Identification of HLA-A24 restricted pre-erythrocytic stage specific T-cell epitopes using Plasmodium falciparum synthetic peptides: a preliminary study.

Fourteen (9 amino acids) peptides of Plasmodium falciparum pre-erythrocytic stage antigens, namely, TRAP, CTRP, LSA-1, STARP and MSP-1, restricted to HLA-A24 and specific to T-cell response were identified. The antigen-specific IFN-gamma responses of these synthetic peptides in malaria exposed and non-malaria exposed healthy adult volunteers were detected using the ex vivo ELISPOT assay. Five peptides from TRAP and CTRP antigens significantly increased IFN-y responses of 1/9 in malaria-exposed volunteers. There is no statistically significant difference in positive T-cell response induced by any peptides in malaria exposed volunteers when evaluated as a group. The frequency of expressed HLA-A24 in malaria-exposed and non-malaria-exposed healthy adults living in northwest and central Thailand was 90% (27/30) and 100% (12/12), respectively. Although no association between positive T-cell response and HLA-A24 was found, due to the low number of positive responders achieved, one positive responder in malaria- exposed group was presented as HLA-24.