In situ hybridization detection of HTLV-I RNA in peripheral blood mononuclear cells of TSP/HAM patients and their spouses

This is the first report of the direct detection of HTLV‐I RNA in uncultured peripheral blood mononuclear cells (PBMNC's) of patients with tropical spastic paraparesis and HTLV‐l‐associated myelopathy (TSP/HAM) and their spouses, using the technique of in situ hybridization. Twenty‐one Colombian patients were tested, all of whom had antibodies to HTLV‐I; the presence of HTLV‐I proviral DNA in their PBMNC's was confirmed by the polymerase chain reaction technique. Of the 21 patients 15 had a clinical diagnosis of tropical spastic paraparesis (TSP/HAM), 5 were asymptomatic relatives, and 1 patient had leukemia. In situ hybridization was positive in samples from 5 patients; 2 of these were TSP/HAM patients and the other 3 were healthy wives of TSP/HAM patients. This study demonstrates for the first time that viral RNA is expressed in uncultured PBMNC's of some patients with TSP/HAM in whom proviral DNA is also present; furthermore, the detection of HTLV‐I RNA in the blood of female partners of TSP/HAM patients clearly illustrates the high likelihood of HTLV‐I transmission through sexual contact.