HTLV-1-infected asymptomatic carriers compared to HAM/TSP patients over-express the apoptosis- and cytotoxicity-related molecules.

HTLV-1 infection causes a chronic progressive debilitating neuroinflammatory disease which is called, HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). One of the host defense mechanisms against viral infection is apoptosis which may control HTLV-1 infection. Therefore, we aimed to investigate this process and its interaction with viral factors in HTLV-1-infected asymptomatic carriers (ACs) compared to HAM/TSP patients. Fas, FasL, TRAIL, perforin, granzyme A, granzyme B, and granulysin gene expression and serum levels of Fas, FasL, TRAIL, and granulysin in the peripheral blood of 21 sex- and age-matched healthy controls (HCs), ACs, and HAM/TSP patients were evaluated. Also, the level of granulysin secretion in the cell culture supernatant was measured. Finally, the correlation of the expression of these molecules with HTLV-1 proviral load (PVL), Tax, and HBZ mRNA expression was analyzed. ACs compared to HAM/TSP patients significantly over-expressed the Fas, FasL, TRAIL, perforin, and granzyme B molecules. Fas, FasL, TRAIL, and granulysin serum levels were not different among studied groups; whereas, the secretion of granulysin was significantly decreased in ACs and HAM/TSP patients compared to HCs. Also, HAM/TSP patients expressed higher levels of HTLV-1 PVL, Tax, and HBZ mRNA. In addition, in ACs, inverse correlations between the Fas, FasL, TRAIL, perforin, granzyme B, and granulysin levels with HBZ mRNA expression were seen. ACs compared to HAM/TSP patients over-expressed the apoptosis- and cytotoxicity-related molecules. It could be concluded that successful control of the HTLV-1 infection and suppression of HAM/TSP development stem from the strong apoptosis and cytotoxic activity in the peripheral blood of ACs.