title: Prevalence of collagen VII-specific autoantibodies in patients with autoimmune and inflammatory diseases.
abstract: BACKGROUND
  Autoimmunity to collagen VII is typically associated with the skin blistering disease epidermolysis bullosa acquisita (EBA), but also occurs occasionally in patients with systemic lupus erythematosus or inflammatory bowel disease. The aim of our present study was to develop an accurate immunoassay for assessing the presence of autoantibodies against collagen VII in large cohorts of patients and healthy donors.
  
  
  METHODS
  Based on in silico antigenic analysis and previous wetlab epitope mapping data, we designed a chimeric collagen VII construct containing all collagen VII epitopes with higher antigenicity. ELISA was performed with sera from patients with EBA (n = 50), Crohn's disease (CD, n = 50), ulcerative colitis (UC, n = 50), bullous pemphigoid (BP, n = 76), and pemphigus vulgaris (PV, n = 42) and healthy donors (n = 245).
  
  
  RESULTS
  By ELISA, the receiver operating characteristics analysis yielded an area under the curve of 0.98 (95% CI: 0.9638-1.005), allowing to set the cut-off at 0.32 OD at a calculated specificity of 98% and a sensitivity of 94%. Running the optimized test showed that serum IgG autoantibodies from 47 EBA (94%; 95% CI: 87.41%-100%), 2 CD (4%; 95% CI: 0%-9.43%), 8 UC (16%; 95% CI: 5.8%-26%), 2 BP (2.63%; 95% CI: 0%-6.23%), and 4 PV (9.52%; 95% CI: 0%-18.4%) patients as well as from 4 (1.63%; 95% CI: 0%-3.21%) healthy donors reacted with the chimeric protein. Further analysis revealed that in 34%, 37%, 16% and 100% of sera autoantibodies of IgG1, IgG2, IgG3, and IgG4 isotype, respectively, recognized the recombinant autoantigen.
  
  
  CONCLUSIONS
  Using a chimeric protein, we developed a new sensitive and specific ELISA to detect collagen specific antibodies. Our results show a low prevalence of collagen VII-specific autoantibodies in inflammatory bowel disease, pemphigus and bullous pemphigoid. Furthermore, we show that the autoimmune response against collagen VII is dominated by IgG4 autoantibodies. The new immunoassay should prove a useful tool for clinical and translational research and should improve the routine diagnosis and disease monitoring in diseases associated with collagen VII-specific autoimmunity.
authors.affiliation: Department of Dermatology, University of Freiburg, Hauptstr, 7, Freiburg 79104, Germany.
authors.forename: Emilia
authors.initials: E
authors.lastname: Licarete
authors.forename: Susanne
authors.initials: S
authors.lastname: Ganz
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Recknagel
authors.forename: Giovanni
authors.initials: G
authors.lastname: Di Zenzo
authors.forename: Takashi
authors.initials: T
authors.lastname: Hashimoto
authors.forename: Michael
authors.initials: M
authors.lastname: Hertl
authors.forename: Giovanna
authors.initials: G
authors.lastname: Zambruno
authors.forename: Gheorghe
authors.initials: G
authors.lastname: Hundorfean
authors.forename: Jonas
authors.initials: J
authors.lastname: Mudter
authors.forename: Markus F
authors.initials: MF
authors.lastname: Neurath
authors.forename: Leena
authors.initials: L
authors.lastname: Bruckner-Tuderman
authors.forename: Cassian
authors.initials: C
authors.lastname: Sitaru
mesh_terms: D001323:Autoantibodies / Q000097:blood*; D001327:Autoimmune Diseases / Q000097:blood* / Q000276:immunology; D002097:C-Reactive Protein / Q000378:metabolism; D002478:Cells, Cultured; D024143:Collagen Type VII / Q000235:genetics / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay; D018604:Epitope Mapping; D000939:Epitopes / Q000235:genetics / Q000276:immunology; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D007249:Inflammation / Q000097:blood* / Q000276:immunology; D018836:Inflammation Mediators / Q000378:metabolism; D015202:Protein Engineering; D017434:Protein Structure, Tertiary / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000276:immunology
chemical_list: D001323:Autoantibodies; D024143:Collagen Type VII; D000939:Epitopes; D007074:Immunoglobulin G; D018836:Inflammation Mediators; D011993:Recombinant Fusion Proteins; D002097:C-Reactive Protein