However , a notable finding of our study was the low recognition frequency of responses to pre-erythrocytic antigens, including the leading vaccine candidates CSP, TRAP, and LSA1. after adjusting for prior malaria exposure (aHR 0. 52, P=. 009). Conclusions. In this high transmission setting, IFN 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. Keywords: malaria, falciparum, IFN, T cell, immunity, antimalarial chemoprevention Plasmodium falciparummalaria continues to be a leading cause of morbidity and mortality in Sub-Saharan Africa [1, 2]. Although children living in endemic settings eventually develop clinical immunity to malaria, most individuals experience numerous infections before clinical protection is achieved. A vaccine to prevent malaria is urgently needed, but progress has been limited by our lack of understanding of both the criticalP. falciparumantigenic targets and the immune effector mechanisms needed to confer protective immunity. Growing evidence suggests that malaria-specific T cells induced by natural infection or by vaccination may protect against clinical disease [38]. T-cell responses to blood-stage antigens, including merozoite surface antigen 1 (MSP1), are frequently observed among children living in endemic settings, and a few studies have found them to be associated with protection from future malaria [4, 8]. However , thus far blood-stage vaccines have not proven efficacious [9]. Several lines of evidence have prompted a growing interest in pre-erythrocytic stage malaria antigens as potential vaccine targets. T-cell responses to the pre-erythrocytic circumsporozoite (CSP) antigen have been shown to correlate with protection from future parasitemia [3, 6], and Cinchocaine a subunit vaccine (RTS, S) incorporating CSP has modestly reduced clinicalP. falciparummalaria in African infants in phase 2 and 3 trials [1012]. T-cell responses to other pre-erythrocytic proteins including TRAP and LSA-1 have also been associated with protection in humans [5, 7, 13, 14]. Moreover, it has long been known that vaccination with irradiated sporozoites, which arrest development during the liver stage, confers sterile protective immunity in humans [1518], suggesting an important role for the T-cell response to pre-erythrocytic antigens in Cinchocaine mediating vaccine-induced immune protection. The use of chemoprevention, either seasonal or year-round, has recently been explored as a public health strategy to prevent mortality and morbidity due to childhood malaria in endemic settings [19, 20]. Although it has been shown to be effective in reducing malaria, concerns have been raised that a rebound increase in malaria incidence may be observed once chemoprevention is stopped, due to delayed development of protective immune responses [21, 22]. However , recent studies suggest that provision of antimalarial Rabbit Polyclonal to ZNF174 drugs that target blood-stage malaria may actually enhance the development of cellular immune responses directed at pre-erythrocytic antigens and, somewhat paradoxically, foster the development of protective immunity, a strategy termed infection-treatment vaccination [2327]. Cinchocaine In these studies, individuals experimentally infected by sporozoites while receiving chloroquine, which prevents blood-stage malaria but allows the clinically silent liver stage infection to develop, consistently exhibited sterile protection upon rechallenge [2527]. These data suggest that limiting exposure to blood-stage infection may actually enhance Cinchocaine the development of immune responses to pre-erythrocytic stages, perhaps due to enhanced exposure to liver stage antigens [28] or avoidance of immunoregulatory mechanisms induced by parasitemia [29]. By analogy, provision of chemoprevention to heavily exposed children might actually encourage pre-erythrocytic responses and foster the development of protective immunity. In this study, we performed a longitudinal evaluation of malaria-specific T-cell responses generated in response to natural infection and compared the responses of children receiving monthly chemoprevention with dihydroartemisinin-piperaquine (DP) to those receiving no chemoprevention as part of a randomized clinical trial. We hypothesized that interferon (IFN) responses to pre-erythrocytic antigens would be associated with protection from malaria, and that selective suppression of blood-stage malaria by chemoprevention given to children living in a high endemicity setting may limit the development of T-cell responses to blood-stage antigens and enhance the development of responses to pre-erythrocytic antigens. == METHODS == == Study Participants and Design == Samples were obtained from children enrolled in a randomized, controlled, open-label trial comparing the efficacy and safety of 3 regimens vs no therapy for the prevention of malaria in Tororo, a district in eastern Uganda with intense year-round malaria transmission and an entomological inoculation rate estimated at 125.