title: Evidence that methylation of hepatitis B virus covalently closed circular DNA in liver tissues of patients with chronic hepatitis B modulates HBV replication.
abstract: Epigenetic factors may modulate chronic Hepatitis B viral infection by affecting virion gene transcription. The aim of this study was to compare the methylation status of the intrahepatic covalently closed circular DNA (cccDNA) CpG island 2 and HBV replication capability. HBV cccDNA was extracted from liver biopsies of 55 HBsAg-positive patients with chronic hepatitis B (32 HBeAg-positive and 23 HBeAg-negative), and was analyzed for methylation status and quantity. The two Hpa II recognition sequences CCpGG in the CpG island 2 were methylated in infected liver tissues from 24 (43.6%) of 55 patients. Positive ratios of cccDNA methylation were significantly higher in HBeAg-negative patients (15/23, 65.2%) than HBeAg-positive patients (9/32, 28.1%) (P < 0.05). The percentage of methylated-cccDNA/total-cccDNA of HBeAg-negative samples (a median of 48%, ranging from 5% to 83%) was significantly higher (P < 0.001) than HBeAg-positive samples (a median of 14%, ranging from 0.26% to 35%). Ratios of relaxed circular DNA (rcDNA) to cccDNA molecules revealed that cccDNA methylation correlated with impaired virion productivity in HBeAg-positive individuals (P < 0.05). The bisulfite DNA sequencing showed that methylation density was significantly higher in HBeAg-negative than in HBeAg-positive patients (P < 0.05). The methylation level of the CpG island 2 of the cccDNA in HBeAg-negative patients was higher than that in HBeAg-positive patients, suggesting that HBV cccDNA methylation may be relevant to replication capability of HBV.
authors.affiliation: State Key Laboratory of Cancer Biology, Department of Pharmacogenomics, School of Pharmacy, The Fourth Military Medical University, Xi'an, China.
authors.forename: Yanhai
authors.initials: Y
authors.lastname: Guo
authors.forename: Yongnian
authors.initials: Y
authors.lastname: Li
authors.forename: Shijie
authors.initials: S
authors.lastname: Mu
authors.forename: Ju
authors.initials: J
authors.lastname: Zhang
authors.forename: Zhen
authors.initials: Z
authors.lastname: Yan
mesh_terms: D000328:Adult; D000368:Aged; D019175:DNA Methylation; D004270:DNA, Circular / Q000378:metabolism*; D004279:DNA, Viral / Q000378:metabolism*; D005260:Female; D006515:Hepatitis B virus / Q000502:physiology*; D019694:Hepatitis B, Chronic / Q000821:virology*; D006801:Humans; D008099:Liver / Q000821:virology*; D008297:Male; D008875:Middle Aged; D014779:Virus Replication; D055815:Young Adult
chemical_list: D004270:DNA, Circular; D004279:DNA, Viral