anti-Dsg3 IgG Research Articles

Differences among Indian and European pemphigus patients based on demographics, clinical parameters and propensity for relapse: results of a prospective bicontinental cohort study.

Limited studies have explored pemphigus variations among different ethnic groups residing in their respective geographical locations. This bicontinental study aimed to compare clinical and immunological parameters in Indian and European pemphigus patients in complete remission, off therapy, or on minimal therapy. 105 patients (India, n= 75; Bulgaria, n=15; Greece, n=15) with pemphigus vulgaris (PV) or pemphigus foliaceous (PF) in complete remission on minimal therapy (n=64) or complete remission off therapy (n=41) were recruited. Demographic, clinical, and immunological parameters were compared. Indian patients were significantly younger, the maximal disease severity during the preceding active disease phase was significantly lower, and treatment duration until complete remission was significantly shorter, compared to European patients. European patients had significantly higher anti-Dsg3 serum levels and higher IgG positivity rate based on direct immunofluorescence microscopy at baseline. Furthermore, European patients revealed higher CD19, CD19+ CD27+ cell counts, compared with patients from India. Of note, none of the European patients (n=30) relapsed within the study period, in contrast to 29/75 (38.6%) Indian patients. Treatment strategies differed significantly between the two cohorts, with more frequent utilization of rituximab to achieve remission in the Indian cohort, while prednisolone was more widely used for maintaining remission in the European cohort. The observed heterogeneity of pemphigus among patients of different ethnicities in terms of demographics, clinical parameters, and propensity for relapse may be due to genetic background or different treatment strategies.

049 Phenotypic and functional analysis of autoreactive CD4+ T cell responses against Desmoglein 3 epitopes in pemphigus vulgaris

Pemphigus vulgaris (PV) is characterized by loss of immune tolerance against the desmosomal components Desmoglein (Dsg) 1 and 3 resulting in pathogenic IgG autoantibodies which cause loss of epithelial cell adhesion in skin and mucous membranes. Autoreactive CD4+ T cells have been shown to be key drivers of PV as they help B cells in maturation and anti-Dsg3 IgG production. Their detection and further characterization is thus important for identification of potential checkpoints and development of novel therapies, although being quite challenging due to their low frequency in peripheral blood.

Detection of rare autoreactive T cell subsets in patients with pemphigus vulgaris.

Analysis of T lymphocyte proliferation and activation after antigenic or mitogenic stimulation is a vital parameter used in the diagnosis of various immuno-deficiencies and during the monitoring of treatment responses. Most applied techniques are based on the incorporation of tritiated thymidine (3H-TdR) or ELISPOT analysis, both rely on rather time-consuming/-intensive ex vivo protocols or encompass inherent drawbacks such as the inability to distinguish specific cell populations (3H-TdR, ELISPOT) or focus on a single cytokine (ELISPOT). Here we aimed at characterizing the rapid expression of intracellular CD154 (CD40L) as a marker for rare antigen-specific CD4+ T cells in pemphigus vulgaris (PV). Upon stimulation with human desmoglein (Dsg) 3, the major autoantigen in PV, the expression of CD154 was significantly increased in PV patients compared to healthy controls (HC) and correlated with anti-Dsg3 IgG titers. Patients with active disease showed higher numbers of Dsg3-reactive CD4+ T cells in CXCR5+ T follicular helper cells. In remittent PV and HC, CXCR5+CD4+ T cells remained largely unaffected by Dsg3. IL-17 and IL-21 expression were significantly induced only in CD154+CD4+ T cells from PV patients, lending themselves as potential novel treatment targets. Additionally, stimulation with immunodominant Dsg3-derived epitopes strongly induced a CD4+ T cell response via CD40-CD154 interaction similar to the human Dsg3 protein. We here established a rapid ex vivo assay allowing the detection of Dsg3-reactive CD4+ T cells from activated systemically available PBMCs, which further supports the crucial concept of antigen-specific T cells in the pathogenesis of PV.

Innate immune activation as cofactor in pemphigus disease manifestation.

