Evidence for anti-Plasmodium falciparum antibodies that cross-react with human T-lymphotropic virus type I proteins in a population in Irian Jaya, Indonesia.

This study was performed to demonstrate the presence of anti-Plasmodium falciparum antibodies in a population living in Irian Jaya, Indonesia that cross-react with human T-lymphotropic virus type I (HTLV-I) proteins. Serum samples from 63 volunteers living in Oksibil, a secluded highland valley in Irian Jaya, were tested for anti-P. falciparum antibodies by an immunofluorescence assay and for anti-HTLV-I antibodies by an enzyme immunoassay (EIA). All samples were positive for anti-P. falciparum antibodies at titers of > or = 1:256. Twenty-four samples were reactive by EIA for HTLV-I, and of these, 23 were tested by western blotting (immunoblotting). Five of the 23 samples were classified as western blot positive and 18 were classified as western blot indeterminate. In competitive blocking assays with malaria proteins, western blot immunoreactivity to all HTLV-I Gag proteins was either reduced or eliminated. Significant reductions in the HTLV-I EIA optical density values of the Oksibil sera occurred when the sera were competitively blocked with the malaria antigens. The optical density values of HTLV-I-positive control sera showed no significant change. Competitive blocking with HTLV-I antigens produced reductions in the optical density values of both the Oksibil sera and the HTLV-I-positive control sera. These data suggest that in this population, anti-P. falciparum antibodies are cross-reactive with HTLV-I proteins in the western blot and EIA tests.