Molecular cloning of a cDNA encoding the porcine type XVII collagen noncollagenous 16 A domain and localization of the domain to the upper part of porcine skin basement membrane zone

Bullous pemphigoid is an autoimmune blistering human skin disease mediated by immunoglobulin (Ig)G autoantibodies targeting skin basement membrane component type XVII collagen, a transmembrane protein. Also designated BP180 and BPAG2, type XVII collagen is an extracellular matrix element essential for the connection between the epidermis and the underlying dermis. In addition to being a target antigen in the human disease bullous pemphigoid, type XVII collagen is also targeted by autoantibodies of canine, feline, equine and porcine patients suffering from a similar blistering skin disease. Previously, enzyme-linked immunosorbent assay and Western blot analyses have shown that autoantibodies from pigs affected with bullous pemphigoid recognize the human NC16A domain of type XVII collagen. To facilitate the development of porcine model of bullous pemphigoid, we isolated cDNA encoding the porcine type XVII collagen NC16A domain using a reverse transcription-polymerase chain reaction technique. The amino acids deduced from the NC16A cDNA showed 61% identity with the sequence of human NC16A. An antibody generated against a 20-amino acid peptide within the porcine NC16A localized the NC16A epitope to the upper part of porcine skin basement membrane zone. Our data provide further information of the porcine bullous pemphigoid target antigen and may help investigators for their further studies of this disease.

Equine bullous pemphigoid IgG autoantibodies target linear epitopes in the NC16A ectodomain of collagen XVII (BP180, BPAG2)

Bullous pemphigoid (BP) is an autoimmune subepithelial blistering dermatosis of humans, dogs, cats and pigs. It is characterized by skin-fixed and circulating IgG autoantibodies that target one or both BP antigens. An immunological homologue of BP in humans was diagnosed in two horses with cutaneous and mucosal ulcerations as well as microscopic subepithelial vesiculation. Immunological investigations revealed similar findings for both the horses. Direct immunofluorescence demonstrated the presence of IgG deposited linearly at the dermoepidermal junction in mucosal and skin biopsy specimens. Indirect immunofluorescence testing confirmed the existence of circulating basement membrane-specific IgG autoantibodies. Using intact and salt-split epithelial substrates, serum IgG were shown to target antigens situated not only at the basal, but also at the lateral and apical aspects of stratum basale keratinocytes. Immunoblotting and ELISA corroborated that the IgG from affected horses, but not those from normal controls, exhibited high immunoreactivity against the NC16A extracellular domain of type XVII collagen (BPAG2, BP180). Equine BP could be proposed, therefore, as another spontaneous model of this most common basement membrane autoimmune dermatosis of humans.

Molecular cloning of canine bullous pemphigoid antigen 2 cDNA and immunomapping of NC16A domain by canine bullous pemphigoid autoantibodies

The autoantibody-mediated subepidermal blistering skin disease bullous pemphigoid affects both humans and dogs. We previously demonstrated that canine bullous pemphigoid patient's autoantibodies targeted skin basement membrane component and a 180-kDa keratinocyte protein. We extend our works to partially isolate the cDNA encoding canine bullous pemphigoid antigen 2 (BPAg2, BP180). Total RNA extracted from a papillomavirus-immortalized canine keratinocyte cell line and a cultured canine squamous carcinoma cell line SCC 2/88 were used to isolate fragments of cDNA encoding BPAg2 by reverse transcription-PCR and 5'-rapid amplification of cDNA end. The isolated sequence included the 5'-untranslated region, the entire intracellular, transmembranous, and extracellular NC16A autoantigenic domains, plus a small segment of the collagenous domain. Sequence analyses of the isolated cDNA showed 87 and 85% identities between canine and human at the nucleotide sequence and at the deduced amino acid sequence levels, respectively. The canine BPAg2 sequence was confirmed by a rabbit antibody raised against a 18-amino acid peptide deduced from the canine NC16A nucleotide sequence. Autoantibodies from canine bullous pemphigoid patients' sera recognized epitopes within the human NC16A domain. The cloning of the cDNA encoding this disease-associated protein may allow us to develop a canine model in dissecting the immunopathologic mechanism underlying bullous pemphigoid.

Novel feline autoimmune blistering disease resembling bullous pemphigoid in humans: IgG autoantibodies target the NC16A ectodomain of type XVII collagen (BP180/BPAG2)

In humans and dogs, bullous pemphigoid (BP) is an autoimmune blistering disease associated with the production of basement membrane autoantibodies that target the 180-kd type XVII collagen (BP180, BPAG2) and/or the 230-kd plakin epidermal isoform BPAG1e (BP230). In two adult cats, an acquired dermatosis and stomatitis was diagnosed as BP subsequent to the fulfillment of the following criteria: 1) presence of cutaneous vesicles, erosions, and ulcers; 2) histologic demonstration of subepidermal vesiculation with inflammatory cells, including eosinophils; 3) in vivo deposition of IgG autoantibodies at the epidermal basement membrane zone; and 4) serum IgG autoantibodies targeting a 180-kd epidermal protein identified as type XVII collagen. In both cats, the antigenic epitopes targeted by IgG autoantibodies were shown to be situated in the NC16A ectodomain of type XVII collagen, a situation similar to that of humans and dogs with BP. Feline BP therefore can be considered a clinical, histopathologic, and immunologic homologue of BP in humans and dogs.

