Background: Pharmacologic activation of latent HIV reservoirs is considered to be a key part of the strategy towards eradicating HIV-1 infection. GS-9620 is a selective TLR7 agonist currently being evaluated in patients with chronic hepatitis B. Based on recent observations of induced plasma viral RNA and reduction of viral DNA in cART-suppressed SIV-infected rhesus monkeys (RM) treated with a close analog (Whitney et al., CROI 2015 submitted), GS-9620 is now also being considered for evaluation in HIV-infected patients. Here we show that GS-9620 activates HIV gene expression ex vivo in PBMCs from HIV-infected patients on cART.
Methods: PBMCs isolated from patients with plasma HIV RNA<50 copies/mL for >12 months were treated with GS-9620 in the presence of ARVs. HIV-1 RNA was quantified in culture supernatants by the AmpliPrep/COBAS® TaqMan® assay. GS-9620-induced cytokines were quantified by Luminex. In selected cultures, CD8 T cell-depleted PBMCs were treated with GS-9620. The effect on the inducible HIV reservoir was assessed by protein kinase C (PKC) agonist-mediated activation of CD4 T cells isolated from GS-9620-treated PBMCs.
Results: In PBMCs from 11 of 12 donors tested, 0.01-1 µM GS-9620 activated HIV RNA expression compared to vehicle control with a 5.8-fold geometric mean maximal activation (range 2.0- to 26.8-fold across donors). Depletion of CD8 T cells increased overall HIV expression without affecting the fold activation induced by GS-9620. While there was no correlation between HIV activation levels and cytokines induced by GS-9620, blocking the type I IFN receptor reduced the maximal HIV expression in all donors assessed (n=4; 85% geometric mean reduction, p<0.05). GS-9620 treatment also reduced subsequent PKC agonist-mediated HIV activation (3 of 4 donors; 74% geometric mean reduction, p<0.05).
Conclusions: GS-9620 activated HIV RNA expression in PBMCs isolated from patients on suppressive cART, a result consistent with observations in SIV-infected RM treated with a related TLR7 agonist. Type I IFN was required for maximal HIV activation by GS-9620. The HIV response to subsequent PKC activation was reduced in CD4 T cells isolated from GS-9620-treated PBMCs, suggesting a potential reduction in the inducible viral reservoir. Together with the results obtained from SIV-infected RM, these data support the clinical testing of GS-9620 in HIV-infected patients on suppressive cART for possible activation and reduction of the viral reservoir.