Interferon-induced IL-10 drives systemic T-cell dysfunction during chronic liver injury.

BACKGROUND & AIMS: Patients with chronic liver disease (CLD), including cirrhosis, are at increased risk of intractable viral infections and are hyporesponsive to vaccination. Hallmarks of CLD and cirrhosis include microbial translocation and elevated levels of type I interferon (IFN-I). We aimed to investigate the relevance of microbiota-induced IFN-I in the impaired adaptive immune responses observed in CLD. METHODS: We combined bile duct ligation (BDL) and carbon tetrachloride (CCl4) models of liver injury with vaccination or lymphocytic choriomeningitis virus infection in transgenic mice lacking IFN-I in myeloid cells (LysM-Cre IFNARflox/flox), IFNAR-induced IL-10 (MX1-Cre IL10flox/flox) or IL-10R in T cells (CD4-DN IL-10R). Key pathways were blocked in vivo with specific antibodies (anti-IFNAR and anti-IL10R). We assessed T-cell responses and antibody titers after HBV and SARS-CoV-2 vaccinations in patients with CLD and healthy individuals in a proof-of-concept clinical study. RESULTS: We demonstrate that BDL- and CCL4-induced prolonged liver injury leads to impaired T-cell responses to vaccination and viral infection in mice, subsequently leading to persistent infection. We observed a similarly defective T-cell response to vaccination in patients with cirrhosis. Innate sensing of translocated gut microbiota induced IFN-I signaling in hepatic myeloid cells that triggered excessive IL-10 production upon viral infection. IL-10R signaling in antigen-specific T cells rendered them dysfunctional. Antibiotic treatment and inhibition of IFNAR or IL-10Ra restored antiviral immunity without detectable immune pathology in mice. Notably, IL-10Ra blockade restored the functional phenotype of T cells from vaccinated patients with cirrhosis. CONCLUSION: Innate sensing of translocated microbiota induces IFN-/IL-10 expression, which drives the loss of systemic T-cell immunity during prolonged liver injury. IMPACT AND IMPLICATIONS: Chronic liver injury and cirrhosis are associated with enhanced susceptibility to viral infections and vaccine hyporesponsiveness. Using different preclinical animal models and patient samples, we identified that impaired T-cell immunity in BDL- and CCL4-induced prolonged liver injury is driven by sequential events involving microbial translocation, IFN signaling leading to myeloid cell-induced IL-10 expression, and IL-10 signaling in antigen-specific T cells. Given the absence of immune pathology after interference with IL-10R, our study highlights a potential novel target to reconstitute T-cell immunity in patients with CLD that can be explored in future clinical studies.

Overlapping Peptides Elicit Distinct CD8+ T Cell Responses following Influenza A Virus Infection.

The presentation of pathogen-derived peptides on MHC class I molecules is essential for the initiation of adaptive CD8+ T cell immunity, which in turn is critical for effective control of many significant human infections. The identification of immunogenic pathogen-derived epitopes and a detailed understanding of how they are recognized by TCRs is essential for the design of effective T cell-based vaccines. In this study, we have characterized the T cell recognition and immune responses in mice to two naturally presented influenza A virus-derived peptides previously identified from virally infected cells via mass spectrometry. These neuraminidase-derived peptides, NA181-190 (SGPDNGAVAV) and NA181-191 (SGPDNGAVAVL), are completely overlapping with the exception of a 1 aa extension at the C terminus of the longer peptide. This minor peptidic difference results in the induction of two completely independent and non-cross-reactive T cell populations that show distinct functional characteristics after influenza A virus infection of B6 mice. We show that the unique TCR reactivity to the overlapping peptides is present in the naive repertoire prior to immune expansion in B6 mice. Moreover, we provide a structural explanation underlying the distinct CD8+ T cell reactivities, which reinforces the concept that peptide length is a key determinant of Ag specificity in CD8+ T cell responses.

