Infection of human endothelial cells by human T-lymphotropic virus type I.

We studied the effects of human T-lymphotropic virus type I (HTLV-I) on human endothelial cells in vitro. During cocultivation with an HTLV-I producer cell line (C91/PL), endothelial cells formed characteristic multinucleated syncytial giant cells. Inoculation with concentrated cell-free supernatant fluid from C91/PL cultures produced similar cytopathic effects, which were neutralized by pretreatment with HTLV-I specific human serum. HTLV-I antigens were detected in the cytoplasm of the multinucleated cells by indirect immunofluorescence. When endothelial cells showed maximal cytopathic changes, reverse transcriptase activity was demonstrated in the supernatant fluid and HTLV-I was isolated by cocultivation with peripheral blood mononuclear cells. This study demonstrates that HTLV-I tropism is not limited to lymphoid cells but extends to human endothelial cells as well.