%0 Journal Article
%T Evaluation of the acquired immune responses to Plasmodium vivax VIR variant antigens in individuals living in malaria-endemic areas of Brazil
%A Tatiane R Oliveira
%A Carmen Fernandez-Becerra
%A Maria Carolina S Jimenez
%A Hernando A Del Portillo
%A Irene S Soares
%J Malaria Journal
%D 2006
%I BioMed Central
%R 10.1186/1475-2875-5-83
%X Seven recombinant proteins representing four vir subfamilies (A, B, C, and E) obtained from a single patient from the Amazon Region were expressed in Escherichia coli as soluble glutathione S-transferase fusion proteins. The different recombinant proteins were compared by ELISA with regard to the recognition by IgM, IgG, and IgG subclass of antibodies from 200 individuals with patent infection.The frequency of individuals that presented antibodies anti-VIR (IgM plus IgG) during the infection was 49%. The frequencies of individuals that presented IgM or IgG antibodies anti-VIR were 29.6% or 26.0%, respectively. The prevalence of IgG antibodies against recombinant VIR proteins was significantly lower than the prevalence of antibodies against the recombinant proteins representing two surface antigens of merozoites of P. vivax: AMA-1 and MSP119 (57.0% and 90.5%, respectively). The cellular immune response to VIR antigens was evaluated by in vitro proliferative assays in mononuclear cells of the individuals recently exposed to P. vivax. No significant proliferative response to these antigens was observed when comparing malaria-exposed to non-exposed individuals.This study provides evidence that there is a low frequency of individuals responding to each VIR antigens in endemic areas of Brazil. This fact may explain the host susceptibility to new episodes of the disease.Plasmodium vivax is the second most prevalent malaria species of world with an estimated 80¨C90 million cases a year [1]. In Americas and Asia, P. vivax is the most prevalent malaria species, and in Brazil it represents more than 75% of the clinical cases reported annually [2].Variant antigens exposed on P. vivax-infected reticulocytes are encoded by a single multigene superfamily termed vir (P. vivax variant genes), with circa 600¨C1,000 copies per haploid genome [3]. Moreover, in silico analysis of vir sequences from endemic regions have demonstrated that sequences can be grouped into different subfamilies
%U http://www.malariajournal.com/content/5/1/83