Human T-cell leukemia virus (HTLV-I) transcripts in fresh and cultured cells of patients with adult T-cell leukemia.

We examined the DNA and RNA of fresh leukemic cells (five patients) and long-term cultured T lymphocytes (four patients) from patients with adult T-cell leukemia for the presence of human T-cell leukemia virus (HTLV-I) sequences. In all cases HTLV-I provirus was found and several species of viral mRNAs were observed in all cell lines. We used HTLV DNA probes representing the gag, pol, and env genes and pX regions and the U3- and U5-specific sequences to characterize the genetic content of the viral transcripts. Although similar RNA sequences were expressed in one HTLV-I provirus-positive specimen of fresh primary leukemic cells, no viral transcripts were found in four other similar specimens. These findings are consistent with the idea that the expression of one or more HTLV-I genes may be involved in initiation of transformation, but consistent expression is not needed for maintaining the neoplastic state.