Immunomapping of basement membrane zone macromolecules in canine salt-split skin

Certain macromolecules of human and canine cutaneous basement membrane zone (BMZ) have shown to have responsibilities for pathogenesis of mechanobullous skin diseases. Salt-split skin by 1 M NaCl have been used for diagnosis of human mechanobullous diseases. However, there have been no studies to characterize canine salt-split skin. Electron microscopy of canine salt-split skin showed the separation within lamina lucida. Indirect immunofluorescence revealed the roof of the cleft was labeled by human patient serum with bullous pemphigoid, whereas laminin, laminin 5, type IV and type VII collagen were labeled at the bottom of the cleft. It is suggested that immunomapping of salt-split skin may be useful for the differential diagnosis of canine mechanobullous diseases.

Paraneoplastic bullous stomatitis in a horse

An adult horse with a 2-month history of anorexia, ataxia, and oral blisters had developed these clinical signs just prior to the appearance and growth of a cervical mass. Bullous stomatitis was characterized histologically as subepidermal clefting. Clinical signs were unresponsive to treatment with antibiotics or corticosteroids; however, surgical removal of the mass coincided with remission of all signs. Histologic findings of the mass were consistent with hemangiosarcoma. Results of indirect immunofluorescence and immunoprecipitation on frozen serum from the horse were characteristic of paraneoplastic pemphigus in human beings, a newly recognized mucocutaneous autoimmune disease associated with neoplasia.

Canine bullous pemphigoid (BP): identification of the 180-kd canine BP antigen by circulating autoantibodies

Human bullous pemphigoid (BP) is an immune-mediated blistering disease characterized by autoantibodies against BP antigens (230/180 kd), which are constitutive glycoproteins of hemidesmosomes found in basal keratinocytes. Blistering diseases similar to human BP have been reported in dogs. IgG deposits at the basement membrane zone (BMZ) are a common feature of canine BP. Although circulating anti-BMZ IgG autoantibodies have been demonstrated in some cases of canine BP, the specific skin protein targeted by these autoantibodies has not been identified. In this study, we characterized the antigenic target of the autoantibodies in the serum from a 3-year-old castrated male Pit Bull Terrier with BP. Direct immunofluorescence of the patient's skin demonstrated IgG deposits at the dermal-epidermal junction. Indirect immunofluorescence demonstrated autoantibodies in the patient's serum that stained the epidermal roof of salt-split canine skin and left the dermal floor unstained. These serum autoantibodies did not stain normal intact dog skin but labeled intact bovine tongue. Direct immunoelectron microscopy of the dog's skin revealed IgG deposits within the hemidesmosomes of the basal keratinocytes. Western immunoblotting experiments showed that canine keratinocytes express both the 230-kd and 180-kd bullous pemphigoid antigens, and the autoantibodies from the patient's serum recognized the 180-kd bullous pemphigoid antigen in proteins extracted from canine and human keratinocytes. Canine BP has many parallel features with human BP including similar immune deposition of IgG within hemidesmosomes and a hemidesmosome-associated 180-kd glycoprotein target for circulating autoantibodies.

Use of tetracycline and niacinamide for treatment of autoimmune skin disease in 31 dogs

A combination of niacinamide and tetracycline was used to treat 31 dogs with various autoimmune skin diseases (discoid lupus erythematosus, pemphigus foliaceus, pemphigus erythematosus, and bullous pemphigoid). Of the 20 dogs with discoid lupus erythematosus, 70% had excellent or good response to treatment. Serious side effects were not noticed in any dog.

Avidin-biotin-peroxidase complex immunohistochemistry to detect immunoglobulin in formalin fixed skin biopsies in canine autoimmune skin disease

Avidin-biotin-peroxidase complex immunohistochemistry was used on formalin fixed, paraffin embedded, trypsin digested, skin biopsies to detect immunoglobulin deposition in dogs with autoimmune skin disease. Immunostaining by the avidin-biotin-peroxidase complex technique revealed intercellular and/or basement membrane immunoglobulin deposits in 27 of 28 dogs considered to have autoimmune skin disease by clinical and histological evaluation and in six of 19 dogs considered to have autoimmune skin disease by clinical evaluation but without histological confirmation. Similar immunostaining was not evident in five biopsies of normal skin or in biopsies from four dogs with noninflammatory dermatoses, but was present in biopsies from one of ten dogs considered by clinical and histological criteria to have an inflammatory dermatosis other than autoimmune skin disease. Detection of immunoglobulin deposits in skin biopsies by avidin-biotin-peroxidase complex immunohistochemistry offers numerous advantages over conventional immunofluorescence methods including the opportunity to precisely compare histological and immunological findings.

