Serological diagnostics in the detection of IgG autoantibodies against human collagen VII in epidermolysis bullosa acquisita: a multicentre analysis.

Epidermolysis bullosa acquisita (EBA) is a rare, potentially devastating autoimmune disease of the skin. IgG autoantibodies directed against type VII collagen (Col7), the major component of anchoring fibrils, induce skin fragility leading to cutaneous and mucocutaneous blister formation, which is mostly of a scarring phenotype. Thus, powerful and reproducible diagnostic assays are critical to establish the diagnosis of EBA early to avoid irreversible sequelae. The present international, retrospective multicentre study included a large cohort of patients with EBA and evaluated the diagnostic power of four different diagnostic assays for the detection of anti-Col7 IgG autoantibodies. Overall, 95 EBA sera and 200 control sera consisting of 100 bullous pemphigoid sera, 50 pemphigus vulgaris sera and 50 sera of healthy controls were tested for anti-Col7 IgG autoantibodies using indirect immunofluorescence (IIF), two commercial enzyme-linked immunosorbent assay (ELISA) systems and Western blot (WB) analysis. EBA sera were taken from patients with positive direct immunofluorescence and IgG reactivity in at least one of the immunoserological assays (IIF, ELISA, WB). A Col7-NC1/NC2 ELISA (MBL, Nagoya, Japan) showed the highest sensitivity (97·9%), followed by a Col7-NC1 ELISA (Euroimmun, Lübeck, Germany) (89·5%), WB with Col7-NC1 (85·3%), and IIF on saline-split human skin (74·7%). The specificities of both ELISA systems were comparable (NC1 98·7%, NC1/NC2 99·3%). Furthermore, WB was more sensitive than IIF, which was more specific. The two commercially available ELISA systems allow for a highly sensitive and specific diagnosis of EBA. The sensitivity of the Col7-NC1/NC2 ELISA is significantly higher compared with the ELISA based on the Col7-NC1 domain only.

Schmidt T ，Hoch M ，Lotfi Jad SS ，Solimani F ，Di Zenzo G ，Marzano AV ，Goebeler M ，Cozzani E ，Kern JS ，Sitaru C ，Lakoš Jukić I ，Sárdy M ，Uzun S ，Jedlickova H ，Gläser R ，Kaneda M ，Eming R ，Göpel G ，Ishii N ，Greene B ，Hashimoto T ，Hertl M ... -  《-》

Comparison of 3 type VII collagen (C7) assays for serologic diagnosis of epidermolysis bullosa acquisita (EBA).

Serologic diagnosis of epidermolysis bullosa acquisita (EBA) relies on the detection of circulating autoantibodies to type VII collagen (C7). We sought to compare the diagnostic performances of a commercialized enzyme-linked immunosorbent assay (ELISA) using C7 noncollagenous (NC) domains (C7-NC1/NC2 ELISA) and indirect immunofluorescence (IIF) biochip test on NC1-C7-expressing transfected cells (IIFT), with a full-length-C7 ELISA developed in our laboratory. C7-NC1/NC2 ELISA, IIFT, and full-length-C7 ELISA were run on 77 nonselected consecutive EBA sera. C7-NC1/NC2 ELISA, IIFT, and full-length-C7 ELISA were positive, respectively, for: 30%, 27%, and 65% of the 77 sera; 43%, 32%, and 80% of 44 sera labeling the salt-split-skin (SSS) floor (F) by IIF (SSS/F(+)); 9%, 22%, and 47% of 32 SSS/F(-) sera; 28%, 28%, and 58% of classic EBA; 41%, 41%, and 82% of inflammatory EBA; and 18%, 0%, and 55% of mucous-membrane-predominant EBA. Significant differences for all sera were found between: the 2 ELISAs for the 77 sera, SSS/F(+) and SSS/F(-) sera, and IIFT versus full-length-C7 ELISA. The retrospective design was a limitation. C7-NC1/NC2 ELISA and IIFT sensitivities for serologic diagnoses of EBA were low. Full-length-C7 ELISA was significantly more sensitive and could serve as a reference test.

Seta V ，Aucouturier F ，Bonnefoy J ，Le Roux-Villet C ，Pendaries V ，Alexandre M ，Grootenboer-Mignot S ，Heller M ，Lièvre N ，Laroche L ，Caux F ，Titeux M ，Hovnanian A ，Prost-Squarcioni C ... -  《-》

Diagnosis and disease severity assessment of epidermolysis bullosa acquisita by ELISA for anti-type VII collagen autoantibodies: an Italian multicentre study.