Molecular mechanisms underlying auto-antibody-induced acantholysis in pemphigus vulgaris are subject of current research to date. To decipher the discrepancy between ubiquitous antibody binding to the epidermal desmosomes, but discontinuous disease manifestation, we were able to identify Ultraviolet A (UVA) as a cofactor for acantholysis. UVA induces interleukin (IL)-1 secretion in keratinocytes, mirroring innate immune system activation. In an in vitro keratinocyte dissociation assay increased fragmentation was observed when UVA was added to anti-Desmoglein 3 Immunoglobulins (anti-Dsg3 IgG). These results were confirmed in skin explants where UVA enhanced anti-Dsg3-mediated loss of epidermal adhesion. The UVA-mediated effect was blocked in vitro by the pan-caspase-inhibitor zVAD-fmk. Thus, we introduce UVA as a caspase-dependent exogenous cofactor for acantholysis which suggests that local innate immune responses largely contribute to overt clinical blister formation upon autoantibody binding to epidermal cells in pemphigus vulgaris.

Trunk-dominant and classic facial pemphigus foliaceus in dogs - comparison of anti-desmocollin-1 and anti-desmoglein-1 autoantibodies and clinical presentations.

Canine trunk-dominant pemphigus foliaceus (PF) is mentioned rarely in the literature. The goal of this study was to provide clinical description of trunk-dominant PF and to demonstrate the prevalence of serum antikeratinocyte, anti-desmocollin-1 (DSC1) and anti-desmoglein-1 (DSG1) antibodies, and determine their diagnostic value in this particular PF phenotype. Clinically relevant information was collected from 31, 25 and 34 dogs with trunk-dominant and facial PF and superficial pyoderma (SP), respectively. Sera from these dogs were tested for antikeratinocyte, anti-DSC1 and anti-DSG1 antibodies using indirect immunofluorescence on canine tissues and DSC1- and DSG1-transfected cells. Sera from healthy dogs and dogs with clinically irrelevant diseases served as controls. Footpad involvement and grouped/polycyclic lesion organisation were identified as features of both PF phenotypes, and not of SP. Antikeratinocyte immunoglobulin (Ig)G was not specific for canine PF. By contrast, antigen-specific IgG was detected only in PF sera; anti-DSC1 IgG in 100% and 58% of dogs with facial and trunk-dominant PF, respectively, and anti-DSG1 IgG in 7% of dogs with trunk-dominant PF only. Trunk-dominant PF shares DSC1 as a major autoantigen with facial PF. The ability to detect anti-DSC1 IgG is lower in trunk-dominant PF, yet despite the lower sensitivity, the positive predictive value and accuracy of this particular anti-DSC1 IgG test are high. A negative test result, however, cannot exclude the diagnosis, and characteristic clinical features such as footpad involvement and/or grouped/polycyclic lesions must be considered when distinguishing trunk-dominant PF from its most relevant differential diagnosis: SP.

Disease progression and response to therapy in pemphigus based on a registry.

Pemphigus diseases are potentially life-threatening and rare autoimmune bullous disorders characterized by blisters and erosions of the skin and mucous membranes. These disorders can be largely divided into two major subtypes: pemphigus vulgaris (PV) and pemphigus foliaceus (PF). The objective of this study was to evaluate the autoantibody profile and response to therapy of PV and PF patients by analyzing the clinicopathological data from a registry for bullous autoimmune dermatoses. In a retrospective study, data from 69 patients with PV and PF were included in the analysis. The Autoimmune Bullous Skin Intensity Score (ABSIS) was used to assess the clinical course, remissions, relapses and severity of the disease at first manifestation and throughout the observation period. ELISA was performed to assess levels of anti-desmoglein (Dsg)-1 and anti-Dsg3 IgG serum autoantibodies. The mean remission time in PV and PF patients was 63 weeks. PV patients with mucosal involvement showed a more favorable healing process. In PV patients with a moderate/high anti-Dsg1 IgG serum level at baseline, anti-Dsg3 IgG levels decreased during the observation period. Our study provides additional insights into the clinical course of patients with PV and PF, revealing that a mucosal phenotype is associated with a higher tendency towards remission.

The Diversity of Serum Anti-DSG3 IgG Subclasses Has a Major Impact on Pemphigus Activity and Is Predictive of Relapses After Treatment With Rituximab.

