokine production (Th1 response) in DNA/protein prime-boost immunization strategies. The increased humoral response to PvMSP-1(19) and PfMSP-1(19) lasted nearly a year after immunization. Therefore, the results of this study are encouraging for the development of multi-species malaria vaccine based on MSP-1(19) antigen.
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Affiliation(s)
- A A Mehrizi
- Malaria and Vector Research Group, Biotechnology Research Center, Pasteur Institute of Iran, Tehran, Iran
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29
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Khan F, Legler PM, Mease RM, Duncan EH, Bergmann-Leitner ES, Angov E. Histidine affinity tags affect MSP1(42) structural stability and immunodominance in mice. Biotechnol J 2011; 7:133-47. [PMID: 22076863 DOI: 10.1002/biot.201100331] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2011] [Revised: 09/23/2011] [Accepted: 11/07/2011] [Indexed: 11/10/2022]
Abstract
Inclusion of affinity tags has greatly facilitated process development for protein antigens, primarily for their recovery from complex mixtures. Although generally viewed as supportive of product development, affinity tags may have unintended consequences on protein solubility, susceptibility to aggregation, and immunogenicity. Merozoite surface protein 1 (MSP1), an erythrocytic stage protein of Plasmodium falciparum and a candidate malaria vaccine, was used to evaluate the impact of a metal ion affinity-tag on both protein structure and the induction of immunity. To this end, codon harmonized gene sequences from the P. falciparum MSP1(42) of FVO and 3D7 parasites were cloned and purified with and without a histidine (His) tag. We report on the influence of His-affinity tags on protein expression levels, solubility, secondary structure, thermal denaturation, aggregation and the impact on humoral and cellular immune responses in mice. While the overall immunogenicity induced by His-tagged MSP1(42) proteins is greater, the fine specificity of the humoral and cellular immune responses is altered relative to anti-parasitic antibody activity and the breadth of T-cell responses. Thus, the usefulness of protein tags may be outweighed by their potential impact on structure and function, stressing the need for caution in their use. See accompanying commentary by Randolph DOI: 10.1002/biot.201100459.
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Affiliation(s)
- Farhat Khan
- Walter Reed Army Institute of Research, Military Malaria Research Program, Malaria Vaccine Branch, Silver Spring, MD, USA
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30
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Cowan GJM, Creasey AM, Dhanasarnsombut K, Thomas AW, Remarque EJ, Cavanagh DR. A malaria vaccine based on the polymorphic block 2 region of MSP-1 that elicits a broad serotype-spanning immune response. PLoS One 2011; 6:e26616. [PMID: 22073118 PMCID: PMC3202563 DOI: 10.1371/journal.pone.0026616] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2011] [Accepted: 09/29/2011] [Indexed: 12/28/2022] Open
Abstract
Polymorphic parasite antigens are known targets of protective immunity to malaria, but this antigenic variation poses challenges to vaccine development. A synthetic MSP-1 Block 2 construct, based on all polymorphic variants found in natural Plasmodium falciparum isolates has been designed, combined with the relatively conserved Block 1 sequence of MSP-1 and expressed in E.coli. The MSP-1 Hybrid antigen has been produced with high yield by fed-batch fermentation and purified without the aid of affinity tags resulting in a pure and extremely thermostable antigen preparation. MSP-1 hybrid is immunogenic in experimental animals using adjuvants suitable for human use, eliciting antibodies against epitopes from all three Block 2 serotypes. Human serum antibodies from Africans naturally exposed to malaria reacted to the MSP-1 hybrid as strongly as, or better than the same serum reactivities to individual MSP-1 Block 2 antigens, and these antibody responses showed clear associations with reduced incidence of malaria episodes. The MSP-1 hybrid is designed to induce a protective antibody response to the highly polymorphic Block 2 region of MSP-1, enhancing the repertoire of MSP-1 Block 2 antibody responses found among immune and semi-immune individuals in malaria endemic areas. The target population for such a vaccine is young children and vulnerable adults, to accelerate the acquisition of a full range of malaria protective antibodies against this polymorphic parasite antigen.
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MESH Headings
- Adolescent
- Adult
- Animals
- Antibodies, Monoclonal/immunology
- Antibodies, Protozoan/blood
- Antibodies, Protozoan/immunology
- Case-Control Studies
- Child
- Child, Preschool
- Cross-Sectional Studies
- Enzyme-Linked Immunosorbent Assay
- Female
- Fluorescent Antibody Technique, Indirect
- Humans
- Immunization
- Immunoblotting
- Immunoglobulin G/immunology
- Macaca mulatta
- Malaria Vaccines/immunology
- Malaria, Falciparum/immunology
- Malaria, Falciparum/prevention & control
- Merozoite Surface Protein 1/immunology
- Mice
- Mice, Inbred DBA
- Plasmodium falciparum/growth & development
- Plasmodium falciparum/immunology
- Rabbits
- Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
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Affiliation(s)
- Graeme J. M. Cowan
- Institute of Immunology and Infection Research, University of Edinburgh, Edinburgh, United Kingdom
| | - Alison M. Creasey
- Institute of Immunology and Infection Research, University of Edinburgh, Edinburgh, United Kingdom
| | - Kelwalin Dhanasarnsombut
- Institute of Immunology and Infection Research, University of Edinburgh, Edinburgh, United Kingdom
| | - Alan W. Thomas
- Biomedical Primate Research Center, Rijswijk, The Netherlands
| | | | - David R. Cavanagh
- Institute of Immunology and Infection Research, University of Edinburgh, Edinburgh, United Kingdom
- * E-mail:
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31
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Angov E. Codon usage: nature's roadmap to expression and folding of proteins. Biotechnol J 2011; 6:650-9. [PMID: 21567958 PMCID: PMC3166658 DOI: 10.1002/biot.201000332] [Citation(s) in RCA: 153] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2011] [Revised: 04/11/2011] [Accepted: 04/13/2011] [Indexed: 02/06/2023]
Abstract
Biomedical and biotechnological research relies on processes leading to the successful expression and production of key biological products. High-quality proteins are required for many purposes, including protein structural and functional studies. Protein expression is the culmination of multistep processes involving regulation at the level of transcription, mRNA turnover, protein translation, and post-translational modifications leading to the formation of a stable product. Although significant strides have been achieved over the past decade, advances toward integrating genomic and proteomic information are essential, and until such time, many target genes and their products may not be fully realized. Thus, the focus of this review is to provide some experimental support and a brief overview of how codon usage bias has evolved relative to regulating gene expression levels.
