Expression of Immune Memory Markers CD8 α α and Interleukin−7 Receptor on CD8+ T Cell Subsets among HIV−1 Infected Patients.

Abstract

Evidence from animal models suggests that the expression of CD8α α homodimer on CD8+ T-cells plays a key role in the generation of long-lived memory cells. However, very little information is available in the human clinical setting. Here, we examined immunophenotypic patterns of CD8+ T-cell subsets expressing CD8α α with other markers involved in generating and maintaining memory cells such as interleukin-7 receptor (IL-7Rα ) and circulating levels of IL-7 and IL-15, in three well-defined groups of human immunodeficiency virus-1 (HIV-1)-infected individuals including aviremic (n=15), viremic (n=31) and slow-progressor (n=15). In addition, immunophenotypic patterns were correlated with immune activation markers (CD38/HLA-DR), which are known to be an important factor in HIV-1 disease pathogenesis. Cell-surface expression of CD8α α , IL-7Rα and CD38/HLA-DR on CD8+ naïve, central memory, pre-terminal and terminal effector memory T-cells was measured by eight-color flow cytometry on freshly peripheral blood samples. IL-7 and IL-15 levels were measured by ELISA and viral loads were assessed by PCR. Group differences in the CD8+ T-cell subsets expressing each antigen tested were evaluated using the unpaired nonparametric Mann Whitney U test. Correlations were determined by Spearman's correlation tests. Compared to slow-progressor subjects, expression of CD8α α was significantly reduced in aviremic and viremic patients and this reduction occurred mainly within naïve and central memory T-cell subsets and not in effector memory compartments. In contrast, persistent antigenemia in viremic patients appeared to lead to IL-7Rα loss mainly on central and effector memory subsets and not on naive T-cells. Compared to aviremic and viremic patients, slow-progressor subjects had lower levels of circulating IL-7, normal levels of IL-15, CD8α α and IL-7Rα , and reduced activated T-cells. Overall, expression of CD8α α was not significantly related to IL-7Rα although negative associations were evidenced within all CD8+ T-cell subsets. However, in viremic patients, naïve and central memory cell subsets expressing CD8α α were positively correlated with viral load but not with CD8+ T-cell subsets expressing immune activation markers. Together, these results provide new insights into the role of CD8α α /IL-7Rα along with immune activation markers in maintaining memory populations during HIV-1 infection. The inter-relationships between these immune memory markers require further investigations, which may help understanding the mechanisms of antiviral control.