Abstract
To achieve a functional cure for HIV, treatment regimens that eradicate latently HIV-infected cells must be established. For this, many groups have attempted to reactivate latently-infected cells to induce cytopathic effects and/or elicit cytotoxic T lymphocyte (CTL)/NK cell-mediated immune responses to kill these cells. We believe that not only the reactivation of latently-infected cells, but also the induction of strong CTL responses, would be required for this. Here, we used typical immune activators that target pattern recognition receptors (PRRs). For our experimental model, we identified eight SIV-infected cynomolgus monkeys that became natural controllers of viremia. Although plasma viral loads were undetectable, we could measure SIV-DNA by qPCR in peripheral blood mononuclear cells (PBMCs). Using these PBMCs, we screened 10 distinct PRR ligands to measure IFN-α and IFN-γ production. Among these, STING ligands, cGAMP and c-di-AMP, and the TLR7/8 agonist R848 markedly increased cytokine levels. Both R848 and STING ligands could reactivate latently-infected cells in both cynomolgus monkeys and human PBMCs in vitro. Furthermore, c-di-AMP increased the frequency of SIV Gag-specific CD8+ T cells including polyfunctional CD8+ T cells, as compared to that in untreated control or R848-treated cells. Together, STING ligands might be candidates for HIV treatment.
Highlights
To achieve a functional cure for HIV, treatment regimens that eradicate latently HIV-infected cells must be established
We studied peripheral blood mononuclear cells (PBMCs) from animals that were isolated before and 40 weeks after simian immunodeficiency virus (SIV) infection, and found that the TLR7/8 agonist R848 and stimulator of interferon genes (STING) ligands, both c-di-AMP and 2′-3′-cGAMP, could dramatically upregulate levels of IFN-α and IFN-γ, and Th1 type cytokine (IL-12p40) and MIP-1β, which have been reported to be inhibitory factors against HIV infection[26], in the culture supernatant
We demonstrated that the number of SIV Gag DNA-positive cells was decreased and the expression levels of SIV Gag mRNA were increased in infected cells, and that SIV Gag-specific cytotoxic T lymphocyte (CTL) responses were boosted with c-di-AMP stimulation
Summary
To achieve a functional cure for HIV, treatment regimens that eradicate latently HIV-infected cells must be established. We studied peripheral blood mononuclear cells (PBMCs) from animals that were isolated before and 40 weeks after SIV infection, and found that the TLR7/8 agonist R848 and stimulator of interferon genes (STING) ligands, both c-di-AMP and 2′-3′-cGAMP, could dramatically upregulate levels of IFN-α and IFN-γ, and Th1 type cytokine (IL-12p40) and MIP-1β, which have been reported to be inhibitory factors against HIV infection[26], in the culture supernatant. We demonstrated that the number of SIV Gag DNA-positive cells was decreased and the expression levels of SIV Gag mRNA were increased in infected cells, and that SIV Gag-specific CTL responses were boosted with c-di-AMP stimulation These findings, regarding the application of STING ligands, might form the basis for the clinical development of new immunostimulatory drugs that could provide a functional cure for HIV
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