Down-regulation of promoter methylation level of CD4 gene after MDV infection in MD-susceptible chicken line

BACKGROUND: Marek’s disease virus (MDV) is an oncovirus that induces lymphoid tumors in susceptible chickens, and may affect the epigenetic stability of the CD4 gene. The purpose of this study was to find the effect of MDV infection on DNA methylation status of the CD4 gene differed between MD-resistant (L6(3)) and –susceptible (L7(2)) chicken lines. METHODS: Chickens from each line were divided into two groups with one group infected by MDV and the other group as uninfected controls. Then, promoter DNA methylation levels of the CD4 gene were measured by Pyrosequencing; and gene expression analysis was performed by quantitative PCR. RESULTS: Promoter methylation of the CD4 gene was found to be down-regulated in L7(2) chickens only after MDV infection. The methylation down-regulation of the CD4 promoter is negatively correlated with up-regulation of CD4 gene expression in the L7(2) spleen at 21 dpi. CONCLUSIONS: The methylation fluctuation and mRNA expression change of CD4 gene induced by MDV infection suggested a unique epigenetic mechanism existed in MD-susceptible chickens.