Self-replicating genetic material presumably provided the architecture necessary for generating the last universal ancestor of all nucleic-acid-based life. As biological complexity increased in the ...billions of years that followed, the same genetic material also morphed into a wide spectrum of viruses and other parasitic genetic elements. The resulting struggle for existence drove the evolution of host defenses, giving rise to a perpetual arms race. This Perspective summarizes the antiviral mechanisms evident across the tree of life, discussing each in their evolutionary context to postulate how the coevolution of host and pathogen shaped the cellular antiviral defenses we know today.
In this Perspective, tenOever summarizes the antiviral mechanisms evident across the tree of life, discussing each in their evolutionary context to postulate how the coevolution of host and pathogen shaped the cellular antiviral defenses we know today.
Gene silencing by small RNAs (sRNAs) occurs in all three domains of life. In recent years, our appreciation of the diverse functions of sRNAs has increased, and we have identified roles for these ...RNAs in cellular differentiation, fitness and pathogen defence. Interestingly, although plants, nematodes and arthropods use sRNAs to combat viral infections, chordates have replaced this defence strategy with one based exclusively on proteins. This limits chordate use of sRNAs to the silencing of genome-encoded transcripts and has resulted in viruses that do not perturb sRNA-related cellular processes. This evolutionary phenomenon provides an opportunity to exploit the pre-existing chordate sRNA pathways in order to generate a range of virus-based biological tools. Here, I discuss the relationship between sRNAs and RNA viruses, detail how microRNA expression can be harnessed to control RNA viruses and describe how RNA viruses can be designed to deliver sRNAs.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Viral pandemics, such as the one caused by SARS-CoV-2, pose an imminent threat to humanity. Because of its recent emergence, there is a paucity of information regarding viral behavior and host ...response following SARS-CoV-2 infection. Here we offer an in-depth analysis of the transcriptional response to SARS-CoV-2 compared with other respiratory viruses. Cell and animal models of SARS-CoV-2 infection, in addition to transcriptional and serum profiling of COVID-19 patients, consistently revealed a unique and inappropriate inflammatory response. This response is defined by low levels of type I and III interferons juxtaposed to elevated chemokines and high expression of IL-6. We propose that reduced innate antiviral defenses coupled with exuberant inflammatory cytokine production are the defining and driving features of COVID-19.
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•SARS-CoV-2 infection induces low IFN-I and -III levels with a moderate ISG response•Strong chemokine expression is consistent across in vitro, ex vivo, and in vivo models•Low innate antiviral defenses and high pro-inflammatory cues contribute to COVID-19
In comparison to other respiratory viruses, SARS-CoV-2 infection drives a lower antiviral transcriptional response that is marked by low IFN-I and IFN-III levels and elevated chemokine expression, which could explain the pro-inflammatory disease state associated with COVID-19.
To better understand host-virus genetic dependencies and find potential therapeutic targets for COVID-19, we performed a genome-scale CRISPR loss-of-function screen to identify host factors required ...for SARS-CoV-2 viral infection of human alveolar epithelial cells. Top-ranked genes cluster into distinct pathways, including the vacuolar ATPase proton pump, Retromer, and Commander complexes. We validate these gene targets using several orthogonal methods such as CRISPR knockout, RNA interference knockdown, and small-molecule inhibitors. Using single-cell RNA-sequencing, we identify shared transcriptional changes in cholesterol biosynthesis upon loss of top-ranked genes. In addition, given the key role of the ACE2 receptor in the early stages of viral entry, we show that loss of RAB7A reduces viral entry by sequestering the ACE2 receptor inside cells. Overall, this work provides a genome-scale, quantitative resource of the impact of the loss of each host gene on fitness/response to viral infection.
