Methylation status of the interferon-gamma gene promoter in chronic hepatitis B

Objective: To evaluate the methylation status at CpG site -55 in the interferon-gamma (IFN-γ) gene promoter and its effect on IFN-γ expression in chronic hepatitis B. Method: The authors recruited 30 patients with HBeAg-positive chronic hepatitis B (CHB), 30 HBeAg-negative CHB patients, and 30 healthy blood donors. Pyrosequencing was used to determine the methylation status at CpG site -55 in the IFN-γ gene promoter following bisulfite treatment of DNA in peripheral blood, mononuclear cells (PBMCs). The expression of IFN-γ was analyzed by real-time RT-PCR and ELISA. HBV DNA in PBMCs was detected by nested PCR. Results: The methylation level at CpG site -55 in the IFN-γ gene promoter was significantly increased, resulting in subsequent down-regulation of the expression of this cytokine in CHB. The methylation level at CpG site -55 was significantly higher in HBeAg-positive patients than in HBeAg-negative ones (P < 0.01) and was also significantly higher in PBMCs from HBV DNA-positive patients than from HBV DNA-negative ones (P < 0.01); the methylation level at CpG site -55 was positively correlated with the amount of HBV DNA in serum (P < 0.01). Conclusion: IFN-γ gene expression appears to be regulated by methylation of the IFN-γ gene promoter in CHB; the methylation level at CpG site -55 is associated with HBV infection.