CRISPR‐Cas13d effectively targets SARS‐CoV‐2 variants, including Delta and Omicron, and inhibits viral infection

The recent pandemic of variants of concern (VOC) of severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) highlights the need for innovative anti‐SARS‐CoV‐2 approaches in addition to vaccines and antiviral therapeutics. Here, we demonstrate that a CRISPR‐Cas13‐based strategy against SARS‐CoV‐2 can effectively degrade viral RNA. First, we conducted a cytological infection experiment, screened CRISPR‐associated RNAs (crRNAs) targeting conserved regions of viruses, and used an in vitro system to validate functional crRNAs. Reprogrammed Cas13d effectors targeting NSP13, NSP14, and nucleocapsid transcripts achieved >99% silencing efficiency in human cells which are infected with coronavirus 2, including the emerging variants in the last 2 years, B.1, B.1.1.7 (Alpha), D614G B.1.351 (Beta), and B.1.617 (Delta). Furthermore, we conducted bioinformatics data analysis. We collected the sequence information of COVID‐19 and its variants from China, and phylogenetic analysis revealed that these crRNA oligos could target almost 100% of the SARS‐CoV family, including the emerging new variant, Omicron. The reprogrammed Cas13d exhibited high specificity, efficiency, and rapid deployment properties;therefore, it is promising for antiviral drug development. This system could possibly be used to protect against unexpected SARS‐CoV‐2 variants carrying multiple mutations. Cas13d‐crRNAs inhibit both ancestral and mutated SARS‐CoV‐2 replication. Cas13d‐crRNAs inhibit both ancestral and mutated SARS‐CoV‐2 replication including Delta. Cas13d‐crRNAs could inhibit Omicron and other SARS family strains and are a potential pan‐SARS inhibition strategy.

CRISPR-Cas13d effectively targets SARS-CoV-2 variants, including Delta and Omicron, and inhibits viral infection.

The recent pandemic of variants of concern (VOC) of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) highlights the need for innovative anti-SARS-CoV-2 approaches in addition to vaccines and antiviral therapeutics. Here, we demonstrate that a CRISPR-Cas13-based strategy against SARS-CoV-2 can effectively degrade viral RNA. First, we conducted a cytological infection experiment, screened CRISPR-associated RNAs (crRNAs) targeting conserved regions of viruses, and used an in vitro system to validate functional crRNAs. Reprogrammed Cas13d effectors targeting NSP13, NSP14, and nucleocapsid transcripts achieved >99% silencing efficiency in human cells which are infected with coronavirus 2, including the emerging variants in the last 2 years, B.1, B.1.1.7 (Alpha), D614G B.1.351 (Beta), and B.1.617 (Delta). Furthermore, we conducted bioinformatics data analysis. We collected the sequence information of COVID-19 and its variants from China, and phylogenetic analysis revealed that these crRNA oligos could target almost 100% of the SARS-CoV family, including the emerging new variant, Omicron. The reprogrammed Cas13d exhibited high specificity, efficiency, and rapid deployment properties; therefore, it is promising for antiviral drug development. This system could possibly be used to protect against unexpected SARS-CoV-2 variants carrying multiple mutations.

Metabolic modeling of single bronchoalveolar macrophages reveals regulators of hyperinflammation in COVID-19.

SARS-CoV-2 infection induces imbalanced immune response such as hyperinflammation in patients with severe COVID-19. Here, we studied the immunometabolic regulatory mechanisms for the pathogenesis of COVID-19. We depicted the metabolic landscape of immune cells, especially macrophages, from bronchoalveolar lavage fluid of patients with COVID-19 at single-cell level. We found that most metabolic processes were upregulated in macrophages from lungs of patients with mild COVID-19 compared to cells from healthy controls, whereas macrophages from severe COVID-19 showed downregulation of most of the core metabolic pathways including glutamate metabolism, fatty acid oxidation, citrate cycle, and oxidative phosphorylation, and upregulation of a few pathways such as glycolysis. Rewiring cellular metabolism by amino acid supplementation, glycolysis inhibition, or PPARγ stimulation reduces inflammation in macrophages stimulated with SARS-CoV-2. Altogether, this study demonstrates that metabolic imbalance of bronchoalveolar macrophages may contribute to hyperinflammation in patients with severe COVID-19 and provides insights into treating COVID-19 by immunometabolic modulation.

Multiomics approach reveals the ubiquitination-specific processes hijacked by SARS-CoV-2.