Publisher Correction: Metabolic characteristics of CD8+ T cell subsets in young and aged individuals are not predictive of functionality.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Metabolic characteristics of CD8+ T cell subsets in young and aged individuals are not predictive of functionality.

Virtual memory T (TVM) cells are antigen-naïve CD8+ T cells that exist in a semi-differentiated state and exhibit marked proliferative dysfunction in advanced age. High spare respiratory capacity (SRC) has been proposed as a defining metabolic characteristic of antigen-experienced memory T (TMEM) cells, facilitating rapid functionality and survival. Given the semi-differentiated state of TVM cells and their altered functionality with age, here we investigate TVM cell metabolism and its association with longevity and functionality. Elevated SRC is a feature of TVM, but not TMEM, cells and it increases with age in both subsets. The elevated SRC observed in aged mouse TVM cells and human CD8+ T cells from older individuals is associated with a heightened sensitivity to IL-15. We conclude that elevated SRC is a feature of TVM, but not TMEM, cells, is driven by physiological levels of IL-15, and is not indicative of enhanced functionality in CD8+ T cells.

The Impact of MHC Class I Dose on Development and Maintenance of the Polyclonal Naive CD8+ T Cell Repertoire.

Naive CD8+ T cell survival in the periphery is critically dependent on tonic TCR signaling through peptide + MHC class I (MHCI) recognition; however, little is known about how natural variation in MHCI levels impacts the naive CD8+ T cell repertoire. Using mice that are hemizygous or homozygous for a single MHCI allele, we showed that despite a reduction in peripheral CD8+ T cell numbers of ∼50% in MHCI hemizygous mice, MHCI levels had no notable impact on the rate of thymic generation or emigration of CD8 single-positive T cells. Moreover, the peripheral T cell repertoire in hemizygous mice showed selective retention of T cell clonotypes with a greater competitive advantage as evidenced by increased expression of CD5 and IL-7Rα. The qualitative superiority of CD8+ T cells retained in hemizygous mice was also seen during influenza A virus infection, in which epitope-specific CD8+ T cells from hemizygous mice had a higher avidity for pMHCI and increased cytokine polyfunctionality, despite a reduced response magnitude. Collectively, this study suggests that natural variation in MHCI expression levels has a notable and biologically relevant impact on the maintenance, but not generation, of the naive CD8+ T cell repertoire.

A dual role for hepatocyte-intrinsic canonical NF-κB signaling in virus control.

BACKGROUND & AIMS: Hepatic innate immune control of viral infections has largely been attributed to Kupffer cells, the liver-resident macrophages. However, hepatocytes, the parenchymal cells of the liver, also possess potent immunological functions in addition to their known metabolic functions. Owing to their abundance in the liver and known immunological functions, we aimed to investigate the direct antiviral mechanisms employed by hepatocytes. METHODS: Using lymphocytic choriomeningitis virus (LCMV) as a model of liver infection, we first assessed the role of myeloid cells by depletion prior to infection. We investigated the role of hepatocyte-intrinsic innate immune signaling by infecting mice lacking canonical NF-κB signaling (IkkßΔHep) specifically in hepatocytes. In addition, mice lacking hepatocyte-specific interferon-α/ß signaling-(IfnarΔHep), or interferon-α/ß signaling in myeloid cells-(IfnarΔMyel) were infected. RESULTS: Here, we demonstrate that LCMV activates NF-κB signaling in hepatocytes. LCMV-triggered NF-κB activation in hepatocytes did not depend on Kupffer cells or TNFR1 signaling but rather on Toll-like receptor signaling. LCMV-infected IkkßΔHep livers displayed strongly elevated viral titers due to LCMV accumulation within hepatocytes, reduced interferon-stimulated gene (ISG) expression, delayed intrahepatic immune cell influx and delayed intrahepatic LCMV-specific CD8+ T cell responses. Notably, viral clearance and ISG expression were also reduced in LCMV-infected primary hepatocytes lacking IKKß, demonstrating a hepatocyte-intrinsic effect. Similar to livers of IkkßΔHep mice, enhanced hepatocytic LCMV accumulation was observed in livers of IfnarΔHep mice, whereas IfnarΔMyel mice were able to control LCMV infection. Hepatocytic NF-κB signaling was also required for efficient ISG induction in HDV-infected dHepaRG cells and interferon-α/ß-mediated inhibition of HBV replication in vitro. CONCLUSIONS: Together, these data show that hepatocyte-intrinsic NF-κB is a vital amplifier of interferon-α/ß signaling, which is pivotal for strong early ISG responses, immune cell infiltration and hepatic viral clearance. LAY SUMMARY: Innate immune cells have been ascribed a primary role in controlling viral clearance upon hepatic infections. We identified a novel dual role for NF-κB signaling in infected hepatocytes which was crucial for maximizing interferon responses and initiating adaptive immunity, thereby efficiently controlling hepatic virus replication.