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Affiliation(s)
- Evelina Angov
- Division of Malaria Vaccine Development, Walter Reed Army Institute of Research, Silver Spring, MD 20910, USA.
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32
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Douglas AD, de Cassan SC, Dicks MDJ, Gilbert SC, Hill AVS, Draper SJ. Tailoring subunit vaccine immunogenicity: maximizing antibody and T cell responses by using combinations of adenovirus, poxvirus and protein-adjuvant vaccines against Plasmodium falciparum MSP1. Vaccine 2011; 28:7167-78. [PMID: 20937436 PMCID: PMC3404461 DOI: 10.1016/j.vaccine.2010.08.068] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2010] [Revised: 08/12/2010] [Accepted: 08/13/2010] [Indexed: 12/15/2022]
Abstract
Subunit vaccination modalities tend to induce particular immune effector responses. Viral vectors are well known for their ability to induce strong T cell responses, while protein-adjuvant vaccines have been used primarily for induction of antibody responses. Here, we demonstrate in mice using a Plasmodium falciparum merozoite surface protein 1 (PfMSP1) antigen that novel regimes combining adenovirus and poxvirus vectored vaccines with protein antigen in Montanide ISA720 adjuvant can achieve simultaneous antibody and T cell responses which equal, or in some cases surpass, the best immune responses achieved by either the viral vectors or the protein vaccine alone. Such broad responses can be achieved either using three-stage vaccination protocols, or with an equally effective two-stage protocol in which viral vectors are admixed with protein and adjuvant, and were apparent despite the use of a protein antigen that represented only a portion of the viral vector antigen. We describe further possible advantages of viral vectors in achieving consistent antibody priming, enhanced antibody avidity, and cytophilic isotype skew. These data strengthen the evidence that tailored combinations of vaccine platforms can achieve desired combinations of immune responses, and further encourage the co-administration of antibody-inducing recombinant protein vaccines with T cell- and antibody-inducing recombinant viral vectors as one strategy that may achieve protective blood-stage malaria immunity in humans.
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Taylor K. Reporting the Implementation of the Three Rs in European Primate and Mouse Research Papers: Are We Making Progress? Altern Lab Anim 2010; 38:495-517. [DOI: 10.1177/026119291003800613] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
It is now more than 20 years since both Council of Europe Convention ETS123 and EU Directive 86/609?EEC were introduced, to promote the implementation of the Three Rs in animal experimentation and to provide guidance on animal housing and care. It might therefore be expected that reports of the implementation of the Three Rs in animal research papers would have increased during this period. In order to test this hypothesis, a literature survey of animal-based research was conducted. A randomly-selected sample from 16 high-profile medical journals, of original research papers arising from European institutions that featured experiments which involved either mice or primates, were identified for the years 1986 and 2006 (Total sample = 250 papers). Each paper was scored out of 10 for the incidence of reporting on the implementation of Three Rs-related factors corresponding to Replacement (justification of non-use of non-animal methods), Reduction (statistical analysis of the number of animals needed) and Refinement (housing aspects, i.e. increased cage size, social housing, enrichment of cage environment and food; and procedural aspects, i.e. the use of anaesthesia, analgesia, humane endpoints, and training for procedures with positive reinforcement). There was no significant increase in overall reporting score over time, for either mouse or primate research. By 2006, mouse research papers scored an average of 0 out of a possible 10, and primate research papers scored an average of 1.5. This review provides systematic evidence that animal research is still not properly reported, and supports the call within the scientific community for action to be taken by journals to update their policies.
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Affiliation(s)
- Katy Taylor
- British Union for the Abolition of Vivisection, London, UK
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34
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Lau OS, Ng DWK, Chan WWL, Chang SP, Sun SSM. Production of the 42-kDa fragment of Plasmodium falciparum merozoite surface protein 1, a leading malaria vaccine antigen, in Arabidopsis thaliana seeds. PLANT BIOTECHNOLOGY JOURNAL 2010; 8:994-1004. [PMID: 20444208 DOI: 10.1111/j.1467-7652.2010.00526.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Malaria is widely associated with poverty, and a low-cost vaccine against malaria is highly desirable for implementing comprehensive vaccination programmes in developing countries. Production of malaria antigens in plants is a promising approach, but its development has been hindered by poor expression of the antigens in plant cells. In the present study, we targeted plant seeds as a low-cost vaccine production platform and successfully expressed the Plasmodium falciparum 42-kDa fragment of merozoite surface protein 1 (MSP1₄₂), a leading malaria vaccine candidate, at a high level in transgenic Arabidopsis seeds. We overcame hurdles of transcript and protein instabilities of MSP1₄₂ in plants by synthesizing a plant-optimized MSP1₄₂ cDNA and either targeting the recombinant protein to protein storage vacuoles or fusing it with a stable plant storage protein. An exceptional improvement in MSP1₄₂ expression, from an undetectable level to 5% of total extractable protein, was achieved with these combined strategies. Importantly, the plant-derived MSP1₄₂ maintains its natural antigenicity and can be recognized by immune sera from malaria-infected patients. Our results provide a strong basis for the development of a plant-based, low-cost malaria vaccine.
