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The dynamics of human T-lymphotropic virus type-1 (HTLV-1) provirus expression in vivo are unknown. There is much evidence to suggest that HTLV-1 gene expression is restricted: this restricted gene expression may contribute to HTLV-1 persistence by limiting the ability of the HTLV-1-specific CD8(+) cell immune response to clear infected cells. In this study, we tested the hypothesis that derepression of HTLV-1 gene expression would allow an increase in CD8(+) cell-mediated lysis of HTLV-1-infected cells. Using histone deacetylase enzyme inhibitors (HDIs) to hyperacetylate histones and increase HTLV-1 gene expression, we found that HDIs doubled Tax expression in naturally infected lymphocytes after overnight culture. However, the rate of CD8(+) cell-mediated lysis of Tax-expressing cells ex vivo was halved. HDIs appeared to inhibit the CD8(+) cell-mediated lytic process itself, indicating a role for the microtubule-associated HDAC6 enzyme. These observations indicate that HDIs may reduce the efficiency of cytotoxic T-cell (CTL) surveillance of HTLV-1 in vivo. The impact of HDIs on HTLV-1 proviral load in vivo cannot be accurately predicted because of the widespread effects of these drugs on cellular processes; we therefore recommend caution in the use of HDIs in nonmalignant cases of HTLV-1 infection.

Original publication




Journal article



Publication Date





3801 - 3807


CD8-Positive T-Lymphocytes, Cells, Cultured, Cohort Studies, Enzyme Inhibitors, Female, Gene Expression Regulation, Viral, Gene Products, tax, HTLV-I Infections, Histone Deacetylase 6, Histone Deacetylase Inhibitors, Histone Deacetylases, Human T-lymphotropic virus 1, Humans, Immunity, Cellular, Male, Proviruses