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Immunol."],"abstract":"<jats:p>Infection with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes COVID-19, a disease that involves significant lung tissue damage. How SARS-CoV-2 infection leads to lung injury remains elusive. The open reading frame 8 (ORF8) protein of SARS-CoV-2 (ORF8<jats:sup>SARS-CoV-2<\/jats:sup>) is a unique accessory protein, yet little is known about its cellular function. We examined the cellular distribution of ORF8<jats:sup>SARS-CoV-2<\/jats:sup> and its role in the regulation of human lung epithelial cell proliferation and antiviral immunity. Using live imaging and immunofluorescent staining analyses, we found that ectopically expressed ORF8<jats:sup>SARS-CoV-2<\/jats:sup> forms aggregates in the cytosol and nuclear compartments of lung epithelial cells. Using <jats:italic>in silico<\/jats:italic> bioinformatic analysis, we found that ORF8<jats:sup>SARS-CoV-2<\/jats:sup> possesses an intrinsic aggregation characteristic at its N-terminal residues 1-18. Cell culture did not reveal any effects of ORF8<jats:sup>SARS-CoV-2<\/jats:sup> expression on lung epithelial cell proliferation and cell cycle progression, suggesting that ORF8<jats:sup>SARS-CoV-2<\/jats:sup> aggregates do not affect these cellular processes. Interestingly, ectopic expression of ORF8<jats:sup>SARS-CoV-2<\/jats:sup> in lung epithelial cells suppressed basal expression of several antiviral molecules, including DHX58, ZBP1, MX1, and MX2. In addition, expression of ORF8<jats:sup>SARS-CoV-2<\/jats:sup> attenuated the induction of antiviral molecules by IFN\u03b3 but not by IFN\u03b2 in lung epithelial cells. Taken together, ORF8<jats:sup>SARS-CoV-2<\/jats:sup> is a unique viral accessory protein that forms aggregates when expressing in lung epithelial cells. It potently inhibits the expression of lung cellular anti-viral proteins at baseline and in response to IFN\u03b3 in lung epithelial cells, which may facilitate SARS-CoV-2 escape from the host antiviral innate immune response during early viral infection. In addition, it seems that formation of ORF8<jats:sup>SARS-CoV-2<\/jats:sup> aggregate is independent from the viral infection. Thus, it would be interesting to examine whether any COVID-19 patients exhibit persistent <jats:italic>ORF8 SARS-CoV-2<\/jats:italic> expression after recovering from SARS-CoV-2 infection. If so, the pathogenic effect of prolonged ORF8<jats:sup>SARS-CoV-2<\/jats:sup> expression and its association with post-COVID symptoms warrant investigation in the future.<\/jats:p>","DOI":"10.3389\/fimmu.2021.679482","type":"journal-article","created":{"date-parts":[[2021,6,9]],"date-time":"2021-06-09T14:21:29Z","timestamp":1623248489000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":47,"title":["SARS-CoV-2 ORF8 Forms Intracellular Aggregates and Inhibits IFN\u03b3-Induced Antiviral Gene Expression in Human Lung Epithelial 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