Importance of Western Blot Analysis in Predicting Infectivity of Anti-HTLV-III/LAV Positive Blood

Stored donor and recipient sera from prospective studies of post-transfusion hepatitis were analysed for the presence of human T-cell lymphotropic virus type-III/lymphadenopathy associated virus (HTLV-III/LAV) antibodies as determined by enzyme-linked immunosorbent assays (ELISA). Of 3961 donor samples given to 461 patients, only 2 (0.05%) contained specific HTLV-III/LAV antibodies as determined by an avidin-biotin-enhanced western blot tech nique. Anti-HTLV-III/LAV was measured before and 3 and 6 months after transfusion in 295 recipients of anti-HTLV-III-negative blood, 7 recipients of ELISA-positive blood which was western blot negative, and 2 recipients of ELISA-positive blood confirmed as specific by western blot. Only the last 2 recipients became infected with HTLV-III/LAV, as assessed by antibody seroconversion (p less than 0.0001). Serocon version occurred early (6 and 8 weeks after transfusion) and was characterised first by antibody to p24 and later by antibody to p41. AIDS has not developed in either patient, but one has a T4/T8 ratio of 0.4 and impaired mitogen responses; the second patient has no evidence of immune dysfunction 4 years after exposure. This study confirms that HTLV-III/LAV infection can be transmitted by blood transfusion and supports the advisability of anti-HTLV-III/LAV testing of all blood donors. It also confirms the validity of western blot testing for HTLV-III/LAV specificity and suggests that ELISA-positive, western-blot-negative blood may not be infectious.