Effects of exogenous interleukin-7 on CD8(+) T-cell survival and function in human T-cell lymphotropic virus type 1 infection.

Interleukin-7 (IL-7) mediates T-cell homeostasis through its effects on T-cell development, survival and function. In human T-cell lymphotropic virus type 1 (HTLV-1) infection, which is causally implicated in adult T-cell leukemia (ATL), the efficiency with which CD8(+) cytotoxic T-lymphocytes (CTLs) clear HTLV-1-infected cells mediates viral control and may be related to disease progression. We report here that CD127 expression in CD8(+) T-cells is independently related to disease status, and that exogenous IL-7 enhances CD8(+) T-cell survival and clearance of HTLV-1 infected cells in vitro. We conclude that CD127 down-regulation may be associated with disease status in HTLV-1 infection, and propose that exogenous IL-7 may be useful immunotherapy or cytokine adjuvant for an anti-ATL therapeutic vaccine.