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

PLoS One. 2014 Aug 22;9(8):e105828. doi: 10.1371/journal.pone.0105828. eCollection 2014.

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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Amino Acid Sequence
  • Animals
  • Brazil
  • Case-Control Studies
  • Child
  • Epitopes, T-Lymphocyte / immunology
  • Female
  • HLA-DQ beta-Chains / genetics
  • HLA-DQ beta-Chains / immunology*
  • HLA-DRB1 Chains / genetics
  • HLA-DRB1 Chains / immunology*
  • Humans
  • Immunoglobulin G / blood*
  • Malaria Vaccines / genetics*
  • Malaria Vaccines / immunology
  • Malaria, Vivax / genetics
  • Malaria, Vivax / immunology*
  • Male
  • Membrane Proteins / genetics
  • Membrane Proteins / immunology*
  • Mice, Inbred BALB C
  • Middle Aged
  • Molecular Sequence Data
  • Plasmodium vivax / pathogenicity
  • Protozoan Proteins / genetics
  • Protozoan Proteins / immunology*
  • Recombinant Proteins / genetics
  • Recombinant Proteins / immunology
  • Young Adult

Substances

  • Epitopes, T-Lymphocyte
  • HLA-DQ beta-Chains
  • HLA-DQB1 antigen
  • HLA-DRB1 Chains
  • Immunoglobulin G
  • Malaria Vaccines
  • Membrane Proteins
  • Protozoan Proteins
  • Recombinant Proteins
  • reticulocyte-binding protein, Plasmodium vivax