title: Genetic characterization and genotyping of hepatitis B virus (HBV) isolates from donors with an occult HBV infection.
abstract: OBJECTIVE
  Screening of Thai blood donors has resulted in the detection of donors with an occult HBV infection (OBI), where HBsAg is undetectable, but hepatitis B virus (HBV) DNA is present in serum in low concentrations. This study was designed to determine whether the occurrence of OBI in donors was linked to the HBV genotype and possibly to mutations in the surface (S) and core (C) gene regions.
  
  
  METHODS
  Mutations in the S and C gene regions in 48 Thai donors with OBI were mapped by sequencing. Genotyping was determined with the INNO-LiPA test and by phylogenetic analysis of sequences from the S and C genes.
  
  
  RESULTS
  The majority of OBI samples were genotype C (81·3%) with 6·3% of samples being genotype B. In addition, two genotype I isolates were identified. Mutations in the S region (100%) were found especially in loop 1 of the major hydrophilic loop (MHL) at positions I110L, T114S, T126I and S113T, whereas mutations in the C region (65%) were within the basal core promoter region (position A1762T/G1764A) and precore region (position G1896A).
  
  
  CONCLUSIONS
  The majority of OBI samples were HBV genotype C, although genotype I, which is newly emerging in Thailand, was also detected. The study demonstrated that OBI was probably not associated with a particular HBV genotype or with certain mutations in the S and C gene regions. However, mutations in the C gene region which could potentially impair viral replication and HBsAg production and potentially lead to OBI were identified.
authors.affiliation: Department of Microbiology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand.
authors.forename: N
authors.initials: N
authors.lastname: Chamni
authors.forename: S
authors.initials: S
authors.lastname: Louisirirotchanakul
authors.forename: S
authors.initials: S
authors.lastname: Oota
authors.forename: T
authors.initials: T
authors.lastname: Sakuldamrongpanish
authors.forename: J
authors.initials: J
authors.lastname: Saldanha
authors.forename: V
authors.initials: V
authors.lastname: Chongkolwatana
authors.forename: S
authors.initials: S
authors.lastname: Phikulsod
mesh_terms: D001483:Base Sequence; D001782:Blood Donors; D004279:DNA, Viral / Q000097:blood; D005128:Eye Diseases / Q000821:virology*; D005838:Genotype; D006509:Hepatitis B / Q000473:pathology* / Q000821:virology; D006512:Hepatitis B Core Antigens / Q000097:blood / Q000145:classification / Q000235:genetics; D006514:Hepatitis B Surface Antigens / Q000097:blood / Q000145:classification / Q000235:genetics; D006515:Hepatitis B virus / Q000235:genetics*; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic
chemical_list: D004279:DNA, Viral; D006512:Hepatitis B Core Antigens; D006514:Hepatitis B Surface Antigens
keywords: genotype I; hepatitis B virus; mutation; occult; sequencing