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Affiliation(s)
- On Sun Lau
- Department of Biology, The Chinese University of Hong Kong, Shatin, Hong Kong, China
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35
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Bergmann-Leitner ES, Mease RM, De La Vega P, Savranskaya T, Polhemus M, Ockenhouse C, Angov E. Immunization with pre-erythrocytic antigen CelTOS from Plasmodium falciparum elicits cross-species protection against heterologous challenge with Plasmodium berghei. PLoS One 2010; 5:e12294. [PMID: 20808868 PMCID: PMC2924390 DOI: 10.1371/journal.pone.0012294] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2010] [Accepted: 07/29/2010] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND The Plasmodium protein Cell-traversal protein for ookinetes and sporozoites (CelTOS) plays an important role in cell traversal of host cells in both, mosquito and vertebrates, and is required for successful malaria infections. CelTOS is highly conserved among the Plasmodium species, suggesting an important functional role across all species. Therefore, targeting the immune response to this highly conserved protein and thus potentially interfering with its biological function may result in protection against infection even by heterologous species of Plasmodium. METHODOLOGY/PRINCIPAL FINDINGS To test this hypothesis, we developed a recombinant codon-harmonized P. falciparum CelTOS protein that can be produced to high yields in the E. coli expression system. Inbred Balb/c and outbred CD-1 mice were immunized with various doses of the recombinant protein adjuvanted with Montanide ISA 720 and characterized using in vitro and in vivo analyses. CONCLUSIONS/SIGNIFICANCE Immunization with PfCelTOS resulted in potent humoral and cellular immune responses and most importantly induced sterile protection against a heterologous challenge with P. berghei sporozoites in a proportion of both inbred and outbred mice. The biological activity of CelTOS-specific antibodies against the malaria parasite is likely linked to the impairment of sporozoite motility and hepatocyte infectivity. The results underscore the potential of this antigen as a pre-erythrocytic vaccine candidate and demonstrate for the first time a malaria vaccine that is cross-protective between species.
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Affiliation(s)
- Elke S Bergmann-Leitner
- Division of Malaria Vaccine Development,
United States Military Malaria Vaccine Program, Walter Reed Army Institute of
Research, Silver Spring, Maryland, United States of America
| | - Ryan M. Mease
- Division of Malaria Vaccine Development,
United States Military Malaria Vaccine Program, Walter Reed Army Institute of
Research, Silver Spring, Maryland, United States of America
| | - Patricia De La Vega
- Division of Malaria Vaccine Development,
United States Military Malaria Vaccine Program, Walter Reed Army Institute of
Research, Silver Spring, Maryland, United States of America
| | - Tatyana Savranskaya
- Division of Entomology, Walter Reed Army
Institute of Research, Silver Spring, Maryland, United States of
America
| | - Mark Polhemus
- Division of Malaria Vaccine Development,
United States Military Malaria Vaccine Program, Walter Reed Army Institute of
Research, Silver Spring, Maryland, United States of America
| | - Christian Ockenhouse
- Division of Malaria Vaccine Development,
United States Military Malaria Vaccine Program, Walter Reed Army Institute of
Research, Silver Spring, Maryland, United States of America
| | - Evelina Angov
- Division of Malaria Vaccine Development,
United States Military Malaria Vaccine Program, Walter Reed Army Institute of
Research, Silver Spring, Maryland, United States of America
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Protective immune responses elicited by immunization with a chimeric blood-stage malaria vaccine persist but are not boosted by Plasmodium yoelii challenge infection. Vaccine 2010; 28:6876-84. [PMID: 20709001 DOI: 10.1016/j.vaccine.2010.08.018] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2010] [Revised: 07/17/2010] [Accepted: 08/02/2010] [Indexed: 11/20/2022]
Abstract
An efficacious malaria vaccine remains elusive despite concerted efforts. Using the Plasmodium yoelii murine model, we previously reported that immunization with the C-terminal 19 kDa domain of merozoite surface protein 1 (MSP1(19)) fused to full-length MSP8 protected against lethal P. yoelii 17XL, well beyond that achieved by single or combined immunizations with the component antigens. Here, we continue the evaluation of the chimeric PyMSP1/8 vaccine. We show that immunization with rPyMSP1/8 vaccine elicited an MSP8-restricted T cell response that was sufficient to provide help for both PyMSP1(19) and PyMSP8-specific B cells to produce high and sustained levels of protective antibodies. The enhanced efficacy of immunization with rPyMSP1/8, in comparison to a combined formulation of rPyMSP1(42) and rPyMSP8, was not due to improved conformation of protective B cell epitopes in the chimeric molecule. Unexpectedly, rPyMSP1/8 vaccine-induced antibody responses were not boosted by exposure to P. yoelii 17XL infected RBCs. However, rPyMSP1/8 immunized and infected mice mounted robust responses to a diverse set of blood-stage antigens. The data support the further development of an MSP1/8 chimeric vaccine but also suggest that vaccines that prime for responses to a diverse set of parasite proteins will be required to maximize vaccine efficacy.
