Fabiola Martin
University of Queensland
Last reviewed: November 2019
Human T-cell Leukemia Virus
Human T-cell Leukemia Virus (HTLV) was discovered in 1980 (1). It is an oncovirus and human retrovirus (2) originating from non-human primates through interspecies transmission in Central Africa many thousands of years ago (3). Just like HIV, HTLV integrates itself into human DNA causing a life-long chronic viral infection (1). However, while HIV-1 infects mainly CD4+ T lymphocytes, HTLV can also infect other types of cells. Rather than producing new viruses to infect new cells with death of the mother cell (as with HIV infection), HTLV, once integrated, activates CD4+ T cells to proliferate mitotically thereby increasing CD4+ T cell counts. HTLV infection is almost entirely cell-associated in humans and, therefore, HTLV RNA is undetectable in blood plasma. So far, four distinct HTLV subtypes, (HTLV-1, 2, 3 and 4) have been discovered (4). HTLV-1 is the most pathogenic subtype.