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The devastating consequences of hepatic failure include hepatic encephalopathy, a severe, life threatening impairment of neuronal function. Hepatic encephalopathy is caused by impaired hepatic clearance of NH 4 + . Cellular NH 4 + uptake is accomplished mainly by the Na + ,K + ,2Cl − cotransporter. Here we show that hepatic clearance of NH 4 + is impaired in TNFα deficient as well as TNFR1&TNFR2 double knockout mice, which both develop hyperammonemia. Despite impaired hepatic clearance of NH 4 + , TNFα deficient mice and TNFR1 deficient mice were protected against acute ammonia intoxication. While 54% of the wild-type mice and 60% of TNFR2 deficient mice survived an NH 4 + load, virtually all TNFα deficient mice and TNFR1 deficient mice survived the treatment. Conversely, TNFα treatment of wild type mice sensitized the animals to the toxic effects of an NH 4 + load. The protection of TNFα-deficient mice against an NH 4 + load was paralleled by decreased cerebral expression of NKCC1. According to the present observations, inhibition of TNFα formation and/or NKCC1 may be strategies to favorably influence the clinical course of hepatic encephalopathy.

Immune evasion of pathogens can modify the course of infection and impact viral persistence and pathology. Here, using different strains of the lymphocytic choriomeningitis virus (LCMV) model system, we show that slower propagation results in limited type I interferon (IFN-I) production and viral persistence. Specifically, cells infected with LCMV-Docile exhibited reduced viral replication when compared to LCMV-WE and as a consequence, infection with LCMV-Docile resulted in reduced activation of bone marrow derived dendritic cells (BMDCs) and IFN-I production in vitro in comparison with LCMV-WE. In vivo, we observed a reduction of IFN-I, T cell exhaustion and viral persistence following infection of LCMV-Docile but not LCMV-WE. Mechanistically, block of intracellular protein transport uncovered reduced propagation of LCMV-Docile when compared to LCMV-WE. This reduced propagation was critical in blunting the activation of the innate and adaptive immune system. When mice were simultaneously infected with LCMV-Docile and LCMV-WE, immune function was restored and IFN-I production, T cell effector functions as well as viral loads were similar to that of mice infected with LCMV-WE alone. Taken together, this study suggests that reduced viral propagation can result in immune evasion and viral persistence.Using different strains of the lymphocytic choriomeningitis virus (LCMV), Xu, Wang et al. show that a slow viral propagation limits type I interferon (IFN-I) production and viral persistence in mice. This study suggests a reduced viral propagation as a mechanism for immune evasion and viral persistence.

Functional T cell exhaustion occurs during chronic viral infection or in tumor settings. Beyer et al . report that chronic inflammation mediated by the cytokine TNF is responsible for this dysfunction and that blockade of this pathway restores immune system–mediated control of viral infection. Persistent viral infections are characterized by the simultaneous presence of chronic inflammation and T cell dysfunction. In prototypic models of chronicity—infection with human immunodeficiency virus (HIV) or lymphocytic choriomeningitis virus (LCMV)—we used transcriptome-based modeling to reveal that CD4 + T cells were co-exposed not only to multiple inhibitory signals but also to tumor-necrosis factor (TNF). Blockade of TNF during chronic infection with LCMV abrogated the inhibitory gene-expression signature in CD4 + T cells, including reduced expression of the inhibitory receptor PD-1, and reconstituted virus-specific immunity, which led to control of infection. Preventing signaling via the TNF receptor selectively in T cells sufficed to induce these effects. Targeted immunological interventions to disrupt the TNF-mediated link between chronic inflammation and T cell dysfunction might therefore lead to therapies to overcome persistent viral infection.

