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Our understanding of the hepatic consequences of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and its resultant coronavirus disease 2019 (COVID-19) has evolved rapidly since the onset of the pandemic. In this Review, we discuss the hepatotropism of SARS-CoV-2, including the differential expression of viral receptors on liver cell types, and we describe the liver histology features present in patients with COVID-19. We also provide an overview of the pattern and relevance of abnormal liver biochemistry during COVID-19 and present the possible underlying direct and indirect mechanisms for liver injury. Furthermore, large international cohorts have been able to characterize the disease course of COVID-19 in patients with pre-existing chronic liver disease. Patients with cirrhosis have particularly high rates of hepatic decompensation and death following SARS-CoV-2 infection and we outline hypotheses to explain these findings, including the possible role of cirrhosis-associated immune dysfunction. This finding contrasts with outcome data in pharmacologically immunosuppressed patients after liver transplantation who seem to have comparatively better outcomes from COVID-19 than those with advanced liver disease. Finally, we discuss the approach to SARS-CoV-2 vaccination in patients with cirrhosis and after liver transplantation and predict how changes in social behaviours and clinical care pathways during the pandemic might lead to increased liver disease incidence and severity. This Review provides mechanistic and clinical insights into COVID-19 in the context of liver disease, discussing the potential underlying biology and clinical features of SARS-CoV-2 infection in patients with pre-existing liver conditions. The management of these patients is also discussed, including SARS-CoV-2 vaccination strategies. Key points Patients with cirrhosis have high rates of hepatic decompensation, acute-on-chronic liver failure and death from respiratory failure following severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and should be prioritized for coronavirus disease 2019 (COVID-19) vaccination. The possible pathogenic mechanisms linking cirrhosis with severe COVID-19 lung disease include increased systemic inflammation, cirrhosis-associated immune dysfunction, coagulopathy and intestinal dysbiosis. Abnormal liver biochemistry values are common in patients with COVID-19; both the prognostic significance of these derangements and whether they are directly attributable to hepatic SARS-CoV-2 infection remain uncertain. Expression profiles of SARS-CoV-2 entry receptors vary across different in vitro and in vivo liver models; however, evidence of specific viral hepatotropism is limited. Liver transplant recipients do not appear to have an increased risk of mortality following SARS-CoV-2 infection compared with the matched general population. The pandemic has been associated with increased alcohol consumption, unhealthy eating habits, and interruptions to hepatology services, which might lead to an upward trend in liver disease incidence and severity.

Acetaminophen (APAP) is the main cause of acute liver failure in the West. Specific efficacious therapies for acute liver failure (ALF) are limited and time-dependent. The mechanisms that drive irreversible acute liver failure remain poorly characterized. Here we report that the recently discovered platelet receptor CLEC-2 (C-type lectin-like receptor) perpetuates and worsens liver damage after toxic liver injury. Our data demonstrate that blocking platelet CLEC-2 signalling enhances liver recovery from acute toxic liver injuries (APAP and carbon tetrachloride) by increasing tumour necrosis factor-α (TNF-α) production which then enhances reparative hepatic neutrophil recruitment. We provide data from humans and mice demonstrating that platelet CLEC-2 influences the hepatic sterile inflammatory response and that this can be manipulated for therapeutic benefit in acute liver injury. Since CLEC-2 mediated platelet activation is independent of major haemostatic pathways, blocking this pathway represents a coagulopathy-sparing, specific and novel therapy in acute liver failure. The molecular mechanisms that drive irreversible acute liver failure remain poorly characterized. Here, the authors show that the recently discovered platelet receptor CLEC-2 (C-type lectin-like receptor) perpetuates and worsens liver damage during acute liver injury by blocking restorative neutrophil driven inflammation.

