Background and Aims
GS‐9688 (selgantolimod) is a toll‐like receptor 8 agonist in clinical development for the treatment of chronic hepatitis B (CHB). Antiviral activity of GS‐9688 has previously been ...evaluated in vitro in HBV‐infected hepatocytes and in vivo in the woodchuck model of CHB. Here we evaluated the potential of GS‐9688 to boost responses contributing to viral control and to modulate regulatory mediators.
Approach and Results
We characterized the effect of GS‐9688 on immune cell subsets in vitro in peripheral blood mononuclear cells of healthy controls and patients with CHB. GS‐9688 activated dendritic cells and mononuclear phagocytes to produce IL‐12 and other immunomodulatory mediators, inducing a comparable cytokine profile in healthy controls and patients with CHB. GS‐9688 increased the frequency of activated natural killer (NK) cells, mucosal‐associated invariant T cells, CD4+ follicular helper T cells, and, in about 50% of patients, HBV‐specific CD8+ T cells expressing interferon‐γ. Moreover, in vitro stimulation with GS‐9688 induced NK‐cell expression of interferon‐γ and TNF‐α, and promoted hepatocyte lysis. We also assessed whether GS‐9688 inhibited immunosuppressive cell subsets that might enhance antiviral efficacy. Stimulation with GS‐9688 reduced the frequency of CD4+ regulatory T cells and monocytic myeloid‐derived suppressor cells (MDSCs). Residual MDSCs expressed higher levels of negative immune regulators, galectin‐9 and programmed death‐ligand 1. Conversely, GS‐9688 induced an expansion of immunoregulatory TNF‐related apoptosis‐inducing ligand+ NK cells and degranulation of arginase‐I+ polymorphonuclear MDSCs.
Conclusions
GS‐9688 induces cytokines in human peripheral blood mononuclear cells that are able to activate antiviral effector function by multiple immune mediators (HBV‐specific CD8+ T cells, CD4+ follicular helper T cells, NK cells, and mucosal‐associated invariant T cells). Although reducing the frequency of some immunoregulatory subsets, it enhances the immunosuppressive potential of others, highlighting potential biomarkers and immunotherapeutic targets to optimize the antiviral efficacy of GS‐9688.
T-cell infiltration into tumors represents a critical bottleneck for immune-mediated control of cancer. We previously showed that this bottleneck can be overcome by depleting immunosuppressive Foxp3
...regulatory T cells (Tregs), a process that can increase frequencies of tumor-infiltrating lymphocytes through promoting the development of specialized portals for lymphocyte entry, namely high endothelial venules (HEVs). In this paper, we used a carcinogen-induced tumor model that allows for coevolution of the tumor microenvironment and the immune response to demonstrate that Treg depletion not only results in widespread disruption to HEV networks in lymph nodes (LNs) but also activates CD8
T cells, which then drive intratumoral HEV development. Formation of these vessels contrasts with ontogenic HEV development in LNs in that the process is dependent on the TNF receptor and independent of lymphotoxin β receptor-mediated signaling. These intratumoral HEVs do not express the chemokine CCL21, revealing a previously undescribed intratumoral blood vessel phenotype. We propose a model where Treg depletion enables a self-amplifying loop of T-cell activation, which promotes HEV development, T-cell infiltration, and ultimately, tumor destruction. The findings point to a need to test for HEV development as part of ongoing clinical studies in patients with cancer.
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The liver provides a tolerogenic immune niche exploited by several highly prevalent pathogens as well as by primary and metastatic tumors. We have sampled healthy and hepatitis B virus (HBV)–infected ...human livers to probe for a subset of T cells specialized to overcome local constraints and mediate immunity. We characterize a population of T-betloEomesloBlimp-1hiHobitlo T cells found within the intrahepatic but not the circulating memory CD8 T cell pool expressing liver-homing/retention markers (CD69+CD103+ CXCR6+CXCR3+). These tissue-resident memory T cells (TRM) are preferentially expanded in patients with partial immune control of HBV infection and can remain in the liver after the resolution of infection, including compartmentalized responses against epitopes within all major HBV proteins. Sequential IL-15 or antigen exposure followed by TGFβ induces liver-adapted TRM, including their signature high expression of exhaustion markers PD-1 and CD39. We suggest that these inhibitory molecules, together with paradoxically robust, rapid, cell-autonomous IL-2 and IFNγ production, equip liver CD8 TRM to survive while exerting local noncytolytic hepatic immunosurveillance.
Foxp3(+) regulatory T cells (Tregs) are often highly enriched within the tumor-infiltrating T cell pool. Using a well-characterised model of carcinogen-induced fibrosarcomas we show that the enriched ...tumor-infiltrating Treg population comprises largely of CXCR3(+) T-bet(+) 'TH1-like' Tregs which are thymus-derived Helios(+) cells. Whilst IL-2 maintains homeostatic ratios of Tregs in lymphoid organs, we found that the perturbation in Treg frequencies in tumors is IL-2 independent. Moreover, we show that the TH1 phenotype of tumor-infiltrating Tregs is dispensable for their ability to influence tumor progression. We did however find that unlike Tconvs, the majority of intra-tumoral Tregs express the activation markers CD69, CD25, ICOS, CD103 and CTLA4 and are significantly more proliferative than Tconvs. Moreover, we have found that CD69(+) Tregs are more suppressive than their CD69- counterparts. Collectively, these data indicate superior activation of Tregs in the tumor microenvironment, promoting their suppressive ability and selective proliferation at this site.
Pharmaceutical synthesis can benefit greatly from the selectivity gains associated with enzymatic catalysis. Here, we report an efficient biocatalytic process to replace a recently implemented ...rhodium-catalyzed asymmetric enamine hydrogenation for the large-scale manufacture of the antidiabetic compound sitagliptin. Starting from an enzyme that had the catalytic machinery to perform the desired chemistry but lacked any activity toward the prositagliptin ketone, we applied a substrate walking, modeling, and mutation approach to create a transaminase with marginal activity for the synthesis of the chiral amine; this variant was then further engineered via directed evolution for practical application in a manufacturing setting. The resultant biocatalysts showed broad applicability toward the synthesis of chiral amines that previously were accessible only via resolution. This work underscores the maturation of biocatalysis to enable efficient, economical, and environmentally benign processes for the manufacture of Pharmaceuticals.
The liver provides a tolerogenic immune niche exploited by several highly prevalent pathogens as well as by primary and metastatic tumors. We have sampled healthy and hepatitis B virus (HBV)-infected ...human livers to probe for a subset of T cells specialized to overcome local constraints and mediate immunity. We characterize a population of T-bet
Eomes
Blimp-1
Hobit
T cells found within the intrahepatic but not the circulating memory CD8 T cell pool expressing liver-homing/retention markers (CD69
CD103
CXCR6
CXCR3
). These tissue-resident memory T cells (T
) are preferentially expanded in patients with partial immune control of HBV infection and can remain in the liver after the resolution of infection, including compartmentalized responses against epitopes within all major HBV proteins. Sequential IL-15 or antigen exposure followed by TGFβ induces liver-adapted T
, including their signature high expression of exhaustion markers PD-1 and CD39. We suggest that these inhibitory molecules, together with paradoxically robust, rapid, cell-autonomous IL-2 and IFNγ production, equip liver CD8 T
to survive while exerting local noncytolytic hepatic immunosurveillance.
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