title: Pep19 drives epitope spreading in periodontitis and periodontitis-associated autoimmune diseases.
abstract: OBJECTIVE
  Epitope spreading is one of valid mechanisms operating in immunopathological processes of infection-induced autoimmune diseases. We hypothesized that the peptide 19 from Porphyromonas gingivalis heat shock protein (HSP) 60 (Pep19) may be the dominant epitope from which epitope-specific immune response to subdominant epitopes may diversify sequentially into autoimmune responses directed at human neoepitopes in P. gingivalis-induced periodontitis and autoimmune diseases. However, the exact feature and mechanism on how Pep19 may drive epitope spreading into human autoantigens in chronic periodontitis or P. gingivalis-induced experimental periodontitis has not been clarified. The present study was performed with the following specific aims: (i) to delineate retrospectively the features of epitope spreading by human cross-sectional analysis; (ii) to demonstrate prospectively the epitope spreading into new antigenic determinants in an ordered, predictable and sequential manner in experimental periodontitis; and (iii) to clarify the mechanism on how immunization with Pep19 may mobilize helper T cells or elicit B-cell responses to human autoantigens and neoantigen.
  
  
  METHODS
  The study was devised for two independent investigations - a cross-sectional analysis on clinical subjects and a prospective analysis on experimental periodontitis - each being subdivided further into two additional independent observations. Cross-sectional dot immunoblot pattern against a panel of peptides of P. gingivalis HSP60 and human HSP60 was performed among age-dependent healthy subjects and between healthy subjects, patients with chronic periodontitis and patients with autoimmune disease, to identify epitope spreading. A peptide-specific T-cell line was established for phenotype analysis and for proliferation assay to an array of identical peptides. An identical prospective analysis was performed in P. gingivalis-induced experimental periodontitis or in Pep19-immunized mice. Cross-reactivity of anti-Pep19 monoclonal antibody was also investigated.
  
  
  RESULTS
  A dominant immune response exclusively to Pep19 prevailed in healthy human subjects (before the age of 40) and mice that persisted in chronic periodontitis and autoimmune diseases without being replaced further by subsequent subdominant epitopes. A sequential epitope spreading provoked by Pep19 to subdominant autoantigen peptide 19 from human HSP60 (Hu19) in most healthy human subjects and mice, and to autoantigen peptide 9 from human HSP60 (Hu9) and neoantigen oxidized low-density lipoprotein (ox-LDL) in P. gingivalis-induced chronic periodontitis and autoimmune diseases could be demonstrated in a reproducible and predictable manner. T-cell proliferative activity to multiple autoantigens Hu19, Hu9 and ox-LDL, and cross-reactivity of anti-Pep19 monoclonal antibody to these epitopes may be proposed as cellular and molecular mechanisms responsible for the phenomenon. Moreover, the predictive value of Pep19 for Hu9 increased remarkably in the disease group when compared with that of the healthy group.
  
  
  CONCLUSIONS
  Taken together, epitope spreading to Hu19, Hu9 and ox-LDL provoked by Pep19 could be proposed as a solid phenomenon observed in P. gingivalis-induced chronic periodontitis and infection-induced autoimmune diseases in a reproducible and predictable manner. T-cell proliferative activity to these peptides and cross-reactivity of anti-Pep19 antibodies to multiple human autoantigens could be proposed as cellular and molecular mechanisms responsible for this phenomenon.
authors.affiliation: Department of Periodontology, School of Dentistry, Pusan National University, Yangsan City, Korea.
authors.forename: E-Y
authors.initials: EY
authors.lastname: Kwon
authors.affiliation: Department of Periodontology, School of Dentistry, Pusan National University, Yangsan City, Korea.
authors.forename: G S
authors.initials: GS
authors.lastname: Cha
authors.affiliation: Department of Molecular Biology, School of Natural Sciences, Pusan National University, Pusan, Korea.
authors.forename: E
authors.initials: E
authors.lastname: Jeong
authors.affiliation: Department of Periodontology, School of Dentistry, Pusan National University, Yangsan City, Korea.
authors.forename: J-Y
authors.initials: JY
authors.lastname: Lee
authors.affiliation: Department of Periodontology, School of Dentistry, Pusan National University, Yangsan City, Korea.
authors.forename: S-J
authors.initials: SJ
authors.lastname: Kim
authors.affiliation: Academy of Immunology and Microbiology, Institute for Basic Science, Pohang, Korea.|Department of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology, Pohang, Korea.|Division of Developmental Immunology, La Jolla Institute for Allergy and Immunology, La Jolla, CA, USA.
authors.forename: C D
authors.initials: CD
authors.lastname: Surh
authors.affiliation: Department of Periodontology, School of Dentistry, Pusan National University, Yangsan City, Korea.
authors.forename: J
authors.initials: J
authors.lastname: Choi
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D016301:Alveolar Bone Loss / Q000000981:diagnostic imaging / Q000473:pathology; D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood / Q000276:immunology; D000942:Antigens, Bacterial / Q000276:immunology*; D001324:Autoantigens / Q000276:immunology; D001327:Autoimmune Diseases / Q000150:complications* / Q000276:immunology*; D001402:B-Lymphocytes / Q000276:immunology; D002460:Cell Line; D049109:Cell Proliferation; D018834:Chaperonin 60 / Q000276:immunology; D002648:Child; D055113:Chronic Periodontitis / Q000150:complications* / Q000000981:diagnostic imaging / Q000276:immunology* / Q000473:pathology; D003429:Cross Reactions / Q000276:immunology; D003430:Cross-Sectional Studies; D003713:Dendritic Cells / Q000276:immunology; D003773:Dental Plaque / Q000276:immunology / Q000473:pathology; D000939:Epitopes / Q000187:drug effects*; D005260:Female; D005881:Gingiva / Q000276:immunology / Q000473:pathology; D006801:Humans; D007114:Immunization; D007074:Immunoglobulin G / Q000097:blood; D008077:Lipoproteins, LDL; D051379:Mice; D008810:Mice, Inbred C57BL; D016966:Porphyromonas gingivalis / Q000276:immunology* / Q000378:metabolism / Q000472:pathogenicity; D011446:Prospective Studies; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology; D055114:X-Ray Microtomography; D055815:Young Adult; D000076202:c-Mer Tyrosine Kinase / Q000276:immunology
chemical_list: D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial; D001324:Autoantigens; D018834:Chaperonin 60; D000939:Epitopes; D007074:Immunoglobulin G; D008077:Lipoproteins, LDL; C097072:MERTK protein, human; D000076202:c-Mer Tyrosine Kinase
keywords: Porphyromonas gingivalis; autoimmunity; epitope spreading; heat shock protein; periodontitis