In silico Identification and Validation of a Linear and Naturally Immunogenic B-Cell Epitope of the Plasmodium vivax Malaria Vaccine Candidate Merozoite Surface Protein-9

• Type of Material: Article
• Authors: Rodrigo Nunes Rodrigues-da-Silva, Fundação Oswaldo Cruz; João Hermínio Martins da Silva, Fundação Oswaldo Cruz; Balwan Singh, Emory University; Jianlin Jiang, Emory University; Esmeralda Meyer, Emory University; Fátima Santos, National Health Foundation, Brazil; Dalma Maria Banic, Fundação Oswaldo Cruz; Alberto Moreno, Emory University; Mary Galinski, Emory University; Joseli Oliveira-Ferreira, Fundação Oswaldo Cruz; Josué da Costa Lima-Junior, Fundação Oswaldo Cruz
• Language: English
• Date: 2016-01-20
• Publisher: Public Library of Science
• Publication Version: Final Published Version
• Copyright Statement: © 2016 Rodrigues-da-Silva et al
• License: Creative Commons Attribution 4.0 International
• Final Published Version (URL): http://dx.doi.org/10.1371/journal.pone.0146951
• Title of Journal or Parent Work: PLoS ONE
• ISSN: 1932-6203
• Volume: 11
• Issue: 1
• Start Page: e0146951
• End Page: e0146951
• Grant/Funding Information: JCLJ is recipient of a FAPERJ-APQ1 (E-26/111.248/2014) and CPNq-Universal research grants (445150/2014-9), JOF is recipient of CNPq Productivity Fellowship.; This work was supported by Brazilian National Research Council – CNPq/PAPES, (Conselho Nacional de Desenvolvimento Científico e Tecnológico/Programa de Apoio Pesquisa Estratégica em Saúde) Fiocruz, the National Institute of Health (NIH Grant #RO1 1R01AI24710), and the Yerkes National Primate Research Center Base Grant (ORIP/OD P51OD011132) awarded by the National Center for Research Resources of the National Institutes of Health.
• Keywords: SYNTHETIC VACCINE; Multidisciplinary Sciences; Science & Technology; BLOOD-STAGE MALARIA; Science & Technology - Other Topics; REDUCED RISK; PROTECTIVE IMMUNITY; IMMUNE-RESPONSES; FALCIPARUM; CIRCUMSPOROZOITE PROTEIN; WEB SERVER; APICAL MEMBRANE ANTIGEN-1; BRAZILIAN AMAZON
• Research Categories: Health Sciences, Pharmacology; Health Sciences, General; Health Sciences, Immunology

Abstract

Synthetic peptide vaccines provide the advantages of safety, stability and low cost. The success of this approach is highly dependent on efficient epitope identification and synthetic strategies for efficacious delivery. In malaria, the Merozoite Surface Protein-9 of Plasmodium vivax (PvMSP9) has been considered a vaccine candidate based on the evidence that specific antibodies were able to inhibit merozoite invasion and recombinant proteins were highly immunogenic in mice and humans. However the identities of linear B-cell epitopes within PvMSP9 as targets of functional antibodies remain undefined. We used several publicly-available algorithms for in silico analyses and prediction of relevant B cell epitopes within PMSP9. We show that the tandem repeat sequence EAAPENAEPVHENA (PvMSP9E795-A808) present at the C-terminal region is a promising target for antibodies, given its high combined score to be a linear epitope and located in a putative intrinsically unstructured region of the native protein. To confirm the predictive value of the computational approach, plasma samples from 545 naturally exposed individuals were screened for IgG reactivity against the recombinant PvMSP9-RIRII729-972 and a synthetic peptide representing the predicted B cell epitope PvMSP9E795-A808. 316 individuals (58%) were responders to the full repetitive region PvMSP9-RIRII, of which 177 (56%) also presented total IgG reactivity against the synthetic peptide, confirming it validity as a B cell epitope. The reactivity indexes of anti-PvMSP9-RIRII and anti-PvMSP9E795-A808 antibodies were correlated. Interestingly, a potential role in the acquisition of protective immunity was associated with the linear epitope, since the IgG1 subclass against PvMSP9E795-A808 was the prevalent subclass and this directly correlated with time elapsed since the last malaria episode; however this was not observed in the antibody responses against the full PvMSP9-RIRII. In conclusion, our findings identified and experimentally confirmed the potential of PvMSP9E795-A808 as an immunogenic linear B cell epitope within the P. vivax malaria vaccine candidate PvMSP9 and support its inclusion in future subunit vaccines.