부산대학교 도서관

The novel coronavirus SARS-CoV-2 is the causative agent of Coronavirus Disease 2019 (COVID-19), a global healthcare and economic catastrophe. Understanding of the host immune response to SARS-CoV-2 is still in its infancy. A 382-nt deletion strain lacking ORF8 (Δ382 herein) was isolated in Singapore in March 2020. Infection with Δ382 was associated with less severe disease in patients, compared to infection with wild-type SARS-CoV-2. Here, we established Nasal Epithelial cells (NECs) differentiated from healthy nasal-tissue derived stem cells as a suitable model for the ex-vivo study of SARS-CoV-2 mediated pathogenesis. Infection of NECs with either SARS-CoV-2 or Δ382 resulted in virus particles released exclusively from the apical side, with similar replication kinetics. Screening of a panel of 49 cytokines for basolateral secretion from infected NECs identified CXCL10 as the only cytokine significantly induced upon infection, at comparable levels in both wild-type and Δ382 infected cells. Transcriptome analysis revealed the temporal up-regulation of distinct gene subsets during infection, with anti-viral signaling pathways only detected at late time-points (72 hours post-infection, hpi). This immune response to SARS-CoV-2 was significantly attenuated when compared to infection with an influenza strain, H3N2, which elicited an inflammatory response within 8 hpi, and a greater magnitude of anti-viral gene up-regulation at late time-points. Remarkably, Δ382 induced a host transcriptional response nearly identical to that of wild-type SARS-CoV-2 at every post-infection time-point examined. In accordance with previous results, Δ382 infected cells showed an absence of transcripts mapping to ORF8, and conserved expression of other SARS-CoV-2 genes. Our findings shed light on the airway epithelial response to SARS-CoV-2 infection, and demonstrate a non-essential role for ORF8 in modulating host gene expression and cytokine production from infected cells. Author summary: Airway epithelial cells are one of the earliest cell types infected in COVID-19 patients. We show that differentiated NECs are a suitable model for studying the dynamics of SARS-CoV-2 infection in vitro, and that the immune response from infected NECs is surprisingly limited. This limited early response to SARS-CoV-2 infection could impair viral clearance, and prolong the duration of infection. This further implies that infiltrating immune cells are the likely source of pro-inflammatory cytokines such as IL-6 and TNFα reported to be elevated in patient sera later during infection. CXCL10 production could represent a major therapeutic node for limiting immune cell infiltration and subsequent cytokine production. The similarities in host-response between SARS-CoV-2 and Δ382 infection in-vitro highlight the plasticity of CoV genomes, and implicate a post-translational (and not a transcriptional) role for ORF8 in modulating the host-response. [ABSTRACT FROM AUTHOR]