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•Genome-wide CRISPR knockout screen identifies host factors for SARS-CoV-2 infection•Top-ranked genes include vacuolar ATPases, Retromer, Commander, and Arp2/3 complex•Validation using CRISPR knockout, RNA interference, and small molecule inhibitors•Reduced infection via increased cholesterol biosynthesis and sequestration of ACE2
To identify potential therapeutic targets for SARS-CoV-2, Daniloski et al. conduct a genome-wide CRISPR screen in human lung epithelial cells. They identify genes and pathways required for SARS-CoV-2 infection, including the vacuolar ATPase proton pump, Retromer, and Commander complexes. Using single-cell transcriptomics, they identify upregulation of cholesterol biosynthesis as a common mechanism underlying viral resistance, in addition to ACE2 sequestration.
SARS-CoV-2 has caused the COVID-19 pandemic. There is an urgent need for physiological models to study SARS-CoV-2 infection using human disease-relevant cells. COVID-19 pathophysiology includes ...respiratory failure but involves other organ systems including gut, liver, heart, and pancreas. We present an experimental platform comprised of cell and organoid derivatives from human pluripotent stem cells (hPSCs). A Spike-enabled pseudo-entry virus infects pancreatic endocrine cells, liver organoids, cardiomyocytes, and dopaminergic neurons. Recent clinical studies show a strong association with COVID-19 and diabetes. We find that human pancreatic beta cells and liver organoids are highly permissive to SARS-CoV-2 infection, further validated using adult primary human islets and adult hepatocyte and cholangiocyte organoids. SARS-CoV-2 infection caused striking expression of chemokines, as also seen in primary human COVID-19 pulmonary autopsy samples. hPSC-derived cells/organoids provide valuable models for understanding the cellular responses of human tissues to SARS-CoV-2 infection and for disease modeling of COVID-19.
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•A hPSC-derived cell and organoid platform is used to study SARS-CoV-2 tissue tropism•Human pancreatic alpha and beta cells are permissive to SARS-CoV-2 infection•Human hepatocyte and cholangiocyte organoids are permissive to SARS-CoV-2 infection•hPSC-derived cells/organoids show similar chemokine responses as COVID-19 tissues
Yang et al. show that hPSC-derived cells and organoids provide valuable models to study SARS-CoV-2 tropism and to model COVID-19. They find that hPSC-derived pancreatic endocrine cells and human adult hepatocyte and cholangiocyte organoids are permissive to SARS-CoV-2 infection.
While RNA interference (RNAi) functions as an antiviral response in plants, nematodes, and arthropods, a similar antiviral role in mammals has remained controversial. Three recent papers provide ...evidence that either favors or challenges this hypothesis. Here, we discuss these new findings in the context of previous research.
There is an urgent need to create novel models using human disease-relevant cells to study severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) biology and to facilitate drug screening. Here, ...as SARS-CoV-2 primarily infects the respiratory tract, we developed a lung organoid model using human pluripotent stem cells (hPSC-LOs). The hPSC-LOs (particularly alveolar type-II-like cells) are permissive to SARS-CoV-2 infection, and showed robust induction of chemokines following SARS-CoV-2 infection, similar to what is seen in patients with COVID-19. Nearly 25% of these patients also have gastrointestinal manifestations, which are associated with worse COVID-19 outcomes
. We therefore also generated complementary hPSC-derived colonic organoids (hPSC-COs) to explore the response of colonic cells to SARS-CoV-2 infection. We found that multiple colonic cell types, especially enterocytes, express ACE2 and are permissive to SARS-CoV-2 infection. Using hPSC-LOs, we performed a high-throughput screen of drugs approved by the FDA (US Food and Drug Administration) and identified entry inhibitors of SARS-CoV-2, including imatinib, mycophenolic acid and quinacrine dihydrochloride. Treatment at physiologically relevant levels of these drugs significantly inhibited SARS-CoV-2 infection of both hPSC-LOs and hPSC-COs. Together, these data demonstrate that hPSC-LOs and hPSC-COs infected by SARS-CoV-2 can serve as disease models to study SARS-CoV-2 infection and provide a valuable resource for drug screening to identify candidate COVID-19 therapeutics.
