retroviral

Retroviral is a term relating to retroviruses, a family of enveloped, positive-sense single-stranded RNA viruses that replicate through a DNA intermediate. Retroviruses have a genome organized as two copies of RNA (a dimer) flanked by long terminal repeats and encode structural (Gag), enzymatic (Pol), and envelope (Env) proteins, with additional regulatory or accessory genes in some lineages.

Upon infection, the viral reverse transcriptase converts the RNA genome into double-stranded DNA, which is integrated into the host genome by the viral integrase enzyme. The integrated DNA, or provirus, is transcribed by the host RNA polymerase II to produce new viral RNAs and mRNAs. The genome typically expresses Gag, Pol, and Env from full-length transcripts, with regulatory genes modulating replication and pathogenesis in certain genera. Virions assemble at intracellular sites and bud from the plasma membrane, maturing after proteolytic processing.

Taxonomy within Retroviridae places two subfamilies: Orthoretrovirinae and Spumaretrovirinae. Orthoretrovirinae contains several genera, including Alpharetrovirus, Betaretrovirus, Gammaretrovirus, Deltaretrovirus, Epsilonretrovirus, and Lentivirus; Spumaretrovirinae contains foamy viruses (Spumavirus). Notable examples include HIV-1 and HIV-2 (Lentivirus), HTLV-1 (Deltaretrovirus), murine leukemia virus (Gammaretrovirus), Rous sarcoma virus (Alpharetrovirus), and foamy viruses, which often display limited pathogenicity in their natural hosts.

Pathogenicity varies widely. Some retroviruses cause cancer, immunodeficiency, or other diseases in humans and animals; others are relatively benign. Retroviruses have also been engineered as vectors for gene therapy and research, exploiting their ability to stably integrate genetic material, while acknowledging safety concerns such as insertional mutagenesis and recombination risks.