Effects of sleep on a high-heat capacity mattress on sleep stages, EEG power spectra, cardiac interbeat intervals and body temperatures in healthy middle-aged men‡.

STUDY OBJECTIVES: This study deals with the question whether a slow (non-disturbing) reduction of core body temperature (CBT) during sleep increases sleep stage N3 and EEG slow wave energy (SWE) and leads to a slowing of heart rate in humans. PARTICIPANTS: Thirty-two healthy male subjects with a mean ± SD age 46 ± 4 years and body mass index 25.2 ± 1.8 kg/m2. METHODS: A high-heat capacity mattress (HM) was used to lower body temperatures in sleep and was compared to a conventional low-heat capacity mattress (LM) in a double-blinded fashion. Polysomnography was performed accompanied by measurements of skin-, core body- and mattress surface-temperatures, and heart rate. EEG power spectral analyses were carried out using Fast Fourier Transform. Interbeat intervals were derived from the electrocardiogram. RESULTS: The HM led to a larger decline in CBT, mediated through higher heat conduction from the core via the proximal back skin onto the mattress together with reduced heart rate. These effects occurred together with a significant increase in sleep stage N3 and standardized slow wave energy (sSWE, 0.791-4.297 Hz) accumulated in NREM sleep. In the 2nd half of the night sSWE increase was significantly correlated with body temperature changes, for example with CBT decline in the same phase. CONCLUSIONS: A HM subtly decreases CBT, leading to an increased amount of sleep stage N3 and of sSWE, as well as a slowing of heart rate.

Gut microbial translocation corrupts myeloid cell function to control bacterial infection during liver cirrhosis.

OBJECTIVE: Patients with liver cirrhosis suffer from increased susceptibility to life-threatening bacterial infections that cause substantial morbidity. METHODS: Experimental liver fibrosis in mice induced by bile duct ligation or CCl4 application was used to characterise the mechanisms determining failure of innate immunity to control bacterial infections. RESULTS: In murine liver fibrosis, translocation of gut microbiota induced tonic type I interferon (IFN) expression in the liver. Such tonic IFN expression conditioned liver myeloid cells to produce high concentrations of IFN upon intracellular infection with Listeria that activate cytosolic pattern recognition receptors. Such IFN-receptor signalling caused myeloid cell interleukin (IL)-10 production that corrupted antibacterial immunity, leading to loss of infection-control and to infection-associated mortality. In patients with liver cirrhosis, we also found a prominent liver IFN signature and myeloid cells showed increased IL-10 production after bacterial infection. Thus, myeloid cells are both source and target of IFN-induced and IL-10-mediated immune dysfunction. Antibody-mediated blockade of IFN-receptor or IL-10-receptor signalling reconstituted antibacterial immunity and prevented infection-associated mortality in mice with liver fibrosis. CONCLUSIONS: In severe liver fibrosis and cirrhosis, failure to control bacterial infection is caused by augmented IFN and IL-10 expression that incapacitates antibacterial immunity of myeloid cells. Targeted interference with the immune regulatory host factors IL-10 and IFN reconstitutes antibacterial immunity and may be used as therapeutic strategy to control bacterial infections in patients with liver cirrhosis.