The emergence and spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has resulted in significant global morbidity, mortality, and societal disruption. A better understanding of ...virus-host interactions may potentiate therapeutic insights toward limiting this infection. Here we investigated the dynamics of the systemic response to SARS-CoV-2 in hamsters by histological analysis and transcriptional profiling. Infection resulted in consistently high levels of virus in the upper and lower respiratory tracts and sporadic occurrence in other distal tissues. A longitudinal cohort revealed a wave of inflammation, including a type I interferon (IFN-I) response, that was evident in all tissues regardless of viral presence but was insufficient to prevent disease progression. Bolstering the antiviral response with intranasal administration of recombinant IFN-I reduced viral disease, prevented transmission, and lowered inflammation in vivo. This study defines the systemic host response to SARS-CoV-2 infection and supports use of intranasal IFN-I as an effective means of early treatment.
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•Generation of a transcriptional atlas of SARS-CoV-2 infection in hamsters•Infection and transmission can be initiated by respiratory or ocular exposure•Systemic inflammation occurs despite little productive replication in distal tissues•Intranasal IFN-I administered pre- or post-virus challenge reduces disease burden
The host response to SARS-CoV-2 results in significant inflammation. To understand this biology, Hoagland et al. utilize infected hamsters to elucidate transcriptional footprints across tissues longitudinally, showing an inflammatory response beyond the site of acute replication. Local administration of IFN-I reduces virus load and improves immune infiltrate.
SARS-CoV-2 infects less than 1% of cells in the human body, yet it can cause severe damage in a variety of organs. Thus, deciphering the non-cell-autonomous effects of SARS-CoV-2 infection is ...imperative for understanding the cellular and molecular disruption it elicits. Neurological and cognitive defects are among the least understood symptoms of COVID-19 patients, with olfactory dysfunction being their most common sensory deficit. Here, we show that both in humans and hamsters, SARS-CoV-2 infection causes widespread downregulation of olfactory receptors (ORs) and of their signaling components. This non-cell-autonomous effect is preceded by a dramatic reorganization of the neuronal nuclear architecture, which results in dissipation of genomic compartments harboring OR genes. Our data provide a potential mechanism by which SARS-CoV-2 infection alters the cellular morphology and the transcriptome of cells it cannot infect, offering insight to its systemic effects in olfaction and beyond.
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•Downregulation of odor detection pathways may explain COVID-19-induced anosmia•SARS-CoV-2-mediated disruption of nuclear architecture may impair odor detection•SARS-CoV-2-mediated nuclear reorganization is non-cell autonomous
SARS-CoV-2 induces non-cell-autonomous effects in olfactory epithelium that disrupts nuclear architecture and downregulates olfactory receptor expression in olfactory sensory neurons.
A novel variant of the SARS-CoV-2 virus carrying a point mutation in the Spike protein (D614G) has recently emerged and rapidly surpassed others in prevalence. This mutation is in linkage ...disequilibrium with an ORF1b protein variant (P314L), making it difficult to discern the functional significance of the Spike D614G mutation from population genetics alone. Here, we perform site-directed mutagenesis on wild-type human-codon-optimized Spike to introduce the D614G variant. Using multiple human cell lines, including human lung epithelial cells, we found that the lentiviral particles pseudotyped with Spike D614G are more effective at transducing cells than ones pseudotyped with wild-type Spike. The increased transduction with Spike D614G ranged from 1.3- to 2.4-fold in Caco-2 and Calu-3 cells expressing endogenous ACE2 and from 1.5- to 7.7-fold in A549
and Huh7.5
overexpressing ACE2. Furthermore,
-complementation of SARS-CoV-2 virus with Spike D614G showed an increased infectivity in human cells. Although there is minimal difference in ACE2 receptor binding between the D614 and G614 Spike variants, the G614 variant is more resistant to proteolytic cleavage, suggesting a possible mechanism for the increased transduction.
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