Transformation of CD8+ T-cells producing a strong cytopathic effect on CD4+ T-cells through syncytium formation by HTLV-II.

Human T-cell leukemia virus type II (HTLV-II) is thought to play an important role in the development of CD8+ T-cell malignancies resembling hairy cell leukemia. In this study, dramatic cytopathic effects characterized by syncytium formation in various CD4+ T-cell lines were observed upon their cocultivation with HTLV-II infected T-cells. The HTLV-II infected T-cells, however, did not die as a result of syncytium formation. HTLV-II also transformed CD4+ T-cells and CD8+ T-cells at various coculture ratios. Furthermore, sera from anti-HTLV-II antibody-positive specific carriers inhibited syncytium formation in the CD4+ T-cells. These results suggest that HTLV-II infection may contribute to the pathogenesis of associated CD8+ T-cell malignancies.