Diagnosis of autoimmune skin disease in the dog: correlation between histopathologic, direct immunofluorescent and clinical findings

Histopathologic, immunopathologic and clinical evaluation of two hundred thirty dogs resulted in a diagnosis of canine autoimmune skin disease (AISD) in eighty four of the suspected cases. Pemphigus foliaceus was the most common diagnosis, followed by bullous pemphigoid and pemphigus vulgaris. The highest percentage of cases were mixed breeds, followed by shelties, collies, German shepherds and poodles. There was no apparent age or sex predilection. Eighty seven percent of the eighty four cases of AISD were diagnosed on the basis of supportive clinical criteria in addition to compatible histopathologic and/or direct immunofluorescent findings. Thirteen percent of the cases with a final clinical diagnosis of AISD lacked supportive immunohistopathologic criteria on biopsy and the diagnosis was based upon clinical appearance, exclusion of other dermatoses, and response to immunosuppressive therapy. This latter group included four cases of SLE diagnosed using a combination of clinical criteria and a positive test for antinuclear antibody. Thirty three percent of the AISD cases were diagnosed on the basis of compatible findings on both histopathology and direct immunofluorescence. A histopathologic diagnosis of AISD was made in sixty nine percent of the cases. Positive direct immunofluorescence was found in fifty two percent of the cases. Thirty five percent of the AISD cases were diagnosed on histopathologic criteria without supportive immunofluorescent findings, while nineteen percent had positive direct immunofluorescence with nonspecific histopathologic changes. The number of definitive positive results was greater for direct immunofluorescence (38%) than for histopathology (25%). There was an equal incidence (21%) of false positive results among non-AISD cases with both tests. Indirect immunofluorescence appears to have little value in the diagnosis of canine AISD. The recommended diagnostic approach to canine AISD involves the use of both histopathologic and immunopathologic evaluations.

Observations of the immunopathology and therapy of canine pemphigus and pemphigoid

Immunopathologic evaluation of 27 dogs with pemphigus and pemphigoid demonstrated that direct immunofluorescence testing was vastly superior to indirect immunofluorescence testing for diagnosis. Therapeutic studies in 31 dogs with pemphigus and pemphigoid demonstrated that glucocorticoids given for systemic effect were unsatisfactory as the sole form of treatment because of lack of efficacy of unacceptable side effects, or both, in over 50% of the cases.

Bullous pemphigoid refractory to recommended dosage of prednisolone in a dog

Bullous pemphigoid in a dog was diagnosed on the basis of clinical, histopathologic, and immunologic criteria. There were widespread ulcerative lesions of the skin. Numerous ulcerative lesions and occasional bullous lesions were on the oral mucous membranes. Histopathologic changes included dermal-epidermal separation, with subepidermal production of bullae. Direct immunofluorescent staining of the skin revealed depositions of immunoglobulin G and of the 3rd component of the complement system. Indirect immunofluorescent staining of donor skin sections pretreated with patient's serum revealed antibasement membrane antibody in the patient's serum. Most of the data in the serum immune profile were within normal ranges. Prednisolone therapy did not effect remission at the dosage of 4.4 mg/kg/day, but led to the beginning of remission within 7 days at a dosage of 6.6 mg/kg/day. The dosage was gradually reduced to 1.1 mg/kg, at 30 days, after which the drug was given on alternate days at that dosage. The healing was complete within 35 days, without any remissions when the dog was last examined (ie, over 6 months).

Pemphigus and pemphigoid in dog and man: comparative aspects

A review of canine pemphigus vulgaris, pemphigus vegetans, pemphigus foliaceus, pemphigus erythematosus, and bullous pemphigoid shows them to share many clinicopathologic similarities with their human counterparts. Because of their numerous analogies in clinical presentations, histopathologic and immunopathologic findings, and therapeutic results, canine and human pemphigus and pemphigoid may represent a valuable area for comparative dermatologic research.

Bullous autoimmune skin disease in the dog: (2) immunopathological assessment

The immunological examinations of two cases of pemphigus vulgaris and four cases of bullous pemphigoid in the dog are reported. Deposits of immunoglobulin and complement were identified betweeen epithelial cells of the pemphigus cases and at the epithelial/connectivce tissue junction in the pemphigoid dogs. The bullous autoimmune diseases must be considered in the differential diagnosis of mucosal and skin ulceration in the dog.

Bullous autoimmune skin disease in the dog: (1) clinical and pathological assessment

The clinical and pathological findings of two cases of pemphigus vulgaris and four cases of bullous pemphigoid in the dog are reported. Clinically these cases were typified by ulcerative lesions of the oral mucous membranes, mucocutaneous junctions and skin. Pathologically there were intraepithelial separation and bulla formation in one of the cases of pemphigus and subepithelial separation and bulla formation in all cases of pemphigoid.