Human T-cell leukemia-lymphoma virus (HTLV): Cloning of an integrated defective provirus and flanking cellular sequences

Human T-cell leukemia-lymphoma virus (HTLV) is the first unequivocal human retrovirus. Seroepidemiological and virus isolation studies indicate that HTVL is etiologically associated with a subtype of adult T-cell malignancy. We have molecularly 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 cellular sequences flanking approximately 5 kilobases of viral sequences including one long terminal 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.