Molecular biology and pathogenesis of the human T-cell leukaemia/lymphotropic virus Type-1 (HTLV-1)

Retroviruses are associated with a variety of diseases, including immunological and neurological disorders, and various forms of cancer. In humans, the Human T‐cell Leukaemia/Lymphotropic virus type 1 (HTLV‐1), which belongs to the Oncovirus family, is the aetiological agent of two diverse diseases: Adult T‐cell leukaemia/lymphoma (ATLL) (Poiesz et al. 1980; Hinuma et al. 1981; Yoshida et al. 1982), as well as the neurological disorder tropical spastic paraparesis/HTLV‐1‐associated myelopathy (TSP/HAM) (Gessain et al. 1985; Rodgers‐Johnson et al. 1985; Osame et al. 1986). HTLV‐1 is the only human retrovirus known to be the aetiological agent of cancer.A genetically related virus, HTLV‐2, has been identified and isolated (Kalyanaraman et al. 1982). However, there has been no demonstration of a definitive aetiological role for HTLV‐2 in human disease to date. Simian T‐cell lymphotropic viruses types 1 and 2 (STLV‐1 and ‐2) and bovine leukaemia virus (BLV) have also been classified in same group, Oncoviridae, based upon their similarities in genetic sequence and structure to HTLV‐1 and ‐2 (Burny et al. 1988; Dekaban et al. 1995; Slattery et al. 1999). This article will focus on HTLV‐1, reviewing its discovery, molecular biology, and its role in disease pathogenesis.