IMMUNOEPIDEMIOLOGY OF PVRII, A PUTATIVE VACCINE CANDIDATE REPRESENTING PLASMODIUM VIVAX DUFFY BINDING PROTEIN, IN SRI LANKAA

Abstract

Study of naturally acquired antibody responses to a potential vaccrne candidate ts rmperatrve to provide insights to vaccine deve opment. Recombinant protein PvRll, a putative vaccine candrdate representrng regron ll of native Plasmodrum vivaxDlffy Bindrng Protein (DBP), was used in ELISA to examine the total (lgG+tgM), igM and tgG isotype antibody responses A reductlon sensiiive ELISA was preformed for toial antrbocjies. Se:-a were collected from acute vivax malaria patients from two endemic areas (EAs) ,rvhere low and unstable malaria conditions prevail, and fronr a non-endemic area (NEA) in Sri Lanka. Pre,yalence of totai antibodies was 50% from Colombo (NEA; N=111),46% from Anuradhapura (EA; N=94) and 41ok fron Kataragarna (EA, N=106) Significantly higher prevaience (Chi square, P<0 05) and magnitude (ANOVA, P<0 0't ) of tota antibodies were recorded from NEA compared with E,As. Total antibody parameters rn all test populatrons,,vere independent of aEe of indivrduals, parasite density and previous exposure. Conformation sensitrve anti-pvRll nronoclonai antibody 2H 1 0 reacted only w th non-reduced pvRil but not with its reduced form. Test sera partially reacted with i'educed PvR1l, and this indicating the recognition of irnear B cell eprtopes. A parailr.l increase in total anlibody response to PvRll linear epitopes wrth rncreasrng e\pcsure v.ras detected n residents of Kataragama. No signrficant difference was detected arnong test populatrons either in anti-PvRli lgM prelavence (Cht square. P>0.05) or magnitude (ANOVA, P>0.05). Prevalence of 19G3 (Chi