Interleukin-2-mediated CD4 T-cell activation correlates highly with effective serological and T-cell responses to SARS-CoV-2 vaccination in people living with HIV.

People living with HIV (PLWH) despite having an appreciable depletion of CD4 + T-cells show a good severe acute respiratory syndrome coronavirus 2 vaccination response. The underlying mechanism(s) are currently not understood. We studied serological and polyfunctional T-cell responses in PLWH receiving anti-retroviral therapy stratified on CD4 + counts as PLWH-high (CD4 ≥ 500 cells/mm 3 ) and PLWH-low (<500 cells/mm 3 ). Responses were assessed longitudinally before the first vaccination (T0), 1-month after the first dose (T1), 3-months (T2), and 6-months (T3) after the second dose. Expectedly, both PLWH-high and -low groups developed similar serological responses after T2, which were also non-significantly different from age and vaccination-matched HIV-negative controls at T3. The immunoglobulin G titers were also protective showing a good correlation with angiotensin-converting enzyme 2-neutralizations (R = 0.628, p = 0.005). While surface and intracellular activation analysis showed no significant difference at T3 between PLWH and controls in activated CD4 + CD154 + and CD4 + memory T-cells, spike-specific CD4 + polyfunctional cytokine expression analysis showed that PLWH preferentially express interleukin (IL)-2 (p < 0.001) and controls, interferon-γ (p = 0.017). CD4 + T-cell counts negatively correlated with IL-2-expressing CD4 + T-cells including CD4 + memory T-cells (Spearman ρ: -0.85 and -0.80, respectively; p < 0.001). Our results suggest that the durable serological and CD4 + T-cell responses developing in vaccinated PLWH are associated with IL-2-mediated CD4 + T-cell activation that likely compensates for CD4 + T-cell depletion in PLWH.