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Secreted ORF8 reprograms macrophages to enhance SARS-CoV-2 infection of lung epithelial cells

ABSTRACT: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) primarily targets the respiratory epithelium, yet severe disease features diffuse lung injury and hyperinflammatory syndromes driven by dysregulated immune activation. Emerging evidence indicates that resident and infiltrating immune cells in the lung can encounter the virus early in infection and, under specific conditions, become infected. This process amplifies local inflammation and facilitates viral propagation in the lower airways and distal lung regions, where angiotensin converting enzyme 2 (ACE2) expression is limited. However, how epithelial and immune cell compartments interact to produce the hallmark pulmonary pathology of SARS-CoV-2 infection remains unresolved. Here we show that secreted ORF8, a SARS-CoV-2 accessory protein, drives inflammatory lung pathology by increasing macrophage permissively to infection, triggering pyroptosis, and amplifying viral replication in alveolar epithelial cells. Co-culture of macrophages with human alveolar type II (AT2) cells overrides ORF8’s previously reported inhibition of AT2 infection, restoring productive viral replication. In vivo, IL-17RA blockade with brodalumab counteracts ORF8 activity, lowering viral burden and attenuating pulmonary inflammation and fibrosis. These findings reveal a paracrine role for ORF8 in reprogramming macrophages, thereby establishing a feedforward proviral circuit that accelerates lung pathology in COVID-19 and are particularly relevant given the recurrent emergence of SARS-CoV-2 variants with either intact or deleted ORF8 since the beginning of the pandemic.

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ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Primary Cell, Blood, Macrophage

SUBMITTER: Robyn Kaake

LAB HEAD: Robyn Midori Kaake

PROVIDER: PXD069220 | Pride | 2026-08-07

REPOSITORIES: Pride

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Project description:Covid-19 syndrome is characterized by an acute lung injury phenotype marked by hypoxemic respiratory failure and high mortality. Alveolar Type 2 (AT2) cells are essential for gas exchange, repair, and regeneration of distal lung epithelium. We have shown that the causative agent, SARS-CoV-2 and other members of the b coronavirus genus induces an ER stress response in vitro however the consequences for host AT2 cell function in vivo are less understood. To study this, two murine models of coronavirus infection were employed– mouse hepatitis virus-1 (MHV-1) in A/J mice and a C57BL6/j adapted SARS-CoV-2 strain. MHV-1 infected mice exhibited dose-dependent weight loss through Day 8 (8dpi) with histological evidence of distal lung injury accompanied by elevated BALF cell counts and total protein. AT2 cells isolated at 4dpi and 8dpi showed evidence of both viral infection and increases in Bip /GRP78 expression, consistent with activation of the unfolded protein response (UPR). AT2 UPR signaling included elevations in spliced XBP-1 indicating activation of IRE1a signaling as well as a biphasic response in PERK signaling mark by phosphorylated eIF2a protein levels and expression of Atf4, Ppp1r15a, and Ddit3. Viral UPR activation was accompanied by marked reductions in AT2 and BALF surfactant protein (SP-B, SP-C) content, increases in surfactant surface tension, and emergence of a re-programmed epithelial cell population (Krt8+, Cldn4+, and Gdf15+) which was attenuated by treatment with the IRE1a inhibitor OPK711. As proof-of-concept, C57BL6 mice infected with mouse-adapted SARS-CoV-2 demonstrated similar lung injury and evidence of disrupted surfactant homeostasis. We conclude that hypoxic respiratory failure from b-coronavirus infection results from an aberrant AT2 cell host response activating multiple ER stress pathways, altering surfactant metabolism / function, and changing AT2 endophenotypes offering a mechanistic link between SARS-CoV-2 infection, AT2 cell biology, and hypoxemic respiratory failure.

