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 living in a rural community (in Minas Gerais State, Brazil) briefly exposed to a Plasmodium vivax malaria outbreak outside of the area in which malaria was endemic. Transmission was interrupted by treatment of all patients 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 positive in approximately 40% and 20% of the subjects 8 months and 7 years after exposure, respectively. Anti-rPv200 IgG was first detected in 61% of the subjects who had had malarial symptoms and remained positive in 47% after 7 years. Among the prophylactically treated group, anti-rPv200 IgG was detected in only 28% after 8 months. The levels of both antibodies decreased with time in all positive subjects.