Project description:We used two different influenza viruses lacking either PB1 or HA to differentiate the antiviral responses generated from primary transcription and full replication, respectively.
Project description:Heldt2012 - Influenza Virus Replication
The model describes the life cycle of influenza A virus in a mammalian cell including the following steps: attachment of parental virions to the cell membrane, receptor-mediated endocytosis, fusion of the virus envelope with the endosomal membrane, nuclear import of vRNPs, viral transcription and replication, translation of the structural viral proteins, nuclear export of progeny vRNPs and budding of new virions. It also explicitly accounts for the stabilization of cRNA by viral polymerases and NP and the inhibition of vRNP activity by M1 protein binding. In short, the model focuses on the molecular mechanism that controls viral transcription and replication.
This model is described in the article:
Modeling the intracellular dynamics of influenza virus replication to understand the control of viral RNA synthesis.
Heldt FS, Frensing T, Reichl U.
J Virol.
Abstract:
Influenza viruses transcribe and replicate their negative-sense RNA genome inside the nucleus of host cells via three viral RNA species. In the course of an infection, these RNAs show distinct dynamics, suggesting that differential regulation takes place. To investigate this regulation in a systematic way, we developed a mathematical model of influenza virus infection at the level of a single mammalian cell. It accounts for key steps of the viral life cycle, from virus entry to progeny virion release, while focusing in particular on the molecular mechanisms that control viral transcription and replication. We therefore explicitly consider the nuclear export of viral genome copies (vRNPs) and a recent hypothesis proposing that replicative intermediates (cRNA) are stabilized by the viral polymerase complex and the nucleoprotein (NP). Together, both mechanisms allow the model to capture a variety of published data sets at an unprecedented level of detail. Our findings provide theoretical support for an early regulation of replication by cRNA stabilization. However, they also suggest that the matrix protein 1 (M1) controls viral RNA levels in the late phase of infection as part of its role during the nuclear export of viral genome copies. Moreover, simulations show an accumulation of viral proteins and RNA toward the end of infection, indicating that transport processes or budding limits virion release. Thus, our mathematical model provides an ideal platform for a systematic and quantitative evaluation of influenza virus replication and its complex regulation.
With the current parameter set, the model reproduces an infection at a multiplicity of infection (MOI) of 10. Figure 2A of the paper is reproduced here, with parameters kDegRnp and kSynP changed to zeros.
Initial conditions and parameter changes that were used to obtain specific figures in the article can be found in Table A2.
The model has the correct value for kAttLo as 4.55e-04. The value of this parameter mentioned as 4.55e-02 in Table 1 of the paper is incorrect. This is checked with the author.
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Project description:Influenza is a major cause of morbidity and mortality worldwide, and the emerging drug resistance poses an increasing challenge to the treatment of influenza virus infection. Therefore, the development of a novel antiviral drugs has become an urgent task to combat against the influenza viruses that are resistant to the current therapeutic treatment. Here, by screening a small molecule chemical compound library, we identified 3-anhydro-6-epi-ophiobolin A (named L435) as a potent anti-influenza agent. Mechanistically, L435 markedly reduced influenza virus replication in vitro and in vivo. Importantly, L435 treatment improved the survival of influenza-virus-infected mice, suggesting that L435 may be a novel therapeutic agent for treatment of influenza virus infections. This microarray experiment was carried out to explore gene expression changes in influenza-virus-infected A549 cells after L435 treatment, and find out why L435 could inhibit the replication of influenza A virus.
Project description:Influenza is a major cause of morbidity and mortality worldwide, and the emerging drug resistance poses an increasing challenge to the treatment of influenza virus infection. Therefore, the development of a novel antiviral drugs has become an urgent task to combat against the influenza viruses that are resistant to the current therapeutic treatment. Here, by screening a small molecule chemical compound library, we identified 3-anhydro-6-epi-ophiobolin A (named L435) as a potent anti-influenza agent. Mechanistically, L435 markedly reduced influenza virus replication in vitro and in vivo. Importantly, L435 treatment improved the survival of influenza-virus-infected mice, suggesting that L435 may be a novel therapeutic agent for treatment of influenza virus infections. This microarray experiment was carried out to explore gene expression changes in influenza-virus-infected A549 cells after L435 treatment, and find out why L435 could inhibit the replication of influenza A virus. Total RNAs were extracted from three different groups of A549 cells that were mock treated, or infected with WSN and treated with DMSO for 12h, or infected with WSN and treated with L435 for 12 h, using TRIzol reagent (Invitrogen, Carlsbad, CA). Three independent experiments were performed. Samples were amplified and labeled using the One-Color Quick Amp Labeling Kit (Agilent p/n 5190-2305).
