Deltaretrovirus

Deltaretrovirus is a genus of the Retroviridae family that includes the human T-lymphotropic viruses HTLV-1 to HTLV-4, simian T-lymphotropic viruses STLV-1 to STLV-4, and bovine leukemia virus (BLV). These viruses are primarily transmitted as cell-associated particles through sexual contact, blood exposure, and, for HTLV-1, mother-to-child transmission via breast milk.

Deltaretroviruses are enveloped, positive-sense RNA retroviruses with a genome organized as 5′ LTR-gag-pol-env-3′ and regulatory genes such as tax and rex. They reverse-transcribe their RNA into DNA and integrate proviral DNA into the host genome, where the provirus may be transcriptionally latent or actively expressed.

Pathogenesis varies by virus. HTLV-1 is associated with adult T-cell leukemia/lymphoma (ATLL) and certain inflammatory diseases; HTLV-2 has weaker disease associations; BLV causes bovine enzootic leukosis. Viral Tax and other regulatory factors promote clonal expansion of infected cells, contributing to persistent infection and oncogenic processes in a range of hosts.

Diagnosis and management: there is no widely available vaccine. Diagnosis relies on serology and molecular tests to detect infection and proviral DNA. Treatment of HTLV-1–associated ATLL is challenging and may involve chemotherapy combined with antiviral therapy such as zidovudine and interferon-α; other deltaretrovirus infections are managed according to species-specific considerations and transmission-prevention measures.