PERSISTENCE OF HUMORAL RESPONSE AGAINST SPOROZOITE AND BLOOD-STAGE MALARIA ANTIGENS 7 YEARS AFTER A BRIEF EXPOSURE TO PLASMODIUM-VIVAX

The persistence of malarial antibodies was evaluated in subjects livin g in a rural community (in Minas Gerais State, Brazil) briefly exposed to a Plasmodium vivax malaria outbreak outside of the area in which m alaria was endemic. Transmission was interrupted by treatment of all p atients and their relatives and/or neighbors, although the latter had neither symptoms nor blood parasites. Antibodies to P. vivax antigens (recombinant proteins from sporozoites [rPvCS] and from blood stages [ rPv200]) were measured in parallel by ELISA with sera collected at two time points after transmission. Anti-rPvCS IgG antibodies were positi ve in similar to 404 and 20% of the subjects 8 months and 7 years afte r exposure, respectively. Anti-rPv200 IgG was first detected in 61% of the subjects who had had malarial symptoms and remained positive in 4 7% after 7 years. Among the prophylactically treated group, anti-rPv20 0 IgG was detected in only 28% after 8 months. The levels of both anti bodies decreased with time in all positive subjects.