The Coronavirus Disease 2019 (COVID-19) caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is a global pandemic that seriously threatens health and socioeconomic development, but the existed antiviral drugs and vaccines still cannot yet halt the spread of the epidemic. Therefore, a comprehensive and profound understanding of the pathogenesis of SARS-CoV-2 is urgently needed to explore effective therapeutic targets. Here, we conducted a multiomics study of SARS-CoV-2-infected lung epithelial cells, including transcriptomic, proteomic, and ubiquitinomic. Multiomics analysis showed that SARS-CoV-2-infected lung epithelial cells activated strong innate immune response, including interferon and inflammatory responses. Ubiquitinomic further reveals the underlying mechanism of SARS-CoV-2 disrupting the host innate immune response. In addition, SARS-CoV-2 proteins were found to be ubiquitinated during infection despite the fact that SARS-CoV-2 itself didn't code any E3 ligase, and that ubiquitination at three sites on the Spike protein could significantly enhance viral infection. Further screening of the E3 ubiquitin ligases and deubiquitinating enzymes (DUBs) library revealed four E3 ligases influencing SARS-CoV-2 infection, thus providing several new antiviral targets. This multiomics combined with high-throughput screening study reveals that SARS-CoV-2 not only modulates innate immunity, but also promotes viral infection, by hijacking ubiquitination-specific processes, highlighting potential antiviral and anti-inflammation targets.

Spike-mediated ACE2 down-regulation was involved in the pathogenesis of SARS-CoV-2 infection.

The ongoing global pandemic of Coronavirus disease 2019 (COVID-19) poses a serious threat to human health, with patients reportedly suffering from thrombus, vascular injury and coagulation in addition to acute and diffuse lung injury and respiratory diseases. Angiotensin converting enzyme 2 (ACE2) as the receptor for SARS-CoV-2 entry, is also an important regulator of renin-angiotensin system (RAS) homeostasis, which plays an unsettled role in the pathogenesis of COVID-19. Here, we demonstrated that SARS-CoV-2 Spike protein activated intracellular signals to degrade ACE2 mRNA. The decrease of ACE2 and higher level of angiotensin (Ang) II were verified in COVID-19 patients. High dose of Ang II induced pulmonary artery endothelial cell death in vitro, which was also observed in the lung of COVID-19 patients. Our finding indicates that the downregulation of ACE2 potentially links COVID-19 to the imbalance of RAS.

SARS-CoV-2 helicase NSP13 hijacks the host protein EWSR1 to promote viral replication by enhancing RNA unwinding activity

Objective Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged in December 2019 and has led to a global coronavirus disease 2019 (COVID-19) pandemic. Currently, incomplete understanding of how SARS-CoV-2 arrogates the host cell to establish its life cycle has led to slow progress in the development of effective drugs. Results In this study, we found that SARS-CoV-2 hijacks the host protein EWSR1 (Ewing Sarcoma breakpoint region 1/EWS RNA binding protein 1) to promote the activity of its helicase NSP13 to facilitate viral propagation. NSP13 is highly conserved among coronaviruses and is crucial for virus replication, providing chemical energy to unwind viral RNA replication intermediates. Treatment with different SARS-CoV-2 NSP13 inhibitors in multiple cell lines infected with SARS-CoV-2 effectively suppressed SARS-CoV-2 infection. Using affinity-purification mass spectrometry, the RNA binding protein EWSR1 was then identified as a potent host factor that physically associated with NSP13. Furthermore, silencing EWSR1 dramatically reduced virus replication at both viral RNA and protein levels. Mechanistically, EWSR1 was found to bind to the NTPase domain of NSP13 and potentially enhance its dsRNA unwinding ability. Conclusion In conclusion, our results pinpoint EWSR1 as a novel host factor for NSP13 that could potentially be used for drug repurposing as a therapeutic target for COVID-19.

SARS-CoV-2 NSP13 Inhibits Type I IFN Production by Degradation of TBK1 via p62-Dependent Selective Autophagy.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which causes coronavirus disease 2019 (COVID-19), has seriously threatened global public health. Severe COVID-19 has been reported to be associated with an impaired IFN response. However, the mechanisms of how SARS-CoV-2 antagonizes the host IFN response are poorly understood. In this study, we report that SARS-CoV-2 helicase NSP13 inhibits type I IFN production by directly targeting TANK-binding kinase 1 (TBK1) for degradation. Interestingly, inhibition of autophagy by genetic knockout of Beclin1 or pharmacological inhibition can rescue NSP13-mediated TBK1 degradation in HEK-293T cells. Subsequent studies revealed that NSP13 recruits TBK1 to p62, and the absence of p62 can also inhibit TBK1 degradation in HEK-293T and HeLa cells. Finally, TBK1 and p62 degradation and p62 aggregation were observed during SARS-CoV-2 infection in HeLa-ACE2 and Calu3 cells. Overall, our study shows that NSP13 inhibits type I IFN production by recruiting TBK1 to p62 for autophagic degradation, enabling it to evade the host innate immune response, which provides new insights into the transmission and pathogenesis of SARS-CoV-2 infection.