ObjectiveThe Fragile X mental retardation (FMR) syndrome is a frequently inherited intellectual disability caused by decreased or absent expression of the FMR protein (FMRP). Lack of FMRP is associated with neuronal degradation and cognitive dysfunction but its role outside the central nervous system is insufficiently studied. Here, we identify a role of FMRP in liver disease.DesignMice lacking Fmr1 gene expression were used to study the role of FMRP during tumour necrosis factor (TNF)-induced liver damage in disease model systems. Liver damage and mechanistic studies were performed using real-time PCR, Western Blot, staining of tissue sections and clinical chemistry.Results Fmr1null mice exhibited increased liver damage during virus-mediated hepatitis following infection with the lymphocytic choriomeningitis virus. Exposure to TNF resulted in severe liver damage due to increased hepatocyte cell death. Consistently, we found increased caspase-8 and caspase-3 activation following TNF stimulation. Furthermore, we demonstrate FMRP to be critically important for regulating key molecules in TNF receptor 1 (TNFR1)-dependent apoptosis and necroptosis including CYLD, c-FLIPS and JNK, which contribute to prolonged RIPK1 expression. Accordingly, the RIPK1 inhibitor Necrostatin-1s could reduce liver cell death and alleviate liver damage in Fmr1null mice following TNF exposure. Consistently, FMRP-deficient mice developed increased pathology during acute cholestasis following bile duct ligation, which coincided with increased hepatic expression of RIPK1, RIPK3 and phosphorylation of MLKL.ConclusionsWe show that FMRP plays a central role in the inhibition of TNF-mediated cell death during infection and liver disease.

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

Immune responses are critical for defense against pathogens. However, prolonged viral infection can result in defective T cell immunity, leading to chronic viral infection. We studied immune activation in response to arenavirus infection during cholestasis using bile duct ligation (BDL). We monitored T cell responses, virus load and liver pathology markers after infection with lymphocytic choriomeningitis virus (LCMV). BDL mice failed to induce protective anti-viral immunity against LCMV and consequently exhibited chronic viral infection. BDL mice exhibited reduced anti-viral T cell immunity as well as reduced type 1 interferon production early after LCMV infection. Consistently, the presence of serum from BDL mice reduced the responsiveness of dendritic cell (DC) and T cell cultures when compared to Sham controls. Following fractionation and mass spectrometry analyses of sera, we identified several serum factors to be upregulated following BDL including bilirubin, bile acids, 78 kDa Glucose regulated protein (GRP78) and liver enzymes. Bilirubin and GRP78 were capable of inhibiting DC and T cell activation. In this work, we demonstrate that liver damage mediated by cholestasis results in defective immune induction following arenavirus infection.

Persistent viral infections are characterized by the simultaneous presence of chronic inflammation and T cell dysfunction. In prototypic models of chronicity--infection with human immunodeficiency virus (HIV) or lymphocytic choriomeningitis virus (LCMV)--we used transcriptome-based modeling to reveal that [CD4.sup.+] T cells were co-exposed not only to multiple inhibitory signals but also to tumor-necrosis factor (TNF). Blockade of TNF during chronic infection with LCMV abrogated the inhibitory gene-expression signature in [CD4.sup.+] T cells, including reduced expression of the inhibitory receptor PD-1, and reconstituted virus-specific immunity, which led to control of infection. Preventing signaling via the TNF receptor selectively in T cells sufficed to induce these effects. Targeted immunological interventions to disrupt the TNF-mediated link between chronic inflammation and T cell dysfunction might therefore lead to therapies to overcome persistent viral infection.

An avian influenza (AI) surveillance was undertaken in Maharashtra state, India during the period 2010–2011. There are no reports of AI surveillance in emus from India. A total of 202 blood samples and 467 tracheal and cloacal swabs were collected from eight emu farms. A hemagglutination inhibition (HI) assay was performed for detection of antibodies against AI H5N1, H7N1, H9N2, and avian paramyxovirus type 1 (APMV-1) viruses. A microneutralization (MN) assay was performed to confirm the presence of neutralizing antibodies against AI H9N2 and to compare with HI assays. A total of 28.2% and 28.7% of samples were positive for antibodies against AI H9N2 by HI and MN assays, respectively, using ≥1∶40 as a cut-off titer; 15.3% samples were positive for APMV-1 by HI assay using a ≥1∶10 cut-off titer. Seropositivity of AI H9N2 was nil in the grower (<1 yr) age group and highest (78%) in the breeder (2–3 yr) age group, whereas seropositivity against APMV-1 was observed in all age groups. Performance of both HI and MN assays was similar, suggesting the utility of using the MN assay along with HI assay for surveillance studies. This is the first report of the seroprevalence of AI H9N2 and APMV-1 in emus in India.

