Long-term variations in human T lymphotropic virus (HTLV)-I and HTLV-II proviral loads and association with clinical data

Background. The human T lymphotropic virus (HTLV)-I or -II proviral load (VL) may be linked to viral pathogenesis, but prospective data on VL and disease outcomes are lacking. Methods. Using data from a prospective cohort study of HTLV disease outcomes, we examined baseline VLs with real-time quantitative polymerase chain reaction in 122 HTLV-I- and 319 HTLV-II-infected subjects and serial VLs over the course of 6 visits in a subset of 30 HTLV-I- and 30 HTLV-II-infected subjects. Cox and logistic-regression models were used to test baseline associations, and repeated-measures analysis was used to study variations in VL over time. Results. Over the course of a median of 10.4 years, HTLV-I VLs decreased slightly (slope, -0.017 log(10) copies/10(6) peripheral blood mononuclear cells [PBMCs]/year; P = .042) and HTLV-II VLs did not change (slope, -0.019 log(10) copies/10(6) PBMCs/year; P = .165). Changes in VL over time were associated positively with alcohol (P = .07) and negatively with black race (P = .03) for HTLV-I and positively with smoking (P = .08) for HTLV-II. In the larger group, there was no association between baseline VL and disease outcomes. In the smaller group with serial VL data, there was an association between increasing VL and bladder or kidney infections for both HTLV-I (P = .005) and HTLV-II (P = .022). Conclusions. HTLV VLs are stable over time, but alcohol and tobacco intake may affect the progression of VLs. The association between increasing VLs and bladder/kidney infection may be explained by early HTLV-related neuropathologic progression.