HLA degenerate T-cell epitopes from Plasmodium falciparum liver stage-specific antigen 1 (LSA-1) are highly conserved in isolates from geographicallydistinct areas

Consider able effort is directed at the development of a malaria vaccine th at elicits antigen-specific T-cell responses against pre-erythrocytic antig ens of Plasmodium falciparum. Genetic restriction of host T-cell responses and polymorphism of target epitopes on parasite antigens pose obstacles to the development of such a vaccine. Liver stage specific antigen-1 (LSA-1) i s a prime candidate vaccine antigen and five T-cell epitopes that are degen erately restricted by HLA molecules common in most populations have been id entified on LSA-1. To define the extent of polymorphism within these T-cell epitopes, the N-terminal non-repetitive region of the LSA-1 gene from Mala ysian P. falciparum field isolates was sequenced and compared with data of isolates from Brazil, Kenya and Papua New Guinea. Three of the T-cell epito pes were completely conserved while the remaining two were highly conserved in the isolates examined. Our findings underscore the potential of includi ng these HLA-degenerate T-cell epitopes of LSA-1 in a subunit vaccine.