Increased plasma interleukin-7 level correlates with decreased CD127 and increased CD132 extracellular expression on T cell subsets in patients with HIV-1 infection

Background. Interleukin ( IL)-7 levels are increased in patients with human immunodeficiency virus type 1 ( HIV-1)-associated lymphopenia; however, the effects of this on IL-7 receptor ( IL-7R) expression, disease progression, and immune reconstitution remain unclear. Methods. Plasma IL-7 levels were measured, by enzyme-linked immunoassay, in patients with primary, chronic, or long-term nonprogressive HIV-1 infection ( PHI, CHI, and LTNP, respectively) before and after 40 - 48 weeks of antiretroviral therapy ( ART). Cell-surface expression and intracellular expression of the IL-7R components CD127 and CD132 were measured by flow cytometry. The effects of IL-7 and cycloheximide on IL-7R expression by peripheral blood mononuclear cells were examined in vitro. Results. Plasma IL-7 levels were increased in both patients with PHI and those with CHI; administration of ART resulted in normalized plasma IL-7 levels in patients with PHI but not in those with CHI. Plasma IL-7 levels positively correlated with CD4(+) T cell immune reconstitution in patients with PHI. In vitro, exogenous IL-7 rapidly down-regulated cell-surface CD127 expression, but not CD132 expression, whereas subsequent reexpression required active protein synthesis. HIV-1 infection resulted in progressive decreases in the CD127(+) 132(-) subset and increases in the CD127(-) 132(+) subset of CD4(+) and CD8(+) T cells. Changes in CD4(+) T cell expression of IL-7R components were evident in patients with LTNP who lost viral control, and these changes preceded increases in plasma IL-7 levels. Conclusions. Perturbations in the IL-7/IL-7R system were clearly associated with disease progression but did not reliably predict immune reconstitution.