State-of-the-art review of human autoimmune blistering diseases (AIBD).

Autoimmune blistering diseases (AIBDs) are a heterogenous group of skin conditions, broadly classified into two categories depending on the location of blister formation: intraepidermal blistering in the pemphigus group and subepidermal blistering in the pemphigoid group. Although AIBDs occur in both humans and animals, the arsenal of data for human AIBDs far exceeds those of their animal counterpart. Therefore, the main purpose of this review is to highlight existing knowledge, and recent advances in the diagnosis and management of AIBDs in humans - to serve as a road map for veterinary dermatologists. AREAS COVERED: Recent findings include complement-independent pathways in the pathogenesis of bullous pemphigoid, as well as the role of desmoglein and desmocollin autoantibodies in inducing acantholysis. Systemic glucocorticoids are the mainstay of treatment for AIBDs in humans, yet their long-term use is associated with severe adverse effects and complications, thereby limiting their use. Therefore, researchers have been exploring new and safer alternative therapeutic options for human AIBDs such as anti-CD20 monoclonal antibodies (Rituximab), Bruton's tyrosine kinase inhibitors (BTKi) and neonatal Fc receptor (FcRn) blockers. EXPERT OPINION: Randomised controlled trial (RCT) level evidence show that Rituximab and short-course GC regimes are more effective and safer than traditional GC treatment for human AIBDs. FcRn blockers such as SYNT001 have shown positive results in preliminary phase 2 clinical trials for treatment of human pemphigus; further trials are required. Rilzabrutinib (PRN1008), an orally administered BTKi, has recently completed phase 2 trials in pemphigus and is in a phase 3 RCT in humans.

Les maladies auto-immunes de clivage (AIBDs) est un groupe hétérogène de maladies cutanées, classifiées en deux catégories dépendantes de la localisation du clivage : intra-épidermique dans le groupe pemphigus et sous-épidermique dans le groupe pemphigoïde. Bien que les AIBDs existent chez l'homme et chez l'animal, l'arsenal de données pour les AIBDs de l'homme est bine plus développé que pour l'animal. Ainsi, le principal objectif de cette revue et de mettre en lumière les connaissances existantes et les avancées récentes du diagnostic et de la gestions des AIBDs de l'homme- afin de servir de carte de route pour les vétérinaires dermatologues. ZONES COUVERTES: Des données récentes comprennent les voies indépendantes du complément dans la pathogénie de la pemphigoïde bulleuse, ainsi que le rôle de la desmogléine et desmocolline dans la formation de l'acantholyse. Les corticoïdes (GC) systémiques sont le principal traitement des AIBDs de l'homme, bien que leur utilisation au long court avec effets secondaires sévères et complications, limitent leur utilisation. Ainsi, les chercheurs ont explorés de nouvelles options thérapeutiques alternatives plus sures pour les AIBDs de l'homme tels que les anticorps monoclonaux anti-CD20 (Ritumimab), les inhibiteurs de tyrosine kinase de Bruton (BTKi) et des bloqueurs de récepteur Fc néonataux (FcRn). POSITION DES EXPERTS: Les niveaux de preuves des essais contrôlés randomisés (RCT) montrent que le Ritumimab et les traitements de corticoïdes de courte durée sont plus efficaces et plus surs que les traitements traditionnels de GC pour les AIBDs de l'homme. Les bloqueurs FcRn tels que SYNT001 ont montré des résultats positifs dans les essais préliminaires cliniques de phase 2 pour le traitement du pemphigus de l'homme ; d'autres études sont nécessaires. Le Rilzabrutinib (PRN1008), un BTKi oral, a récemment fini un essai de phase 2 dans le pemphigus et une étude de phase 3 RCT chez l'homme.

