title: Antibodies Directed against a Peptide Epitope of a Klebsiella pneumoniae-Derived Protein Are Present in Ankylosing Spondylitis.
abstract: Ankylosing spondylitis (AS) is a chronic inflammatory arthritis of unknown origin. Its autoimmune origin has been suggested but never proven. Several reports have implicated Klebsiella pneumoniae as a triggering or perpetuating factor in AS; however, its role in the disease pathogenesis remains debated. Moreover, despite extensive investigations, a biomarker for AS has not yet been identified. To clarify these issues, we screened a random peptide library with pooled IgGs obtained from 40 patients with AS. A peptide (AS peptide) selected from the library was recognized by serum IgGs from 170 of 200 (85%) patients with AS but not by serum specimens from 100 healthy controls. Interestingly, the AS peptide shows a sequence similarity with several molecules expressed at the fibrocartilaginous sites that are primarily involved in the AS inflammatory process. Moreover, the peptide is highly homologous to a Klebsiella pneumoniae dipeptidase (DPP) protein. The antibody affinity purified against the AS peptide recognizes the autoantigens and the DPP protein. Furthermore, serum IgG antibodies against the Klebsiella DPP121-145 peptide epitope were detected in 190 of 200 patients with AS (95%), 3 of 200 patients with rheumatoid arthritis (1.5%) and only 1 of 100 (1%) patients with psoriatic arthritis. Such reactivity was not detected in healthy control donors. Our results show that antibodies directed against an epitope of a Klebsiella pneumoniae-derived protein are present in nearly all patients with AS. In the absence of serological biomarkers for AS, such antibodies may represent a useful tool in the diagnosis of the disease.
authors.affiliation: Immunology Area, Pediatric Hospital Bambino Gesù, Rome, Italy.
authors.forename: Antonio
authors.initials: A
authors.lastname: Puccetti
authors.affiliation: Immunology Area, Pediatric Hospital Bambino Gesù, Rome, Italy.
authors.forename: Marzia
authors.initials: M
authors.lastname: Dolcino
authors.affiliation: Department of Medicine, University of Verona, Verona, Italy.
authors.forename: Elisa
authors.initials: E
authors.lastname: Tinazzi
authors.affiliation: Department of Medicine, University of Verona, Verona, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Moretta
authors.affiliation: Rheumatology Department of Lucania, San Carlo Hospital of Potenza, Potenza, Italy.|Rheumatology Department of Lucania, Madonna delle Grazie Hospital of Matera, Matera, Italy.
authors.forename: Salvatore
authors.initials: S
authors.lastname: D'Angelo
authors.affiliation: Rheumatology Department of Lucania, San Carlo Hospital of Potenza, Potenza, Italy.|Rheumatology Department of Lucania, Madonna delle Grazie Hospital of Matera, Matera, Italy.
authors.forename: Ignazio
authors.initials: I
authors.lastname: Olivieri
authors.affiliation: Department of Medicine, University of Verona, Verona, Italy.
authors.forename: Claudio
authors.initials: C
authors.lastname: Lunardi
mesh_terms: D000595:Amino Acid Sequence; D000907:Antibodies, Bacterial / Q000097:blood* / Q000276:immunology*; D001324:Autoantigens / Q000276:immunology; D001426:Bacterial Proteins / Q000737:chemistry / Q000276:immunology*; D000939:Epitopes / Q000276:immunology*; D005260:Female; D006801:Humans; D007249:Inflammation / Q000097:blood / Q000276:immunology; D007711:Klebsiella pneumoniae / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D019151:Peptide Library; D010455:Peptides / Q000737:chemistry / Q000276:immunology*; D017386:Sequence Homology, Amino Acid; D013167:Spondylitis, Ankylosing / Q000097:blood* / Q000276:immunology*
chemical_list: D000907:Antibodies, Bacterial; D001324:Autoantigens; D001426:Bacterial Proteins; D000939:Epitopes; D019151:Peptide Library; D010455:Peptides