IN-VIVO PROVIRAL BURDEN AND VIRAL-RNA EXPRESSION IN T-CELL SUBSETS OFPATIENTS WITH HUMAN T-LYMPHOTROPIC VIRUS TYPE-1-ASSOCIATED MYELOPATHYTROPICAL SPASTIC PARAPARESIS

We used in situ hybridization combined with immunocytochemistry, cell sorting, and the polymerase chain reaction (PCR) to investigate clinic al events in three asymptomatic carriers of human T lymphotrophic viru s type-1 (HTLV-1) and ten patients with HTLV-1-associated myelopathy/t ropical spastic paraparesis (HAM/TSP). The objective was to determine which T cell subset of peripheral blood mononuclear cells (PBMC), CD3 or CD8, were infected by HTLV-1 and the manner in which HTLV-1 provira l DNA was expressed at the level of the single cell. Both CD4-positive and CD8-positive cells of the PBMC from five patients with HAM/TSP we re infected with HTLV-1. The proportion of HTLV-1-infected cells was 2 .5-40% in the CD4-positive subset and 1.0-65% in the CD8-positive subs et, when quantified by PCR using HTLV-1-infected MT2 cells as a positi ve standard. Proviral DNA of HTLV-1 was expressed in both CD4-positive cells and CD8-positive cells of the PBMC from six patients with HAM/T SP and three asymptomatic HTLV-1 carriers. In patients with HAM/TSP, t he proportion of the cells expressing HTLV-1 proviral DNA was 0.02-0.1 % in both subsets. In asymptomatic carriers, the expression of HTLV-1 proviral DNA was 0.01-0.02% in the CD4-positive subset and 0.01% in th e CD8-positive subset. Therefore, HTLV-1 possessed similar in vivo cel lular tropism for both CD4-positive cells and CD8-positive cells and H TLV-1 proviral DNA was expressed in vivo in both circulating T cell su bsets. These results suggest that the immunologic states of patients w ith HAM/TSP are modulated by the viral gene expression in bath T cell subsets.