Preventing SARS-CoV-2 infection by modulating viral host receptors, such as angiotensin-converting enzyme 2 (ACE2) 1 , could represent a new chemoprophylactic approach for COVID-19 that complements vaccination 2 , 3 . However, the mechanisms that control the expression of ACE2 remain unclear. Here we show that the farnesoid X receptor (FXR) is a direct regulator of ACE2 transcription in several tissues affected by COVID-19, including the gastrointestinal and respiratory systems. We then use the over-the-counter compound z-guggulsterone and the off-patent drug ursodeoxycholic acid (UDCA) to reduce FXR signalling and downregulate ACE2 in human lung, cholangiocyte and intestinal organoids and in the corresponding tissues in mice and hamsters. We show that the UDCA-mediated downregulation of ACE2 reduces susceptibility to SARS-CoV-2 infection in vitro, in vivo and in human lungs and livers perfused ex situ. Furthermore, we reveal that UDCA reduces the expression of ACE2 in the nasal epithelium in humans. Finally, we identify a correlation between UDCA treatment and positive clinical outcomes after SARS-CoV-2 infection using retrospective registry data, and confirm these findings in an independent validation cohort of recipients of liver transplants. In conclusion, we show that FXR has a role in controlling ACE2 expression and provide evidence that modulation of this pathway could be beneficial for reducing SARS-CoV-2 infection, paving the way for future clinical trials. FXR regulates the levels of ACE2 in tissues of the respiratory and gastrointestinal systems that are affected by COVID-19, and inhibiting FXR with ursodeoxycholic acid downregulates ACE2 and reduces susceptibility to SARS-CoV-2 infection.

The role of the endothelium in protecting from chronic liver disease and TGFβ-mediated fibrosis remains unclear. Here we describe how the endothelial transcription factor ETS-related gene (ERG) promotes liver homoeostasis by controlling canonical TGFβ-SMAD signalling, driving the SMAD1 pathway while repressing SMAD3 activity. Molecular analysis shows that ERG binds to SMAD3, restricting its access to DNA. Ablation of ERG expression results in endothelial-to-mesenchymal transition (EndMT) and spontaneous liver fibrogenesis in EC-specific constitutive hemi-deficient ( Erg cEC-Het ) and inducible homozygous deficient mice ( Erg iEC-KO ), in a SMAD3-dependent manner. Acute administration of the TNF-α inhibitor etanercept inhibits carbon tetrachloride (CCL 4 )-induced fibrogenesis in an ERG-dependent manner in mice. Decreased ERG expression also correlates with EndMT in tissues from patients with end-stage liver fibrosis. These studies identify a pathogenic mechanism where loss of ERG causes endothelial-dependent liver fibrogenesis via regulation of SMAD2/3. Moreover, ERG represents a promising candidate biomarker for assessing EndMT in liver disease. The transcription factor ERG is key to endothelial lineage specification and vascular homeostasis. Here the authors show that ERG balances TGFβ signalling through the SMAD1 and SMAD3 pathways, protecting the endothelium from endothelial-to-mesenchymal transition and consequent liver fibrosis in mice via a SMAD3-dependent mechanism.

Lisinopril is an ACE inhibitor commonly used in the treatment of cardiovascular and renal disease. Rarely, ACE inhibitors have been associated with cholestatic jaundice and hepatitis, with potential risk of fulminant hepatic failure if continued. There is limited information available regarding the risk of hepatic failure secondary to lisinopril use, with a handful of case reports demonstrating drug-induced liver injury at varying time scales from drug initiation. In this case, we present a man with symptoms of cholestatic jaundice, a blistering skin rash and flare of chronic plaque psoriasis, 27 months after lisinopril initiation for hypertension. Biochemical, serological and radiological investigations of an alternative cause for his jaundice were unremarkable. Cessation of lisinopril led to a rapid and sustained improvement in liver biochemistry and a significant improvement in his chronic plaque psoriasis.

A male in his teens with a history of liver transplant for biliary atresia (aged 2 years) and autoimmune haemolytic anaemia (AIHA, aged 6 years) presented with jaundice, dark urine, fatigue and chest discomfort that began 48 hours after the first dose of SARS-CoV-2 Pfizer-BioNTech vaccine (BNT162b2 mRNA). Investigations revealed a warm AIHA picture. Over 4 weeks the patient developed life-threatening anaemia culminating in haemoglobin of 35 g/L (after transfusion), lactate dehydrogenase of 1293 units/L and bilirubin of 228 µmol/L, refractory to standard treatment with corticosteroids and rituximab. An emergency splenectomy was performed that slowed haemolysis but did not completely ameliorate it. Eculizumab, a terminal complement pathway inhibitor, was initiated to arrest intravascular haemolysis and showed a favourable response. AIHA is rare but described after the SARS-CoV-2 Pfizer-BioNTech vaccine. This case highlights the rare complication of AIHA, the use of emergency splenectomy for disease control, and the use of eculizumab.