Epidermolysis bullosa acquisita (EBA) is a rare autoimmune mucocutaneous bullous disease caused by autoantibodies against type VII collagen, a component of anchoring fibrils that stabilizes dermoepidermal adherence. Type VII collagen is composed of a collagenous domain linked by the noncollagenous (NC)1 and NC2 domains.  To assess the repeatability, sensitivity and specificity of a recently developed enzyme-linked immunosorbent assay (ELISA) for detection of anti-type VII collagen autoantibodies, and to ascertain whether they may be a marker of disease activity in EBA. Using this ELISA, which was able to recognize autoantibodies against the NC1 and NC2 epitopes of type VII collagen, we tested 14 EBA sera, 30 healthy control sera and 113 disease control sera. In the EBA sera group, 12 out of the 14 samples were positive in ELISA, with autoantibody titres varying from 7·2 to 127·9UmL(-1) (cutoff value <6), the sensitivity of the method being 86%. Among the controls, only two bullous pemphigoid sera tested positive, the specificity being 98·6%. A good correlation was found between EBA disease severity, expressed as autoimmune bullous skin disorder intensity score, and the serum levels of anti-collagen VII autoantibodies, measured by ELISA (n =14; r=0·965; P=0·0001). The intra- and interassay coefficients of variation of the ELISA method ranged from 6·3% to 18·3%.  This NC1+NC2 ELISA can be a practical assay for the diagnosis of EBA. The correlation between autoantibody titres and disease severity suggests its usefulness as a marker of disease activity in EBA However, this should be confirmed by studies on larger series of patients.

Marzano AV ，Cozzani E ，Fanoni D ，De Pità O ，Vassallo C ，Berti E ，Parodi A ，Crosti C ，Cugno M ... -  《-》

Detection of anti-type VII collagen IgE antibodies in epidermolysis bullosa acquisita.

Epidermolysis bullosa acquisita (EBA) is a rare pemphigoid disease involving autoantibodies to type VII collagen (COL7), a major structural component of anchoring fibrils. IgE autoantibodies to type XVII collagen (BP180) have been identified in bullous pemphigoid (BP), the prototype of pemphigoid diseases. Although the pathogenic relevance of IgG anti-COL7 has been investigated, that of IgE in EBA remains unclear. To reveal the presence and pathogenic relevance of IgE anti-COL7 in EBA. We examined IgE antibodies in 109 patients with EBA by indirect immunofluorescence (IIF) and enzyme-linked immunosorbent assay (ELISA). IIF with normal human skin revealed IgE reactivity in the basement membrane zone in 29 (26·6%) cases. To verify whether the IgE antibodies were specific to COL7, we performed IIF with 21 clearly positive cases and the skin of a patient with dystrophic EBA, which does not involve COL7. All cases showed negative results, indicating that IgE antibodies were specific to COL7. In a modified IgG COL7 ELISA for IgE, 16 (14·7%) cases were positive (three and 13 cases were negative and positive on IIF, respectively). We compared anti-COL7 IgG and IgE, and found a weak but significant correlation (r = 0·459, P < 0·001). EBA is clinically divided into a mechanobullous (MB; noninflammatory) type and an inflammatory (INF) type resembling BP. Of the IIF-positive cases, 11 of 30 (37%) had INF and nine of 48 (19%) had MB. This study is the first to demonstrate the presence of circulating anti-COL7 IgE in patients with EBA, which may correlate with the clinical phenotype.

Koga H ，Teye K ，Yamashita K ，Ishii N ，Tsuruta D ，Nakama T ... -  《-》

Development of NC1 and NC2 domains of type VII collagen ELISA for the diagnosis and analysis of the time course of epidermolysis bullosa acquisita patients.

Epidermolysis bullosa acquisita (EBA) is an acquired autoimmune mechanobullous disease. EBA patients possess autoantibodies against type VII collagen which is composed of a collagenous domain flanked by non-collagenous NC1 and NC2 domains. It was reported that major epitopes reside within the NC1 domain and minor epitopes reside within NC2 domain. The aim of this study is to develop a sensitive and specific ELISA to facilitate the diagnosis of EBA. We developed ELISAs using recombinant NC1 domain produced by mammalian expression system and recombinant NC2 domain produced by mammalian or bacterial expression system to characterize autoantibodies in EBA. Next, we developed an ELISA using a combination of the NC1 (mammalian expression) and NC2 (bacterial expression). We tested the ELISAs with 49 EBA sera, 55 normal control sera, 20 pemphigus vulgaris and 20 bullous pemphigoid sera. When we evaluated the 49 EBA sera using the NC1 and NC2 ELISAs, 38 (77.5%) reacted with NC1 domain only, 7 sera (14.2%) reacted with both NC1 and NC2 domains, and one serum (2%) reacted with NC2 domain only. Therefore, to increase the sensitivity of the assay, we developed an ELISA coated with a mixture of recombinant NC1 and NC2 domains, resulting in 93.8% sensitivity and 98.1% specificity. By analyzing the time course of two EBA patients, ELISA scores fluctuated in parallel with their disease activity. We conclude that the NC1+NC2 ELISA can be a practical assay for the diagnosis and follow up of the antibody titers of EBA patients.

Saleh MA ，Ishii K ，Kim YJ ，Murakami A ，Ishii N ，Hashimoto T ，Schmidt E ，Zillikens D ，Shirakata Y ，Hashimoto K ，Kitajima Y ，Amagai M ... -  《-》