BACKGROUND & AIMS Chronic hepatitis C virus infection activates an intrahepatic immune response, leading to increased expression of interferon (IFN)-stimulated genes and activation of natural killer (NK) cells—the most prevalent innate immune cell in the liver. We investigated whether the elimination of HCV with direct-acting antiviral agents normalizes expression of IFN-stimulated genes and NK cell function. METHODS We used multicolor flow cytometry to analyze NK cells from liver and blood of 13 HCV-infected patients who did not respond to treatment with pegylated interferon and ribavirin. Samples were collected before and during IFN-free treatment with daclatasvir and asunaprevir therapy and compared with those from blood of 13 healthy individuals (controls). Serum levels of CXCL10 and CXCL11 were measured by ELISA. RESULTS Before treatment, all patients had increased levels of CXCL10 or CXCL11 and a different NK cell phenotype from controls, characterized by increased expression of HLA-DR, NKp46, NKG2A, CD85j, pSTAT1, STAT1, and TNF-related apoptosis-inducing ligand (TRAIL). NK cells from patients also had increased degranulation and decreased production of IFNγ and TNFα compared with NK cells from controls. Nine patients had an end-of-treatment response (undetectable virus) and 4 had virologic breakthrough between weeks 4 and 12 of therapy. A rapid decrease in viremia and level of inflammatory cytokines in all patients was associated with decreased activation of intrahepatic and blood NK cells; it was followed by restoration of a normal NK cell phenotype and function by week 8 in patients with undetectable viremia. This normalized NK cell phenotype was maintained until week 24 (EOT). CONCLUSIONS DAA-mediated clearance of HCV is associated with loss of intrahepatic immune activation by IFNα, indicated by decreased levels of CXCL10 and CXCL11 and normalization of NK cell phenotype and function.

Hepatitis B virus (HBV) infects hepatocytes specifically and causes immune mediated liver damage. How HBV interacts with the innate immunity at the early phase of infection, either with the hepatocytes or other cells in the liver remains controversial. To address this question, we utilized various cell culture models and humanized Alb-uPA/SCID mice. All these models were unable to mount an interferon (IFN) response despite robust HBV replication. To elucidate the mechanisms involved in the lack of IFN response, we examined whether HBV actively inhibits innate immune functions of hepatocytes. By treating HBV infected cells with known inducers of IFN signaling pathway, we observed no alteration of either sensing or downstream IFN response by HBV. We showed that the DNA innate sensing pathways are poorly active in hepatocytes, consistent with the muted innate immune recognition of HBV. Upon exposure to high-level HBV, macrophages could be activated with increased inflammatory cytokine expressions. Conclusion: HBV behaves like a “stealth” virus and is not sensed by nor actively interferes with the intrinsic innate immunity of the infected hepatocytes. Macrophages are capable of sensing HBV but require exposure to high HBV titers, potentially explaining the long “window period” during acute infection and HBV’s propensity to chronic infection.

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 to 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 (IFNG) by MAIT cells was dependent on monocyte-derived interleukin 18 (IL18), and was reduced in patients with HCV infection in response to T-cell receptor-mediated but not cytokine-mediated stimulation, as compared to 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.

Early, vigorous intrahepatic induction of interferon (IFN)-stimulated gene (ISG) induction is a feature of hepatitis C virus (HCV) infection, even though HCV inhibits the induction of type I IFNs in vitro. To identify the cytokines and cells that drive ISG induction and mediate antiviral activity during acute HCV infection, type I and III IFN responses were studied in (1) serial liver biopsies and plasma samples obtained from 6 chimpanzees throughout acute HCV infection and (2) primary human hepatocyte (PHH) cultures upon HCV infection. Type I IFNs were minimally induced at the messenger RNA (mRNA) level in the liver and were undetectable at the protein level in plasma during acute HCV infection of chimpanzees. In contrast, type III IFNs, in particular, interleukin (IL)-29 mRNA and protein, were strongly induced and these levels correlated with ISG expression and viremia. However, there was no association between intrahepatic or peripheral type III IFN levels and the outcome of acute HCV infection. Infection of PHH with HCV recapitulated strong type III and weak type I IFN responses. Supernatants from HCV-infected PHH cultures mediated antiviral activity upon transfer to HCV-replicon–containing cells. This effect was significantly reduced by neutralization of type III IFNs and less by neutralization of type I IFNs. Furthermore, IL-29 production by HCV-infected PHH occurred independently from type I IFN signaling and was not enhanced by the presence of plasmacytoid dendritic cells. Conclusion Hepatocyte-derived type III IFNs contribute to ISG induction and antiviral activity, but are not the principal determinant of the outcome of HCV infection.

