IL-15 and HIV infection: lessons for immunotherapy and vaccination.

IL-15 is a pleiotropic and multifunctional cytokine that has a diverse array of distinct biological effects in the body. It plays a crucial role in host defense from viral and non-viral intracellular pathogens. The cytokine is essential for the development and differentiation of NK cells and for homeostatic expansion of CD8+ memory T cells, NKT cells and certain subsets of intestinal intra-epithelial lymphocytes (iIEL).

Peripheral blood cytotoxic gammadelta T lymphocytes from patients with human immunodeficiency virus type 1 infection and AIDS lyse uninfected CD4+ T cells, and their cytocidal potential correlates with viral load.

Progression of human immunodeficiency virus type 1 (HIV-1) infection in humans is marked by declining CD4+-T-cell counts and increasing virus load (VL). Cytotoxic T lymphocytes (CTL) play an important role in the lysis of HIV-infected cells, especially during the early phase of asymptomatic infection. CTL responses in the later phase of disease progression may not be as effective since progressors with lower CD4+-T-cell counts have consistently higher VL despite having elevated CTL counts.