TLR7 Agonist GS-9620 Is a Potent Inhibitor of Acute HIV-1 Infection in Human Peripheral Blood Mononuclear Cells.

Rujuta A Bam,Tomas Cihlar,Gregg S Jones,Christian R Frey,Andrew Mulato,Alivelu Irrinki,Joseph Hesselgesser,Derek Hansen,Stephen R Yant

doi:10.1128/aac.01369-16

Abstract

ABSTRACTGS-9620 is a potent and selective oral Toll-like receptor 7 (TLR7) agonist that directly activates plasmacytoid dendritic cells (pDCs). GS-9620 suppressed hepatitis B virus (HBV) in animal models of chronic infection and transiently activated HIV expression ex vivo in latently infected peripheral blood mononuclear cells (PBMCs) from virally suppressed patients. Currently, GS-9620 is under clinical evaluation for treating chronic HBV infection and for reducing latent reservoirs in virally suppressed HIV-infected patients. Here, we investigated the in vitro anti-HIV-1 activity of GS-9620. GS-9620 potently inhibited viral replication in PBMCs, particularly when it was added 24 to 48 h prior to HIV infection (50% effective concentration = 27 nM). Depletion of pDCs but not other immune cell subsets from PBMC cultures suppressed GS-9620 antiviral activity. Although GS-9620 was inactive against HIV in purified CD4+ T cells and macrophages, HIV replication was potently inhibited by conditioned medium derived from GS-9620-treated pDC cultures when added to CD4+ T cells prior to infection. This suggests that GS-9620-mediated stimulation of PBMCs induced the production of a soluble factor(s) inhibiting HIV replication in trans. GS-9620-treated PBMCs primarily showed increased production of interferon alpha (IFN-α), and cotreatment with IFN-α-blocking antibodies reversed the HIV-1-inhibitory effect of GS-9620. Additional studies demonstrated that GS-9620 inhibited a postentry event in HIV replication at a step coincident with or prior to reverse transcription. The simultaneous activation of HIV-1 expression and inhibition of HIV-1 replication are important considerations for the clinical evaluation of GS-9620 since these antiviral effects may help restrict potential local HIV spread upon in vivo latency reversal.

Highlights

GS-9620 is a potent and selective oral Toll-like receptor 7 (TLR7) agonist that directly activates plasmacytoid dendritic cells
Activation of TLR7 signaling pathways leads to the release of antiviral and proinflammatory cytokines, such as type I interferons (IFN-␣ and IFN-␤), that help the host rapidly mount an immune response to infection with an invasive pathogen
We investigated the ability of GS-9620, a potent and selective oral small-molecule agonist of TLR7, to inhibit human immunodeficiency virus (HIV) replication in vitro in total peripheral blood mononuclear cells (PBMCs) and cell cultures depleted of specific immune cell subsets

Summary

Introduction

GS-9620 is a potent and selective oral Toll-like receptor 7 (TLR7) agonist that directly activates plasmacytoid dendritic cells (pDCs). GS-9620 was inactive against HIV in purified CD4ϩ T cells and macrophages, HIV replication was potently inhibited by conditioned medium derived from GS-9620-treated pDC cultures when added to CD4ϩ T cells prior to infection This suggests that GS-9620-mediated stimulation of PBMCs induced the production of a soluble factor(s) inhibiting HIV replication in trans. Ligand binding to TLR7 results in activation of this receptor, recruitment of the cytoplasmic adaptor protein MyD88, and activation of the transcription factors nuclear factor kappa light chain enhancer of activated B cells (NF-␬B) and interferon regulatory factor 7 (IRF7) These factors translocate to the nucleus and trigger the production of various cytokines, including the type I interferons (IFNs) interferon alpha (IFN-␣) and IFN-␤, which act in both an autocrine and a paracrine fashion on infected and uninfected cells to produce an antiviral response. TLR7/8 triggering may have a dichotomous effect in HIV infection by preventing infection of CD4ϩ T cells while activating HIV expression in others

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Conclusion