Prospective study of HTLV-I infection in an initially asymptomatic cohort

A prospective clinical study of 20 initially asymptomatic HTLV-I-seropositi ve carriers was commenced in 1991 to determine the natural history of the i nfection in relation to HTLV-I proviral load, immune responses, and lymphoc yte phenotype. Proviral load varied widely between carriers but was relativ ely constant within an individual over time. The lymphocyte phenotype and p revalence of activated lymphocytes were not predictive or disease and the m agnitude of the cytotoxic T-lymphocyte response to HTLV-I was independent o f proviral load. Incident conditions, some related to HTLV-I infection, inc luding a case of HTLV-I-associated myelopathy (HAM), were documented in 9 c arriers. Development of myelopathy and uveitis was associated with high per ipheral blood HTLV-I proviral load that predated symptoms. Persistently hig h proviral load appears to predate the development of HTLV-I-associated inf lammation in neuro-ophthalmic tissue.