Reversal of the CD8(+) T-Cell Exhaustion Induced by Chronic HIV-1 Infection Through Combined Blockade of the Adenosine and PD-1 Pathways

BACKGROUND: Targeting immune checkpoints for HIV treatment potentially provides a double benefit resulting from the ability to restore viral-specific CD8(+) T-cell functions and enhance HIV production from reservoir cells. Despite promising pre-clinical data, PD-1 blockade alone in HIV-1-infected patients with advanced cancer has shown limited benefits in controlling HIV, suggesting the need for additional targets beyond PD-1. CD39 and PD-1 are highly co-expressed on CD8(+) T cells in HIV-1 infection. However, the characteristics of CD39 and PD-1 dual-positive CD8(+) T-cell subsets in chronic HIV-1 infection remain poorly understood. METHODS: This study enrolled 72 HIV-1-infected patients, including 40 treatment naïve and 32 ART patients. A total of 11 healthy individuals were included as controls. Different subsets of CD8(+) T cells defined by CD39 and/or PD-1 expression were studied by flow cytometry. The relationships between the frequencies of the different subsets and parameters indicating HIV-1 disease progression were analyzed. Functional (i.e., cytokine secretion, viral inhibition) assays were performed to evaluate the impact of the blockade of adenosine and/or PD-1 signaling on CD8(+) T cells. RESULTS: The proportions of PD-1(+), CD39(+), and PD-1(+)CD39(+) CD8(+) T cells were significantly increased in treatment naïve patients but were partially lowered in patients on antiretroviral therapy. In treatment naïve patients, the proportions of PD-1(+)CD39(+) CD8(+) T cells were negatively correlated with CD4(+) T-cell counts and the CD4/CD8 ratio, and were positively correlated with viral load. CD39(+)CD8(+) T cells expressed high levels of the A2A adenosine receptor and were more sensitive to 2-chloroadenosine-mediated functional inhibition than their CD39(-) counterparts. In vitro, a combination of blocking CD39/adenosine and PD-1 signaling showed a synergic effect in restoring CD8(+) T-cell function, as evidenced by enhanced abilities to secrete functional cytokines and to kill autologous reservoir cells. CONCLUSION: In patients with chronic HIV-1 infection there are increased frequencies of PD-1(+), CD39(+), and PD-1(+)CD39(+) CD8(+) T cells. In treatment naïve patients, the frequencies of PD-1(+)CD39(+) CD8(+) T cells are negatively correlated with CD4(+) T-cell counts and the CD4/CD8 ratio and positively correlated with viral load. Combined blockade of CD39/adenosine and PD-1 signaling in vitro may exert a synergistic effect in restoring CD8(+) T-cell function in HIV-1-infected patients.