Negative modulation of suppressive HIV-specific regulatory T cells by IL-2 adjuvanted therapeutic vaccine

The potential benefit in using IL-2 in immunotherapy for cancer and autoimmunity has been linked to the modulation of immune responses, which partly relies on a direct effect on Tregs populations.Here, we revisited the role of IL-2 in HIV infection and investigated whether its use as an adjuvant with therapeutic vaccination, impacts on HIV-specific responses.Antiretroviral therapy treated-patients were randomized to receive 4 boosts of vaccination (ALVACHIV/Lipo-6T, weeks 0/4/8/12) followed by 3 cycles of IL-2 (weeks 16/24/32) before treatment interruption (TI) at week40.IL-2 administration increased significantly HIV-specific CD4 + CD25 + CD134 + T-cell responses, which inversely correlated with viral load after TI (r = -0.7,p <0.007) in the vaccine/IL-2 group.IL-2 increased global CD25 + CD127 low FoxP3 + Tregs (p <0.05) while it decreased HIV-but not CMV-specific CD39 + FoxP3 + CD25 + CD134 + Tregs (p <0.05).HIV-specific Tregs were inversely correlated with IFN-γ producing specific-effectors (p = 0.03) and positively correlated with viral load (r = 0.7, p = 0.01), revealing their undesired presence during chronic infection.Global Tregs, but not HIV-specific Tregs, inversely correlated with a decrease in exhausted PD1 + CD95 + T-cells (p = 0.001).Altogether, our results underline the negative impact of HIV-specific Tregs on HIV-specific effectors and reveal the beneficial use of IL-2 as an adjuvant as its administration increases global Tregs that impact on T-cell exhaustion and decreases HIV-specific CD39 + Tregs by shifting the balance towards effectors. Author summaryInterleukin-2 (IL-2) has been used in immunotherapy for cancer and autoimmunity and its beneficial effect has been linked to the modulation of immune responses, which partly relies on a direct effect on Tregs populations.In this study, we assessed the role of IL-2 in HIV infection and investigated whether its use as an adjuvant with therapeutic vaccination, impacts on HIV-specific responses.We show that IL-2 administration increased HIV-specific CD4 + CD25 + CD134 + T-cell responses which inversely correlated with viral