BACKGROUND. Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory coronavirus 2 (SARS-CoV-2), has become a pandemic. This study addresses the clinical and immunopathological characteristics of severe COVID-19. METHODS. Sixty-nine patients with COVID-19 were classified into severe and nonsevere groups to analyze their clinical and laboratory characteristics. A panel of blood cytokines was quantified over time. Biopsy specimens from 2 deceased cases were obtained for immunopathological, ultrastructural, and in situ hybridization examinations. RESULTS. Circulating cytokines, including IL-8, IL-6, TNF-α, IP10, MCP1, and RANTES, were significantly elevated in patients with severe COVID-19. Dynamic IL-6 and IL-8 were associated with disease progression. SARS-CoV-2 was demonstrated to infect type II and type I pneumocytes and endothelial cells, leading to severe lung damage through cell pyroptosis and apoptosis. In severe cases, lymphopenia, neutrophilia, depletion of CD4 ⁺ and CD8 ⁺ T lymphocytes, and massive macrophage and neutrophil infiltrates were observed in both blood and lung tissues. CONCLUSIONS. A panel of circulating cytokines could be used to predict disease deterioration and inform clinical interventions. Severe pulmonary damage was predominantly attributed to both cytopathy caused by SARS-CoV-2 and immunopathologic damage. Strategies that prohibit pulmonary recruitment and overactivation of inflammatory cells by suppressing cytokine storm might improve the outcomes of patients with severe COVID-19.

Metabolic reprogramming universally occurs in cancer. Mitochondria act as the hubs of bioenergetics and metabolism. The morphodynamics of mitochondria, comprised of fusion and fission processes, are closely associated with mitochondrial functions and are often dysregulated in cancer. In this study, we aim to investigate the mitochondrial morphodynamics and its functional consequences in human liver cancer. We observed excessive activation of mitochondrial fusion in tumor tissues from hepatocellular carcinoma (HCC) patients and in vitro cultured tumor organoids from cholangiocarcinoma (CCA). The knockdown of the fusion regulator genes, OPA1 (Optic atrophy 1) or MFN1 (Mitofusin 1), inhibited the fusion process in HCC cell lines and CCA tumor organoids. This resulted in inhibition of cell growth in vitro and tumor formation in vivo, after tumor cell engraftment in mice. This inhibitory effect is associated with the induction of cell apoptosis, but not related to cell cycle arrest. Genome-wide transcriptomic profiling revealed that the inhibition of fusion predominately affected cellular metabolic pathways. This was further confirmed by the blocking of mitochondrial fusion which attenuated oxygen consumption and cellular ATP production of tumor cells. In conclusion, increased mitochondrial fusion in liver cancer alters metabolism and fuels tumor cell growth.

Hepatotropic viruses naturally have narrow host and tissue tropisms, challenging the development of robust experimental models. The advent of organoid technology provides a unique opportunity for moving the field forward. Here, we demonstrate that three-dimensional cultured organoids from fetal and adult human liver with cholangiocyte or hepatocyte phenotype support hepatitis E virus (HEV) replication. Inoculation with infectious HEV particles demonstrates that human liver–derived organoids support the full life cycle of HEV infection. By directing organoids toward polarized monolayers in a transwell system, we observed predominantly apical secretion of HEV particles. Genome-wide transcriptomic and tRNAome analyses revealed robust host responses triggered by viral replication. Drug screening in organoids identified brequinar and homoharringtonine as potent HEV inhibitors, which are also effective against the ribavirin resistance variant harboring G1634R mutation. Thus, successful recapitulation of HEV infection in liver-derived organoids shall facilitate the study of virus-host interactions and development of antiviral therapies.

Background and Aims: HEV infection is the most common cause of liver inflammation, but the pathogenic mechanisms remain largely unclear. We aim to explore whether HEV infection activates inflammasomes, crosstalk with antiviral interferon response, and the potential of therapeutic targeting. Approach and Results: We measured IL‐1β secretion, the hallmark of inflammasome activation, in serum of HEV‐infected patients and rabbits, and in cultured macrophage cell lines and primary monocyte‐derived macrophages. We found that genotypes 3 and 4 HEV infection in rabbits elevated IL‐1β production. A profound increase of IL‐1β secretion was further observed in HEV‐infected patients (1,733 ± 1,234 pg/mL; n = 70) compared to healthy persons (731 ± 701 pg/mL; n = 70). Given that macrophages are the drivers of inflammatory response, we found that inoculation with infectious HEV particles robustly triggered NOD‐like receptor family pyrin domain‐containing 3 (NLRP3) inflammasome activation in primary macrophages and macrophage cell lines. We further revealed that the ORF2 capsid protein and the formed integral viral particles are responsible for activating inflammasome response. We also identified NF‐κB signaling activation as a key upstream event of HEV‐induced NLRP3 inflammasome response. Interestingly, inflammasome activation antagonizes interferon response to facilitate viral replication in macrophages. Pharmacological inhibitors and clinically used steroids can effectively target inflammasome activation. Combining steroids with ribavirin simultaneously inhibits HEV and inflammasome response without cross‐interference. Conclusions: HEV infection strongly activates NLRP3 inflammasome activation in macrophages, which regulates host innate defense and pathogenesis. Therapeutic targeting of NLRP3, in particular when combined with antiviral agents, represents a viable option for treating severe HEV infection.