Human T-cell leukemia/lymphoma viruses. Life cycle, pathogenicity, epidemiology, and diagnosis.

Human T-cell leukemia/lymphoma virus type I (HTLV-I) was discovered in 1980, and it subsequently was found to be the cause of adult T-cell leukemia/lymphoma. A progressive neurologic disease known as tropical spastic paraparesis, or HTLV-I-associated myelopathy, has also been linked to infection with HTLV-I. A related virus, HTLV type II (HTLV-II), has been isolated from patients with hairy-cell leukemia, but it has not been proved to be the cause of any disease. In late 1988, US blood banks began screening all blood donations for antibodies to HTLV-I/II. This program has resulted in the identification of many unexpectedly seropositive blood donors and provided much information about the prevalence of HTLV-I/II in the United States. In this article, I review the replication of these agents, as well as their pathogenesis, diagnosis, and mechanisms of spread.