IntroductionWe studied the distribution and in vitro pathogenicity of anti-DSG3 IgG subclasses during the course of pemphigus vulgaris (PV).MethodsWe longitudinally studied the distribution of anti-DSG3 IgG subclasses (before versus after treatment) in sera from PV patients, using an addressable-laser bead immunoassay (ALBIA). The in vitro pathogenicity of corresponding sera was tested using keratinocyte dissociation and immunofluorescence assays.ResultsSixty-five sera were assessed at baseline (33 from patients treated with rituximab and 32 with corticosteroids). Sixty-three percent of these baseline sera contained 2 or more anti-DSG3 IgG subclasses versus 35.7% of sera from patients in complete remission (CR) and 75.0% of sera from patients with persistent disease activity after treatment. IgG4 was the most frequently detected anti-DSG3 IgG subclass, both in patients with disease activity and in those in CR. The presence of three or more anti-DSG3 IgG subclasses was predictive of relapse, in particular when it included IgG3, with a positive predictive value of 62.5% and a negative predictive value of 92%. While anti-DSG3 IgG4 Abs from sera collected before treatment were most often pathogenic, anti-DSG3 IgG4 from sera collected after treatment were pathogenic only after adjusting their titer to the one measured before treatment. The IgG3 fraction containing anti-DSG3 Abs also had an in vitro pathogenic effect. The disappearance of the pathogenic effect of some sera after removal of anti-DSG3 IgG3 suggested an additional effect of this IgG subclass.ConclusionThe serum levels and number of anti-DSG3 IgG subclasses drive the pathogenic effect of pemphigus sera and may predict the occurrence of relapses.

IgM to IgG Class Switching Is a Necessary Step for Pemphigus Phenotype Induction in Desmoglein 3–Specific B Cell Receptor Knock-in Mouse

Pemphigus vulgaris is an autoimmune blistering disease caused by IgG targeting desmoglein 3 (Dsg3), an adhesion molecule of keratinocytes. Anti-Dsg3 IgG production is prevented in healthy individuals, but it is unclear how Dsg3-specific B cells are regulated. To clarify the immunological condition regulating Dsg3-specific B cells, a pathogenic anti-Dsg3 Ig (AK23) knock-in mouse was generated. AK23 knock-in B cells developed normally without undergoing deletion or acquiring an anergic phenotype in vivo. The knock-in B cells showed Ca2+ influx upon IgM cross-linking and differentiated into AK23-IgG+ B cells after LPS and IL-4 stimulation in vitro that induced a pemphigus phenotype after adoptive transfer into Rag2 -/- mice. However, the knock-in mouse itself produced AK23-IgM but little IgG without blisters in vivo. Dsg3 immunization and skin inflammation caused AK23-IgG production and a pemphigus phenotype in vivo. Furthermore, Fcgr2b deficiency or haploinsufficiency spontaneously induced AK23-IgG production and a pemphigus phenotype with poor survival rates in AK23 knock-in mice. To assess Fcgr2b involvement in Ig class-switch efficiency, postswitch transcripts of B cells were quantified and significantly higher in Fcgr2b -/- and Fcgr2b +/- mice than wild-type mice in a gene dose-dependent manner. Finally, RNA sequencing revealed reduced expression of FCGR2B and FcγRIIB-related genes in patient B cells. These results indicated that Dsg3-specific B cells do not spontaneously perform pathogenic class switching in vivo, and pemphigus phenotype induction was prevented under normal conditions. Attenuated FcγRIIB signaling is also one of the drivers for pathogenic class switching and is consistent with immunological features identified from clinical samples. This study unveiled a characteristic immune state silencing autoreactive B cells in mice.