Las enfermedades autoinmunes ampulosas (AIBDs, por sus siglas en inglés) son un grupo heterogéneo de afecciones cutáneas, que se clasifican ampliamente en dos categorías según la ubicación de la formación de ampollas: ampollas intraepidérmicas en el grupo de pénfigo y ampollas subepidérmicas en el grupo de penfigoides. Aunque los AIBD ocurren tanto en humanos como en animales, el arsenal de datos para los AIBD humanos supera con creces a los de sus homólogos animales. Por lo tanto, el propósito principal de esta revisión es resaltar el conocimiento existente y los avances recientes en el diagnóstico y manejo de los AIBD en humanos, para que sirva como una hoja de ruta para los dermatólogos veterinarios. ÁREAS CUBIERTAS: los hallazgos recientes incluyen vías independientes del complemento en la patogenia del penfigoide ampuloso, así como el papel de los autoanticuerpos de desmogleína y desmocolina en la inducción de acantólisis. Los glucocorticoides sistémicos son el pilar del tratamiento para los AIBD en humanos, sin embargo, su uso a largo plazo se asocia con efectos adversos graves y complicaciones, lo que limita su uso. Por lo tanto, los investigadores han estado explorando opciones terapéuticas alternativas nuevas y más seguras para las AIBDs humanas, como los anticuerpos monoclonales anti-CD20 (Rituximab), los inhibidores de la tirosina quinasa de Bruton (BTKi) y los bloqueadores del receptor de Fc neonatal (FcRn). OPINIÓN DE EXPERTOS: la evidencia a nivel de ensayos controlados aleatorios (RCT) muestra que los regímenes de Rituximab y GC de ciclo corto son más efectivos y más seguros que el tratamiento GC tradicional para los AIBD humanos. Los bloqueadores de FcRn como SYNT001 han mostrado resultados positivos en ensayos clínicos preliminares de fase 2 para el tratamiento del pénfigo humano; se requieren más pruebas. Rilzabrutinib (PRN1008), un BTKi administrado por vía oral, ha completado recientemente ensayos de fase 2 en pénfigo y se encuentra en un RCT de fase 3 en humanos.

As doenças autoimunes bolhosas (DAIBs) são um grupo heterógeno de dermatopatias, amplamente classificadas em duas categorias, dependendo da localização da formação das bolhas: bolhas intraepidermais no grupo do pênfigo e bolhas subepidermais no grupo penfigoide. Apesar das DAIBs ocorrerem tanto nos humanos quanto nos animais, o arsenal de dados sobre as DAIBs humanas é muito maior que o existente para animais. Desta forma, o principal propósito desta revisão é destacar o conhecimento existente, e os recentes avanços no diagnóstico e manejo das DAIBs em humanos - para servir como um roteiro para os dermatologistas veterinários. ÁREAS ABORDADAS: Os achados recentes incluem vias independentes do complemento na patogênese do penfigoide bolhoso, bem como a função dos autoanticorpos anti-desmogleína e anti-desmocolina induzindo acantólise. Glicocorticoides sistêmicos são a base do tratamento das DAIBs em humanos, apesar de seu uso prolongado ser associado a reações adversas e complicações graves,9R limitando assim o seu uso. Desta forma, os pesquisadores têm explorado novas alternativas terapêuticas mais seguras para as DAIBs humanas, tais como os anticorpos monoclonais anti-CD20 (Rituximab), inibidores de tirosina quinase de Bruton (BRKi) e bloqueadores de receptores Fc neonatais (FcRn). OPINIÃO DO ESPECIALISTA: Evidências de ensaios clínicos randomizados e controlados (RCT) demonstram que o Rituximab e terapias de curta duração com GC são mais eficazes e seguros que a terapia tradicional com GC para DAIBs humanas. Os bloqueadores de FcRn, como SYNT001, demostraram resultados positivos em ensaios clínicos preliminares de fase 2 para o tratamento de pênfigo humano; mais ensaios são necessários. Ensaios de fase 2 em pênfigo com o Rilzabrutinib (PRN1008), um BTKi administrado por via oral, foram concluídos e estão conduzindo os ensaios RCT de fase 3 em humanos.

[Therapy of bullous pemphigoid in a Warmblood gelding]. / Therapie eines bullösen Pemphigoids bei einem Warmblutwallach.

A 15-year-old Warmblood gelding was presented with multiple large, ulcerative, and crusty dermal lesions that had been existing for 4 years. Histopathology of a skin biopsy revealed cleft formation at the dermal-epidermal junction beneath the basal cells and above the basement membrane leading to the diagnosis of bullous pemphigoid. Immunosuppressive therapy with dexamethasone and azathioprine was initiated and after 14 weeks full remission of the ulcers was achieved. Scar tissue formation was evident in the areas of the formerly affected lesions. Following medication tapering over a period of 5 months, long-term therapy was continued with a maintenance dose of 0.5 mg/kg azathioprine daily. The ulcerative lesions recurred after 63 weeks of disease stabilization. Additionally, adverse drug reactions (acute laminitis and increased susceptibility to infections) were evident and the gelding was euthanized due to animal welfare considerations.

Bullous pemphigoid-like skin blistering disease in a rhesus macaque (Macaca mulatta).

Autoimmune bullous disease is very uncommon in non-human primates. We observed a bullous skin disease in a male rhesus monkey while conducting porcine islet xenotransplantation. Fifty days after the transplantation, multiple bullous skin lesions were observed. There was no mucosal involvement. Skin biopsy results demonstrated a subepidermal blister with no necrotic keratinocytes. Immunofluorescent staining showed linear IgG deposition at the roof of the blister. These skin lesions spontaneously disappeared. Considering these results, this monkey was diagnosed with bullous pemphigoid (BP). As far as we know, this is the first report of BP in non-human primates.

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.