HTLV

HTLV, or human T-cell leukemia virus, either of two viruses now known to cause certain forms of human blood-cell cancer (see Leukemia). HTLV-I and HTLV-II were first identified in the late 1970s. They cause cancer by attacking the cells known as T lymphocytes (see Immune System), causing the cells to proliferate uncontrollably and to invade various tissues. Both HTLVs are viruses of the retrovirus type, distinguished from other viruses because they code their genetic instructions in RNA instead of DNA molecules (see Nucleic Acids). Another retrovirus in 1983 and 1984 was linked with cases of acquired immunodeficiency syndrome, or AIDS, and was tentatively labeled HTLV-III by the U.S. research team that isolated the virus. The French research team that isolated an apparently identical virus, however, objected to this classification, and by common agreement the virus that causes AIDS is now known as the human immunodeficiency virus, or HIV.