Intravenous Ig Regulates Anti-Desmoglein 3 IgG Production in B220– Antibody-Producing Cells in Mice with Pemphigus Vulgaris

Intravenous Ig (IVIG) is a treatment option for intractable cases of pemphigus vulgaris (PV), an autoimmune blistering disease caused by autoantibodies against desmoglein 3 (DSG3). To investigate the efficacy of IVIG on autoantibody secretion, we produced PV model mice by adoptive transfer of immunized Dsg3-/- splenocytes to Rag2-/- mice. We found that circulating anti-DSG3 IgG ELISA titer decreased in PV model mice after 5 days of treatment with IVIG compared with PBS-treated mice, whereas the F(ab')2 fragment did not suppress the anti-DSG3 IgG titer. enzyme-linked immunospot assay revealed that IVIG treatment reduced the frequency of anti-DSG3 antibody-secreting cells in the spleen but not in lymph nodes and bone marrow. Moreover, this reduction was observed only in the splenic B220- fraction but not in the B220+ fraction. Furthermore, IVIG decreased the serum levels of anti-DSG3 IgG, even after a significant reduction of its titer, owing to antibody-mediated CD20+ B cell depletion. In addition, IVIG suppressed anti-DSG3 IgG production in B220-CD138+ plasma cells derived from PV model mice exvivo. These results indicate that IVIG reduced autoantibody production in B220- cells containing plasma cells in PV model mice, and this function may indicate one of the mechanisms of action of IVIG on PV.

Ca2+ signalling is critical for autoantibody-induced blistering of human epidermis in pemphigus.

Pemphigus is a severe bullous autoimmune skin disease. Pemphigus foliaceus (PF) is characterized by antidesmoglein (Dsg) 1 IgG causing epidermal blistering; mucosal pemphigus vulgaris (mPV) by anti-Dsg3 IgG inducing erosions in the mucosa; and mucocutaneous pemphigus vulgaris (PV) by affecting both, with autoantibodies targeting Dsg1 and Dsg3. To characterize the Ca2+ flux pathway and delineate its importance in pemphigus pathogenesis and clinical phenotypes caused by different antibody profiles. Immunoprecipitation, Ca2+ flux analysis, Western blotting, immunofluorescence staining, dissociation assays and a human skin exvivo model were used. PV IgG and PF IgG, but neither Dsg3-specific monoclonal antibody (AK23) nor mPV IgG, caused Ca2+ influx in primary human keratinocytes. Phosphatidylinositol 4-kinase α interacts with Dsg1 but not with Dsg3. Its downstream target - phospholipase-C-γ1 (PLC) - was activated by PV IgG and PF IgG but not AK23 or mPV IgG. PLC releases inositol 1,4,5-trisphosphate (IP3) causing IP3 receptor (IP3R) activation and Ca2+ flux from the endoplasmic reticulum into the cytosol, which stimulates Ca2+ release-activated channels (CRAC)-mediated Ca2+ influx. Inhibitors against PLC, IP3R and CRAC effectively blocked PV IgG and PF IgG-induced Ca2+ influx; ameliorated alterations of Dsg1 and Dsg3 localization, and reorganization of keratin and actin filaments; and inhibited loss of cell adhesion invitro. Finally, inhibiting PLC or IP3R was protective against PV IgG-induced blister formation and redistribution of Dsg1 and Dsg3 in human skin exvivo. Ca2+ -mediated signalling is important for epidermal blistering and dependent on the autoantibody profile, which indicates different roles for signalling complexes organized by Dsg1 and Dsg3. Interfering with PLC and Ca2+ signalling may be a promising approach to treat epidermal manifestations of pemphigus.

Antigen-specific B cell depletion for precision therapy of mucosal pemphigus vulgaris.

Desmoglein 3 chimeric autoantibody receptor T cells (DSG3-CAART) expressing the pemphigus vulgaris (PV) autoantigen DSG3 fused to CD137-CD3ζ signaling domains, represent a precision cellular immunotherapy approach for antigen-specific B cell depletion. Here, we present definitive preclinical studies enabling a first-in-human trial of DSG3-CAART for mucosal PV. DSG3-CAART specifically lysed human anti-DSG3 B cells from PV patients and demonstrated activity consistent with a threshold dose in vivo, resulting in decreased target cell burden, decreased serum and tissue-bound autoantibodies, and increased DSG3-CAART engraftment. In a PV active immune model with physiologic anti-DSG3 IgG levels, DSG3-CAART inhibited antibody responses against pathogenic DSG3 epitopes and autoantibody binding to epithelial tissues, leading to clinical and histologic resolution of blisters. DSG3 autoantibodies stimulated DSG3-CAART IFN-γ secretion and homotypic clustering, consistent with an activated phenotype. Toxicology screens using primary human cells and high-throughput membrane proteome arrays did not identify off-target cytotoxic interactions. These preclinical data guided the trial design for DSG3-CAART and may help inform CAART preclinical development for other antibody-mediated diseases.

