title: Identification of the major antigenic protein of Helicobacter cinaedi and its immunogenicity in humans with H. cinaedi infections.
abstract: Helicobacter cinaedi infection is now recognized as an increasingly important emerging disease. Its pathogenesis and epidemiological features are not fully understood, however. Here, we investigated the antigenic protein of H. cinaedi and the immunological response to it in H. cinaedi-infected patients. We constructed a genomic library of H. cinaedi from an H. cinaedi clinical isolate, and various H. cinaedi recombinant proteins were expressed. We identified the 30-kDa protein, encoded in an 822-bp H. cinaedi genome, as a major antigen, which was specifically recognized by serum from an H. cinaedi-immunized rabbit and H. cinaedi-infected patients. The gene encoding this 30-kDa antigen had high sequence similarity with genes encoding putative membrane proteins of bacteria. To evaluate whether the 30-kDa protein can be applied in serological testing for H. cinaedi infections, the recombinant protein was expressed in Escherichia coli as a His-tagged fusion protein and purified by Ni(2+) affinity chromatography. Western blot analysis revealed strong immunoreactivity of the 31-kDa fusion protein with serum antibody from patients infected with H. cinaedi, but such an immunoreaction was absent or was very weak with uninfected control serum. An enzyme-linked immunosorbent assay using this H. cinaedi major antigen showed significantly high antibody titers for H. cinaedi-infected subjects compared with those of various control groups. We therefore conclude that the 30-kDa putative membrane protein is a major antigen of H. cinaedi and is useful for immunological and serological testing for clinical diagnosis and for further epidemiological study of H. cinaedi infection in humans.
authors.affiliation: Department of Microbiology, Graduate School of Medical Sciences, Kumamoto University, Kumamoto 860-8556, Japan.
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Iwashita
authors.forename: Shigemoto
authors.initials: S
authors.lastname: Fujii
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Kawamura
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Okamoto
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Sawa
authors.forename: Takayuki
authors.initials: T
authors.lastname: Masaki
authors.forename: Akira
authors.initials: A
authors.lastname: Nishizono
authors.forename: Shuichi
authors.initials: S
authors.lastname: Higashi
authors.forename: Toshio
authors.initials: T
authors.lastname: Kitamura
authors.forename: Fumio
authors.initials: F
authors.lastname: Tamura
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Sasaki
authors.forename: Takaaki
authors.initials: T
authors.lastname: Akaike
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000595:Amino Acid Sequence; D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood*; D000942:Antigens, Bacterial / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D005260:Female; D016998:Helicobacter / Q000145:classification / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D016481:Helicobacter Infections / Q000276:immunology; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D008875:Middle Aged; D008969:Molecular Sequence Data; D011817:Rabbits; D017422:Sequence Analysis, DNA
chemical_list: D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D008565:Membrane Proteins