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37
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Allele specificity of gamma interferon responses to the carboxyl-terminal region of Plasmodium falciparum merozoite surface protein 1 by Kenyan adults with naturally acquired immunity to malaria. Infect Immun 2010; 78:4431-41. [PMID: 20696832 DOI: 10.1128/iai.00415-10] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cross-sectional seroepidemiological studies of populations naturally exposed to Plasmodium falciparum suggest an association between protection from malaria and circulating antibodies to the carboxyl terminus of merozoite surface protein 1 (MSP1). Questions remain regarding the significance of cell-mediated immunity to MSP1 in conferring protection and inducing immunologic memory. Vaccine constructs have been based on the 42-kDa recombinant MSP1 protein (MSP1(42)), which includes the 19-kDa (MSP1(19)) and 33-kDa (MSP1(33)) fragments containing the major B- and T-cell epitopes, respectively. To evaluate T-cell responses to the MSP1(33) fragment, two libraries of overlapping 18-mer peptides from the 3D7 and FVO MSP1(33) regions were used to screen a cohort of asymptomatic Kenyan adults. Gamma interferon (IFN-γ) measured by enzyme-linked immunospot assay (ELISPOT) at multiple time points assessed the magnitude and stability of these responses. The percentage of individuals with IFN-γ responses to single MSP1(33) peptides ranged from nil to 24%, were clustered among a subset of peptides, and were not consistently recalled over time. In comparison to peptide responses, IFN-γ ELISPOT responses to recombinant MSP1(42) were more prevalent, more frequently elicited by the 3D7 as opposed to the FVO allele, and more stable over time. The prevailing MSP1(33) genotype infection was 3D7, with few mixed infections and no sole FVO infections. This study demonstrates that immunity against MSP1(33) after cumulative natural infections consists of low-magnitude and difficult-to-detect IFN-γ responses. Although immunity against MSP1 alone will not confer protection against malaria, demonstrating a relative and sustained increase in T-cell immunity to MSP1 after vaccination would be a reasonable measurement of vaccine responsiveness.
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Maestre A, Muskus C, Duque V, Agudelo O, Liu P, Takagi A, Ntumngia FB, Adams JH, Sim KL, Hoffman SL, Corradin G, Velez ID, Wang R. Acquired antibody responses against Plasmodium vivax infection vary with host genotype for duffy antigen receptor for chemokines (DARC). PLoS One 2010; 5:e11437. [PMID: 20664684 PMCID: PMC2896388 DOI: 10.1371/journal.pone.0011437] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2009] [Accepted: 04/04/2010] [Indexed: 01/28/2023] Open
Abstract
Background Polymorphism of the Duffy Antigen Receptor for Chemokines (DARC) is associated with susceptibility to and the severity of Plasmodium vivax malaria in humans. P. vivax uses DARC to invade erythrocytes. Individuals lacking DARC are ‘resistant’ to P. vivax erythrocytic infection. However, susceptibility to P. vivax in DARC+ individuals is reported to vary between specific DARC genotypes. We hypothesized that the natural acquisition of antibodies to P. vivax blood stages may vary with the host genotype and the level of DARC expression. Furthermore, high parasitemia has been reported to effect the acquisition of immunity against pre-erythrocytic parasites. We investigated the correlation between host DARC genotypes and the frequency and magnitude of antibodies against P. vivax erythrocytic stage antigens. Methodology/Findings We assessed the frequencies and magnitudes of antibody responses against P. vivax and P. falciparum sporozoite and erythrocytic antigens in Colombian donors from malaria-endemic regions. The frequency and level of naturally-acquired antibodies against the P. vivax erythrocytic antigens merozoite surface protein 1 (PvMSP1) and Duffy binding protein (PvDBP) varied with the host DARC genotypes. Donors with one negative allele (FY*B/FY*Bnull and FY*A/FY*Bnull) were more likely to have anti-PvMSP1 and anti-PvDBP antibodies than those with two positive alleles (FY*B/FY*B and FY*A/FY*B). The lower IgG3 and IgG1 components of the total IgG response may account for the decreased responses to P. vivax erythrocytic antigens with FY*A/FY*B and FY*B/FY*B genotypes. No such association was detected with P. falciparum erythrocytic antigens, which does not use DARC for erythrocyte invasion. Conclusion/Significance Individuals with higher DARC expression, which is associated with higher susceptibility to P. vivax infection, exhibited low frequencies and magnitudes of P. vivax blood-stage specific antibody responses. This may indicate that one of the primary mechanisms by which P. vivax evades host immunity is through DARC indirectly down-regulating humoral responses against erythrocytic invasion and development.
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Affiliation(s)
- Amanda Maestre
- Grupo Salud y Comunidad, Facultad de Medicina, Universidad de Antioquia, Medellín, Colombia
| | - Carlos Muskus
- Programa de Estudio y Control de Enfermedades Tropicales (PECET), Facultad de Medicina, Universidad de Antioquia, Medellín, Colombia
| | - Victoria Duque
- Programa de Estudio y Control de Enfermedades Tropicales (PECET), Facultad de Medicina, Universidad de Antioquia, Medellín, Colombia
| | - Olga Agudelo
- Programa de Estudio y Control de Enfermedades Tropicales (PECET), Facultad de Medicina, Universidad de Antioquia, Medellín, Colombia
| | - Pu Liu
- Seattle Biomedical Research Institute (SBRI), Seattle, Washington, United States of America
| | - Akihide Takagi
- Seattle Biomedical Research Institute (SBRI), Seattle, Washington, United States of America
| | | | - John H. Adams
- University of South Florida, Tampa, Florida, United States of America
| | - Kim Lee Sim
- Protein Potential LLC., Rockville, Maryland, United States of America
| | | | | | - Ivan D. Velez
- Programa de Estudio y Control de Enfermedades Tropicales (PECET), Facultad de Medicina, Universidad de Antioquia, Medellín, Colombia
| | - Ruobing Wang
- Seattle Biomedical Research Institute (SBRI), Seattle, Washington, United States of America
- * E-mail:
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39
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McHenry AM, Barnwell JW, Adams JH. Plasmodium vivax DBP binding to Aotus nancymaae erythrocytes is Duffy antigen dependent. J Parasitol 2010; 96:225-7. [PMID: 19799492 DOI: 10.1645/ge-2281.1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Plasmodium vivax is the second leading cause of malaria worldwide. Invasion of human erythrocytes by P. vivax merozoites is dependent upon the interaction between the parasite Duffy binding protein (PvDBP) and the erythrocyte Duffy antigen receptor. Therefore, disruption of this vital interaction is an attractive target for therapeutic intervention. Although Aotus nancymaae is a commonly used primate model for human P. vivax infections, it has not been confirmed that the interaction between Ao. nancymaae erythrocytes and P. vivax is Duffy antigen dependent. Our results indicate that normal Ao. nancymaae erythrocytes readily bind to PvDBPII and that this binding is completely abolished with chymotrypsin treatment of the erythrocytes. Furthermore, the results of our inhibition assays show a dose-dependent decrease in binding with increasing amounts of anti-PvDBPII polyclonal rabbit sera or anti-Fy6 monoclonal antibody. These data indicate that the interaction between Ao. nancymaae erythrocytes and P. vivax DBPII is Duffy antigen dependent, validating this model system for in vivo studies of anti-PvDBP inhibition.
