Immunoepidemiology of Plasmodium vivax Merozoite Surface Protein-4 (PVMSP-4) in Sri Lanka: A Preliminary Study

Abstract

Natural antibody (IgG + IgM) responses to putative vaccine candidate, Plasmodium vivax Merozoite Surface Protein-4, in acute vivax malaria patients in endemic and non-endemic areas of Sri Lanka, were assayed by indirect ELISA using PvMSP-4 baculovirus derived recombinant protein. The study populations were from two vivax malaria endemic areas, Anuradhapura and Kataragama and from a nonendemic area, Colombo. PvMSP4 appeared to be immunogenic in all test populations with a prevalence of 80%, 62% and 62% from Colombo, Anuradhapura and Kataragama, respectively. A significantly higher prevalence and antibody magnitude was recorded for non-endemic Colombo, but with no significant differences between individuals previously not exposed to malaria and those with prior exposure. A positive trend in responders from Kataragama was evident between the antibody prevalence and previous exposure. We previously reported the antibody response to PvMSP-1 (p19 and p42) using the same battery of sera, and when comparisons were drawn, more than 80% from each test area responded to at least one of the three antigens tested. Importantly, 7%, 11% and 4% of individuals from Colombo, Anuradhapura, and Kataragama, respectively, preferentially recognized PvMSP-4. Responders to MSP-1p42 and p19 in paired combination showed higher prevalence compared with combinations of MSP-1 with MSP-4.