Non-HIV retroviral associations with rheumatic disease.

While the human T-cell lymphotropic virus type I (HTLV-I) is the recognized cause of adult T cell leukemia, it is also associated with non-neoplastic, ostensibly autoimmune conditions, such as tropical spastic paraparesis. Moreover,among carriers of HTLV-I, the virus is strongly implicated in the development of a type of arthritis, which resembles rheumatoid arthritis (RA). Mice transgenic for HTLV-I tax develop RA-like pathology and Sjögren's syndrome. Patients with RA and SS in HTLV-I nonendemic regions, such as the United States, are usually serologically negative for antibodies to the structural proteins of HTLV. However, they appear to harbor HTLV-I tax in their peripheral blood mononuclear cells three times as often as individuals who present as healthy blood donors. Because HTLV-I tax transactivates numerous inflammatory cytokines and is not normally found in the human genome, treatment with tax antisense oligonucleotides may provide a new therapeutic approach for selected RA patients proven to be HTLV-I "tax only" positive.