title: Protective roles of grass carp Ctenopharyngodon idella Mx isoforms against grass carp reovirus.
abstract: BACKGROUND
  Myxovirus resistance (Mx) proteins are crucial effectors of the innate antiviral response against a wide range of viruses, mediated by the type I interferon (IFN-I) signaling pathway. However, the antiviral activity of Mx proteins is diverse and complicated in different species.
  
  
  RESULTS
  In the current study, two novel Mx genes (CiMx1 and CiMx3) were identified in grass carp (Ctenopharyngodon idella). CiMx1 and CiMx3 proteins exhibit high sequence identity (92.1%), and low identity with CiMx2 (49.2% and 49.5%, respectively) from the GenBank database. The predicted three-dimensional (3D) structures are distinct among the three isoforms. mRNA instability motifs also display significant differences in the three genes. The spatial and temporal expression profiles of three C. idella Mx genes and the IFN-I gene were investigated by real-time fluorescence quantitative RT-PCR (qRT-PCR) following infection with grass carp reovirus (GCRV) in vivo and in vitro. The results demonstrated that all the four genes were implicated in the anti-GCRV immune response, that mRNA expression of Mx genes might be independent of IFN-I, and that CIK cells are suitable for antiviral studies. By comparing expression patterns following GCRV challenge or poly(I:C) treatment, it was observed that GCRV blocks mRNA expression of the four genes. To determine the functions of Mx genes, three CiMx cDNAs were cloned into expression vectors and utilized for transfection of CIK cells. The protection conferred by each recombinant CiMx protein against GCRV infection was evaluated. Antiviral activity against GCRV was demonstrated by reduced cytopathic effect, lower virus titer and lower levels of expressed viral transcripts. The transcription of IFN-I gene was also monitored.
  
  
  CONCLUSIONS
  The results indicate all three Mx genes can suppress replication of grass carp reovirus and over-expression of Mx genes mediate feedback inhibition of the IFN-I gene.
authors.affiliation: College of Animal Science and Technology, Northwest A&F University, Shaanxi Key Laboratory of Molecular Biology for Agriculture, Yangling, Shaanxi, China.
authors.forename: Limin
authors.initials: L
authors.lastname: Peng
authors.forename: Chunrong
authors.initials: C
authors.lastname: Yang
authors.forename: Jianguo
authors.initials: J
authors.lastname: Su
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002347:Carps / Q000235:genetics / Q000276:immunology* / Q000378:metabolism / Q000821:virology; D018076:DNA, Complementary / Q000235:genetics; D005393:Fish Diseases / Q000235:genetics / Q000276:immunology* / Q000378:metabolism / Q000821:virology*; D019204:GTP-Binding Proteins / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D007370:Interferon Type I / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D008969:Molecular Sequence Data; D064547:Myxovirus Resistance Proteins; D010802:Phylogeny; D020033:Protein Isoforms; D020871:RNA Stability; D012087:Reoviridae / Q000276:immunology*; D012088:Reoviridae Infections / Q000276:immunology / Q000378:metabolism / Q000662:veterinary* / Q000821:virology; D016415:Sequence Alignment / Q000379:methods; D014779:Virus Replication / Q000235:genetics / Q000276:immunology
chemical_list: D018076:DNA, Complementary; D007370:Interferon Type I; D064547:Myxovirus Resistance Proteins; D020033:Protein Isoforms; D019204:GTP-Binding Proteins