Tlymphotropic

T-lymphotropic refers to viruses and other agents that preferentially infect T-lymphocytes. In humans, the best studied members are the human T-lymphotropic viruses HTLV-1 and HTLV-2, which are retroviruses in the Retroviridae family, genus Deltaretrovirus. HTLV-1 is the most characterized, while HTLV-2 has fewer proven disease associations. Other primate and human T-lymphotropic viruses have been described in the broader literature.

Infection and biology: After entry, HTLV proviruses integrate into the host cell genome and can persist for life. Viral genes such as Tax and HBZ influence T-cell growth and immune signaling, promoting clonal expansion of infected cells and, in some cases, oncogenesis or inflammatory disease. Proviral load and host factors influence disease risk.

Clinical associations: HTLV-1 infection can cause adult T-cell leukemia/lymphoma (ATLL) and HTLV-1–associated myelopathy/tropical spastic paraparesis (HAM/TSP). Some HTLV-2 infections have been linked to milder neurological syndromes or remain asymptomatic. Other diseases are not firmly established as caused by HTLV-1 or HTLV-2.

Epidemiology and transmission: HTLV-1 and HTLV-2 are transmitted via vertical routes (breastfeeding), sexual contact, and exposure to infected blood. Endemic regions include parts of Japan, the Caribbean, West and Central Africa, and parts of South America. Global prevalence is low but concentrated in these areas.

Diagnosis and prevention: Laboratory diagnosis relies on serology to detect antibodies, with confirmatory tests or molecular assays to distinguish HTLV-1 from HTLV-2. There is no widely available cure or vaccine; management focuses on treating associated diseases and preventing transmission through blood donor screening, safe sex, and counseling on breastfeeding in infected mothers where guidelines exist.