IFNγ Responses to Pre-erythrocytic and Blood-stage Malaria Antigens Exhibit Differential Associations With Past Exposure and Subsequent Protection

Background. The malaria-specific T-cell response is believed to be important for protective immunity. Antimalarial chemoprevention may affect this response by altering exposure to malaria antigens. Methods.aEuro integral We performed interferon gamma (IFN gamma) ELISpot assays to assess the cellular immune response to blood-stage and pre-erythrocytic antigens longitudinally from 1 to 3 years of age in 196 children enrolled in a randomized trial of antimalarial chemoprevention in Tororo, Uganda, an area of high transmission intensity. Results.aEuro integral IFN gamma responses to blood-stage antigens, particularly MSP1, were frequently detected, strongly associated with recent malaria exposure, and lower in those adherent to chemoprevention compared to nonadherent children and those randomized to no chemoprevention. IFN gamma responses to pre-erythrocytic antigens were infrequent and similar between children randomized to chemoprevention or no chemoprevention. Responses to blood-stage antigens were not associated with subsequent protection from malaria (aHR 0.96, P = .83), but responses to pre-erythrocytic antigens were associated with protection after adjusting for prior malaria exposure (aHR 0.52, P = .009). Conclusions.aEuro integral In this high transmission setting, IFN gamma responses to blood-stage antigens were common and associated with recent exposure to malaria but not protection from subsequent malaria. Responses to pre-erythrocytic antigens were uncommon, not associated with exposure but were associated with protection from subsequent malaria.