Dysregulated hematopoiesis in bone marrow marks severe COVID-19.

Severe coronavirus disease 2019 (COVID-19) is often indicated by lymphopenia and increased myelopoiesis; however, the underlying mechanism is still unclear, especially the alteration of hematopoiesis. It is important to explore to what extent and how hematopoietic stem cells contribute to the impairment of peripheral lymphoid and myeloid compartments in COVID-19 patients. In this study, we used single-cell RNA sequencing to assess bone marrow mononuclear cells from COVID-19 patients with peripheral blood mononuclear cells as control. The results showed that the hematopoietic stem cells in these patients were mainly in the G1 phase and prone to apoptosis, with immune activation and anti-viral responses. Importantly, a significant accumulation of immature myeloid progenitors and a dramatic reduction of lymphoid progenitors in severe cases were identified, along with the up-regulation of transcription factors (such as SPI1, LMO4, ETS2, FLI1, and GATA2) that are important for the hematopoietic stem cell or multipotent progenitor to differentiate into downstream progenitors. Our results indicate a dysregulated hematopoiesis in patients with severe COVID-19.

SARS-CoV-2 promotes RIPK1 activation to facilitate viral propagation.

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is the ongoing global pandemic that poses substantial challenges to public health worldwide. A subset of COVID-19 patients experience systemic inflammatory response, known as cytokine storm, which may lead to death. Receptor-interacting serine/threonine-protein kinase 1 (RIPK1) is an important mediator of inflammation and cell death. Here, we examined the interaction of RIPK1-mediated innate immunity with SARS-CoV-2 infection. We found evidence of RIPK1 activation in human COVID-19 lung pathological samples, and cultured human lung organoids and ACE2 transgenic mice infected by SARS-CoV-2. Inhibition of RIPK1 using multiple small-molecule inhibitors reduced the viral load of SARS-CoV-2 in human lung organoids. Furthermore, therapeutic dosing of the RIPK1 inhibitor Nec-1s reduced mortality and lung viral load, and blocked the CNS manifestation of SARS-CoV-2 in ACE2 transgenic mice. Mechanistically, we found that the RNA-dependent RNA polymerase of SARS-CoV-2, NSP12, a highly conserved central component of coronaviral replication and transcription machinery, promoted the activation of RIPK1. Furthermore, NSP12 323L variant, encoded by the SARS-CoV-2 C14408T variant first detected in Lombardy, Italy, that carries a Pro323Leu amino acid substitution in NSP12, showed increased ability to activate RIPK1. Inhibition of RIPK1 downregulated the transcriptional induction of proinflammatory cytokines and host factors including ACE2 and EGFR that promote viral entry into cells. Our results suggest that SARS-CoV-2 may have an unexpected and unusual ability to hijack the RIPK1-mediated host defense response to promote its own propagation and that inhibition of RIPK1 may provide a therapeutic option for the treatment of COVID-19.

Quasispecies of SARS-CoV-2 revealed by single nucleotide polymorphisms (SNPs) analysis.

New SARS-CoV-2 mutants have been continuously indentified with enhanced transmission ever since its outbreak in early 2020. As an RNA virus, SARS-CoV-2 has a high mutation rate due to the low fidelity of RNA polymerase. To study the single nucleotide polymorphisms (SNPs) dynamics of SARS-CoV-2, 158 SNPs with high confidence were identified by deep meta-transcriptomic sequencing, and the most common SNP type was C > T. Analyses of intra-host population diversity revealed that intra-host quasispecies' composition varies with time during the early onset of symptoms, which implicates viral evolution during infection. Network analysis of co-occurring SNPs revealed the most abundant non-synonymous SNP 22,638 in the S glycoprotein RBD region and 28,144 in the ORF8 region. Furthermore, SARS-CoV-2 variations differ in an individual's respiratory tissue (nose, throat, BALF, or sputum), suggesting independent compartmentalization of SARS-CoV-2 populations in patients. The positive selection analysis of the SARS-CoV-2 genome uncovered the positive selected amino acid G251V on ORF3a. Alternative allele frequency spectrum (AAFS) of all variants revealed that ORF8 could bear alternate alleles with high frequency. Overall, the results show the quasispecies' profile of SARS-CoV-2 in the respiratory tract in the first two months after the outbreak.