HTLV-I/II seroindeterminate Western blot reactivity in a cohort of patients with neurological disease

The human T-cell lymphotropic virus type I(HTLV-I) is associated with a chr onic, progressive neurological disease known as HTLV-I-associated myelopath y/tropical spastic paraparesis, Screening for HTLV-I involves the detection of virus-specific serum antibodies by EIA and confirmation by Western blot . HTLV-I/II seroindeterminate Western blot patterns have been described wor ldwide. However, the significance of this blot pattern is unclear. We ident ified 8 patients with neurological disease and an HTLV-I/II seroindetermina te Western blot pattern, none of whom demonstrated increased spontaneous pr oliferation and HTLVI-specific cytotoxic T lymphocyte activity. However, HT LV-I tax sequence was amplified from the peripheral blood lymphocytes of 4 of them. These data suggest that patients with chronic progressive neurolog ical disease and HTLV-I/II Western blot seroindeterminate reactivity may ha rbor either defective HTLV-I, novel retrovirus with partial homology to HTL V-I, or HTLVI in low copy number.