Homotypic Cell-cell Adhesion Induced by Human T Cell Leukemia Virus Type 1 Tax Protein in T Cell Lines

Cell-cell adhesion is involved in the processes of cell growth, activation and migration, and inflammation. T cells infected with human T cell leukemia virus type 1 (HTLV-1) exhibit a high degree of homotypic cell-cell adhesion in vitro. In this study, we investigated the involvement of the viral protein Tax in such process. Expression of Tax in an interleukin (IL)-2-dependent mouse T cell line (CTLL-2) increased homotypic cell-cell adhesion; however, less cell adhesion was induced by Tax than that observed in HTLV-1-infected T cell lines. Moreover, Tax induced cell-cell adhesion in a human T cell line, in which the expression of Tax is inducible. Microscopic examination also revealed Tax-induced morphologic changes, including rounding of CTLL-2 cells, increased cell volume, and increased nucleus size. Taken together, our results suggest that Tax induces cell-cell adhesion and morphologic changes in HTLV-1-infected cells. Tax may thus play a role in persistent HTLV-1 infection and the pathogenesis of associated disease.