Many safe and effective severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) vaccinations dramatically reduce risks of coronavirus disease 2019 (COVID‐19) complications and deaths. We aimed to describe cases of SARS‐CoV‐2 infection among patients with chronic liver disease (CLD) and liver transplant (LT) recipients with at least one prior COVID‐19 vaccine dose. The SECURE‐Liver and COVID‐Hep international reporting registries were used to identify laboratory‐confirmed COVID‐19 in CLD and LT patients who received a COVID‐19 vaccination. Of the 342 cases of lab‐confirmed SARS‐CoV‐2 infections in the era after vaccine licensing, 40 patients (21 with CLD and 19 with LT) had at least one prior COVID‐19 vaccination, including 12 who were fully vaccinated (≥2 weeks after second dose). Of the 21 patients with CLD (90% with cirrhosis), 7 (33%) were hospitalized, 1 (5%) was admitted to the intensive care unit (ICU), and 0 died. In the LT cohort (n = 19), there were 6 hospitalizations (32%), including 3 (16%) resulting in mechanical ventilation and 2 (11%) resulting in death. All three cases of severe COVID‐19 occurred in patients who had a single vaccine dose within the last 1‐2 weeks. In contemporary patients with CLD, rates of symptomatic infection, hospitalization, ICU admission, invasive ventilation, and death were numerically higher in unvaccinated individuals. Conclusion: This case series demonstrates the potential for COVID‐19 infections among patients with CLD and LT recipients who had received the COVID‐19 vaccination. Vaccination against SARS‐CoV‐2 appears to result in favorable outcomes as attested by the absence of mechanical ventilation, ICU, or death among fully vaccinated patients.

The UK system allocates donor livers to the blood group and weight compatible individual waitlisted with the highest predicted incremental survival (transplant benefit score, TBS) for each organ under consideration. It does not account for travel time between donating and transplanting centre. Longer travel has implications for cold ischaemic time, energy use and cost. This study simulates including travel time in organ allocation.A probabilistic Monte Carlo simulation was developed incorporating pseudorandom determination of organ offers and recipient characteristics re-sampled from historic data. Pre- and post-transplant survival was estimated using the TBS algorithm. Hospital-specific data on donation and implantation activity 2023–2024 were used for proportional allocation; travel time via Google Maps API. Simulation parameters were set to an initial waitlist of 500 and to transplant approximately 1000/year. Each year-long simulation was repeated 20 times using different pseudorandom number generator seeds with and without allowance for donor-centre travel time. Travel time allocation was to the nearest centre within a variable TBS margin of the national top-ranked recipient.Baseline travel time was estimated at median 2.8 (IQR 1.7–4.5) hours/organ. Travel time was lowest for Birmingham 2.5 (1.8–3.0) hours/organ and highest for Edinburgh at 6.5 (4.7–7.5) hours/organ. In simulation, the median gap in TBS days between first and second ranked compatible recipients was 39.9 (10.0–174.4) days; for travel time 1.6 (0.4–2.9). There was no correlation between these (r2=0.001).Incorporating travel time with a 25-day margin was associated with median travel time reducing to 2.4 (1.3–4.1) hours with no change in predicted mortality. Travel time was reduced in all centres. Further extensions of the TBS margins produced further reductions in travel time (p<0.0001) but not outcomes as assessed by deaths pre-transplant or population life years (p=NS) at 20 simulations [table 1].In simulation, minimising travel time by allocating within a margin from the top-ranked potential recipient by TBS resulted in significant reductions in total travel. At smaller TBS margins and the assessed number of simulations, there was no significant difference in simulated population outcomes. Geography and travel time should be considered for addition to the allocation algorithm.Abstract O19 Table 1 TBS Margin (d) Median travel time (h) Total deaths Deaths pre-transplant Population life years 0/baseline 2.8 (1.7–4.5) 161 (155–168) 118 (114–126) 998.9 (986.2–1012.9) 25 2.4 (1.3–4.1) 161 (155–168) 118 (114–125) 996.9 (984.4–1013.3) 50 2.2 (1.2–3.9) 161 (155–172) 121 (114–124) 999.1 (984.3–1013.3) 75 2.0 (1.1–3.5) 165 (157–170) 121 (116–127) 996.6 (983.8–1013.1) 100 1.8 (1.1–3.3) 164 (158–169) 121 (116–126) 995.7 (985.4–1012.3) 150 1.7 (0.9–3.0) 164 (160–171) 122 (117–127) 996.6 (984.1–1011.2)