Antigen-specific B cell depletion with desmoglein 3 chimeric autoantibody receptor T cells (DSG3-CAART) for targeted therapy of mucosal pemphigus vulgaris

Abstract Chimeric autoantibody receptors (CAARs) direct T cells to kill autoantigen-specific B cells. We previously established proof-of-concept for the CAAR approach using gene-engineered T cells expressing CAARs comprising DSG3, the autoantigen in the autoimmune blistering disease mucosal pemphigus vulgaris, fused to CD137-CD3ζ signaling domains. Here, we present results of preclinical studies that supported the DSG3-CAART investigational new drug application. DSG3-CAART demonstrated activity related to dose in a passive transfer polyclonal anti-DSG3 hybridoma mouse model of mucosal pemphigus vulgaris, resulting in reversal of the rising serum anti-DSG3 antibody titers, target cell burden, and IgG deposition in epithelial tissues, as well as increased DSG3-CAART engraftment relative to dose. We further evaluated DSG3-CAART efficacy in a novel exploratory active immune mouse model with physiologic levels of circulating anti-DSG3 IgG, which demonstrated decreased antibody responses against pathogenic DSG3 epitopes and autoantibody binding to epithelial tissues, leading to clinical and histologic resolution of blisters. High-throughput screening of a membrane protein array with soluble DSG3 CAAR did not identify verifiable off-target toxicities. These preclinical studies have enabled a first-in-human clinical trial of DSG3-CAART in mucosal pemphigus vulgaris and provide a foundation that may inform the preclinical development of future CAAR T cell therapies for antigen-specific B cell depletion in other autoantibody-mediated diseases.

Identification of Autoreactive B Cell Subpopulations in Peripheral Blood of Autoimmune Patients With Pemphigus Vulgaris.

Pemphigus vulgaris (PV) is a rare blistering disease caused by IgG autoantibodies against the epidermal adhesion molecules desmoglein (Dsg)3 and Dsg1 providing a well-characterized paradigm of an antibody-mediated organ-specific autoimmune disease. In PV patients who have achieved clinical remission after B cell-depleting therapy, relapses often coincide with a reoccurrence of B cells and Dsg-specific autoantibodies. Here, we analyzed Dsg3-specific B cell subpopulations (i.e., total CD19+ B cells, CD19+CD27−B cells, CD19+CD27+ memory B cells, and CD19+CD27hiCD38hi plasmablasts) in peripheral blood of both PV patients (n = 14) at different stages of disease and healthy individuals (n = 14) by flow cytometry using fluorescently labeled recombinant human Dsg3 protein. Applying this approach, Dsg3-specific B cells could be detected at low frequencies (0.11–0.53% of CD19+ B cells) and numbers of Dsg3-specific memory B cells were significantly increased in PV patients in clinical remission receiving minimal immunosuppressive therapy. Finally, we confirmed in vitro that Dsg3-reactive memory B cells were able to produce anti-Dsg3 IgG autoantibodies upon ex vivo activation. Thus, monitoring of Dsg3-specific B cells in PV is of particular interest to further characterize the immunopathogenesis of PV.

Paraneoplastic autoimmune multiorgan syndrome (PAMS): Beyond the single phenotype of paraneoplastic pemphigus.

