Development of ELISA for the specific determination of autoantibodies against envoplakin and periplakin in paraneoplastic pemphigus

IntroductionIn paraneoplastic pemphigus (PNP), indirect immunofluorescence microscopy using rat bladder sections is widely used to search for circulating autoantibodies which are predominantly directed against envoplakin and periplakin. A sensitive and specific detection system for envoplakin/periplakin-specific autoantibodies is not yet available.MethodsOverlapping fragments spanning envoplakin and periplakin, respectively, were analyzed for their ability to bind PNP-specific autoantibodies by immunoblotting and ELISA in sera from patients with PNP (n = 31), pemphigus vulgaris (n = 30), and bullous pemphigoid (n = 50) as well as healthy volunteers (n = 140). The results were compared with those obtained by immunoblotting of extract of cultured human keratinocytes.ResultsImmunoblot analysis revealed that most sera contained antibodies against the N-termini of both plakins as well as against the C-terminus of envoplakin. By ELISA, reactivities against envoplakin1–481, envoplakin1626–2033, and periplakin1–324 were found in 25 (80.6%), 25 (80.6%), and 23 (74.2%) PNP sera, and in 1 (1.2%), 3 (3.7%), and 2 (2.5%) control sera, respectively.ConclusionsThe new ELISA based on an N-terminal fragment of envoplakin shows a high diagnostic accuracy to detect circulating autoantibodies in PNP. It is easy to be setup and standardized and can help to differentiate PNP patients from those with pemphigus vulgaris.