Nonalcoholic fatty liver disease (NAFLD) is the most common liver pathology worldwide. In mice and humans, NAFLD progression is characterized by the appearance of TREM2-expressing macrophages in the liver. However, their mechanistic contributions to disease progression have not been completely elucidated. Here, we show that TREM2⁺ macrophages prevent the generation of a pro-inflammatory response elicited by LPS-laden lipoproteins in vitro. Further, Trem2 expression regulates bone-marrow-derived macrophages (BMDMs) and Kupffer cell capacity to phagocyte apoptotic cells in vitro, which is dependent on CD14 activation. In line with this, loss of Trem2 resulted in an increased pro-inflammatory response, which ultimately aggravated liver fibrosis in murine models of NAFLD. Similarly, in a human NAFLD cohort, plasma levels of TREM2 were increased and hepatic TREM2 expression was correlated with higher levels of liver triglycerides and the acquisition of a fibrotic gene signature. Altogether, our results suggest that TREM2⁺ macrophages have a protective function during the progression of NAFLD, as they are involved in the processing of pro-inflammatory lipoproteins and phagocytosis of apoptotic cells and, thereby, are critical contributors for the re-establishment of liver homeostasis.

The relevance of acute hepatitis E virus (HEV) infections has been underestimated for a long time. In the past, HEV infection had been interpreted falsely as a disease limited to the tropics until the relevance of autochthonous HEV infections in the Western world became overt. Due to increased awareness, the incidence of diagnosed autochthonous HEV infections (predominantly genotype 3) in industrialized countries has risen within the last decade. The main source of infections in industrialized countries seems to be infected swine meat, while infections with the tropical HEV genotypes 1 and 2 usually are mainly transmitted fecal-orally by contaminated drinking water. In the vast majority of healthy individuals, acute HEV infection is either clinically silent or takes a benign self-limited course. In patients who develop a symptomatic HEV infection, a short prodromal phase with unspecific symptoms is followed by liver specific symptoms like jaundice, itching, uncoloured stool and darkened urine. Importantly, tropical HEV infections may lead to acute liver failure, especially in pregnant women, while autochthonous HEV infections may lead to acute-on-chronic liver failure in patients with underlying liver diseases. Immunosuppressed individuals, such as transplant recipients or human immunodeficiency virus (HIV)-infected patients, are at risk for developing chronic hepatitis E, which may lead to liver fibrosis and cirrhosis in the long term. Importantly, specific treatment options for hepatitis E are not approved by the regulation authorities, but off-label ribavirin treatment seems to be effective in the treatment of chronic HEV-infection and may reduce the disease severity in patients suffering from acute liver failure.

The combination of boceprevir or telaprevir with peginterferon-alfa and ribavirin for the treatment of patients infected with HCV genotype 1 has led to significantly increased rates of sustained virological response (SVR) in phase III trials. There is only limited data regarding the safety and efficacy in a “real-life” cohort.

Background: Proton-pump inhibitors (PPI) are liberally prescribed in patients with liver cirrhosis. Observational studies link PPI therapy in cirrhotic patients with an increased risk for infectious complications, hepatic encephalopathy and an increased risk for hospitalization and mortality. However, patients with liver cirrhosis are also considered to be at risk for peptic ulcer bleeding. The STOPPIT trial evaluates if discontinuation of a pre-existing PPI treatment delays a composite endpoint of re-hospitalization and/or death in patients (recently) hospitalized with liver cirrhosis compared to patients on continued PPI medication. Methods: The STOPPIT-trial is a prospective, multicentre, randomized, double-blinded, placebo-controlled, parallel-group trial. In total, 476 patients with complicated liver cirrhosis who already receive long-term PPI therapy without evidence-based indication are 1:1 randomized to receive either esomeprazole 20 mg (control group) or placebo (intervention group) for 360 days. Patients with an indication for PPI therapy (such as a recent diagnosis of peptic ulcers, severe reflux esophagitis, severe hemorrhagic gastritis, recent endoscopic therapy for oesophageal varices) are excluded. The primary composite endpoint is the time-to re-hospitalization and/or death. Secondary endpoints include rates of re-hospitalization, mortality, occurrence of infections, hepatic decompensation and acute-on-chronic liver failure. The safety endpoint is defined as manifestation of an evidence-based indication for PPI re-therapy. The impact of PPI continuation or discontinuation on the intestinal microbiota will be studied. The recruitment will take place at 18 study sites throughout Germany. Recruitment has started in April 2021. Discussion: The STOPPIT trial is the first clinical trial to study the effects of PPI withdrawal on relevant outcome variables in patients with complicated liver cirrhosis. If the hypothesis that PPI withdrawal improves clinical outcomes of cirrhosis patients is confirmed, this would argue for a strong restriction of the currently liberal prescription practice of PPIs in this population. If, on the other hand, the trial demonstrates an increased risk of gastrointestinal bleeding events in patients after PPI withdrawal, this could create a rationale for a more liberal, prophylactic PPI treatment in patients with liver cirrhosis. Trial registration: EU clinical trials register EudraCT 2019-005008-16 (registered December 27, 2019). ClinicalTrials.gov NCT04448028 (registered June 25, 2020). German Clinical Trials Register DRKS00021290 (registered March 10, 2021).

Patients with autoimmune hepatitis (AIH) experience increased mortality and severe side effects from non-specific immunosuppressive therapy, highlighting an urgent need for targeted treatment approaches. Here, we aimed to delineate the cellular and molecular network underlying AIH within its spatial context and to validate a key therapeutic target in a clinical trial. We employed computational modelling, multi-omics analyses, and functional experiments to map the immune landscape of AIH. In addition, we conducted a steroid-free open-label phase IIa clinical trial using infliximab, a TNF-targeting antibody, in patients with AIH. Our studies revealed that myeloid cell and hepatocyte-derived IL-15 promotes cytotoxicity and proliferation of liver auto-aggressive CD8⁺ T cells. Full execution of their cytotoxic program is licensed by TNF derived from clonally expanded liver-resident CD4⁺ T cells. AIH hepatocytes respond to TNF by increasing expression of adhesion molecules, making them targets for both CD8⁺ and CD4⁺ T cells. In the clinical trial, targeting TNF with infliximab demonstrated efficacy as an entirely steroid-free AIH treatment. These findings elucidate the immune network in AIH and identify TNF as one of the central network nodes. Accordingly, our findings provide the basis for novel targeted, steroid-free immune therapies, including the use of infliximab. European Union Clinical Trials Register (EudraCT No.: 2017-003311-19). These findings have significant implications for the treatment of autoimmune hepatitis (AIH). By mapping the spatial and functional immune network within the AIH liver, this study identifies IL-15 and TNF as central drivers of T cell-mediated cytotoxicity, offering new precision targets for intervention. The successful use of infliximab as a steroid-free therapy in a phase II trial marks a pivotal step toward safer, more specific treatment options for patients with AIH. This research not only advances our understanding of AIH pathogenesis, but also sets the stage for broader application of immune-targeted therapies in autoimmune liver diseases.