Transforming growth factor-beta enhances human T-cell leukemia virus type I infection.

Human T-cell leukemia virus type I (HTLV-I), the causative agent of adult T-cell leukemia/lymphoma, is transmitted vertically by breast milk and sexually by semen. The transforming growth factor-beta (TGF-beta), a pleiotropic cytokine that is abundant in breast milk and semen, facilitates replication of HTLV-I in lymphocytes derived from asymptomatic HTLV-I carriers and transmission to cord blood lymphocytes in vitro. Transient expression assays revealed that TGF-beta can transactivate HTLV-I long terminal repeat promoter. These results suggest that TGF-beta may play a role in replication and transmission of HTLV-I.