Mechanism Of Anti-FMDV In Equine Thyroid Epithelial Cells

Although a disease of low mortality, the global impact of foot and mouth disease (FMD) cannot be underestimated because of the huge numbers of animals affected. This impact can be either direct losses due to decreased output and changes in herd structure or indirect losses caused by costs of FMD control, poor access to markets and limited use of improved production technologies. It is estimated that annual impact of FMD in terms of visible production losses and vaccination in endemic regions alone amount to between US$6.5 and 21 billion. In addition, outbreaks in FMD free countries and zones cause losses of >US$1.5 billion a year. Therefore, understanding the mechanism of FMDV infection and further control is particularly important.Horses are not considered susceptible to foot-and-mouth disease virus (FMDV), but the underlying mechanisms remain unclear. We use gene expression profiling technology, to clarify the mechanism of horses against FMDV infection. The main works and results were as follows,1In this study, the comparison of integrin receptor utilization by FMDV in bovine and equine thyroid epithelial cells (BTYECs and ETYECs) showed almost equal efficiency. SW480 cells, which are non-permissive for FMDV, become susceptible to infection upon transfection with the integrin cβ3, hβ3 or cβ6, and hβ3 subunits. In addition, the results indicate that FMDV could utilize huav/hβ3 and huav/hβ6 integrins with equal or higher efficiency than those of bovine homolog. Results in transfected COS-1 cells showed that for each viruses, the co-transfection of cells with a bovine β subunit and either a bovine or equine av subunit resulted in almost the same efficiency to the co-transfection of cells with an equine β subunit and a bovine or equine av subunit. Worth of noting, In ETYECs, FMDV infection led to none virus production but earlier-stage and higher-rate apoptosis than in BTYECs.2 Applying gene-expression-profile technology, we attempt to find the genes of difference in expression. Controls and infected BTYECs and ETYECs by FMDV strains, namely, O/CHA/1999, A/CHA/2009, and Asia 1/JS/2005 at 2,4,8,12,24,36, and 48 hpi. After K-MEAN clustering, GO and KEGG analysis, there are 66 genes of great difference in expression between BTYECs and ETYECs。Though some key genes are activated in both ETYECs and BTYECs, the gene levels of ETYECs changed early at 2hpi, while those of BTYECs changed mostly at 4hpi or 12hpi.66 genes are mainly mapped to PI3K-Akt and TLR signaling pathway. Further, we tested the genes among these two signaling pathway. The results indicated both BTYECs and ETYECs can activate TLR3-IRF-7-IFNα1/β1 and TLR9-Myd88-IRF-7-IFNα1/β1 though the activation in BTYECs lags behind the changes in ETYECs.å'ŒPI3K-Akt signaling pathway and Toll-like receptor pathway (TLRP) (TLR3/TLR9-IRF-7-IFNα1/β1). In addition, virus activated PI3K-Akt3-Bim pro-apoptosis pathway while PI3K-Akt3-Bcl2 anti-apoptosis axes in ETYECs and BTYECs, respectively.3 To determine whether the antiviral ability of ETYECs is related to these two signaling pathways, we transiently overexpressed and interfered TLR3, myeloid differentiating factor 88 (MyD88), and interferon regulatory factor 7 (IRF-7) in BTYECs. We also suppressed Akt by Akt-X inhibitor. The changes in TLR pathway (except for interference of MyD88), inhibition by Akt-X, and superimposition of Akt-inhibition and MyD88-interference in BTYECs all showed attenuation of viral replication.In summary, our study demonstrated for the first time that, in ETYECs, FMDV activated PI3K-Akt-Bim axis pro-apoptotic way, TLR9-Myd88-IRF-7-IFNα1/β1 and TLR3-IRF-7-IFNα1/β1 antiviral pathway. The PI3K-Akt signaling pathway and TLR pathway destroyed the entire FMDV virulent process through antiviral effects of type I interferons and pro-apoptosis in ETYECs.