retrovirus /-vī″rəs/ [L, retro + virus] , any of a family of ribonucleic acid (RNA) viruses containing the enzyme reverse transcriptase in the virion. The genetic information of the virus is stored in a molecule of single-stranded ribonucleic acid. After entering the target cell, the virus uses reverse transcriptase to direct the cell to make viral deoxyribonucleic acid (DNA). The DNA becomes integrated into the DNA of the host cell. Retroviruses are enveloped and assemble their capsids in the cytoplasm of the host cell. Retroviruses are used in laboratory research to import foreign DNA into a cell. They are transmitted by sexual contact with an infected person, through exposure to infected blood or blood products, and perinatally from an infected mother to the child. Human immunodeficiency virus (HIV1, HIV2), which causes acquired immunodeficiency syndrome, is a retrovirus. Other retroviruses include members of the Oncornaviridae family, such as human T cell lymphotropic virus type 1 (HTLV-1) and human T cell lymphotropic virus type 2, which cause adult T cell leukemia, hairy cell leukemia, tropical spastic paresis, and HTLV-1-associated myelopathy.
