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. © 1995 Wiley‐Liss, Inc.