title: Occult hepatitis B virus infection in hepatitis B vaccinated children in Taiwan.
abstract: OBJECTIVE
  Presence of occult HBV infection in HBV vaccinated children remains largely unknown. The aim of this study was to investigate the prevalence of occult HBV infection among HBV vaccinated children in Taiwan.
  
  
  METHODS
  Forty-six HBsAg negative sera from vaccinated children were enrolled randomly. HBV serum markers were detected by ELISA, and the titers of HBV DNA were determined by quantitative real-time PCR. Pre-S, S and pre-core/core genes were amplified by nested PCR and analyzed.
  
  
  RESULTS
  Anti-HBs was detected in 23 (50%) children, and the positivity decreased according to age. Five (10.9%) children were classified into occult HBV infection by positivity of nested PCR in at least two regions; they had a low titer (mean titer 1.60x10(4)copies/ml). Sequence analyses of S gene showed occult isolates were variants; no G145R but C139S vaccine escape mutant was found. Variation and deletion were found in pre-S region; pre-S deletion was more frequent in 3' terminus of pre-S1 which leads to loss of immune epitopes and function sites.
  
  
  CONCLUSIONS
  This pilot study indicates that the prevalence of occult HBV infection is 10.9% in HBV vaccinated children. Since this is a small study, a study of a large population is needed to confirm the findings herein.
authors.affiliation: Department of Pediatrics, Shin Kong Wu Ho-Su Memorial Hospital, Taipei, Taiwan.
authors.forename: Shu-Chi
authors.initials: SC
authors.lastname: Mu
authors.forename: Yu-Min
authors.initials: YM
authors.lastname: Lin
authors.forename: Guey-Mei
authors.initials: GM
authors.lastname: Jow
authors.forename: Bing-Fang
authors.initials: BF
authors.lastname: Chen
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D002648:Child; D002675:Child, Preschool; D004279:DNA, Viral / Q000097:blood; D005260:Female; D006509:Hepatitis B / Q000453:epidemiology* / Q000517:prevention & control; D006514:Hepatitis B Surface Antigens / Q000097:blood / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D017325:Hepatitis B Vaccines / Q000276:immunology*; D006515:Hepatitis B virus / Q000145:classification / Q000235:genetics; D006801:Humans; D007223:Infant; D008297:Male; D008969:Molecular Sequence Data; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D015995:Prevalence; D011498:Protein Precursors / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D013624:Taiwan / Q000453:epidemiology; D014611:Vaccination
chemical_list: D004279:DNA, Viral; D006514:Hepatitis B Surface Antigens; D017325:Hepatitis B Vaccines; D011498:Protein Precursors; C050807:presurface protein 2, hepatitis B surface antigen