HTLV-1

HTLV-I is an abbreviation for human T-cell lymphotropic virus type 1, also called human T-cell leukemia type 1, a virus that has been seriously implicated in several kinds of diseases, including HTLV-I-associated myelopathy, and as a virus cancer link for leukemia.HTLV-1 has six reported subtypes (subtypes A to F). The great majority of infections are caused by the cosmopolitan subtype A. HTLV was discovered by Robert Gallo and colleagues in 1980. Between 1 in 20 and 1 in 25 infected persons are thought to develop cancer as a result of the virus. HTLV-1 infection is thought to spread only through dividing cells since, reverse transcriptase generates proviral DNA from genomic viral RNA, and the provirus is integrated into the host genome by viral integrase after transmission. Therefore, the quantification of provirus reflects the number of HTLV-1-infected cells. So, an increase in numbers of HTLV-1-infected cells using cell division, by actions of accessory viral genes, especially tax, may provide an enhancement of infectivity tax expression induces proliferation, inhibits the apoptosis of HTLV-1-infected cells and, conversely, evokes the host immune response, including cytotoxic T cells, to kill virus-infected cells.