title: Occult hepatitis B virus infection: influence of S protein variants.
abstract: BACKGROUND
  In occult hepatitis B viral infection (OBI), the persistence of hepatitis B virus (HBV) DNA is associated with a lack of hepatitis B surface antigen (HBsAg). To assess the possible role of HBsAg immune escape variants in OBI patients, variability in the HBV S gene was evaluated for OBI patients as well as chronic HBV infection patients from the same families.
  
  
  METHODS
  We selected 17 HBV DNA-positive/HBsAg-negative patients (OBI group) and 15 HBV DNA- and HBsAg-positive patients from OBI families (control group). The S gene was amplified and cloned, and at least 15 clones per patient were sequenced and analyzed.
  
  
  RESULTS
  Although the incidence of stop codon mutations within the S region was higher in the OBI group (13.6 %) than in the control group (1.5 %, P < 0.001), this type of mutation, together with insertion and deletion mutations, was prevalent in only three OBI patients. In the major hydrophilic region (MHR), a median of 0.75 residues were altered in every 100 residues for the OBI patients, whereas 0.95 out of 100 residues were changed in the control group (P = 0.428). Furthermore, some variants that are generally considered immune escape variants, such as mutations at positions s145, s147, and s123, were only observed in less than 5 % of all the clones sequenced, in either OBI or control group.
  
  
  CONCLUSIONS
  Our data suggest that HBsAg variants may not play a major role in OBI pathogenesis.
authors.affiliation: Department of Infectious Diseases, the First Affiliated Hospital, Anhui Medical University, Hefei, 230022, China. zzh1974cn@163.com.|School of Pharmacy, Anhui Medical University, Hefei, China. zzh1974cn@163.com.
authors.forename: Zhenhua
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Department of Infectious Diseases, the First Affiliated Hospital, Anhui Medical University, Hefei, 230022, China. lingzhang1984@sina.com.
authors.forename: Ling
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Department of Infectious Diseases, the First Affiliated Hospital, Anhui Medical University, Hefei, 230022, China. tina383-tt@qq.com.
authors.forename: Yu
authors.initials: Y
authors.lastname: Dai
authors.affiliation: Department of Infectious Diseases, the First Affiliated Hospital, Anhui Medical University, Hefei, 230022, China. zhangyafei198@126.com.
authors.forename: Yafei
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: School of Pharmacy, Anhui Medical University, Hefei, China. lijun@ahmu.edu.cn.
authors.forename: Jun
authors.initials: J
authors.lastname: Li
authors.affiliation: Department of Infectious Diseases, the First Affiliated Hospital, Anhui Medical University, Hefei, 230022, China. aaylixu@qq.com.
authors.forename: Xu
authors.initials: X
authors.lastname: Li
mesh_terms: D000293:Adolescent; D000328:Adult; D019943:Amino Acid Substitution; D015415:Biomarkers; D002648:Child; D018388:Codon, Terminator; D005260:Female; D014644:Genetic Variation; D005838:Genotype; D006509:Hepatitis B / Q000097:blood / Q000276:immunology / Q000821:virology*; D006514:Hepatitis B Surface Antigens / Q000235:genetics* / Q000276:immunology; D006515:Hepatitis B virus / Q000235:genetics* / Q000276:immunology; D019694:Hepatitis B, Chronic / Q000097:blood / Q000276:immunology / Q000821:virology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009154:Mutation; D010375:Pedigree; D055815:Young Adult
chemical_list: D015415:Biomarkers; D018388:Codon, Terminator; D006514:Hepatitis B Surface Antigens