Histone deacetylase inhibition reduces deleterious cytokine release induced by ingenol stimulation

Introduction: Though antiretroviral therapy has led to viral suppression and increased quality of life for patients living with HIV-1, strategies to eliminate the HIV-1 latent reservoir are still necessary to eliminate HIV. Latency reversal with superior latency reversal agents (LRAs) such as protein kinase C (PKC) agonists is a promising strategy for unveiling and eliminating the latent HIV-1 reservoir. However, PKC agonists induce T cell activation and deleterious pro-inflammatory cytokine production. Secondary pharmacological agents combined with LRAs have been previously shown to reduce deleterious pro-inflammatory cytokine secretion without inhibiting HIV-1 viral reactivation. Histone deacetylase inhibitors (HDACi) are also known for inhibiting deleterious pro-inflammatory cytokines in the context of graft-versus-host disease and rheumatoid arthritis in addition to being known to synergize with PKC agonists. In this study we investigated whether HDACi and other epigenetic modifiers could decrease PKC-induced pro-inflammatory cytokines secretion while simultaneously synergizing with the PKC agonists Ingenol-3,20-dibenzoate, to enhance latency reversal. Methods: We screened an epigenetic modifier library in health donor human peripheral blood mononuclear cells (PBMCs) to identify compounds (hits) that reduced intracellular IL-6 pro-inflammatory cytokine production induced by PKC agonist Ingenol-3,20-dibenzoate. We then further tested reducers of intracellular IL-6 (hits) for their ability to synergize with Ingenol-3,20-dibenzoate in the J-LAT 10.6 model of HIV-1 latency. The most promising epigenetic modifier from both screens, the HDACi Panobinostat, was then further tested for its ability to reduce pro-inflammatory cytokines and synergize with Ingenol-3,20-dibenzoate. Results: We show that co-treatment with Ingenol-3,20-dibenzoate and Panobinostat reduces pro-inflammatory cytokines and enhances latency reversal in vitro. Panobinostat suppressed pro-inflammatory cytokine production when combined with Ingenol-3,20-dibenzoate ex vivo when using aviremic patient cells, but antagonized Ingenol-3,20-dibenzoate dependent latency reversal ex vivo. Conclusion: The combination of Panobinostat and Ingenol-3,20-dibenzoate reduces deleterious cytokine production but is not a suitable latency reversal combination therapy.