Screening of blood donations for HTLV-I/II.

T HE HUMAN T-cell lymphotropic viruses type I and type II (HTLV-I and HTLV-II) are closely related human retroviruses and have similar biological properties, genetic organization, and tropism for T lymphocytes. They were the first 2 retroviruses to be identified in humans in 19801 and 1982, respectively? They belong to the Oncovirinae subfamily, are typically lymphoproliferative, and are able to induce cellular transformation. HTLV-I is the cause of both a hematopoietic malignancy, adult T-cell leukemia/lymphoma (ATL), ~,3,4 as well as a progressive myelopathy called tropical spastic paraparesis (TSP) or HTLVI-associated myelopathy (HAM). 5,6 A very small proportiofi (2% to 5%) of HTLV-I-infected individuals go on to develop ATL within their lifetime. The estimated average time between infection and malignancy is 30 to 50 years. 7 Epidemiological data indicate that ATL develops mainly in individuals infected at birth and that ATL has, so far, never been observed in persons infected by transfusion. TSP/HAM have been described in every area where HTLV-I is endemic, and this neurological syndrome occurs with the same frequency as ATL. 8 Typically, the onset of TSP/HAM is during the fourth decade of life. 9 However, transfusion of HTLV-I-infected blood can result in a rapid development of this disease. 10 No clear disease association has been described for HTLV-II other than extremely rare cases of atypical hairy cell leukemia. Recently, HTLV-II has also been detected in a small number of patients with spastic myelopathy. 11,12