title: 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.
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.
authors.affiliation: Laboratório de Imunoparasitologia, Instituto Oswaldo Cruz, Fundação Oswaldo Cruz (FIOCRUZ), Rio de Janeiro, RJ, Brazil.
authors.forename: Rodrigo Nunes
authors.initials: RN
authors.lastname: Rodrigues-da-Silva
authors.affiliation: Computational Modeling Group-FIOCRUZ-CE, Fortaleza, Brazil.
authors.forename: João Hermínio
authors.initials: JH
authors.lastname: Martins da Silva
authors.affiliation: Emory Vaccine Center, Yerkes National Primate Research Center, Emory University, Atlanta, GA, United States of America.
authors.forename: Balwan
authors.initials: B
authors.lastname: Singh
authors.affiliation: Emory Vaccine Center, Yerkes National Primate Research Center, Emory University, Atlanta, GA, United States of America.
authors.forename: Jianlin
authors.initials: J
authors.lastname: Jiang
authors.affiliation: Environmental Health and Safety Office, Emory University, Atlanta, GA, United States of America.
authors.forename: Esmeralda V S
authors.initials: EV
authors.lastname: Meyer
authors.affiliation: National Health Foundation, Department of Entomology, Central Laboratory, Porto Velho, RO, Brazil.
authors.forename: Fátima
authors.initials: F
authors.lastname: Santos
authors.affiliation: Laboratory of Simulids and Onchocerciasis "Malaria and Onchocerciasis Research", Oswaldo Cruz Institute, Oswaldo Cruz Foundation, Rio de Janeiro, Brazil.
authors.forename: Dalma Maria
authors.initials: DM
authors.lastname: Banic
authors.affiliation: Emory Vaccine Center, Yerkes National Primate Research Center, Emory University, Atlanta, GA, United States of America.|Division of Infectious Diseases, Department of Medicine, Emory University School of Medicine, Emory University, Atlanta, GA, United States of America.
authors.forename: Alberto
authors.initials: A
authors.lastname: Moreno
authors.affiliation: Emory Vaccine Center, Yerkes National Primate Research Center, Emory University, Atlanta, GA, United States of America.|Division of Infectious Diseases, Department of Medicine, Emory University School of Medicine, Emory University, Atlanta, GA, United States of America.
authors.forename: Mary R
authors.initials: MR
authors.lastname: Galinski
authors.affiliation: Laboratório de Imunoparasitologia, Instituto Oswaldo Cruz, Fundação Oswaldo Cruz (FIOCRUZ), Rio de Janeiro, RJ, Brazil.
authors.forename: Joseli
authors.initials: J
authors.lastname: Oliveira-Ferreira
authors.affiliation: Laboratório de Imunoparasitologia, Instituto Oswaldo Cruz, Fundação Oswaldo Cruz (FIOCRUZ), Rio de Janeiro, RJ, Brazil.
authors.forename: Josué da Costa
authors.initials: Jda C
authors.lastname: Lima-Junior
mesh_terms: D000818:Animals; D000913:Antibodies, Protozoan / Q000235:genetics / Q000276:immunology*; D003198:Computer Simulation; D018985:Epitopes, B-Lymphocyte / Q000235:genetics / Q000276:immunology*; D007074:Immunoglobulin G / Q000235:genetics / Q000276:immunology; D017780:Malaria Vaccines / Q000235:genetics / Q000276:immunology*; D008565:Membrane Proteins / Q000235:genetics / Q000276:immunology*; D051379:Mice; D010455:Peptides / Q000235:genetics / Q000276:immunology*; D010966:Plasmodium vivax / Q000235:genetics / Q000276:immunology*; D015800:Protozoan Proteins / Q000235:genetics / Q000276:immunology*
chemical_list: D000913:Antibodies, Protozoan; D018985:Epitopes, B-Lymphocyte; D007074:Immunoglobulin G; D017780:Malaria Vaccines; D008565:Membrane Proteins; D010455:Peptides; D015800:Protozoan Proteins; C455300:merozoite surface protein 9, Plasmodium