STING Ligand-Mediated Priming of Functional CD8⁺ T Cells Specific for HIV-1-Protective Epitopes from Naive T Cells

Functional HIV-1-specific CD8⁺ T cells primed from naive T cells are expected to act as effector T cells in a "shock-and-kill" therapeutic strategy for an HIV-1 cure since less functional HIV-1-specific CD8⁺ T cells are elicited from memory T cells in HIV-1-infected individuals on combined antiretroviral therapy (cART). CD8⁺ T cells specific for HIV-1 conserved and protective epitopes are candidates for such T cells. We investigated the priming with STING ligand of CD8⁺ T cells specific for HLA-B*52:01 or HLA-C*12:02-restricted protective epitopes from naive T cells. STING ligand 3'3'-cGAMP effectively primed CD8⁺ T cells specific for 3 of 4 HLA-B*52:01-restricted epitopes but failed to prime those specific for all 3 HLA-C*12:02-restricted epitopes from the naive T cells of HIV-1-uninfected individuals having an HLA-B*52:01-C*12:02 protective haplotype. These HLA-B*52:01-restricted CD8⁺ T cells had a strong ability to suppress HIV-1 replication and expressed a high level of cytolytic effector molecules. The viral suppression ability of these T cells was significantly correlated with the expression level of perforin and showed a trend for a positive correlation with the expression level of CD107a. The present study highlighted the priming with STING ligand of functional CD8⁺ T cells specific for protective epitopes, which T cells would contribute as effector T cells to a shock-and-kill therapy. IMPORTANCE The current "shock-and-kill" therapeutic strategy for HIV cure has been directed toward eliminating latent viral reservoirs by reactivation of latent reservoirs with latency-reversing agents followed by eradication of these cells by immune-mediated responses. Although HIV-1-specific T cells are expected to eradicate viral reservoirs, the function of these T cells is reduced in HIV-1-infected individuals with long-term cART. Therefore, priming of HIV-1-specific T cells with high function from naive T cells is to be expected in these individuals. In this study, we demonstrated the priming with STING ligand 3'3'-cGAMP of CD8⁺ T cells specific for HIV-1-protective epitopes from naive T cells. cGAMP primed CD8⁺ T cells specific for 3 HLA-B*52:01-restricted protective epitopes, which cells expressed a high level of cytolytic effector molecules and effectively suppressed HIV-1 replication. The present study suggested that the priming with STING ligand of functional CD8⁺ T cells specific for protective epitopes would be useful in a therapy for an HIV-1 cure.