Isolation of new lymphotropic retrovirus from two siblings with haemophilia B, one with AIDS.

A human T-lymphotropic retrovirus was isolated from cultured T lymphocytes from two siblings with haemophilia B. Patient 2 was healthy, but patient 1 had acquired immunodeficiency syndrome. The retrovirus differed from human T-cell leukaemia virus (HTLV) but it was similar to the lymphadenopathy-associated retrovirus (LAV) in its morphology and its major core protein (P25). Both patients had antibodies against LAV and patient 1's retrovirus, detected by an enzyme-linked immunosorbent assay or a radioimmunoprecipitation assay. Seroepidemiological data indicated the transmission of this retrovirus by plasma products.