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Epitope mapping of BP230 leading to a novel enzyme-linked immunosorbent assay for autoantibodies in bullous pemphigoid

Authors


  • Funding sources
    This work was supported by the Deutsche Forschungsgemeinschaft through the Schleswig-Holstein Cluster of Excellence (EXC 306/1) to E.S. and D.Z.

  • Conflicts of interest
    I.M.B., C.D., C.P., L.K. and S.S. are employees of EUROIMMUN AG, Lübeck, Germany. W.Sc. and W.St. are board members of EUROIMMUN AG. D.Z. has received funding for scientific cooperation from EUROIMMUN AG. E.S. declares no conflict of interest.

Enno Schmidt.
E-mail: enno.schmidt@uk-sh.de

Summary

Background  Bullous pemphigoid (BP) is an autoimmune subepidermal blistering disease characterized by circulating autoantibodies against BP180 and BP230. For BP180, the NC16A domain has previously been identified as the main antigenic target in BP, while data about the diagnostic value of epitopes on BP230 were inconclusive.

Objectives  To identify the most appropriate epitopes on BP230 to be applied in a simple, sensitive, and highly specific enzyme-linked immunosorbent assay (ELISA) for routine detection of serum autoantibodies.

Methods  Ten overlapping linear fragments covering the whole length of BP230 were expressed in Escherichia coli. Based on Western blot analysis with sera from patients with BP (= 49) and healthy controls (= 94), the diagnostic performance of the fragments was compared by receiver operating characteristics curve analysis. The BP230-C3 fragment comprising the C-terminal portion (amino acids 2326–2649) was subsequently applied in a novel ELISA. The operating characteristics of this ELISA were analysed by probing sera from patients with BP (= 118), pemphigus vulgaris (= 50), rheumatoid arthritis and other inflammatory arthritides (= 170), and systemic lupus erythematosus (= 56), and from healthy blood donors (= 483).

Results  Among all the fragments, BP230-C3 provided the best efficiency in serologically diagnosing BP by Western blot. An ELISA employing BP230-C3 revealed a diagnostic sensitivity of 56·8% and specificity of 97·6%. Its diagnostic added value amounted to 4·2% compared with the anti-BP180-NC16A-4X ELISA alone.

Conclusions  Recombinant BP230-C3 is a suitable target antigen for the detection of serum autoantibodies against BP230.

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