title: Evaluation of naturally acquired IgG antibodies to a chimeric and non-chimeric recombinant species of Plasmodium vivax reticulocyte binding protein-1: lack of association with HLA-DRB1*/DQB1* in malaria exposed individuals from the Brazilian Amazon.
abstract: The development of modular constructs that include antigenic regions targeted by protective immune responses is an attractive approach for subunit vaccine development. However, a main concern of using these vaccine platforms is how to preserve the antigenic identity of conformational B cell epitopes. In the present study we evaluated naturally acquired antibody responses to a chimeric protein engineered to contain a previously defined immunodominant domain of the Plasmodium vivax reticulocyte binding protein-1 located between amino acid positions K435-I777. The construct also includes three regions of the cognate protein (F571-D587, I1745-S1786 and L2235-E2263) predicted to contain MHC class II promiscuous T cell epitopes. Plasma samples from 253 naturally exposed individuals were tested against this chimeric protein named PvRMC-RBP1 and a control protein that includes the native sequence PvRBP123-751 in comparative experiments to study the frequency of total IgG and IgG subclass reactivity. HLA-DRB1 and HLA-DQB1 allelic groups were typed by PCR-SSO to evaluate the association between major HLA class II alleles and antibody responses. We found IgG antibodies that recognized the chimeric PvRMC-RBP1 and the PvRBP123-751 in 47.1% and 60% of the studied population, respectively. Moreover, the reactivity index against both proteins were comparable and associated with time of exposure (p<0.0001) and number of previous malaria episodes (p<0.005). IgG subclass profile showed a predominance of cytophilic IgG1 over other subclasses against both proteins tested. Collectively these studies suggest that the chimeric PvRMC-RBP1 protein retained antigenic determinants in the PvRBP1435-777 native sequence. Although 52.9% of the population did not present detectable titers of antibodies to PvRMC-RBP1, genetic restriction to this chimeric protein does not seem to occur, since no association was observed between the HLA-DRB1* or HLA-DQB1* alleles and the antibody responses. This experimental evidence strongly suggests that the identity of the conformational B cell epitopes is preserved in the chimeric protein.
authors.affiliation: Laboratory of Immunoparasitology, Oswaldo Cruz Institute, Oswaldo Cruz Foundation, (FIOCRUZ), Rio de Janeiro, RJ, Brazil.
authors.forename: Amanda Ribeiro
authors.initials: AR
authors.lastname: Ferreira
authors.affiliation: Emory Vaccine Center, Yerkes National Primate Research Center, Emory University, Atlanta, Georgia, 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, Georgia, United States of America.
authors.forename: Monica
authors.initials: M
authors.lastname: Cabrera-Mora
authors.affiliation: Laboratory of Immunoparasitology, Oswaldo Cruz Institute, Oswaldo Cruz Foundation, (FIOCRUZ), Rio de Janeiro, RJ, Brazil.
authors.forename: Alana Cristina
authors.initials: AC
authors.lastname: Magri De Souza
authors.affiliation: Histocompatibility and Cryopreservation Laboratory, Rio de Janeiro State University, Rio de Janeiro, Brazil.
authors.forename: Maria Teresa
authors.initials: MT
authors.lastname: Queiroz Marques
authors.affiliation: Histocompatibility and Cryopreservation Laboratory, Rio de Janeiro State University, Rio de Janeiro, Brazil.
authors.forename: Luis Cristovão Sobrino
authors.initials: LC
authors.lastname: Porto
authors.affiliation: National Health Foundation, Department of Entomology, Central Laboratory, Porto Velho, RO, Brazil.
authors.forename: Fatima
authors.initials: F
authors.lastname: Santos
authors.affiliation: Laboratory for Simuliidae and Onchocerciasis, Oswaldo Cruz Institute, Oswaldo Cruz Foundation, (FIOCRUZ), Rio de Janeiro, RJ, Brazil.
authors.forename: Dalma Maria
authors.initials: DM
authors.lastname: Banic
authors.affiliation: Department of Pathology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America.
authors.forename: J Mauricio
authors.initials: JM
authors.lastname: Calvo-Calle
authors.affiliation: Laboratory of Immunoparasitology, Oswaldo Cruz Institute, Oswaldo Cruz Foundation, (FIOCRUZ), Rio de Janeiro, RJ, Brazil.
authors.forename: Joseli
authors.initials: J
authors.lastname: Oliveira-Ferreira
authors.affiliation: Emory Vaccine Center, Yerkes National Primate Research Center, Emory University, Atlanta, Georgia, United States of America; Division of Infectious Diseases, Department of Medicine, Emory University, Atlanta, Georgia, United States of America.
authors.forename: Alberto
authors.initials: A
authors.lastname: Moreno
authors.affiliation: Laboratory of Immunoparasitology, Oswaldo Cruz Institute, Oswaldo Cruz Foundation, (FIOCRUZ), Rio de Janeiro, RJ, Brazil.
authors.forename: Josué Da Costa
authors.initials: JC
authors.lastname: Lima-Junior
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000595:Amino Acid Sequence; D000818:Animals; D001938:Brazil; D016022:Case-Control Studies; D002648:Child; D018984:Epitopes, T-Lymphocyte / Q000276:immunology; D005260:Female; D059866:HLA-DQ beta-Chains / Q000235:genetics / Q000276:immunology*; D059811:HLA-DRB1 Chains / Q000235:genetics / Q000276:immunology*; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood*; D017780:Malaria Vaccines / Q000235:genetics* / Q000276:immunology; D016780:Malaria, Vivax / Q000235:genetics / Q000276:immunology*; D008297:Male; D008565:Membrane Proteins / Q000235:genetics / Q000276:immunology*; D008807:Mice, Inbred BALB C; D008875:Middle Aged; D008969:Molecular Sequence Data; D010966:Plasmodium vivax / Q000472:pathogenicity; D015800:Protozoan Proteins / Q000235:genetics / Q000276:immunology*; D011994:Recombinant Proteins / Q000235:genetics / Q000276:immunology; D055815:Young Adult
chemical_list: D018984:Epitopes, T-Lymphocyte; D059866:HLA-DQ beta-Chains; C069051:HLA-DQB1 antigen; D059811:HLA-DRB1 Chains; D007074:Immunoglobulin G; D017780:Malaria Vaccines; D008565:Membrane Proteins; D015800:Protozoan Proteins; D011994:Recombinant Proteins; C075483:reticulocyte-binding protein, Plasmodium vivax