Project description:Influenza A virus has a broad cellular tropism in the respiratory tract. Infected epithelial cells sense the infection and initiate an antiviral response. To define the antiviral response at the earliest stages of infection we used two different single cycle replication reporter viruses. These tools demonstrated heterogeneity in virus replication levels in vivo. Transcriptional profiling demonstrated tiers of interferon stimulated gene responses that were dependent on the magnitude of virus replication. Uninfected cells and cells with blunted replication expressed a distinct and potentially protective ISG signature. Finally, we used these single cycle reporter viruses to determine the antiviral landscape during virus spread, which unveiled disparate protection mediated by IFN. Together these results highlight the complexity of virus-host interactions within the infected lung and suggest that magnitude and round of replication tune the antiviral response.
Project description:Analyses of AP-MS experiments performed in HEK 293T cells infected with the influenza A/WSN/33 virus. In half of the experiments the virus was modified to contain a C-terminal Strep tag on the polymerase subunit PB2. Full details in York et al. 'Interactome analysis of the influenza A virus transcription/replication machinery identifies protein phosphatase 6 as a cellular factor required for efficient virus replication.'
Project description:While hundreds of genes are induced by Type I interferons, their roles in restricting the influenza life cycle remain mostly unknown. Using a loss-of-function CRISPR screen in cells pre-stimulated with Type I interferon, we identified a small number of factors required for restricting influenza A virus replication. In addition to the known components of the interferon signaling pathway, we found a new factor, Replication Termination Factor 2 (RTF2). RTF2 restricts influenza, at least, at the nuclear stage of the viral life cycle based on several lines of evidence. First, a deficiency in RTF2 leads to higher levels of viral primary transcription, even in the presence of cycloheximide to block genome replication and secondary transcription. Second, cells that lack RTF2 have enhanced activity of a viral reporter that depends solely on four viral proteins that carry out replication and transcription in the nucleus. Third, when RTF2 protein is mislocalized outside the nucleus, it is not able to restrict replication. Furthermore, the absence of RTF2 not only led to enhanced viral transcription but also to reduced expression of anti-viral factors in response to interferon. RTF2 thus inhibits primary influenza transcription, likely acts in the nucleus, and contributes to upregulation of antiviral effectors in response to Type I interferons
Project description:Influenza A virus (IAV) infection causes acute respiratory disease with potential severe and deadly complications. Viral pathogenesis is not only due to the direct cytopathic effect of viral infections but also to the exacerbated host inflammatory responses. Influenza viral infection can activate various host signaling pathways that function to activate or inhibit viral replication. Our previous studies have shown that a receptor tyrosine kinase TrkA plays an important role in the replication of influenza viruses in vitro, but its biological roles and functional mechanisms in influenza viral infection have not been characterized. Here we show that IAV infection strongly activates TrkA in vitro and in vivo. Using a chemical-genetic approach to specifically control TrkA kinase activity through a small molecule compound 1NMPP1 in a TrkA knock-in (TrkA KI) mouse model, we show that 1NMPP1-mediated TrkA inhibition completely protected mice from a lethal IAV infection by significantly reducing viral loads and lung inflammation. Using primary lung cells isolated from the TrkA KI mice, we show that specific TrkA inhibition reduced viral RNA synthesis in airway epithelial cells (AECs) but not in alveolar macrophages (AMs). Transcriptomic analysis confirmed the cell-type-specific role of TrkA in viral RNA synthesis, and identified distinct gene expression patterns under the TrkA regulation in IAV-infected AECs and AMs. Among the TrkA-activated targets are various proinflammatory cytokines and chemokines such as IL6, IL-1, IFNs, CCL-5, and CXCL9, supporting the role of TrkA in mediating lung inflammation. Indeed, TrkA inhibitor 1NMPP1 administered after the peak of IAV replication, though had no effect on viral load, was able to decrease lung inflammation and provide partial protection in mice. Taken together, our results have demonstrated for the first time an important biological role of TrkA signaling in IAV infection, identified its cell-type-specific contribution to viral replication, and revealed its functional mechanism in virus-induced lung inflammation. This study suggests TrkA as a novel host target for therapeutics against influenza viral disease.