title: A novel hepatitis B virus mutant with A-to-G at nt551 in the surface antigen gene.
abstract: OBJECTIVE
  Hepatitis B surface antigen (HBsAg) mutant of hepatitis B virus (HBV) is one of the important factors that result in immune escape and cause failure of immunization. In this study we reported and characterized a novel HBV mutant with A-to-G at nt551 and intended to provide theoretical data for prevention of HBV infection in China.
  
  
  METHODS
  A methodology comprising polymerase chain reaction (PCR) amplifying, M13 bacteriophage cloning and nucleotide sequencing was used to analyze the sera of the pediatric patient who was hepatitis B (HB) immune failure. Expression plasmids containing the mutant S gene and a wild-type (adr) S gene were constructed respectively and the recombinant HBsAg were expressed in COS-7 cells under the regulation of SV40 early promoter. The recombinant proteins were investigated for their immunological reactivity with different monoclonal antibodies (mAb) against "a" determinant and vaccine-raised human neutralizing antibodies.
  
  
  RESULTS
  It was found that there was a new point mutation at nt551 of the HBV (adr) genome from A to G, leading to a substitution of methionine (Met) to valine (Val) at position 133 in the "a" determinant of HBsAg. Compared to the wild-type HBsAg, the binding activity of the mutant HBsAg to mAbs (A6, A11 and S17) and to vaccine-raised human anti-hepatitis B surface antibody (anti-HBs) decreased significantly.
  
  
  CONCLUSIONS
  According to the facts that the patient has been immunized with HB vaccine and that the serum is anti-HBs positive and HBsAg negative, and based on the nucleotide sequence analysis of the mutant HBV S gene and its alteration of antigenicity, the HBV is considered to be a new vaccine-induced immune escape mutant different from the known ones.
authors.affiliation: Huadong Research Institute for Medical Biotechnics, Nanjing 210002, Jiangsu Province, China. chenhuabiao@hotmail.com
authors.forename: Hua-Biao
authors.initials: HB
authors.lastname: Chen
authors.forename: De-Xing
authors.initials: DX
authors.lastname: Fang
authors.forename: Fa-Qing
authors.initials: FQ
authors.lastname: Li
authors.forename: Hui-Ying
authors.initials: HY
authors.lastname: Jing
authors.forename: Wei-Guo
authors.initials: WG
authors.lastname: Tan
authors.forename: Su-Qin
authors.initials: SQ
authors.lastname: Li
mesh_terms: D000409:Alanine; D000595:Amino Acid Sequence / Q000235:genetics; D019943:Amino Acid Substitution; D001483:Base Sequence / Q000235:genetics; D002675:Child, Preschool; D005998:Glycine; D006514:Hepatitis B Surface Antigens / Q000235:genetics*; D006515:Hepatitis B virus / Q000235:genetics*; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D017354:Point Mutation / Q000235:genetics*
chemical_list: D006514:Hepatitis B Surface Antigens; D000409:Alanine; D005998:Glycine