title: Fragmented CagA protein is highly immunoreactive in Japanese patients.
abstract: BACKGROUND
  High-molecular-weight cell-associated proteins (HM-CAP) assay is the most popular serological immunoassay worldwide and has been developed from US isolates as the antigens. The accuracy is reduced when the sera are from adults and children in East Asia including Japan. To overcome the reduced accuracy, an enzyme immunoassay using Japanese strain-derived HM-CAP (JHM-CAP) was developed, in which the antigens were prepared by exactly the same procedure as HM-CAP. The performance of JHM-CAP was better than that of HM-CAP in Japanese adults as well as in children. The higher sensitivity was because of the presence of 100-kDa protein that was absent in the preparation of HM-CAP antigen.
  
  
  METHODS
  Immunoblot analysis and peptide mass fingerprinting methods were used to identify the distinctive 100-kDa protein present in JHM-CAP antigens. The peptide sequence and identification were analyzed by Mascot Search on the database of Helicobacter pylori. The identified protein was confirmed by immunoblot with a specific antibody and inhibition assay by the sera.
  
  
  RESULTS
  The distinctive 100-kDa protein was a fragment of CagA derived from Japanese clinical isolates, and the sera of Japanese patients had strongly reacted to the protein, probably to the exposed epitope on the fragmented CagA. The fragmentation of CagA had occurred in the process of antigen preparation in Japanese isolates, not in US isolates even under the same preparation.
  
  
  CONCLUSIONS
  The distinctive 100-kDa protein was a fragment of CagA protein of H. pylori derived from Japanese clinical isolates, and Japanese patients including children are likely to react strongly to the exposed epitopes on fragmented CagA.
authors.affiliation: Department of Gastroenterology, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama, Japan.
authors.forename: Kazuki
authors.initials: K
authors.lastname: Yamada
authors.forename: Toshiro
authors.initials: T
authors.lastname: Sugiyama
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Mihara
authors.forename: Shinya
authors.initials: S
authors.lastname: Kajiura
authors.forename: Seiko
authors.initials: S
authors.lastname: Saito
authors.forename: Yuko
authors.initials: Y
authors.lastname: Itaya
authors.forename: Hidemoto
authors.initials: H
authors.lastname: Yamawaki
authors.forename: Takayuki
authors.initials: T
authors.lastname: Ando
authors.forename: Takahiko
authors.initials: T
authors.lastname: Kudo
authors.forename: Ayumu
authors.initials: A
authors.lastname: Hosokawa
authors.forename: Masumi
authors.initials: M
authors.lastname: Okuda
authors.forename: Kenichi
authors.initials: K
authors.lastname: Fukunaga
authors.forename: Junko K
authors.initials: JK
authors.lastname: Akada
authors.forename: Teruko
authors.initials: T
authors.lastname: Nakazawa
mesh_terms: D000328:Adult; D000595:Amino Acid Sequence; D000907:Antibodies, Bacterial / Q000276:immunology; D000942:Antigens, Bacterial / Q000235:genetics / Q000276:immunology*; D001426:Bacterial Proteins / Q000235:genetics / Q000276:immunology*; D016481:Helicobacter Infections / Q000276:immunology / Q000382:microbiology*; D016480:Helicobacter pylori / Q000235:genetics / Q000276:immunology*; D006801:Humans; D015151:Immunoblotting; D007564:Japan; D008969:Molecular Sequence Data
chemical_list: D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial; D001426:Bacterial Proteins; C080866:cagA protein, Helicobacter pylori