Paraneoplastic autoimmune multiorgan syndrome (PAMS) is characterized by a heterogenous group of signs and symptoms including severe desquamative stomatitis, a polymorphous cutaneous eruption, humoral immunity against plakin proteins, contribution of cell-mediated autoimmunity and commonly a progressive respiratory failure. Autoantibodies in PAMS target a wide array of antigens including plakins, cadherins, alpha-2-macroglobulin like 1 (A2ML1), BP180, plakophilin-3, and several neuromuscular antigens. Originally described as paraneoplastic pemphigus in 1990 due to some of its clinical and immunologic similarities to classic pemphigus (pemphigus vulgaris and pemphigus foliaceus), PAMS is a multiorganopathy with several distinct features from these classic forms of pemphigus. Epidemiologically, PAMS is associated with underlying neoplasia and has a differing HLA-II allele predisposition compared to classic forms of pemphigus. Clinically, lesion morphology is polymorphous, and lesion distribution fundamentally differs from that seen in classic pemphigus. PAMS has a significantly higher mortality rate and a poorer response to treatments typically effective in pemphigus. Histologically, PAMS is characterized by the presence of interface dermatitis, vacuolar changes, and dyskeratotic keratinocytes which are not seen in classic pemphigus. PAMS demonstrates not only intercellular IgG as seen in classic pemphigus, but the presence of linear basement membrane zone deposition. Antibodies against desmoglein 3 (Dsg3) map to a broader array of epitopes than in pemphigus vulgaris and there is a higher prevalence of complement binding anti-Dsg3 IgG autoantibodies in PAMS. Autoantibodies can in rare cases be absent in the more cell-mediated form of PAMS. Considering these numerable differences, we review the entity of PAMS, and provide similarities and differences to classic forms of pemphigus.

Keratinocyte Binding Assay Identifies Anti-Desmosomal Pemphigus Antibodies Where Other Tests Are Negative.

The serological diagnosis of pemphigus relies on the detection of IgG autoantibodies directed against the epithelial cell surface by indirect immunofluorescence (IIF) on monkey esophagus and against desmoglein 1 (Dsg1) and Dsg3 by ELISA. Although being highly sensitive and specific tools, discrepancies can occur. It is not uncommon that sera testing positive by ELISA give a negative result by IIF and vice versa. This brings diagnostic challenges wherein pemphigus has to be ascertained or ruled out, especially when no biopsy is available. We utilized the ability of anti-Dsg3 and anti-Dsg1 IgG to bind in specific desmosomal patterns to living cells to investigate these discrepancies between IIF and ELISA. Living cultured primary normal human keratinocytes were grown under differentiating conditions to induce adequate expression of Dsg1 and Dsg3, incubated with patient serum for 1 h, and then stained to visualize bound IgG. We investigated two different groups; sera from patients with a positive direct immunofluorescence (DIF) and inconsistent serological findings (n = 43) and sera with positive ELISA or IIF but with negative DIF (n = 60). As positive controls we used 50 sera from patients who fulfilled all diagnostics criteria, and 10 sera from normal human subjects served as negative controls. In the DIF positive group, IgG from 39 of the 43 sera bound to the cells in a desmosomal pattern while in the DIF negative group none of the 60 sera bound to the cells. This shows that for pemphigus patients, ELISA and IIF can be negative while anti-desmosomal antibodies are present and vice versa that ELISA and IIF can be positive in non-pemphigus cases. In absence of a biopsy for DIF, such findings may lead to misdiagnosis.

049 Development of active mouse models to recapitulate pemphigus subtypes and to evaluate response to therapy

Pemphigus is an autoimmune bullous disease characterized by loss of adhesion caused by autoantibodies (PVIgG) against keratinocyte antigens, desmogleins (Dsg1 and Dsg3) and non-Dsg proteins, such as acetylcholine receptors (AChR) or Desmocollin (Dsc3). Different PVIgG result in diverse clinical phenotypes. In order to recapitulate the features of human pemphigus, to evaluate the role of different antigens, and to test the response to therapy, we generated an active mouse model. We produced murine recombinant proteins (rDsg1, rDsg3, rDsc3, rAChRM3, rAChRNα7 and rAChRNα9). We then immunized Dsg3-/- mice with mouse rDsg3, and adoptively transferred their splenocytes into C57BL/6 Rag2-/- (Rag2) immunodeficient mice, that express Dsg3. Recipient mice stably produce the pathogenic anti-Dsg3 IgG and exhibit the features of pemphigus vulgaris, as shown by clinical score and Dsg3 levels (ELISA). We also generated the pemphigus foliaceous active mouse model, by breaking the immunological tolerance in WT mice with rDsg1. Similarly, we created a Dsg1/Dsg3 mouse model by transferring the combined splenocytes from mice immunized with rDsg1 and mice immunized with rDsg3 into Rag2 mice. The Dsg1/Dsg3 mouse model displays the most severe phenotype, reproduces symptoms of mucocutaneous PV in patients, as well as the same level of intraepithelial detachment and inter-keratinocyte deposits of IgG. Moreover, only the Dsg1/Dsg3 mice significantly responded to treatment with methylprednisolone in a time-dependent manner (clinical score and ELISA). In conclusion, we created new tools that could 1. improve the knowledge on pemphigus pathomechanisms; 2. serve for the identification of new therapeutic targets; 3. allow a long-term pre-clinical observation with or without current and novel therapies

