CELLULAR-IMMUNITY TO MEROZOITE SURFACE PROTEIN-2 (FC27 AND 3D7) IN PAPUA-NEW-GUINEAN CHILDREN - TEMPORAL VARIATION AND RELATION TO CLINICALAND PARASITOLOGICAL STATUS

A prospective study in 207 children aged 0.5-15 years was carried out in a highly endemic area of Papua New Guinea to examine the relationsh ip between cellular responses to Plasmodium falciparum merozoite surfa ce protein 2 (MSP2) and malaria infection and morbidity. In vitro prol iferation, IFN-gamma and IL-4 induction were measured against two reco mbinant proteins of MSP2, FC27 and 3D7 as well as against a form of th e 3D7 MSP2 lacking the central repetitive sequences (d3D7). The preval ence of proliferative response was generally low, 6% for FC27, 9% for 3D7 and 11% for d3D7. A higher prevalence of IL-4 response was obtaine d being 27% for FC27, 34% for 3D7 and 30% for d3D7 while the prevalenc e of IFN-gamma response was 13%, 15% and 18%, respectively. There was no correlation between age and proliferative responses; in contrast cy tokine production increased with age for all three anti gens. When pro liferation or stimulation of either cytokine was used to assess T-cell activation the frequency of responders increased to 39%, 47% and 46% for FC27, 3D7 and d3D7 respectively. Analysis of the relation of T cel l responses to concurrent infection and morbidity showed that lymphopr oliferative response only to d3D7 was significantly associated with pa rasitaemia; while lymphoproliferative responses to all 3 MSP2 antigens were highest in the group of clinical malaria cases. There was no sig nificant correlation between proliferation or cytokine production to M SP2 and concurrent or subsequent malaria morbidity.