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Affiliation(s)
- A M McHenry
- Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana 46556, USA
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40
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Woehlbier U, Epp C, Hackett F, Blackman MJ, Bujard H. Antibodies against multiple merozoite surface antigens of the human malaria parasite Plasmodium falciparum inhibit parasite maturation and red blood cell invasion. Malar J 2010; 9:77. [PMID: 20298576 PMCID: PMC2847572 DOI: 10.1186/1475-2875-9-77] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2009] [Accepted: 03/18/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Plasmodium falciparum merozoites expose at their surface a large protein complex, which is composed of fragments of merozoite surface protein 1 (MSP-1; called MSP-183, MSP-130, MSP-138, and MSP-142) plus associated processing products of MSP-6 and MSP-7. During erythrocyte invasion this complex, as well as an integral membrane protein called apical membrane antigen-1 (AMA-1), is shed from the parasite surface following specific proteolysis. Components of the MSP-1/6/7 complex and AMA-1 are presently under development as malaria vaccines. METHODS The specificities and effects of antibodies directed against MSP-1, MSP-6, MSP-7 on the growth of blood stage parasites were studied using ELISA and the pLDH-assay. To understand the mode of action of these antibodies, their effects on processing of MSP-1 and AMA-1 on the surface of merozoites were investigated. RESULTS Antibodies targeting epitopes located throughout the MSP-1/6/7 complex interfere with shedding of MSP-1, and as a consequence prevent erythrocyte invasion. Antibodies targeting the MSP-1/6/7 complex have no effect on the processing and shedding of AMA-1 and, similarly, antibodies blocking the shedding of AMA-1 do not affect cleavage of MSP-1, suggesting completely independent functions of these proteins during invasion. Furthermore, some epitopes, although eliciting highly inhibitory antibodies, are only poorly recognized by the immune system when presented in the structural context of the intact antigen. CONCLUSIONS The findings reported provide further support for the development of vaccines based on MSP-1/6/7 and AMA-1, which would possibly include a combination of these antigens.
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Affiliation(s)
- Ute Woehlbier
- Zentrum für Molekulare Biologie (ZMBH), University of Heidelberg, Im Neuenheimer Feld 282, D-69120 Heidelberg, Germany
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Immunogenic properties of a recombinant fusion protein containing the C-terminal 19 kDa of Plasmodium falciparum merozoite surface protein-1 and the innate immunity agonist FliC flagellin of Salmonella typhimurium. Vaccine 2010; 28:2818-26. [PMID: 20170765 DOI: 10.1016/j.vaccine.2010.02.004] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2009] [Revised: 01/30/2010] [Accepted: 02/03/2010] [Indexed: 12/17/2022]
Abstract
In a recent study, we demonstrated the immunogenic properties of a new malaria vaccine polypeptide based on a 19 kDa C-terminal fragment of the merozoite surface protein-1 (MSP1(19)) from Plasmodium vivax and an innate immunity agonist, the Salmonella enterica serovar Typhimurium flagellin (FliC). Herein, we tested whether the same strategy, based on the MSP1(19) component of the deadly malaria parasite Plasmodium falciparum, could also generate a fusion polypeptide with enhanced immunogenicity. The His(6)FliC-MSP1(19) fusion protein was expressed from a recombinant Escherichia coli and showed preserved in vitro TLR5-binding activity. In contrast to animals injected with His(6)MSP1(19), mice subcutaneously immunised with the recombinant His(6)FliC-MSP1(19) developed strong MSP1(19)-specific systemic antibody responses with a prevailing IgG1 subclass. Incorporation of other adjuvants, such as CpG ODN 1826, complete and incomplete Freund's adjuvants or Quil-A, improved the IgG responses after the second, but not the third, immunising dose. It also resulted in a more balanced IgG subclass response, as evaluated by the IgG1/IgG2c ratio, and higher cell-mediated immune response, as determined by the detection of antigen-specific interferon-gamma secretion by immune spleen cells. MSP1(19)-specific antibodies recognised not only the recombinant protein, but also the native protein expressed on the surface of P. falciparum parasites. Finally, sera from rabbits immunised with the fusion protein alone inhibited the in vitro growth of three different P. falciparum strains. In summary, these results extend our previous observations and further demonstrate that fusion of the innate immunity agonist FliC to Plasmodium antigens is a promising alternative to improve their immunogenicity.
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42
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In vitro growth-inhibitory activity and malaria risk in a cohort study in mali. Infect Immun 2009; 78:737-45. [PMID: 19917712 DOI: 10.1128/iai.00960-09] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Immunity to the asexual blood stage of Plasmodium falciparum is complex and likely involves several effector mechanisms. Antibodies are thought to play a critical role in malaria immunity, and a corresponding in vitro correlate of antibody-mediated immunity has long been sought to facilitate malaria vaccine development. The growth inhibition assay (GIA) measures the capacity of antibodies to limit red blood cell (RBC) invasion and/or growth of P. falciparum in vitro. In humans, naturally acquired and vaccine-induced P. falciparum-specific antibodies have growth-inhibitory activity, but it is unclear if growth-inhibitory activity correlates with protection from clinical disease. In a longitudinal study in Mali, purified IgGs, obtained from plasmas collected before the malaria season from 220 individuals aged 2 to 10 and 18 to 25 years, were assayed for growth-inhibitory activity. Malaria episodes were recorded by passive surveillance over the subsequent 6-month malaria season. Logistic regression showed that greater age (odds ratio [OR], 0.78; 95% confidence interval [95% CI], 0.63 to 0.95; P = 0.02) and growth-inhibitory activity (OR, 0.50; 95% CI, 0.30 to 0.85; P = 0.01) were significantly associated with decreased malaria risk in children. A growth-inhibitory activity level of 40% was determined to be the optimal cutoff for discriminating malaria-immune and susceptible individuals in this cohort, with a sensitivity of 97.0%, but a low specificity of 24.3%, which limited the assay's ability to accurately predict protective immunity and to serve as an in vitro correlate of antibody-mediated immunity. These data suggest that antibodies which block merozoite invasion of RBC and/or inhibit the intra-RBC growth of the parasite contribute to but are not sufficient for the acquisition of malaria immunity.
