Background:  CD127 expression is decreased in T cells of HIV⁺ patients, and tends to normalize on HAART. Recent attention has been paid to this receptor as a potential tool in the clinical setting. We evaluated the expression of CD127 in several CD4 and CD8 T-cell subsets, as well as the level of activation and evolution of these cells during successful HAART.

Methods:  We analyzed 22 HIV⁺ patients who initiated HAART and maintained <50 HIV RNA copies/mL for 24 months. CD127, CD45RA, CD27, and CD38 were simultaneously measured on CD4 and CD8 T cells by flow cytometry. CD38 was evaluated using a quantitative assay. Interleukin-7 (IL-7) was measured with a highly sensitivity ELISA. All measurements were performed at months 0, 12, and 24 of HAART. A paired Student’s t-test was used for comparisons at different time points. A multivariate linear regression analysis was performed to examine the influence of IL-7, CD4, and HIV RNA on CD127 expression.

Results:  At baseline CD127 expression was similar in CD4 and CD8 T cells. The lowest CD127 expression was seen in RA⁺27^– (4%±7 and 15%±7 for CD4 and CD8) and the highest in RA^–27⁺ cells (55%±13 and 61%±27 for CD4 and CD8). Baseline activation was higher in CD127^– than in CD127⁺ cells, being the greatest difference seen in the RA^–27⁺ subset (8123±3320 vs 1408±911 and 10735±4766 vs 1023±1027 CD38 molecules/cell for CD4 and CD8). IL-7 and HIV RNA inversely correlated with several CD127⁺ T-cell subsets. Activation of total CD8⁺ cells and of different CD127^– and CD127⁺ subsets (except for RA⁺27⁺ cells) was negatively correlated with CD4 count and positively with HIV RNA.

After 24 months on HAART, CD127 expression significantly increased on total CD8 cells and in all distinct subsets but RA⁺27⁺ cells. Activation significantly decreased in all CD8⁺ subsets but RA⁺27⁺ and RA^–27⁺127^– cells. Activation of CD4 cells significantly decreased in RA^–27^–127^– and RA^–27⁺127^– subsets. CD4 increase at month 24 inversely correlated with activation of CD4⁺RA^–27⁺127⁺ cells and with CD127 expression on CD8⁺ cells.

Conclusions:  CD127 expression in HIV infection is differentially regulated in distinct CD4 and CD8 T-cell subsets. The level of activation is higher in cells lacking this marker. HAART increases CD127 expression and decreases activation mainly in CD127^– cells; 2 of the CD127⁺ cell subsets showed a good correlation with the extent of CD4 reconstitution on HAART, suggesting that this marker could be useful in the management of HIV⁺ patients.