Project description:The coronavirus disease 2019 (COVID-19) pandemic has affected nearly 700 million and claimed more than 6 million lives. However, the large heterogeneity in disease susceptibility and severity of illness (SOI) remains poorly understood. A growing body of evidence suggests that alveolar epithelial cell type 2 (AT2), which constitute 10-15% of all alveolar cells and are critical for alveolar homeostasis, are the primary targets of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection and damage to AT2s may directly contribute to disease severity and poor prognosis in COVID-19 patients. Our in-vitro modeling of SARS-CoV-2 infection, in well-characterized, highly uniform, (r2 at 95% CI = 0.92 ± 0.03), induced pluripotent stem cell (iPSC) derived AT2s from 10 participants of our Mexican American Family Study, showed interindividual variability in infection susceptibility and the post-infection cellular viral load. To understand the underlying mechanism of the AT2’s capacity to regulate SARS-CoV-2 infection and cellular viral load, we performed a systematic characterization of the pre- and post-SARS-CoV-2 challenged AT2 transcriptomes. A total of 1,393 genes were found significantly (Oneway ANOVA FDR corrected p ≤ 0.05; FC abs ≥ 2.0) differentially expressed (DE) between pre- and post-SARS-CoV-2 infection-challenged AT2 and suggest significant upregulation of viral infection-related cellular innate immune response pathways (p-value ≤ 0.05; activation z-score ≥ 3.5), whilst the cholesterol and xenobiotic related metabolic pathways were significantly downregulated (p-value ≤ 0.05; activation z-score ≤ - 3.5). Interestingly, pre-infection expression of 238 DE genes showed a high correlation with the post-infection SARS-CoV-2 viral load (FDR corrected p-value ≤ 0.05, and r2-absolute ≥ 0.57). The 85 genes whose expression was negatively correlated with the viral load showed significant enrichment in viral recognition and cytokine-mediated innate immune GO biological processes (p-value range: 4.65x10-10 to 2.24x10-6). The 153 genes whose expression was positively correlated with the viral load showed significant enrichment in cholesterol homeostasis, extracellular matrix, and MAPK/ERK pathway-related GO biological processes (p-value range: 5.06x10-5 to 6.53x10-4). Overall, our results strongly suggest that AT2s pre-infection innate immunity and metabolic state affects their susceptibility to SARS-CoV-2 infection and viral load.

Project description:Background: Type I interferons (IFNs) are essential to the clearance of viral diseases, in part by initiating upregulation of IFN regulated genes (IRGs). A clear distinction between genes upregulated directly by virus and genes upregulated by secondary IFN production has not been made. Here we investigated the genes regulated by IFN-a2b compared to the genes regulated by SARS-CoV infection in ferrets. Methods: We characterized early host immune responses in peripheral blood and lung necropsies of ferrets injected with IFN-a2b or infected with SARS-CoV/Tor 2 strain, using microarray analysis on the Affymetrix platform. Results: We identified a common IRG signature that was upregulated in both SARS-CoV infected ferrets as well as in ferrets injected with IFN-a2b. We also identified unique patterns of gene expression for leukocyte activation, cell adhesion and complement pathways between IFN-a2b injection and SARS-CoV infection. Conclusions: Our results define the effects of IFN-a2b on the immune system of ferrets highlighting genes regulated by IFN during SARS-CoV infection. We have shown the similarities and differences of top funcional gene groups as well as pathways that play key roles in early immune responses in ferrets in response to IFN-a2b or SARS-CoV. Key words: ferret, gene expression, SARS, interferon. Keywords: time course In experiments with IFN-a2b, for peripheral blood, 15 ferrets were randomly allocated to 3 groups: Day 0, 5 ferrets (no IFN injection), day 1, 6 ferrets (injected), and day 2, 4 ferrets (injected). For lung necropsies of injected ferrets with IFN-a2b, we used 12 ferrets in 3 groups: 4 ferrets, day 0 (no IFN injection), 4 ferrets, day 1 (injected) and 4 ferrets, day 2 (injected). Experimental groups for SARS-CoV infection was as follows: For peripheral blood, 3 and 4 ferrets for day 0 (no infection) and day 2 (infection) respectively. For lung neceropsies, a total of 9 ferrets in 3 groups, each with 3 replicates for day 0 (no infection), day 1 (infection) and day 2 (infection).

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	2024-05-09-decoys-reviewed-contam-UP000005640.fasta	Fasta
	FP-PDV.db	Other
	MSstats.csv	Csv
	MetadataTable.txt	Txt
	checksum.txt	Txt

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Secreted ORF8 reprograms macrophages to enhance SARS-CoV-2 infection of lung epithelial cells

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