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-I-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.