In people with HIV (PWH), elevated expression of immune checkpoints (IC) persists despite ART, leading to T-cell exhaustion. We aimed to determine if blocking single or multiple IC would enhance HIV-specific T cell function ex vivo.
Bulk PBMC obtained from 11 PWH on suppressive ART were stimulated with either gag, nef or Cytomegalovirus, Epstein-Barr Virus and Influenza (CEF) peptides in the presence of blocking antibodies to six IC molecules, including CTLA-4, PD-1, PD-L1, TIM-3, TIGIT and LAG-3 or relevant isotype controls. Antibodies were tested alone, in all dual combinations and using a cocktail of all six antibodies. Intracellular cytokine staining was used to determine production of CD107a, IFN?, TNF? and IL-2 in total and subsets of CD4+ and CD8+ T cells. Fold changes (FC) for IC antibodies compared to isotype controls were obtained. Bliss independence model was used to determine if the effect was synergistic.
We detected a significant increase in the percentage of cells expressing IFN? and TNF? but not IL-2 or CD107a following stimulation with gag and nef peptides. The addition of single IC antibodies or all six together led to minimal change in cytokine production. In contrast, we observed a statistically significant increase in the percentage of gag-specific cells expressing CD107a in the presence of anti-LAG-3 combined with anti-TIGIT (median fold change, FC compared to isotype controls 1.75x) and anti-CTLA-4 (median FC 1.38x) in HIV-specific CD4+ T cells. We also observed increased frequency of cells expressing IL-2 (median FC 1.26 – 2.17x) with combinations of CTLA-4, TIGIT, TIM-3, PD-L1 and LAG-3, in both HIV-specific CD4+ and CD8+ T cells. The largest FC increase in IL-2 was observed when anti-CTLA-4 was combined with any other antibodies, except anti-PD1.
Multiples combinations of two IC antibodies (including LAG-3, CTLA-4 or TIGIT) can enhance the frequency of polyfunctional HIV-specific T cells ex vivo in samples obtained from PWH on suppressive ART. The increased production of IL-2 with dual IC blockage could have a significant functional effect on both proliferation and cytotoxicity. Given the better safety profile of anti-LAG-3 and anti-TIGIT, these novel antibodies should be further explored in strategies to control HIV in the absence of ART.