Antibodies Directed against a Peptide Epitope of a Klebsiella pneumoniae-Derived Protein Are Present in Ankylosing Spondylitis

Antonio Puccetti, Marzia Dolcino, Elisa Tinazzi, Francesca Moretta, Salvatore D'Angelo, Ignazio Olivieri, Claudio Lunardi

Research output: Contribution to journalArticlepeer-review


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.

Original languageEnglish
Pages (from-to)e0171073
JournalPLoS One
Issue number1
Publication statusPublished - 2017


  • Amino Acid Sequence
  • Antibodies, Bacterial/blood
  • Autoantigens/immunology
  • Bacterial Proteins/chemistry
  • Epitopes/immunology
  • Female
  • Humans
  • Inflammation/blood
  • Klebsiella pneumoniae/immunology
  • Male
  • Middle Aged
  • Peptide Library
  • Peptides/chemistry
  • Sequence Homology, Amino Acid
  • Spondylitis, Ankylosing/blood


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