Background:  Interleukin-7 (IL-7) is known to be a key cytokine in T cell development and proliferation. In HIV infection, increased IL-7 levels in plasma correlate to high plasma viral load and decreased CD4⁺ cell numbers. Similarly, T cells expressing the IL-7 receptor CD127 are reduced in HIV⁺ individuals suggesting a preferential loss of CD127⁺ cells. Here, we provide evidence for the preferential loss of CD127⁺, CCR5⁺, memory, CD4⁺ T cells in HIV infection and the increased proliferation of the CD127⁻, CCR5⁺ subtype.

Methods:  We have studied the expression of CD127 in different lymphocyte subpopulations in HIV-infected individuals and HIV negative donors. We used 4-color flow cytometry analysis of CD3, CD4, CD127, CD45RO, CCR5, and CXCR4; IL-7 levels were measured by ELISA in plasma. Plasma viral load and absolute CD4 and CD8 cell counts were measured by the amplicor test or flow cytometry, respectively. Non-parametric t-test (Mann-Whitney) and Spearman´s coefficient were used to establish significant differences and correlations among different parameters.

Results:  Mean viral load and CD4 cell counts were 5.14±5.6 log copies/mL and 475±278 cell/µL. Mean IL-7 was 4.4±3 pg/mL in a cohort of 54 HIV⁺ individuals. The proportion of CD127 negative T cells were significantly (p = 0.0009) higher in HIV⁺ individuals than in HIV⁻ donors. The proportion of CD127^– T cells correlates (r = 0.69, p = 0.004) with viral load and inversely with CD4 T cell numbers (r = –0.67, p = 0.007). Therefore, HIV⁺ individuals with low CD4 T cells showed an increased proportion of CD127^– cells. Furthermore, HIV⁺ individuals showed an increased proportion of memory (CD45RO⁺) CD4⁺CD127^– cells as compared to negative donors. In this cell subset the proportion of CCR5⁺ cells, but not CCR5^– or CXCR4⁺ was increased (p = 0.0009) when comparing to HIV^– donors.

Conclusions:  The CD4⁺CD45R0⁺CD127^–CCR5⁺ T subpopulation could better define the observed increase in the percentage of CD127^– T cells in HIV⁺ individuals suggesting that the preferential expansion of this subpopulation or a specific depletion of CD4⁺CD45R0⁺CD127⁺CCR5⁺ T cells as a consequence of infection.