Influence of mitomycin C on the replication of influenza viruses

Targeting hub genes and pathways of innate immune response in COVID-19: A network biology perspective

The current pandemic of 2019 novel coronavirus disease (COVID-19) caused by a novel virus strain, 2019-nCoV/SARS-CoV-2 have posed a serious threat to global public health and economy. It is largely unknown how the human immune system responds to this infection. A better understanding of the immune response to SARS-CoV-2 will be important to develop therapeutics against COVID-19. Here, we have used transcriptomic profile of human alveolar adenocarcinoma cells (A549) infected with SARS-CoV-2 and employed a network biology approach to generate human-virus interactome. Network topological analysis discovers 15 SARS-CoV-2 targets, which belongs to a subset of interferon (IFN) stimulated genes (ISGs). These ISGs (IFIT1, IFITM1, IRF7, ISG15, MX1, and OAS2) can be considered as potential candidates for drug targets in the treatments of COVID-19. We have identified significant interaction between ISGs and TLR3 agonists, like poly I: C, and imiquimod, and suggests that TLR3 agonists can be considered as a potential drug for drug repurposing in COVID-19. Our network centric analysis suggests that moderating the innate immune response is a valuable approach to target COVID-19.

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Differential gene expression analysis of SARS-CoV-2 infected transcriptome

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Network based Human-SRAS-CoV-2 interactome analysis

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Interferon (IFN) stimulated genes (ISGs) are the most important targets.

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TLR3 agonists, like poly I:C, and imiquimod are identified as potential drugs.

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Targeting the innate immune response is a valuable approach against COVID-19.

Block to influenza virus replication in cells preirradiated with ultraviolet light

Ultraviolet (uv) irradiation of CEF cells immediately before infection with influenza A (fowl plague) virus inhibited virus growth; no inhibition of the growth of a parainfluenza virus (Newcastle disease virus) could be detected in irradiated cells. The kinetics of inhibition after various doses of uv irradiation were multihit, with an extrapolation number of two. When irradiated cells were allowed to photoreactivate by exposure to visible light for 16 hr their capacity to support influenza virus replication was largely restored; this process was sensitive to caffeine, suggesting that it required DNA repair. In CEF cells exposed to 360 ergs/mm(2) of uv radiation the rate of synthesis of host cellular RNA was reduced by more than 90%, and that of host cellular protein by 40-50%, as judged by incorporation of precursor molecules into an acid-insoluble form. When such irradiated cells were infected with influenza virus all the genome RNA segments were transcribed, but the overall concentration of virus-specific poly (A)-containing cRNA was reduced about 50-fold. Within this population of cRNA molecules, the RNAs coding for late proteins (HA, NA, and M) were reduced in amount relative to the other segments. The rates of synthesis of the M and HA proteins were specifically reduced in uv-irradiated cells, but the rates of synthesis of the P, NP, and NS proteins were only slightly reduced compared to normal cells. Immunofluorescent studies showed that, in uv-irradiated cells, NP migrated into the nucleus early after infection and later migrated out into the cytoplasm, as in normal cells. In contrast to normal cells, no specific immunofluorescence associated with M protein could be observed in uv-irradiated cells. It is concluded that uv-induced damage to host cellular DNA alters the pattern of RNA transcription in CEF cells infected with influenza virus, and that this results in a block to late protein synthesis which stops virus production.

Susceptibility of human skeletal muscle culture to influenza virus infection. Part 2. Ultrastructural cytopathology

Cultured post-fused human skeletal muscle monolayers exposed to WSN influenza A virus were analyzed by scanning and transmission electron microscopy. At 12-14h post-inoculation (p.i.), affected mononuclear cells retracted from the cell surface, but remained anchored to the substrate by taut filar processes. Retraction was accompanied by shortening of microvilli, appearance of hemispherical cytoplasmic protrusions and corrugation of the surface proper. These changes were more pronounced at 24 and 48h p.i. The rounded, moribund mononuclear cells eventually detached from the substratum. Surface alterations were accompanied by the intracellular appearance of electron-dense nuclear inclusions (often associated with the nucleolus) and paracrystalline ribosomestudded cytoplasmic bodies, which increased in size and number with time. In myotubes, distinct surface alterations appeared later (24h p.i.). Early myotube retraction was accompanied by accentuation of the longitudinally oriented surface pleats and appearance of "blebs" followed by cell-rounding. At 48-72 h, many myotubes detached from the substratum. The surfaces of those still adhering appeared corrugated. Intranuclear and cytoplasmic inclusions accumulated, and budding virions, often filamentous, could be demonstrated at the plasmalemma of mononuclear cells and myotubes. Late (end-stage) cytopathic effects included clumping of chromatin, breakdown of the nuclear envelope, disappearance of cortical and endoplasmic cytofilaments, mitochondrial swelling, and vesiculation of surface membranes. The lesions leading to cell injury and cell death appeared to be due to massive accumulation of virus-induced products that altered cellular metabolism, with physical and functional abnormalities of surface membranes.

Synthesis of influenza virus polypeptides in cells resistant to alpha-amanitin: evidence for the involvement of cellular RNA polymerase II in virus replication

Influenza virus polypeptides were not synthesized in wild-type CHO-S-infected cells in the presence of alpha-amanitin, but were synthesized in CHO-Amal cells, a mutant cell line whose DNA-dependent RNA polymerase II is specifically resistant to this drug, indicating that this cellular enzyme is involved in influenza virus replication. The results of experiments designed to detect viral polypeptides synthesized from primary transcripts suggest that the synthesis of a cellular RNA species by RNA polymerase II is required for primary transcription of the influenza virus genome.

Inhibition of influenza virus replication by -amanitin: mode of action

The replication of influenza virus in chick embryo fibroblast cells is inhibited by alpha-amanitin added during the first 2 hr of infection at concentrations similar to those required to inhibit cellular DNA-dependent RNA polymerase form II in vivo. Of two periods of increased RNA synthesis observed in cells infected with influenza virus, only the first, occurring from 0 to 2 hr after infection, is sensitive to alpha-amanitin. During this early period, there is a stimulation of the activity of DNA-dependent RNA polymerase II of nuclei isolated from infected cells. The data suggest that DNA transcription mediated by polymerase II is essential for influenza virus replication.

Isolation and partial characterization of nucleic acid of influenza virus

The principal ribonucleic acid (RNA) component isolated from purified equine influenza virus has an approximate sedimentation coefficient (S(20,W)) of 21S in sucrose gradient containing 0.1 m NaCl. Three other components of 18S, 14S, and 8S were also detected. All the RNA components have characteristics of single-stranded RNA. The average base composition of the principal RNA components is cytosine, 22.2; adenine, 22.9; guanine, 22.3; and uridine, 32.6. There was no qualitative difference in the RNA isolated from noninfectious virus particles compared to that from infectious virions.