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Pichyangkul S, Tongtawe P, Kum-Arb U, Yongvanitchit K, Gettayacamin M, Hollingdale MR, Limsalakpetch A, Stewart VA, Lanar DE, Dutta S, Angov E, Ware LA, Bergmann-Leitner ES, House B, Voss G, Dubois MC, Cohen JD, Fukuda MM, Heppner DG, Miller RS. Evaluation of the safety and immunogenicity of Plasmodium falciparum apical membrane antigen 1, merozoite surface protein 1 or RTS,S vaccines with adjuvant system AS02A administered alone or concurrently in rhesus monkeys. Vaccine 2009; 28:452-62. [PMID: 19857448 DOI: 10.1016/j.vaccine.2009.10.022] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2008] [Revised: 09/29/2009] [Accepted: 10/07/2009] [Indexed: 11/15/2022]
Abstract
In an effort to broaden the immune response induced by the RTS,S/AS02(A),vaccine, we have evaluated the immunogenicity of the RTS,S antigen when combined with MSP1(42) and with AMA1, antigens derived from the asexual blood stage. The objectives of this study were (i) to determine whether MSP1(42) and AMA1 vaccines formulated with the AS02(A) Adjuvant System were safe and immunogenic in the rhesus monkey model; (ii) to investigate whether MSP1(42) or AMA1 induced immune interference to each other, or to RTS,S, when added singly or in combinations at a single injection site; (iii) in the event of immune interference, to determine if this could be reduced when antigens were administered at separate sites. We found that MSP1(42) and AMA1 were safe and immunogenic, eliciting antibodies, and Th1 and Th2 responses using IFN-gamma and IL-5 as markers. When malaria antigens were delivered together in one formulation, MSP1(42) and RTS,S reduced AMA1-specific antibody responses as measured by ELISA however, only MSP1(42) lowered parasite growth inhibitory activity of anti-AMA1 antibodies as measured by in vitro growth inhibition assay. Unlike RTS,S, MSP1(42) significantly reduced AMA1 IFN-gamma and IL-5 responses. MSP1(42) suppression of AMA1 IFN-gamma responses was not seen in animals receiving RTS,S+AMA1+MSP1(42) suggesting that RTS,S restored IFN-gamma responses. Conversely, AMA1 had no effect on MSP1(42) antibody and IFN-gamma and IL-5 responses. Neither AMA1 alone or combined with MSP1(42) affected RTS,S antibody or IFN-gamma and IL-5 responses. Immune interference by MSP1(42) on AMA1 antibody responses was also evident when AMA1, MSP1(42) and RTS,S were administered concurrently at separate sites. These results suggest that immune interference may be complex and should be considered for the design of multi-antigen, multi-stage vaccines against malaria.
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Affiliation(s)
- S Pichyangkul
- Department of Immunology and Medicine, Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand.
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Bergmann-Leitner ES, Duncan EH, Angov E. MSP-1p42-specific antibodies affect growth and development of intra-erythrocytic parasites of Plasmodium falciparum. Malar J 2009; 8:183. [PMID: 19650894 PMCID: PMC2729774 DOI: 10.1186/1475-2875-8-183] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2009] [Accepted: 08/03/2009] [Indexed: 11/10/2022] Open
Abstract
Background Antibodies are the main effector molecules in the defense against blood stages of the malaria parasite Plasmodium falciparum. Understanding the mechanisms by which vaccine-induced anti-blood stage antibodies work in protecting against malaria is essential for vaccine design and testing. Methods The effects of MSP-1p42-specific antibodies on the development of blood stage parasites were studied using microscopy, flow cytometry and the pLDH assay. To determine allele-specific effects, if present, allele-specific antibodies and the various parasite clones representative of these alleles of MSP-1 were employed. Results The mode of action of anti-MSP-1p42 antibodies differs among the parasite clones tested: anti-MSP-1p42 sera act mainly through invasion-inhibitory mechanisms against FVO parasites, by either preventing schizonts from rupturing or agglutinating merozoites upon their release. The same antibodies do not prevent the rupture of 3D7 schizonts; instead they agglutinate merozoites and arrest the development of young parasites at the early trophozoite stage, thus acting through both invasion- and growth inhibitory mechanisms. The second key finding is that antibodies have access to the intra-erythrocytic parasite, as evidenced by the labeling of developing merozoites with fluorochrome-conjugated anti-MSP-1p42 antibodies. Access to the parasite through this route likely allows antibodies to exert their inhibitory activities on the maturing schizonts leading to their inability to rupture and be released as infectious merozoites. Conclusion The identification of various modes of action by which anti-MSP-1 antibodies function against the parasite during erythrocytic development emphasizes the importance of functional assays for evaluating malaria vaccines and may also open new avenues for immunotherapy and vaccine development.
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Affiliation(s)
- Elke S Bergmann-Leitner
- US Military Malaria Vaccine Program, Walter Reed Army Institute of Research, Silver Spring, MD 20910, USA.
