The Cartilage Matrix Protein Subdomain of Type VII Collagen Is Pathogenic for Epidermolysis Bullosa Acquisita

Abstract

Epidermolysis bullosa acquisita (EBA) is an acquired bullous disease of the skin characterized by IgG autoantibodies against type VII (anchoring fibril) collagen. We previously defined four immunodominant antigenic epitopes within the noncollagenous 1 (NC1) domain of type VII collagen. In this study, we produced an additional recombinant fusion protein from the NC1 domain corresponding to the N-terminal 227 amino acids (residues 1 to 227), which contains homology with cartilage matrix protein (CMP). Using enzyme-linked immunosorbent assay and immunoblot analysis, we tested sera from EBA patients (n ‫؍‬ 32), bullous systemic lupus erythematosus patients (n ‫؍‬ 3), bullous pemphigoid patients (n ‫؍‬ 15), and normal humans (n ‫؍‬ 12). Twenty-six of 32 EBA sera and two of three bullous systemic lupus erythematosus sera reacted with the CMP domain, whereas none of the control sera did. Affinity-purified anti-CMP EBA antibodies injected into hairless mice produced the clinical, histological, immunological, and ultrastructural features of EBA. F(ab) 2 fragments generated from anti-CMP EBA autoantibodies did not induce disease. Our studies provide the first evidence that EBA autoantibodies to the CMP subdomain of NC1 are pathogenic and induce blister formation. This is the first antigenic epitope on type VII collagen demonstrated to be a pathogenic target for EBA autoantibodies. Epidermolysis bullosa acquisita (EBA) is a severe, chronic, subepidermal bullous disease of the skin and mucosa characterized by skin fragility, blisters in traumaprone sites, scarring with milia formation, and nail dystrophy.1 It is a prototypic autoimmune disease in which EBA patients have in vivo tissue-bound and circulating IgG autoantibodies directed against type VII collagen, a major component of anchoring fibrils, structures that anchor the epidermis onto the dermis.2-8 EBA autoantibodies bind to type VII collagen within anchoring fibrils. EBA patients have a diminution of normal anchoring fibrils and subsequent epidermal-dermal disadherence. The clinical appearance of EBA patients and the histology of their cutaneous lesions are often very reminiscent of hereditary dystrophic epidermolysis bullosa. These two diseases are etiologically unrelated but share the common feature of decreased anchoring fibrils. In the case of inherited dystrophic epidermolysis bullosa, the cause of decreased or absent anchoring fibrils is a genetic defect in the gene that encodes for type VII collagen. 9,10Type VII collagen is composed of three identical ␣ chains, each consisting of a 145-kd central collagenous triple-helical segment characterized by repeating Gly-X-Y amino acid sequences, flanked by a large 145-kd amino-terminal noncollagenous domain (NC1), and a small 34-kd carboxyl-terminal noncollagenous domain (NC2). 6 -8,11,12 Within the extracellular space, type VII collagen molecules form anti-parallel, tail-to-tail dimers stabilized by disulfide bonding through a small carboxylterminal NC2 overlap between two type VII collagen molecules. The anti-para...

B Cells, Dendritic Cells, and Macrophages Are Required To Induce an Autoreactive CD4 Helper T Cell Response in Experimental Epidermolysis Bullosa Acquisita

“…In vivo evidence for pathogenicity-relevant epitopes has been obtained by Ab transfer studies and immunization of mice. Transferring Abs directed to either the cartilage matrix protein domain (12) or multiple epitopes located within the FNIII domains (10) into mice induced skin blisters. Similarly, immunization with a protein covering epitopes from the end of the sixth to the beginning of the ninth FNIII (mCOL7C) induced skin lesions (20).…”

“…Especially, use of autoantibody transfer into mice has unraveled mechanisms leading to blister formation (7)(8)(9)(10)(11)(12)(13)). Yet, insights into the loss of tolerance and autoantibody production cannot be provided by autoantibody transfer models.…”

Immune reactivity to type VII collagen: implications for gene therapy of recessive dystrophic epidermolysis bullosa

“…The 612-codon COL7A1 open reading frame in this patient encodes the most immunogenic part of the type VII collagen NC1 domain, namely the cartilage matrix protein subdomain. [36][37][38][39] Expression of this protein region in patient 10, and the development of immune tolerance to the major epitopes therein, may thus explain this moderate naive response to full-length type VII collagen.…”

Clinical features and diagnosis of epidermolysis bullosa acquisita

“…In addition, IgA antitype VII collagen reactivity, either exclusively or in combination with IgG autoantibodies, is observed in 50-60% of patients [26,27,66]. The pathogenic relevance of antibodies against type VII collagen has clearly been shown in several in vivo and in vitro models [67][68][69][70][71] reviewed in [6]. Incubation of cryosections of normal human skin with sera of EBA patients followed by incubation with neutrophils from healthy volunteers leads to dermal-epidermal split formation [69].…”

“…Incubation of cryosections of normal human skin with sera of EBA patients followed by incubation with neutrophils from healthy volunteers leads to dermal-epidermal split formation [69]. Injection of antitype VII collagen antibodies in mice results in a skin disease that clinically and immunopathologically mimics the human disease [61, 67,[71][72][73]. While these models well reflect characteristic features of human EBA, they only reproduce the effector phase of EBA, i.e.…”