Background:

During HIV infection, effective combined antiretroviral therapy suppresses viral replication and restores the number of circulating CD4+ T cells. However, 15%–30% of treated patients show a discordant response to combined antiretroviral therapy. Myeloid-derived suppressor cells (MDSC) are expanded in HIV+ patients; to better understand the role of MDSC on CD4 T-cell recovery, we evaluated the frequency of MDSC in HIV+ patients under combined antiretroviral therapy and its association with immunologic response.

Methods:

We enrolled 60 HIV+ patients, including complete responders (R, n= 44), virologic nonresponders (VNR, n= 5), and immunologic nonresponders (INR, n= 11). The frequency of circulating MDSC and the percentage of activated and naïve CD4 T cells were evaluated by flow cytometry. Plasmatic cytokine levels were analyzed by automated ELISA.

Results:

As previously observed, polymorphonuclear MDSC (PMN-MDSC) frequency was higher in HIV+ patients compared with healthy donors. Furthermore, PMN-MDSC percentage was higher in INR than R patients, and a significant association between MDSC frequency and immunologic failure was confirmed by a receiver operator characteristic analysis. Accordingly, an inverse correlation was found between the percentages of PMN-MDSC and naïve CD4 T cells. A positive correlation was observed between PMN-MDSC frequency and the percentage of human leucocyte antigen locus DR+ CD4 T cells and the plasmatic level of IL-1β and IL-8.

Conclusion:

Our results show that a high frequency of PMN-MDSC persists in INR, possibly because of immune activation, contributing to CD4 T-cell recovery failure. These findings further highlight the detrimental role of MDSC during HIV infection, suggesting these cells as a possible new therapeutic target.