Anti-HBV response to toll-like receptor 7 agonist GS-9620 is associated with intrahepatic aggregates of T cells and B cells

Background & Aims: GS-9620, an oral agonist of toll-like receptor 7, is in clinical development for the treatment of chronic hepatitis B (CHB). GS-9620 was previously shown to induce prolonged suppression of serum viral DNA and antigens in the chimpanzee and woodchuck models of CHB. Herein, we investigated the immunomodulatory mechanisms underlying these antiviral effects. Methods: Archived liver biopsies and paired peripheral blood mononuclear cell samples from a previous chimpanzee study were analyzed by RNA sequencing, quantitative reverse transcription PCR, immunohistochemistry (IHC) and in situ hybridization (ISH). Results: GS-9620 treatment of CHB chimpanzees induced an intrahepatic transcriptional profile significantly enriched with genes associated with hepatitis B virus (HBV) clearance in acutely infected chimpanzees. Type I and II interferon, CD8(+) T cell and B cell transcriptional signatures were associated with treatment response, together with evidence of hepatocyte death and liver regeneration. IHC and ISH confirmed an increase in intrahepatic CD8(+) T cell and B cell numbers during treatment, and revealed that GS-9620 transiently induced aggregates predominantly comprised of CD8(+) T cells and B cells in portal regions. There were no follicular dendritic cells or IgG-positive cells in these lymphoid aggregates and very few CD11b(+) myeloid cells. There was no change in intrahepatic natural killer cell number during GS-9620 treatment. Conclusion: The antiviral response to GS-9620 treatment in CHB chimpanzees was associated with an intrahepatic interferon response and formation of lymphoid aggregates in the liver. Our data indicate these intrahepatic structures are not fully differentiated follicles containing germinal center reactions. However, the temporal correlation between development of these T and B cell aggregates and the antiviral response to treatment suggests they play a role in promoting an effective immune response against HBV. (C) 2017 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.