A novel lateral flow immunoassay for the rapid detection of anti-Dsg3 IgG serum autoantibodies in pemphigus vulgaris.

Pemphigus vulgaris (PV) is a severe autoimmune blistering disease of the skin and mucous membranes. As autoantibodies play an essential role in the disease pathogenesis, the serological detection of anti-desmoglein 3 IgG represents a central tool in the diagnosis of the disease. In this study, we show the validation of a novel lateral flow immunoassay (LFIA) which rapidly detects anti-desmoglein 3 (Dsg3) IgG in human serum. In contrast to other diagnostic procedures, the assay is compact and simple to perform and delivers a fast"yes" or "no" answer within 10minutes without additional hardware requirements for test evaluation. For validation, a blinded collection of 200 sera including 100 sera from 14 PV patients, 75 sera from 24 bullous pemphigoid patients and 25 sera from 6 patients with pemphigus foliaceus collected at different time points during disease was used. Presence or non-presence of anti-Dsg3 IgG within sera was confirmed using a commercially available Dsg3-ELISA. For qualitative evaluation, Dsg3-LFIA test results were assessed by two independent groups of human observers. Furthermore, quantitative evaluation using POCScan reader was applied. The Dsg3-LFIA demonstrated reliable test results with a sensitivity and specificity of 78.1% and 97.1%, respectively. Test results from POCScan and human observers showed a substantial agreement. The Dsg3-LFIA represents a new diagnostic tool for the immediate and reliable detection of anti-desmoglein 3 serum IgG autoantibodies that does not require additional hardware. Further prospective trials are warranted to validate the Dsg3 LFIA in pemphigus.

Antidesmoglein 1 and 3 antibodies in healthy subjects of a population in the Peruvian high amazon.

The objective of this study was to determine the presence of anti-Dsg1 and Dsg3 antibodies in healthy subjects of the high Peruvian Amazon (Tuemal, Rodriguez de Mendoza province, department of Amazonas) to establish the theoretical presence of environmental factors or triggers in the area. Cross-sectional study. The study population included persons of any age or gender, clinically healthy, who were evaluated by a dermatologist to confirm the absence of blistering diseases. Blood samples were analyzed by indirect immunofluorescence (IIF), immunoprecipitation (IP), anti-Dsg1 IgM antibody (Ab) enzyme-linked immunosorbent assay (ELISA), as well as anti-Dsg1 and anti-Dsg3 IgG Ab ELISA. Participants included 21 healthy subjects comprised of 61.9% males and 38.1% females; 47.6% had a positive anti-Dsg1 Ab ELISA for total IgG (or any subclasses). IIF detected antibodies against intercellular spaces in one subject. Anti-Dsg1 Ab IP was mildly positive in 33.3% of the subjects. Anti-Dsg1 IgG subclasses found positive were: IgG1 (19.0%), IgG2 (33.3%), and IgG3 (28.6%); none of the samples were positive for anti-Dsg1 Ab IgM ELISA, and 23.8% of the subjects were positive for anti-Dsg3 Ab ELISA. The age distribution was similar for subjects positive for anti-Dsg1 and anti-Dsg3 Ab ELISA, with higher frequencies found among the 20-29 and 40-49year-old age groups. A fraction of healthy subjects of the high Peruvian Amazon developed anti-Dsg1 and anti-Dsg3 antibodies, demonstrating the possible presence of environmental factors for endemic pemphigus (EP) at a higher altitude than previously described.

