Molecular cloning and analysis of a new variant of human T‐cell leukemia virus (HTLV‐Ib) from an African patient with adult T‐cell leukemia‐lymphoma

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Abstract
We report the identification and characterization of a new variant of HTLV‐I in an African patient with adult T‐cell leukemia/lymphoma (ATL). Proviral sequences were detected by Southern blot analysis in three T‐cell lines established from this patient's peripheral blood lymphocytes (PBL) and lymph‐node cells. We molecularly cloned and analyzed proviruses from two of these cell lines, one established by direct culture of PBL and one established by co‐cultivation of PBL with cord‐blood T cells. These two HTLV clones contained full‐length proviruses which were identical to each other in 44 out of 44 restriction enzyme sites. They were closely related to, but distinct from, the prototype HTLV‐I, having divergence in their envelope and 5′ pX regions and therefore represented a new variant of HTLV‐I. We designated it as HTLV‐Ib. Despite the genomic differences, however, HTLV‐Ib retained its tropism for OKT4+ lymphocytes as well as its ability to initiate and maintain transformation of these cells. The finding of a variant of HTLV‐I in this African ATL patient, along with the results of recent seroepidemiological studies, extends to the African continent the prevalence of HTLV‐I associated malignancy previously identified in the Caribbean and Japan.