title: Are in vitro hepatitis B core promoter mutations important for clinical alterations in viral load?
abstract: In vitro studies of HBV core promoter mutations in hepatoma cell lines suggest that some mutations in core promoter transcription factor binding sites result in reduced core promoter activity and viral replication. We sought to validate this hypothesis using clinical samples with viral load differences before and after HBeAg seroconversion. A consensus sequence for transcription factor binding sites/regulatory regions was constructed based on published studies. Serum from two time points in 33 seroconverters and 10 interferon non-responders (controls) were utilized. Genotyping, HBV DNA quantification and direct sequencing of core promoter were performed. There were 216 new mutations following HBeAg seroconversion but few in controls. Mutations or mismatches to consensus transcription factor/regulatory region sequences clustered at nucleotide positions appeared genotype-specific, non-group specific or baseline mismatches and were discounted as having significant impact on viral replication. Only a few mutations in three seroconverters (9.1%) were specific, while 39.4% had no new mutations that could be attributed to reduction in viral load following HBeAg seroconversion. In 51.5% of patients, mutations were of uncertain significance because they occurred in demonstrated non-critical clustered nucleotide positions. Core promoter mutations post-seroconversion did not correlate with in vitro induced mutations that reduced the promoter activity.
authors.affiliation: Department of Medicine, National University of Singapore, 5 Lower Kent Ridge Road, Singapore 119074, Singapore.
authors.forename: Yan
authors.initials: Y
authors.lastname: Cheng
authors.forename: Bee Leng
authors.initials: BL
authors.lastname: Seet
authors.forename: Carmen Shair Ling
authors.initials: CS
authors.lastname: Ong
authors.forename: Shanthi
authors.initials: S
authors.lastname: Wasser
authors.forename: Theresa May Chin
authors.initials: TM
authors.lastname: Tan
authors.forename: Frank Josef
authors.initials: FJ
authors.lastname: Peter
authors.forename: Seng Gee
authors.initials: SG
authors.lastname: Lim
mesh_terms: D000328:Adult; D001665:Binding Sites; D016384:Consensus Sequence; D004252:DNA Mutational Analysis; D004279:DNA, Viral / Q000737:chemistry / Q000235:genetics; D005838:Genotype; D006509:Hepatitis B / Q000276:immunology / Q000821:virology*; D006512:Hepatitis B Core Antigens / Q000235:genetics*; D006513:Hepatitis B e Antigens / Q000097:blood; D006515:Hepatitis B virus / Q000235:genetics* / Q000276:immunology / Q000302:isolation & purification / Q000502:physiology; D006801:Humans; D009154:Mutation; D011401:Promoter Regions, Genetic; D017422:Sequence Analysis, DNA; D019562:Viral Load; D014779:Virus Replication / Q000235:genetics
chemical_list: D004279:DNA, Viral; D006512:Hepatitis B Core Antigens; D006513:Hepatitis B e Antigens