Human T-cell leukemia-lymphoma -integrated defective provirus and f) (human type C retrovirus/T-cell leukemia/molecular cloning/integi

Human T-cell leukemia-lymphoma virus (HTLV) is the first unequivocal human retrovirus. Seroepidemiological and virus isolation studies-indicate that HTLV is etiologically as- sociated with a subtype of adult T-cell malignancy. We have mo- lecularly cloned approximately 1 kilobase of sequences derived from the 5' and 3' termini of the HTLV.genome. Use of these clones as probes allowed isolation of a 9.8-kilobase EcoRI fragment from a genomic DNA library of an HTLV-infected neoplastic T- cell line (CR). Analysis of this clone revealed the presence of cel- lular sequences flanking approximately 5 kilobases of viral se- quences including one long terminal repeat sequence. The 5' and 3' clones, as well as subclones derived from different regions of the genomic clone, were used as probes to compare integrated proviruses and viral RNA expression in different HLTV-infected neoplastic T cell lines. The results indicate that the infected cells are of clonal origin with respect to the virus integration sites and they express multiple viral mRNA species including a 35S RNA. Human T-cell leukemia-lymphoma virus (HTLV) was first iso- lated in our laboratory from cultured T cells of an adult black patient, who was a United States resident, with a malignant lymphoma involving mature T cells (1). Subsequent seroepi- demiological studies (2-7) and repeated virus isolations (refs. 8-11; M. Popovic, personal communication) have associated HTLV with a subtype of adult T-cell leukemia occurring world- wide but with prevalence in certain geographical areas, includ- ing southwestern Japan, the Caribbean, South America, and certain parts of the southeastern United States. -HTLV is an exogenous type C retrovirus with no extensive homology to other known animal retroviruses (12). Nucleotide sequences of HTLV have been demonstrated in DNA of virus-positive tumor cells (12) including fresh leukemia cells (ref. 10; M. S. Reitz, Jr.,, personal communication). In order to extend these observations and survey a greater number of fresh and cultured cells from patients with different malignancies and to achieve better understanding of the nature of the provirus integration events, it was necessary to obtain molecular clones of at least portions of the HTLV genome as probes. In this paper we report the molecular cloning of the 5' and 3' terminal viral sequences, as well as an integrated, de- fective HTLV provirus with flanking cellular sequences. Anal- yses of these cloned viral sequences and their use as probes to analyze integrated proviruses and viral mRNA expressions in different HTLV-infected cell lines are also presented.