Longevity of naturally-acquired antibody response to Plasmodium Vivax merozoite surface protein 1 paralog vaccine candidate

Abstract

Plasmodium vivax merozoite surface protein 1 paralog (PvMSP1P) is a glycosylphosphatidylinositol anchored blood-stage protein expressed on merozoite surface. It is proposed as a blood-stage vaccine candidate against P. vivax because of its ability to induce immune responses on natural P. vivax exposure and in immunized animal. Here, cross-sectional survey and longitudinal study were conducted for monitoring the longevity of antibody and memory B cell responses to PvMSP1P during and after infection with P. vivax. The antibody titer and neutralizing antibodies against PvMSP1P-erythrocyte binding were demonstrated by using enzyme-linked immunosorbent assay (ELISA) and in vitro erythrocyte inhibition binding assay (EIBA) respectively. In addition, memory B cell response to PvMSP1P was also performed using flow cytometric analysis and enzyme-linked immunospot (ELISPOT) assay. The seroprevalence of anti-PvMSP1P response was significantly higher in acutely infected P. vivax patients, 73% of total 40 individuals had a seropositive response to this antigen. The positive anti-PvMSP1P response was maintained up to 9 months post-infection. The high responder group from PvMSP1P-seropositive patients strongly inhibited the binding to erythrocytes and some individuals had a stable anti-PvMSP1P neutralizing antibody for at least 12 months post-infection. Interestingly, this persistence of antibody response was associated with the presence of PvMSP1P-specific memory B cells and the maintenance of circulating CD19+CD10-CD27+ cells at post-infection. Altogether, PvMSP1P antigen has immunogenicity in induction of antibody response and memory B cell development during infection which could be maintained after recovered from infection. Therefore, PvMSP1P antigen should also be considered as a reliable vaccine candidate for blood-stage P. vivax