Natural killer (NK) cells exhibit a polarized phenotype with increased cytotoxicity and decreased IFN- γ production in chronic hepatitis C virus (HCV) infection. Here we asked whether this is due to type I interferon (IFN)-induced expression and phosphorylation levels of signal transducer and activator of transcription (STAT) molecules in NK cells and whether it affects the response and refractoriness of NK cells to IFN-α-based therapy of hepatitis C. STAT1 levels in NK cells were significantly higher in patients with chronic HCV infection than in uninfected controls. STAT1 levels and induction of phosphorylated STAT1 (pSTAT1) increased further during IFN-α-based therapy with preferential STAT1 over STAT4 phosphorylation. Induction of pSTAT1 correlated with increased NK cytotoxicity (TRAIL expression and degranulation) and decreased IFN-γ production. NK cells from patients with a greater than 2 log10 first phase HCV RNA decline to IFN-α-based therapy (>99% IFN effectiveness) displayed strong pSTAT1 induction in vivo and were refractory to further stimulation in vitro. In contrast, NK cells from patients with a less than 2 log10 first phase HCV RNA decline exhibited lower pSTAT1 induction in vivo (p=0.024) but retained greater IFN-α responsiveness in vitro (p=0.024). NK cells of all patients became refractory to in vivo and in vitro stimulation by IFN-α during the second phase virological response. Conclusion These data show that IFN-α-induced modulation of STAT1/4 phosphorylation underlies the polarization of NK cells towards increased cytotoxicity and decreased IFN-γ production in HCV infection, and that NK cell responsiveness and refractoriness correlate to the antiviral effectiveness of IFN-α-based therapy.

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We analyzed the effects of a single 14-day course of teplizumab treatment on metabolic function and immune cells among participants in a previously reported randomized controlled trial of nondiabetic relatives at high risk for type 1 diabetes (T1D). In an extended follow-up (923-day median) of a previous report of teplizumab treatment, we found that the median times to diagnosis were 59.6 and 27.1 months for teplizumab- and placebo-treated participants, respectively (HR = 0.457, P = 0.01). Fifty percent of teplizumab-treated but only 22% of the placebo-treated remained diabetes-free. Glucose tolerance, C-peptide area under the curve (AUC), and insulin secretory rates were calculated, and relationships to T cell subsets and function were analyzed. Teplizumab treatment improved beta cell function, reflected by average on-study C-peptide AUC (1.94 versus 1.72 pmol/ml; P = 0.006). Drug treatment reversed a decline in insulin secretion before enrollment, followed by stabilization of the declining C-peptide AUC seen with placebo treatment. Proinsulin:C-peptide ratios after drug treatment were similar between the treatment groups. The changes in C-peptide with teplizumab treatment were associated with increases in partially exhausted memory KLRG1+TIGIT+CD8+ T cells (r = 0.44, P = 0.014) that showed reduced secretion of IFNγ and TNFα. A single course of teplizumab had lasting effects on delay of T1D diagnosis and improved beta cell function in high-risk individuals. Changes in CD8+ T cell subsets indicated that partially exhausted effector cells were associated with clinical response. Thus, this trial showed improvement in metabolic responses and delay of diabetes with immune therapy.

ObjectivesTo characterise the clinical features, immune manifestations and molecular mechanisms in a recently described autoinflammatory disease caused by mutations in TRNT1, a tRNA processing enzyme, and to explore the use of cytokine inhibitors in suppressing the inflammatory phenotype.MethodsWe studied nine patients with biallelic mutations in TRNT1 and the syndrome of congenital sideroblastic anaemia with immunodeficiency, fevers and developmental delay (SIFD). Genetic studies included whole exome sequencing (WES) and candidate gene screening. Patients’ primary cells were used for deep RNA and tRNA sequencing, cytokine profiling, immunophenotyping, immunoblotting and electron microscopy (EM).ResultsWe identified eight mutations in these nine patients, three of which have not been previously associated with SIFD. Three patients died in early childhood. Inflammatory cytokines, mainly interleukin (IL)-6, interferon gamma (IFN-γ) and IFN-induced cytokines were elevated in the serum, whereas tumour necrosis factor (TNF) and IL-1β were present in tissue biopsies of patients with active inflammatory disease. Deep tRNA sequencing of patients’ fibroblasts showed significant deficiency of mature cytosolic tRNAs. EM of bone marrow and skin biopsy samples revealed striking abnormalities across all cell types and a mix of necrotic and normal-appearing cells. By immunoprecipitation, we found evidence for dysregulation in protein clearance pathways. In 4/4 patients, treatment with a TNF inhibitor suppressed inflammation, reduced the need for blood transfusions and improved growth.ConclusionsMutations of TRNT1 lead to a severe and often fatal syndrome, linking protein homeostasis and autoinflammation. Molecular diagnosis in early life will be crucial for initiating anti-TNF therapy, which might prevent some of the severe disease consequences.