An avian influenza (AI) surveillance was undertaken in Maharashtra state, India during the period 2010-2011. There are no reports of AI surveillance in emus from India. A total of 202 blood samples and 467 trachéal and cloacal swabs were collected from eight emu farms. A hemagglutination inhibition (HI) assay was performed for detection of antibodies against AI H5N1, H7N1, H9N2, and avian paramyxovirus type 1 (APMV-1) viruses. A microneutralization (MN) assay was performed to confirm the presence of neutralizing antibodies against AI H9N2 and to compare with HI assays. A total of 28.2% and 28.7% of samples were positive for antibodies against AI H9N2 by HI and MN assays, respectively, using ≥ 1: 40 as a cut-off titer; 15.3% samples were positive for APMV-1 by HI assay using a ≥ 1: 10 cut-off titer. Seropositivity of AI H9N2 was nil in the grower (< 1 yr) age group and highest (78%) in the breeder (2— 3 yr) age group, whereas seropositivity against APMV-1 was observed in all age groups. Performance of both HI and MN assays was similar, suggesting the utility of using the MN assay along with HI assay for surveillance studies. This is the first report of the seroprevalence of AI H9N2 and APMV-1 in emus in India. Un programa de vigilancia para la influenza aviar se llevó a cabo en el estado de Maharashtra, en la India durante el período 2010-2011. No hay informes de programas de vigilancia para la influenza aviar de emúes en la India. Un total de 202 muestras de sangre y 467 hisopos traqueales y cloacales se obtuvieron de ocho granjas de emúes. Se llevó a cabo un ensayo de inhibición de la hemaglutinación (HI) para la detección de anticuerpos contra los subtipos H5N1, H7N1 y H9N2 de influenza, y para el paramixovirus aviar tipo 1 (APMV-1). Se realizó un ensayo de microneutralización para confirmar la presencia de anticuerpos neutralizantes contra la influenza aviar H9N2, y comparar con los ensayos de inhibición de la hemoaglutinación. Un total de 28.2% y 28.7% de las muestras fueron positivas para anticuerpos contra la influenza aviar H9N2 mediante inhibición de la hemaglutinación y los ensayos de microneutralización, respectivamente, con título de corte de ≥ 1: 40, un 15.3% de las muestras fueron positivas para APMV-1 mediante un ensayo de inhibición de la hemoaglutinación con un título de corte de ≥ 1: 10. La seropositividad de la influenza aviar H9N2 fue nula en las aves en crecimiento (menores de 1 año) y fue la mayor en los reproductores (78%) de dos a tres años de edad, mientras que la seropositividad contra APMV-1 se observó en todos los grupos de edades. El desempeño de ambos ensayos de inhibición de la hemoaglutinación y de microneutralización fue similar, lo que sugiere la utilidad de usar el ensayo de microneutralización junto con el ensayo de inhibición de la hemoaglutinación para estudios de vigilancia. Este es el primer informe de la seroprevalencia de la influenza aviar H9N2 y del APMV-1 en los emúes de la India.

Persistent viral infections are characterized by the simultaneous presence of chronic inflammation and T cell dysfunction. In prototypic models of chronicity-infection with human immunodeficiency virus (HIV) or lymphocytic choriomeningitis virus (LCMV)-we used transcriptome-based modeling to reveal that CD4 super(+) T cells were co-exposed not only to multiple inhibitory signals but also to tumor-necrosis factor (TNF). Blockade of TNF during chronic infection with LCMV abrogated the inhibitory gene-expression signature in CD4 super(+) T cells, including reduced expression of the inhibitory receptor PD-1, and reconstituted virus-specific immunity, which led to control of infection. Preventing signaling via the TNF receptor selectively in T cells sufficed to induce these effects. Targeted immunological interventions to disrupt the TNF-mediated link between chronic inflammation and T cell dysfunction might therefore lead to therapies to overcome persistent viral infection.