Characterization, Expression Pattern and Antiviral Activities of Mx Gene in Chinese Giant Salamander, Andrias davidianus

Abstract

Mx, Myxovirus resistance is an important interferon-stimulated protein that mediates antiviral responses. In this study, the expression and activities of Chinese giant salamander, Andrias davidianus Mx gene, AdMx, were investigated. The AdMx cDNA sequence contains an open reading frame (ORF) of 2112 nucleotides, encoding a putative protein of 703 aa. Meanwhile, AdMx possesses the conserved tripartite GTP binding motif and a dynamin family signature. qRT-PCR analysis revealed a broad expression of AdMx in vivo, with the highest expression levels in brain, kidney and spleen. The AdMx expression level in kidney, spleen and muscle significantly increased at 6 h after Chinese giant salamander iridovirus (GSIV) infection and peaked at 48 h, while that in muscle cell line (GSM) was not noticeably up-regulated until 72 h post infection. Additionally, a plasmid expressing AdMx was constructed and transfected into the Chinese giant salamander GSM cells. The virus load and gene copies in AdMx over-expressed cells were significantly reduced compared with those in the control cells. Moreover, compared to the control cells, a lower level of virus major capsid protein (MCP) synthesis in AdMx over-expressed cells was confirmed by Western blot. These results collectively suggest that Mx plays an important antiviral role in the immune responses against GSIV in Chinese giant salamander.

Evidence for a Novel Antiviral Mechanism of Teleost Fish: Serum-Derived Exosomes Inhibit Virus Replication through Incorporating Mx1 Protein

“…Mx proteins are against many RNA and DNA viruses [ 25 , 26 ]. A recent study shows that overexpressed Andrias davidianus Mx (AdMx) in the Chinese giant salamander’s muscle cells significantly reduced Chinese giant salamander iridovirus (GSIV) replication indicating that the Mx shows potential antiviral properties against iridoviruses [ 27 ]. In the present study, the localization of Mx1 protein in exosomes was identified.…”

“…MFF-1 cells were grown and maintained in Dulbecco’s modified Eagle’s medium (DMEM) supplemented with 10% fetal bovine serum (FBS) at 27 °C in 5% CO 2 [ 28 ]. The MFF-1 cell line was highly susceptible to the ISKNV [ 27 ]. In our lab, this cell line is used to ISKNV passage and isolate from disease-infected fish [ 28 ].…”

Developing a Virus-Binding Bacterium Expressing Mx Protein on the Bacterial Surface to Prevent Grouper Nervous Necrosis Virus Infection

“…Mx proteins have been used as hallmarks of interferon production and viral infection in vertebrates [17,32,33]. They have broad antiviral activity, such as prevention of viral RNA synthesis and protein expression, and they can inhibit the replication of many types of viruses, including Chinese giant salamander iridovirus, hepatitis B virus, reoviruses, and nodavirus [34][35][36][37][38]. Chen et al demonstrated that gMx proteins could inhibit the synthesis of nodavirus RNA-dependent RNA polymerase, bind to the nodavirus coat protein, and inhibit viral replication.…”

The Immune System and the Antiviral Responses in Chinese Giant Salamander, Andrias davidianus

“…IRF3 expression was increased in the spleen at 3 hpi (28). Type I IFN transcript levels were upregulated in peripheral blood leukocytes at 12 hpi, while Mx transcripts levels were upregulated in the spleen at 6 hpi and in the kidney at 12 hpi (70,71). Inflammatory genes such as TNF-a and IL-1b were significantly induced in the spleen at 3 dpi and in the kidney at 7 dpi, while the macrophage migration inhibitor (mif) gene was induced in the spleen at 3 dpi and in the kidney at 12 dpi.…”

“…Although LGP2 lacks CARD domain in other vertebrate (69), the structure signature of AdLGP2 has not been investigated. The RLR activation pathway induces IFN regulatory factor 3 (IRF3) regulated type-I interferon response and subsequently stimulates the production of IFN-stimulated genes (ISGs) including ISG15 and the Myxovirus resistance (Mx) gene, which has been characterized in the Chinese giant salamander (28,(69)(70)(71). Further characterization of the RLR pathway in A. davidianus should now be undertaken and in particular the absence of adapter IPS-1 will have to be confirmed.…”