Intestinal IL-1ß Plays a Role in Protecting against SARS-CoV-2 Infection.

The intestine is constantly balancing the maintenance of a homeostatic microbiome and the protection of the host against pathogens such as viruses. Many cytokines mediate protective inflammatory responses in the intestine, among them IL-1ß. IL-1ß is a proinflammatory cytokine typically activated upon specific danger signals sensed by the inflammasome. SARS-CoV-2 is capable of infecting multiple organs, including the intestinal tract. Severe cases of COVID-19 were shown to be associated with a dysregulated immune response, and blocking of proinflammatory pathways was demonstrated to improve patient survival. Indeed, anakinra, an Ab against the receptor of IL-1ß, has recently been approved to treat patients with severe COVID-19. However, the role of IL-1ß during intestinal SARS-CoV-2 infection has not yet been investigated. Here, we analyzed postmortem intestinal and blood samples from patients who died of COVID-19. We demonstrated that high levels of intestinal IL-1ß were associated with longer survival time and lower intestinal SARS-CoV-2 RNA loads. Concurrently, type I IFN expression positively correlated with IL-1ß levels in the intestine. Using human intestinal organoids, we showed that autocrine IL-1ß sustains RNA expression of IFN type I by the intestinal epithelial layer. These results outline a previously unrecognized key role of intestinal IL-1ß during SARS-CoV-2 infection.

Obesity and diabetes mellitus are associated with SARS-CoV-2 outcomes without influencing signature genes of extrapulmonary immune compartments at the RNA level.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) which is responsible for eliciting Coronavirus disease 2019 (COVID-19) still challenges healthcare services worldwide. While many patients only suffer from mild symptoms, patients with some pre-existing medical conditions are at a higher risk for a detrimental course of disease. However, the underlying mechanisms determining disease course are only partially understood. One key factor influencing disease severity is described to be immune-mediated. In this report, we describe a post-mortem analysis of 45 individuals who died from SARS-CoV-2 infection. We could show that although sociodemographic factors and premedical conditions such as obesity and diabetes mellitus reduced survival time in our cohort, they were not associated with changes in the expression of immune-related signature genes at the RNA level in the blood, the gut, or the liver between these different groups. Our data indicate that obesity and diabetes mellitus influence SARS-CoV-2-related mortality, without influencing the extrapulmonary gene expression of immunity-related signature genes at the RNA level.

IL-22 promotes liver regeneration after portal vein ligation.

Background: Insufficient remnant liver volume (RLV) after the resection of hepatic malignancy could lead to liver failure and mortality. Portal vein ligation (PVL) prior to hepatectomy is subsequently introduced to increase the remnant liver volume and improve the outcome of hepatic malignancy. IL-22 has previously been reported to promote liver regeneration, while facilitating tumor development in the liver via Steap4 upregulation. Here we performed PVL in mouse models to study the role of IL-22 in liver regeneration post-PVL. Methods: Liver weight and volume was measured via magnetic resonance imaging (MRI). Immunohistochemistry for Ki67 and hepatocyte growth factor (HGF) was performed. IL-22 was analyzed by flow cytometry and quantitative polymerase chain reaction (qPCR) was used for acquisition of Il-33, Steap4, Fga, Fgb and Cebpd. To analyze signaling pathways, mice with deletion of STAT3 and a neutralizing antibody for IL-22 were used. Results: The remnant liver weight and volume increased over time after PVL. Additionally, we found that liver regenerative molecules, including Ki67 and HGF, were significantly increased in remnant liver at day 3 post-PVL, as well as IL-22. Administration of IL-22 neutralizing antibody could reduce Ki67 expression after PVL. The upregulation of IL-22 after PVL was mainly derived from innate cells. IL-22 blockade resulted in lower levels of IL-33 and Steap4 in the remnant liver, which was also the case in mice with deletion of STAT3, the main downstream signaling molecule of IL-22, in hepatocytes. Conclusion: IL-22 promotes liver regeneration after PVL. Thus, a combination of IL-22 supplementation and Steap4 blockade could potentially be applied as a novel therapeutic approach to boost liver regeneration without facilitating tumor progression after PVL.

TNFα aggravates detrimental effects of SARS-CoV-2 infection in the liver.

Coronavirus disease 2019 (COVID-19) is caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). This virus does not only lead to pulmonary infection but can also infect other organs such as the gut, the kidney, or the liver. Recent studies confirmed that severe cases of COVID-19 are often associated with liver damage and liver failure, as well as the systemic upregulation of pro-inflammatory cytokines such as tumor necrosis factor-alpha (TNFα). However, the impact these immune mediators in the liver have on patient survival during SARS-CoV-2 infection is currently unknown. Here, by performing a post-mortem analysis of 45 patients that died from a SARS-CoV-2 infection, we find that an increased expression of TNFA in the liver is associated with elevated mortality. Using publicly available single-cell sequencing datasets, we determined that Kupffer cells and monocytes are the main sources of this TNFα production. Further analysis revealed that TNFα signaling led to the upregulation of pro-inflammatory genes that are associated with an unfavorable outcome. Moreover, high levels of TNFA in the liver were associated with lower levels of interferon alpha and interferon beta. Thus, TNFα signaling in the infected SARS-CoV-2 liver correlates with reduced interferon levels and overall survival time.