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Chowdhury DR, Angov E, Kariuki T, Kumar N. A potent malaria transmission blocking vaccine based on codon harmonized full length Pfs48/45 expressed in Escherichia coli. PLoS One 2009; 4:e6352. [PMID: 19623257 PMCID: PMC2709910 DOI: 10.1371/journal.pone.0006352] [Citation(s) in RCA: 105] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2009] [Accepted: 06/19/2009] [Indexed: 12/05/2022] Open
Abstract
Malaria caused by Plasmodium falciparum is responsible for nearly 1 million deaths annually. Although much progress has been made in the recent past, the development of a safe, effective and affordable malaria vaccine has remained a challenge. A vaccine targeting sexual stages of the parasite will not only reduce malaria transmission by female Anopheles mosquitoes, but also reduce the spread of parasites able to evade immunity elicited by vaccines targeting pre-erythrocytic and erythrocytic asexual stages. We focused our studies on Pfs48/45, a protein expressed in the sexual stages developing within an infected person and one of the most promising transmission-blocking vaccine targets. Functional immunogenicity of Pfs48/45 protein requires proper disulfide bond formation, consequently evaluation of the immunogenicity of recombinant full-length Pfs48/45 has been hampered by difficulties in expressing properly folded protein to date. Here we present a strategy involving harmonization of codons for successful recombinant expression of full length Pfs48/45 in Escherichia coli. The purified protein, designated CH-rPfs48/45, was recognized by monoclonal antibodies directed against reduction-sensitive conformational epitopes in the native protein. Immunogenicity evaluation in mice revealed potent transmission blocking activity in membrane feeding assays of antisera elicited by CH-rPfs48/45 formulated in three different adjuvants, i.e. Alum, Montanide ISA-51 and complete Freund's adjuvant. More importantly, CH-rPfs48/45 formulated with Montanide ISA-51 when administered to nonhuman primates (Olive baboons, Papio anubis) resulted in uniformly high antibody responses (ELISA titers >2 million) in all five animals. Sera from these animals displayed greater than 93% blocking activity in membrane feeding assays after a single immunization, reaching nearly complete blocking after a booster dose of the vaccine. The relative ease of expression and induction of potent transmission blocking antibodies in mice and nonhuman primates provide a compelling rationale and basis for development of a CH-rPfs48/45 based malaria transmission blocking vaccine.
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Affiliation(s)
- Debabani Roy Chowdhury
- Department of Molecular Microbiology and Immunology, Johns Hopkins University, Bloomberg School of Public Health, Baltimore, Maryland, United States of America
| | - Evelina Angov
- U.S. Military Malaria Vaccine Program, Walter Reed Army Institute of Research- Naval Medical Research Center (WRAIR-NMRC), Division of Malaria Vaccine Development, Silver Spring, Maryland, United States of America
| | - Thomas Kariuki
- Institute of Primate Research, National Museums of Kenya, Nairobi, Kenya
| | - Nirbhay Kumar
- Department of Molecular Microbiology and Immunology, Johns Hopkins University, Bloomberg School of Public Health, Baltimore, Maryland, United States of America
- * E-mail:
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Dent AE, Chelimo K, Sumba PO, Spring MD, Crabb BS, Moormann AM, Tisch DJ, Kazura JW. Temporal stability of naturally acquired immunity to Merozoite Surface Protein-1 in Kenyan adults. Malar J 2009; 8:162. [PMID: 19607717 PMCID: PMC2719655 DOI: 10.1186/1475-2875-8-162] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2009] [Accepted: 07/16/2009] [Indexed: 11/10/2022] Open
Abstract
Background Naturally acquired immunity to blood-stage Plasmodium falciparum infection develops with age and after repeated infections. In order to identify immune surrogates that can inform vaccine trials conducted in malaria endemic populations and to better understand the basis of naturally acquired immunity it is important to appreciate the temporal stability of cellular and humoral immune responses to malaria antigens. Methods Blood samples from 16 adults living in a malaria holoendemic region of western Kenya were obtained at six time points over the course of 9 months. T cell immunity to the 42 kDa C-terminal fragment of Merozoite Surface Protein-1 (MSP-142) was determined by IFN-γ ELISPOT. Antibodies to the 42 kDa and 19 kDa C-terminal fragments of MSP-1 were determined by serology and by functional assays that measure MSP-119 invasion inhibition antibodies (IIA) to the E-TSR (3D7) allele and growth inhibitory activity (GIA). The haplotype of MSP-119 alleles circulating in the population was determined by PCR. The kappa test of agreement was used to determine stability of immunity over the specified time intervals of 3 weeks, 6 weeks, 6 months, and 9 months. Results MSP-1 IgG antibodies determined by serology were most consistent over time, followed by MSP-1 specific T cell IFN-γ responses and GIA. MSP-119 IIA showed the least stability over time. However, the level of MSP-119 specific IIA correlated with relatively higher rainfall and higher prevalence of P. falciparum infection with the MSP-119 E-TSR haplotype. Conclusion Variation in the stability of cellular and humoral immune responses to P. falciparum blood stage antigens needs to be considered when interpreting the significance of these measurements as immune endpoints in residents of malaria endemic regions.
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Affiliation(s)
- Arlene E Dent
- Case Western Reserve University, Cleveland, OH, USA.
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Coppel RL. Vaccinating with the genome: a Sisyphean task? Trends Parasitol 2009; 25:205-12. [PMID: 19359219 DOI: 10.1016/j.pt.2009.02.006] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2008] [Revised: 01/27/2009] [Accepted: 02/09/2009] [Indexed: 11/24/2022]
Abstract
Human trials of subunit vaccines against the asexual blood stage of malaria are yielding disappointing results, supporting the premise that a single recombinant protein will not be particularly efficacious and that additional proteins must be added. The genome sequence of Plasmodium falciparum offers a large number of additional candidates, but which should be chosen? Various criteria have been suggested to rank the additional candidates, but in the absence of even a partially effective asexual-stage vaccine, the criteria remain unvalidated. These issues are discussed here, together with some suggestions as to how the development of an asexual-stage vaccine could be progressed.
