The frequency of HBV genomic methylation in the liver was reported to vary among patients, but the detailed mechanism is still unknown. In this study, the effects of HBV genome methylation on HBV replication were investigated in vitro. A total of 6 plasmids containing 1.24-fold the HBV genome of different genotypes (subgenotypes A1, A2, B1, and C2) were purified after in vitro methylation with CpG methyltransferase (M.SssI) and transfected into HepG2 cells. In genotype B and C strains, methylation markedly decreased the amount of hepatitis B e antigen (HBeAg) in the culture supernatant. A reduction of hepatitis B surface antigen (HBsAg) was found in some HBV strains but the reduction was smaller than that of HBeAg. There was no significant difference in particle-associated HBV DNA in the culture supernatant. These findings suggest that HBV genomic methylation might be involved in the HBeAg decline in genotype B and C, in part, and that the reduction of HBsAg was less than that of HBeAg. In conclusion, this study showed that the effect of HBV genomic methylation differs among HBV genotypes, suggesting a potential explanation for the different clinical outcomes of genotypes A, B, and C.

中文翻译：

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病毒DNA甲基化对乙型肝炎病毒蛋白表达的影响取决于病毒的基因型。

据报道，患者肝脏中HBV基因组甲基化的频率有所不同，但具体机制仍不清楚。在这项研究中，体外研究了HBV基因组甲基化对HBV复制的影响。在用CpG甲基转移酶（M.SssI）进行体外甲基化后，共纯化了6个质粒，它们含有不同基因型（亚基因型A1，A2，B1和C2）的HBV基因组的1.24倍，并转染到HepG2细胞中。在基因型B和C菌株中，甲基化显着降低了培养上清液中的乙型肝炎e抗原（HBeAg）数量。在某些HBV株中发现乙型肝炎表面抗原（HBsAg）减少，但减少幅度小于HBeAg。培养上清液中与颗粒相关的HBV DNA没有显着差异。这些发现表明，HBV基因组甲基化可能部分涉及基因型B和C的HBeAg下降，并且HBsAg的下降小于HBeAg的下降。总之，这项研究表明，HBV基因型甲基化的影响在HBV基因型之间是不同的，这为基因型A，B和C的不同临床结局提供了可能的解释。