INTRODUCTION: In 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.
METHODS: Overlapping 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.
RESULTS: Immunoblot 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 envoplakin(1-481), envoplakin(1626-2033), and periplakin(1-324) 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.
CONCLUSIONS: The 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.