Non-pathogenic pemphigus foliaceus (PF) IgG acts synergistically with a directly pathogenic PF IgG to increase blistering by p38MAPK-dependent desmoglein 1 clustering

BackgroundPemphigus foliaceus (PF) is an autoimmune blistering disease caused by autoantibodies (Abs) against desmoglein 1 (Dsg1). PF sera contain polyclonal Abs which are heterogeneous mixture of both pathogenic and non-pathogenic Abs, as shown by isolation of monoclonal Abs (mAbs). ObjectiveTo investigate how pathogenic and non-pathogenic anti-Dsg1 Abs contribute to blister formation in PF. MethodsUsing organ-cultured human skin, we compared the effect of a single pathogenic anti-Dsg1 IgG mAb, a single non-pathogenic anti-Dsg1 IgG mAb, and their mixture on blister formation as analyzed by histology, subcellular localization of IgG deposits and desmosomal proteins by confocal microscopy, and desmosomal structure by electron microscopy. In addition, we measured keratinocyte adhesion by an in vitro dissociation assay. Results24h after injection, a single pathogenic anti-Dsg1 IgG caused a subcorneal blister with IgG and Dsg1 localized linearly on the cell surface of keratinocytes. A single non-pathogenic anti-Dsg1 IgG bound linearly on the keratinocytes but did not induce blisters. A pathogenic and a non-pathogenic IgG mAb injected together caused an aberrant granular pattern of IgG and Dsg1 in the lower epidermis with blister formation in the superficial epidermis. Electron microscopy demonstrated that the mixture of mAbs shortened desmosomal lengths more than a single mAb in the basal and spinous layers. Furthermore, although Dsg1 clustering required both cross-linking of Dsg1 molecules by the non-pathogenic IgG plus a pathogenic antibody, the latter could be in the form of a monovalent single chain variable fragment, suggesting that loss of trans-interaction of Dsg1 is required for clustering. Finally, a p38MAPK inhibitor blocked Dsg1 clustering. When pathogenic strength was measured by the dissociation assay, a mixture of pathogenic and non-pathogenic IgG mAbs disrupted keratinocyte adhesion more than a single pathogenic mAb. This pathogenic effect was only partially suppressed by the p38MAPK inhibitor. ConclusionThese findings indicate that a polyclonal mixture of anti-Dsg1 IgG antibodies enhances pathogenic activity for blister formation associated with p38MAPK-dependent Dsg1 clustering and that not only pathogenic antibodies but also non-pathogenic antibodies coordinately contribute to blister formation in PF.

Mucosal Pemphigus Vulgaris Anti-Dsg3 IgG Is Pathogenic to the Oral Mucosa of Humanized Dsg3 Mice

There are two major clinical subsets of pemphigus vulgaris (PV), mucosal PV (mPV) and mucocutaneous PV (mcPV). The mPV subset exhibits anti-human desmoglein (Dsg) 3 autoantibodies that fail to recognize murine Dsg3; thus, passive transfer experiments of mPV IgG into WT mice have been unsuccessful at inducing disease. We therefore generated a fully humanized Dsg3 (hDSG3) murine model utilizing a human Dsg3 transgenic animal crossed to the murine Dsg3 knockout line. Expression of hDsg3 in the mucosa rescues the murine Dsg3 knockout phenotype. Well characterized mPV sera bind mucosal epithelia from the hDsg3 mice, but not mucosal tissues from WT mice by as detected by indirect immunofluorescence. The majority of mPV sera preferentially recognize hDsg3 compared to mDsg3 by immunoprecipitation as well. Passive transfer of mPV IgG into adult hDsg3 mice, but not WT mice, induces suprabasilar acantholysis in mucosal tissues, thus confirming pathogenicity of mPV anti-hDsg3 IgG in vivo. Human anti-hDsg3 antibodies are detected in perilesional mucosa as well as in sera of recipient mice by immunofluorescence. These findings suggest that the Dsg3 epitopes targeted by pathogenic mPV IgG are human specific. This hDsg3 mouse model will be invaluable in studying the clinical transition from mPV to mcPV.