Mapping of a human T-lymphotropic virus type I gag protein epitope that cross-reacts with anti-Plasmodium falciparum antibodies.

Studies in Palawan, Philippines, and Irian Jaya, Indonesia, showed that indeterminate human T-lymphotropic virus type I (HTLV-I) Western blot immunoreactivity is due to cross-reacting anti-Plasmodium falciparum antibodies. To further define this immunoreactivity, mapping studies were conducted using the HTLV-I p19 protein to identify the precise epitope that reacts with these antibodies. Anti-P. falciparum antibody-positive sera from Palawan, Philippines, and Irian Jaya, Indonesia, were studied using overlapping synthetic peptides. Immunoreactivity was localized to residues 108-120 of p19. Further analysis of the sera with 5 biotinylated synthetic peptides showed that the cross-reactive epitope consists of the sequence PDSDPQI (amino acid residues 110-116), which was shown to be homologous to a 7 amino acid sequence on the Exp-1 protein of the P. falciparum blood stage parasite. This is the first study that identifies a specific HTLV-I protein epitope that cross-reacts with malaria antibodies.