Interferon revisited: Peering behind the lines of antiviral defense.
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ABSTRACT:
SUBMITTER: Virzi A
PROVIDER: S-EPMC7351677 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Secretion of interferons (IFNs) from virus-infected cells is a hallmark of host antiviral immunity and in fact, IFNs exert their antiviral activities through the induction of antiviral proteins. The IFN-induced protein with tetratricopeptide repeats (IFITs) family is among hundreds of IFN-stimulated genes. This family contains a cluster of duplicated loci. Most mammals have IFIT1, IFIT2, IFIT3 and IFIT5; however, bird, marsupial, frog and fish have only IFIT5. Regardless of species, IFIT5 is always adjacent to SLC16A12. IFIT family genes are predominantly induced by type I and type III interferons and are regulated by the pattern recognition and the JAK-STAT signaling pathway. IFIT family proteins are involved in many processes in response to viral infection. However, some viruses can escape the antiviral functions of the IFIT family by suppressing IFIT family genes expression or methylation of 5' cap of viral molecules. In addition, the variants of IFIT family genes could significantly influence the outcome of hepatitis C virus (HCV) therapy. We believe that our current review provides a comprehensive picture for the community to understand the structure and function of IFIT family genes in response to pathogens in human, as well as in animals.
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Project description:Mixed lineage kinase domain-like protein (MLKL) is the terminal effector of necroptosis, a form of regulated necrosis. Optimal activation of necroptosis, which eliminates infected cells, is critical for antiviral host defense. MicroRNAs (miRNAs) regulate the expression of genes involved in various biological and pathological processes. However, the roles of miRNAs in necroptosis-associated host defense remain largely unknown. We screened a library of miRNAs and identified miR-324-5p as the most effective suppressor of necroptosis. MiR-324-5p downregulates human MLKL expression by specifically targeting the 3'UTR in a seed region-independent manner. In response to interferons (IFNs), miR-324-5p is downregulated via the JAK/STAT signaling pathway, which removes the posttranscriptional suppression of MLKL mRNA and facilitates the activation of necroptosis. In influenza A virus (IAV)-infected human primary macrophages, IFNs are induced, leading to the downregulation of miR-324-5p. MiR-324-5p overexpression attenuates IAV-associated necroptosis and enhances viral replication, whereas deletion of miR-324-5p potentiates necroptosis and suppresses viral replication. Hence, miR-324-5p negatively regulates necroptosis by manipulating MLKL expression, and its downregulation by IFNs orchestrates optimal activation of necroptosis in host antiviral defense.
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Project description:Mixed lineage kinase domain-like protein (MLKL) is the terminal effector of necroptosis, a form of regulated necrosis. Optimal activation of necroptosis, which eliminates infected cells, is critical for antiviral host defense. MicroRNAs (miRNAs) regulate the expression of genes involved in various biological and pathological processes. However, the roles of miRNAs in necroptosis-associated host defense remain largely unknown. We screened a library of miRNAs and identified miR-324-5p as the most effective suppressor of necroptosis. MiR-324-5p downregulates human MLKL expression by specifically targeting the 3'UTR in a seed region-independent manner. In response to interferons (IFNs), miR-324-5p is downregulated via the JAK/STAT signaling pathway, which removes the posttranscriptional suppression of MLKL mRNA and facilitates the activation of necroptosis. In influenza A virus (IAV)-infected human primary macrophages, IFNs are induced, leading to the downregulation of miR-324-5p. MiR-324-5p overexpression attenuates IAV-associated necroptosis and enhances viral replication, whereas deletion of miR-324-5p potentiates necroptosis and suppresses viral replication. Hence, miR-324-5p negatively regulates necroptosis by manipulating MLKL expression, and its downregulation by IFNs orchestrates optimal activation of necroptosis in host antiviral defense.
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Project description:Equine herpesvirus 1 (EHV1) is considered as a major pathogen of Equidae, causing symptoms from mild respiratory disease to late-term abortion and neurological disorders. Different EHV1 strains circulating in the field have been characterized to be of abortigenic or neurovirulent phenotype. Both variants replicate in a plaque-wise manner in the epithelium of the upper respiratory tract (URT), where the abortigenic strains induce more prominent viral plaques, compared to the neurovirulent strains. Considering the differences in replication at the URT, we hypothesized that abortigenic strains may show an increased ability to modulate the type I IFN secretion/signaling pathway, compared to strains that display the neurovirulent phenotype. Here, we analyze IFN levels induced by abortigenic and neurovirulent EHV1 using primary respiratory epithelial cells (EREC) and respiratory mucosa ex vivo explants. Similar levels of IFNα (~70 U/ml) were detected in explants inoculated with both types of EHV1 strains from 48 to 72 hpi. Second, EREC and mucosa explants were treated with recombinant equine IFNα (rEqIFNα) or Ruxolitinib (Rux), an IFN signaling inhibitor, prior to and during inoculation with abortigenic or neurovirulent EHV1. Replication of both EHV1 variants was suppressed by rEqIFNα. Further, addition of Rux increased replication in a concentration-dependent manner, indicating an IFN-susceptibility for both variants. However, in two out of three horses, at a physiological concentration of 100 U/ml of rEqIFNα, an increase in abortigenic EHV1 replication was observed compared to 10 U/ml of rEqIFNα, which was not observed for the neurovirulent strains. Moreover, in the presence of Rux, the plaque size of the abortigenic variants remained unaltered, whereas the typically smaller viral plaques induced by the neurovirulent variants became larger. Overall, our results demonstrate the importance of IFNα in the control of EHV1 replication in the URT for both abortigenic and neurovirulent variants. In addition, our findings support the speculation that abortigenic variants of EHV1 may have developed anti-IFN mechanisms that appear to be absent or less pronounced in neurovirulent EHV1 strains.
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