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Affiliation(s)
- Ross L Coppel
- Department of Microbiology, Monash University, Clayton, Victoria 3800, Australia.
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Ogutu BR, Apollo OJ, McKinney D, Okoth W, Siangla J, Dubovsky F, Tucker K, Waitumbi JN, Diggs C, Wittes J, Malkin E, Leach A, Soisson LA, Milman JB, Otieno L, Holland CA, Polhemus M, Remich SA, Ockenhouse CF, Cohen J, Ballou WR, Martin SK, Angov E, Stewart VA, Lyon JA, Heppner DG, Withers MR. Blood stage malaria vaccine eliciting high antigen-specific antibody concentrations confers no protection to young children in Western Kenya. PLoS One 2009; 4:e4708. [PMID: 19262754 PMCID: PMC2650803 DOI: 10.1371/journal.pone.0004708] [Citation(s) in RCA: 224] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2008] [Accepted: 01/05/2009] [Indexed: 11/19/2022] Open
Abstract
Objective The antigen, falciparum malaria protein 1 (FMP1), represents the 42-kDa C-terminal fragment of merozoite surface protein-1 (MSP-1) of the 3D7 clone of P. falciparum. Formulated with AS02 (a proprietary Adjuvant System), it constitutes the FMP1/AS02 candidate malaria vaccine. We evaluated this vaccine's safety, immunogenicity, and efficacy in African children. Methods A randomised, double-blind, Phase IIb, comparator-controlled trial.The trial was conducted in 13 field stations of one mile radii within Kombewa Division, Nyanza Province, Western Kenya, an area of holoendemic transmission of P. falciparum. We enrolled 400 children aged 12–47 months in general good health.Children were randomised in a 1∶1 fashion to receive either FMP1/AS02 (50 µg) or Rabipur® rabies vaccine. Vaccinations were administered on a 0, 1, and 2 month schedule. The primary study endpoint was time to first clinical episode of P. falciparum malaria (temperature ≥37.5°C with asexual parasitaemia of ≥50,000 parasites/µL of blood) occurring between 14 days and six months after a third dose. Case detection was both active and passive. Safety and immunogenicity were evaluated for eight months after first immunisations; vaccine efficacy (VE) was measured over a six-month period following third vaccinations. Results 374 of 400 children received all three doses and completed six months of follow-up. FMP1/AS02 had a good safety profile and was well-tolerated but more reactogenic than the comparator. Geometric mean anti-MSP-142 antibody concentrations increased from1.3 µg/mL to 27.3 µg/mL in the FMP1/AS02 recipients, but were unchanged in controls. 97 children in the FMP1/AS02 group and 98 controls had a primary endpoint episode. Overall VE was 5.1% (95% CI: −26% to +28%; p-value = 0.7). Conclusions FMP1/AS02 is not a promising candidate for further development as a monovalent malaria vaccine. Future MSP-142 vaccine development should focus on other formulations and antigen constructs. Trial Registration Clinicaltrials.gov NCT00223990
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Affiliation(s)
- Bernhards R Ogutu
- US Army Medical Research Unit-Kenya and the Centre for Clinical Research, Kenya Medical Research Institute, Nairobi, Kenya.
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Reed ZH, Kieny MP, Engers H, Friede M, Chang S, Longacre S, Malhotra P, Pan W, Long C. Comparison of immunogenicity of five MSP1-based malaria vaccine candidate antigens in rabbits. Vaccine 2009; 27:1651-60. [DOI: 10.1016/j.vaccine.2008.10.093] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2006] [Revised: 10/21/2008] [Accepted: 10/27/2008] [Indexed: 10/21/2022]
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Prediction of merozoite surface protein 1 and apical membrane antigen 1 vaccine efficacies against Plasmodium chabaudi malaria based on prechallenge antibody responses. CLINICAL AND VACCINE IMMUNOLOGY : CVI 2008; 16:293-302. [PMID: 19116303 DOI: 10.1128/cvi.00230-08] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
For the development of blood-stage malaria vaccines, there is a clear need to establish in vitro measures of the antibody-mediated and the cell-mediated immune responses that correlate with protection. In this study, we focused on establishing correlates of antibody-mediated immunity induced by immunization with apical membrane antigen 1 (AMA1) and merozoite surface protein 1(42) (MSP1(42)) subunit vaccines. To do so, we exploited the Plasmodium chabaudi rodent model, with which we can immunize animals with both protective and nonprotective vaccine formulations and allow the parasitemia in the challenged animals to peak. Vaccine formulations were varied with regard to the antigen dose, the antigen conformation, and the adjuvant used. Prechallenge antibody responses were evaluated by enzyme-linked immunosorbent assay and were tested for a correlation with protection against nonlethal P. chabaudi malaria, as measured by a reduction in the peak level of parasitemia. The analysis showed that neither the isotype profile nor the avidity of vaccine-induced antibodies correlated with protective efficacy. However, high titers of antibodies directed against conformation-independent epitopes were associated with poor vaccine performance and may limit the effectiveness of protective antibodies that recognize conformation-dependent epitopes. We were able to predict the efficacies of the P. chabaudi AMA1 (PcAMA1) and P. chabaudi MSP1(42) (PcMSP1(42)) vaccines only when the prechallenge antibody titers to both refolded and reduced/alkylated antigens were considered in combination. The relative importance of these two measures of vaccine-induced responses as predictors of protection differed somewhat for the PcAMA1 and the PcMSP1(42) vaccines, a finding confirmed in our final immunization and challenge study. A similar approach to the evaluation of vaccine-induced antibody responses may be useful during clinical trials of Plasmodium falciparum AMA1 and MSP1(42) vaccines.
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