Characterization and distribution of nucleic acid sequences of a novel type C retrovirus isolated from neoplastic human T lymphocytes.

A type C retrovirus (designated HTLV) recently isolated from a cell line derived from a lymph node and later from peripheral blood of a person with cutaneous T-cell lymphoma (mycosis fungoides) was characterized by nucleic acid hybridization experiments. HTLV [3H]cDNA hybridized 90% to its own 70S RNA with kinetics consistent with the genetic complexity of other retroviruses, but it did not hybridize substantially to RNA or proviral DNA from any animal retroviruses (types B, C, and D), including those from nonhuman primates. Conversely, [3H]cDNA from other retroviruses did not hybridize to RNA or DNA of the human T-cell line producing HTLV. HTLV proviral sequences were present (two to three copies per haploid genome) in DNA of these cells, and homologous sequences were present in the cell cytoplasmic RNA (0.3% viral sequences by weight). HTLV-related nucleic acid sequences were not found in DNA from various other human tissues. The results indicate that HTLV is a new class of type C virus that is not an endogenous (genetically transmitted) retrovirus in man.