title: Immunization with Porphyromonas gingivalis enolase induces autoimmunity to mammalian α-enolase and arthritis in DR4-IE-transgenic mice.
abstract: OBJECTIVE
  To examine the hypothesis that the subset of rheumatoid arthritis (RA) characterized by antibodies to citrullinated α-enolase is mediated by Porphyromonas gingivalis enolase in the context of DR4 alleles.
  
  
  METHODS
  Recombinant human α-enolase and P gingivalis enolase, either citrullinated or uncitrullinated, were used to immunize DR4-IE-transgenic mice and control mice (class II major histocompatibility complex-deficient [class II MHC(-/-)] and C57BL/6 wild-type mice). Arthritis was quantified by measurement of ankle swelling in the hind paws and histologic examination. Serum IgG reactivity with α-enolase and citrullinated α-enolase was assayed by Western blotting and enzyme-linked immunosorbent assay (ELISA). Antibodies to peptide 1 of citrullinated α-enolase (CEP-1) and its arginine-bearing control peptide, REP-1, were also assessed by ELISA.
  
  
  RESULTS
  Significant hind-ankle swelling (≥0.3 mm) occurred in DR4-IE-transgenic mice immunized with citrullinated human α-enolase (9 of 12 mice), uncitrullinated human α-enolase (9 of 12 mice), citrullinated P gingivalis enolase (6 of 6 mice), and uncitrullinated P gingivalis enolase (6 of 6 mice). Swelling peaked on day 24. None of the control groups developed arthritis. The arthritic joints showed synovial hyperplasia and erosions, but there was a paucity of leukocyte infiltration. Antibodies to human α-enolase, both citrullinated and unmodified, and to CEP-1 and REP-1 were detectable in all immunized mice except the class II MHC(-/-) control mice.
  
  
  CONCLUSIONS
  This is the first animal model that links an immune response to P gingivalis enolase to an important subset of RA, defined by antibodies to citrullinated α-enolase in the context of DR4. The fact that arthritis and anti-CEP-1 antibodies were induced independent of citrullination of the immunizing antigen suggests that the unmodified form of α-enolase may be important in initiating the corresponding subset of human RA.
authors.affiliation: Kennedy Institute of Rheumatology, Imperial College London, London, UK.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Kinloch
authors.forename: Saba
authors.initials: S
authors.lastname: Alzabin
authors.forename: William
authors.initials: W
authors.lastname: Brintnell
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Wilson
authors.forename: Lillian
authors.initials: L
authors.lastname: Barra
authors.forename: Natalia
authors.initials: N
authors.lastname: Wegner
authors.forename: David A
authors.initials: DA
authors.lastname: Bell
authors.forename: Ewa
authors.initials: E
authors.lastname: Cairns
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Venables
mesh_terms: D000818:Animals; D001169:Arthritis, Experimental / Q000097:blood / Q000139:chemically induced / Q000276:immunology*; D015551:Autoimmunity / Q000187:drug effects* / Q000276:immunology; D004195:Disease Models, Animal; D015804:HLA-DR4 Antigen / Q000235:genetics*; D000949:Histocompatibility Antigens Class II / Q000235:genetics; D006801:Humans; D007114:Immunization; D007074:Immunoglobulin G / Q000097:blood; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D010751:Phosphopyruvate Hydratase / Q000009:adverse effects / Q000276:immunology / Q000494:pharmacology*; D016966:Porphyromonas gingivalis / Q000201:enzymology*; D011994:Recombinant Proteins / Q000494:pharmacology
chemical_list: D015804:HLA-DR4 Antigen; D000949:Histocompatibility Antigens Class II; D007074:Immunoglobulin G; D011994:Recombinant Proteins; D010751:Phosphopyruvate Hydratase