Intra-Hepatic Depletion of Mucosal-Associated Invariant T Cells in Hepatitis C Virus-Induced Liver Inflammation.

BACKGROUND & AIMS: Chronic hepatitis affects phenotypes of innate and adaptive immune cells. Mucosal-associated invariant T (MAIT) cells are enriched in the liver as compared with the blood, respond to intra-hepatic cytokines, and (via the semi-invariant T-cell receptor) to bacteria translocated from the gut. Little is known about the role of MAIT cells in livers of patients with chronic hepatitis C virus (HCV) infection and their fate after antiviral therapy. METHODS: We collected blood samples from 42 patients with chronic HCV infection who achieved a sustained virologic response after 12 weeks of treatment with sofosbuvir and velpatasvir. Mononuclear cells were isolated from blood before treatment, at weeks 4 and 12 during treatment, and 24 weeks after the end of treatment. Liver biopsies were collected from 37 of the patients prior to and at week 4 of treatment. Mononuclear cells from 56 blood donors and 10 livers that were not suitable for transplantation were used as controls. Liver samples were assessed histologically for inflammation and fibrosis. Mononuclear cells from liver and blood were studied by flow cytometry and analyzed for responses to cytokine and bacterial stimulation. RESULTS: The frequency of MAIT cells among T cells was significantly lower in blood and liver samples of patients with HCV infection than of controls (median, 1.31% vs 2.32% for blood samples, P = .0048; and median, 4.34% vs 13.40% for liver samples, P = .001). There was an inverse correlation between the frequency of MAIT cells in the liver and histologically determined levels of liver inflammation (r = -.5437, P = .0006) and fibrosis (r = -.5829, P = .0002). MAIT cells from the liver had higher levels of activation and cytotoxicity than MAIT cells from blood (P < .0001). Production of interferon gamma by MAIT cells was dependent on monocyte-derived interleukin 18, and was reduced in patients with HCV infection in response to T-cell receptor-mediated but not cytokine-mediated stimulation, as compared with controls. Anti-viral therapy rapidly decreased liver inflammation and MAIT cell activation and cytotoxicity, and increased the MAIT cell frequency among intra-hepatic but not blood T cells. The MAIT cell response to T-cell receptor-mediated stimulation did not change during the 12 weeks of antiviral therapy. CONCLUSIONS: In analyses of paired blood and liver samples from patients with chronic HCV infection before, during, and after antiviral therapy with sofosbuvir and velpatasvir, we found that intrahepatic MAIT cells are activated by monocyte-derived cytokines and depleted in HCV-induced liver inflammation.

Rapid decrease in hepatitis C viremia by direct acting antivirals improves the natural killer cell response to IFNα.

OBJECTIVE: Chronic HCV infection is characterised by innate immune activation with increased interferon-stimulated genes (ISG) expression and by an altered phenotype of interferon-responsive natural killer (NK) cells. Here, we asked whether a rapid reduction in viremia by daclatasvir (DCV) and asunaprevir (ASV) improves the response to pegylated interferon (PegIFN) in patients who had previously failed a standard course of PegIFN/ribavirin (RBV) therapy. DESIGN: Twenty-two HCV-infected non-responders to previous PegIFN/RBV therapy were studied for IFN-responsiveness of NK cells during quadruple (QUAD) therapy with DCV, ASV, PegIFN and RBV. A direct comparison of early NK cell responses in PegIFN/RBV therapy and QUAD therapy was performed for seven patients using paired cryopreserved peripheral blood mononuclear cells (PBMC) from both treatment courses. As a validation cohort, nine DCV/ASV-treated patients were studied for their NK cell response to in vitro stimulation with IFNα. RESULTS: The 24 h virological response to QUAD therapy correlated with an increase in signal transducer and activator of transcription 1 (STAT1), phosphorylated STAT1 (pSTAT1) and tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) expression in NK cells, and the STAT1/pSTAT1/TRAIL induction was greater during QUAD therapy than during previous PegIFN/RBV therapy. Successful QUAD therapy as well as successful IFN-free DCV/ASV regimen resulted in an improved functional NK cell response (degranulation and TRAIL expression) to in vitro stimulation with IFNα. CONCLUSIONS: IFN-responsiveness can be improved by inhibiting HCV replication and reducing the HCV-induced activation of the innate immune response. This may provide a rationale for clinical trials of a brief period of direct acting antiviral therapy followed by PegIFN/RBV therapy to reduce the overall treatment costs in low-income and middle-income countries. TRIAL REGISTRATION NUMBERS: NCT01888900 and NCT00718172.

Mammalian Nkx2.2+ perineurial glia are essential for motor nerve development.

BACKGROUND: All vertebrate peripheral nerves connect the central nervous system (CNS) with targets in the periphery and are composed of axons, layers of ensheathing glia and connective tissue. Although the structure of these conduits is well established, very little is known about the origin and developmental roles of some of their elements. One understudied component, the perineurium, ensheaths nerve fascicles and is a component of the blood-nerve-barrier. In zebrafish, the motor nerve perineurium is composed of CNS-derived nkx2.2a(+) perineurial glia, which establish the motor exit point (MEP) during development. To determine if mouse perineurial cells also originate within the CNS and perform a similar function, we created a Nkx2.2:EGFP transgenic reporter line. RESULTS: In conjunction with RNA expression analysis and antibody labeling, we observed Nkx2.2(+) cells along peripheral motor nerves at all stages of development and in adult tissue. Additionally, in mice lacking Nkx2.2, we demonstrate that Nkx2.2(+) perineurial glia are essential for motor nerve development and Schwann cell differentiation. CONCLUSIONS: Our studies reveal that a subset of mouse perineurial cells are CNS-derived, express Nkx2.2, and are essential for motor nerve development. This work highlights an under-appreciated but essential contribution of CNS-derived cells to the development of the mammalian peripheral nervous system (PNS).