Detection of rare cases of HTLV-I and -II infections and high numbers of HTLV-seroindeterminate results in Bavarian blood donors

Background: In order to evaluate the prevalence of human T-cell lymphotropi c virus type I and II (HTLV-I/-II) infections in Germany, the Bavarian bloo d donor population was screened. Material and Methods: Between 1991 and 199 4 around 1.5 million donations from about 375,000 blood donors of the Bavar ian Red Cross (BRK) were tested for HTLV-I/-II in an antibody screening tes t. Sera repeatedly reactive in the screening test at the BRK blood bank wer e further assayed in additional enzyme-linked immunosorbent assays (ELISA), Western blot (WB) and radioimmunoprecipitation assay (RIPA). Selected dono rs were analyzed by polymerase chain reaction (PCR). Results: Only 4 HTLV-I /-II infections could be confirmed by WB and by RIPA, indicating a seroprev alence of 0.001%. Three positive donors were American soldiers and the four th one was a German woman. Out of 609 sera reactive in at least two antibod y screening tests, only 4 could be confirmed in WB as HTLV-I or -II positiv e. However, reactivity of these sera appears not to be related to an HTLV-I or -II infection, as shown by selected samples testing negative by RIPA an d PCR. Conclusions: HTLV-I/-II seroprevalence in Bavarian blood donors is v ery low which implies that a general testing of all blood donations should not be recommended. However, donors with sexual partners from HTLV-endemic regions should be tested. Concerning serological diagnosis, we would sugges t to modify the WHO-based interpretation criteria in countries with low HTL V prevalences: Only sera with antibodies to 1 or 2 Gag and the 2 recombinan t Env proteins should be considered HTLV positive.