Serological, epidemiological, and molecular differences between human T-cell lymphotropic virus type 1 (HTLV-1)-Seropositive healthy carriers and persons with HTLV-I gag indeterminate western blot patterns from the Caribbean

To investigate the significance of serological human T-cell lymphotropic vi rus type 1 (HLTV-1) Gag indeterminate Western blot (WB) patterns in the Car ibbean, a 6-year (1993 to 1998) cross-sectional study was conducted with 37 ,724 blood donors from Guadeloupe (French West Indies), whose sera were rou tinely screened by enzyme immunoassay (EIA) for the presence of HTLV-1 and -2 antibodies. By using stringent WE criteria, 77 donors (0.20%) were confi rmed HTLV-1 seropositive, whereas 150 (0.40%; P < 0.001) were considered HT LV seroindeterminate. Among them, 41.3% (62) exhibited a typical HTLV-1 Gag indeterminate profile (HGIP). Furthermore 76 (50.7%) out of the 150 HTLV-s eroindeterminate subjects were sequentially retested, with a mean duration of follow-up of 18.3 months (range, 1 to 70 months). Of these, 55 (72.4%) w ere still EIA positive and maintained the same WE profile whereas the other s became EIA negative. This follow-up survey included 33 persons with an HG IP. Twenty-three of them (69.7%) had profiles that did not evolve over time . Moreover, no case of HTLV-1 seroconversion could be documented over time by studying such sequential samples. HTLV-1 seroprevalence was characterize d by an age-dependent curve, a uniform excess in females, a significant rel ation with hepatitis B core (HBc) antibodies, and a microcluster distributi on along the Atlantic coast of Guadeloupe. In contrast, the persons with an HGIP were significantly younger, had a 1:1 sex ratio, did not present any association with HBc antibodies, and were not clustered along the Atlantic facade. These divergent epidemiological features, together with discordant serological screening test results for subjects with HGIP and with the lack of HTLV-1 proviral sequences detected by PCR in their peripheral blood mon onuclear cell DNA, strongly suggest that an HGIP does not reflect true HTLV -1 infection. In regard to these data, healthy blood donors with HGIP shoul d be reassured that they are unlikely to be infected with HTLV-1 or HTLV-2.