deltaretroviruses

Deltaretroviruses are a genus of enveloped, positive-sense RNA viruses in the family Retroviridae. Like other retroviruses, they carry two copies of single-stranded RNA and use reverse transcriptase to integrate a DNA provirus into the host genome. They are classified as complex retroviruses because their genomes encode regulatory and accessory proteins (notably Tax and Rex) that modulate viral replication and host-cell interactions.

Prominent members include human T‑lymphotropic virus type 1 (HTLV‑1) and type 2 (HTLV‑2), and bovine leukemia virus (BLV). HTLV‑1 is the causative agent of adult T‑cell leukemia/lymphoma (ATL) and is associated with a chronic inflammatory neurologic disorder known as HTLV‑1–associated myelopathy/tropical spastic paraparesis (HAM/TSP). HTLV‑2 is less clearly linked to disease but has been associated with rare neurologic and hematologic conditions. BLV causes enzootic bovine leukosis in cattle.

Deltaretroviruses establish persistent infection by integrating into host DNA and spreading largely by cell-to-cell transmission, often via virological synapses. Diagnosis relies on serologic assays (ELISA, Western blot) and molecular detection (PCR). There are no broadly effective antiviral cures; management of HTLV‑related diseases includes supportive care, chemotherapy for ATL, and in some settings antiretroviral or interferon-based regimens. Prevention strategies focus on blood screening, safe-sex practices, avoiding breastfeeding by infected mothers when feasible, and control measures in livestock.

Epidemiology is regionally variable, with HTLV‑1 endemic foci in parts of Japan, the Caribbean, South America, and Africa. Ongoing research addresses pathogenesis, host immune responses, and vaccine or therapeutic development.