Human T-lymphotropic virus type I/II infections in volunteer blood donors from Northern and Western Greece: increased prevalence in one blood bank unit

BACKGROUND: Blood donors are routinely screened for antibodies to human T-cell lymphotropic viruses type I and II (HTLV-I and HTLV-II) in the United States, Canada, Japan, and some European countries. Previous reports from our group in relatively small numbers of donors have shown a zero prevalence of HTLV-I/II markers in our region. In this study, seven blood banks in the north and west of Greece participated in order to determine whether mandatory screening of blood donations for HTLV-I/II infection should be established. METHODS: Sera from 51,714 consecutive donors were investigated for anti-HTLV-I/II using two commercially available enzyme immunoassays (EIAs). Reactive samples in one or both EIAs were repeatedly evaluated further by Western blot, which is specific for both confirmation and differentiation of HTLV-I and HTLV-II seroreactivities. Investigation for HTLV DNA was also done in all EIA-reactive donors, irrespective of the WB result, using a combination assay based on the polymerase chain reaction (PCR) and a DNA EIA. RESULTS: A total of 115 donors (0.222%; 95% CI 0.018-0.26%) were initially considered reactive for anti-HTLV-I/II by EIAs. However, only 7 of the 115 were confirmed as positive by WB (five HTLV-I and two HTLV-I/II). Thus, the prevalence of anti-HTLV-I/II in donors from northern and western Greece was 0.013% (95% CI 0.003-0.023%). Interestingly, the majority of WB-confirmed anti-HTLV-positive individuals were detected in the blood bank of Corfu (5/7, all anti-HTLV-I). This prevalence (5/15383; 0.032%; 95% CI 0.004-0.061%) was six times the prevalence found at the other blood banks combined (2/36331; 0.0055%; 95% CI 0-0.013%), but it was not statistically significant. None of the EIA-reactive donors had detectable HTLV DNA. CONCLUSIONS: The very low prevalence of confirmed anti-HTLV-I/II infection markers in northern and western Greek blood donors, together with the negative PCR results in EIA-reactive subjects, indicates that anti-HTLV-I/I routine screening is not really justified in this area of our country. However, the increased prevalence of WB-confirmed anti-HTLV-I-positive donors in the Corfu blood bank calls for further prospective and careful investigation in order to address whether this finding represents a real cluster phenomenon of HTLV infection.