In celiac disease, a subset of autoantibodies against transglutaminase binds toll-like receptor 4 and induces activation of monocytes

BACKGROUND

Celiac disease is a small intestine inflammatory disorder with multiple organ involvement, sustained by an inappropriate immune response to dietary gluten. Anti-transglutaminase antibodies are a typical serological marker in patients with active disease, and may disappear during a gluten-free diet treatment. Involvement of infectious agents and innate immunity has been suggested but never proven. Molecular mimicry is one of the mechanisms that links infection and autoimmunity.

METHODS AND FINDINGS

In our attempt to clarify the pathogenesis of celiac disease, we screened a random peptide library with pooled sera of patients affected by active disease after a pre-screening with the sera of the same patients on a gluten-free diet. We identified a peptide recognized by serum immunoglobulins of patients with active disease, but not by those of patients on a gluten-free diet. This peptide shares homology with the rotavirus major neutralizing protein VP-7 and with the self-antigens tissue transglutaminase, human heat shock protein 60, desmoglein 1, and Toll-like receptor 4. We show that antibodies against the peptide affinity-purified from the sera of patients with active disease recognize the viral product and self-antigens in ELISA and Western blot. These antibodies were able to induce increased epithelial cell permeability evaluated by transepithelial flux of [(3)H] mannitol in the T84 human intestinal epithelial cell line. Finally, the purified antibodies induced monocyte activation upon binding Toll-like receptor 4, evaluated both by surface expression of activation markers and by production of pro-inflammatory cytokines.

CONCLUSIONS

Our findings show that in active celiac disease, a subset of anti-transglutaminase IgA antibodies recognize the viral protein VP-7, suggesting a possible involvement of rotavirus infection in the pathogenesis of the disease, through a mechanism of molecular mimicry. Moreover, such antibodies recognize self-antigens and are functionally active, able to increase intestinal permeability and induce monocyte activation. We therefore provide evidence for the involvement of innate immunity in the pathogenesis of celiac disease through a previously unknown mechanism of engagement of Toll-like receptor 4.

Desmoglein Versus Non-desmoglein Signaling in Pemphigus Acantholysis

Although it is accepted that pemphigus antibody binding to keratinocytes (KCs) evokes an array of intracellular biochemical events resulting in cell detachment and death, the triggering events remain obscure. It has been postulated that the binding of pemphigus vulgaris IgG (PVIgG) to KCs induces "desmosomal" signaling. Because in contrast to integrins and classical cadherins, desmoglein (Dsg) molecules are not known to elicit intracellular signaling, and because PV patients also produce non-Dsg autoantibodies, we investigated the roles of both Dsg and non-desmoglein PV antigens. The time course studies of KCs treated with PVIgG demonstrated that the activity of Src peaked at 30 min, EGF receptor kinase (EGFRK) at 60 min, and p38 MAPK at 240 min. The Src inhibitor PP2 decreased EGFRK and p38 activities by approximately 45 and 30%, respectively, indicating that in addition to Src, PVIgG evokes other triggering events. The shrinkage of KCs (cell volume reduction) became significant at 120 min, keratin aggregation at 240 min, and an increase of TUNEL positivity at 360 min. Pretreatment of KCs with PP2 blocked PVIgG-dependent cell shrinkage and keratin aggregation by approximately 50% and TUNEL positivity by approximately 25%. The p38 MAPK inhibitor PD169316 inhibited these effects by approximately 15, 20, and 70%, respectively. Transfection of KCs with small interfering RNAs that silenced expression of Dsg1 and/or Dsg3 proteins, blocked approximately 50% of p38 MAPK activity but did not significantly alter the PVIgG-dependent rise in Src and EGFRK activities. These results indicate that activation of p38 MAPK is a late signaling step associated with collapse of the cytoskeleton and disassembly of desmosomes caused by upstream events involving Src and EGFRK. Therefore, the early acantholytic events are triggered by non-Dsg antibodies.

Isolation of pathogenic monoclonal anti-desmoglein 1 human antibodies by phage display of pemphigus foliaceus autoantibodies

Pemphigus foliaceus (PF) is a blistering disease caused by autoantibodies to desmoglein 1 (Dsg1) that cause loss of epidermal cell adhesion. To better understand PF pathophysiology, we used phage display to isolate anti-Dsg1 mAbs as single-chain variable fragments (scFvs) from a PF patient. Initial panning of the library isolated only non-pathogenic scFvs. We then used these scFvs to block non-pathogenic epitopes and were able to isolate two unique scFvs, each of which caused typical PF blisters in mice or human epidermis models, showing that a single mAb can disrupt Dsg1 function to cause disease. Both pathogenic scFvs bound conformational epitopes in the N terminus of Dsg1. Other PF sera showed a major antibody response against the same or nearby epitopes defined by these pathogenic scFvs. Finally, we showed restriction of the heavy-chain gene usage of all anti-Dsg1 clones to only five genes, which determined their immunological properties despite promiscuous light-chain gene usage. These mAbs will be useful for studying Dsg1 function and mechanisms of blister formation in PF and for developing targeted therapies and tools to monitor disease activity.

Advances in pemphigus and its endemic pemphigus foliaceus (Fogo Selvagem) phenotype: a paradigm of human autoimmunity

Pemphigus encompasses a group of organ specific, antibody mediated autoimmune diseases of the skin characterized by keratinocyte detachment that leads to the development of blisters and erosions, which can become life-threatening. The pathogenic autoantibodies recognize desmogleins, which are members of the desmosomal cadherin family of cell adhesion molecules. Desmoglein 3 is targeted in pemphigus vulgaris while desmoglein 1 is targeted in pemphigus foliaceus and its endemic form, Fogo Selvagem. This review will briefly define the salient features of pemphigus and the proposed steps in pathogenesis. We will then summarize the most recent advances in three important areas of investigation: (i) epidemiologic, genetic, and immunologic features of Fogo Selvagem, (ii) molecular mechanisms of injury to the epidermis, and (iii) novel therapeutic strategies targeting specific steps in disease pathogenesis. The advances in each of these three seemingly separate areas contribute to the overall understanding of the pemphigus disease model. These recent advancements also underscore the dynamic interplay between the treatment of patients in a clinical setting and basic science research and have led to an integrative understanding of disease pathogenesis and treatment, allowing pemphigus to serve as a paradigm of human autoimmunity.

Delineation of diversified desmoglein distribution in stratified squamous epithelia: implications in diseases

Desmogleins play critical roles in cell adhesion and skin blistering diseases, as they are the target antigens of autoimmune antibodies and bacterial toxins. We recently cloned several novel members of the desmoglein gene family, bringing the number of desmogleins to four in the rat and human genomes and six in the mouse. Here, we have produced a monoclonal antibody to a cytoplasmic epitope of Dsg4, assessed its specificity and compared it to several existing Dsg1-3 antibodies. We also demonstrated cross-reactivity of commercially available and often used Dsg1 antibodies. Using these tools, we delineated the unique expression patterns of each desmoglein isoform in various human and mouse stratified squamous epithelia, including skin, hair, palm, and oral mucosa. Interestingly, in the epidermis, the expression of each desmoglein correlates with their gene arrangement in the cadherin locus. In human, Dsg4 was detected primarily in the granular and cornified cell layers of the epidermis, while present throughout all differentiated layers of the oral mucosa and palm, and in the matrix cells of anagen hair bulb. Similar pattern of expression for Dsg4 was observed in mouse, with the exception that it was expressed at significantly lower levels in the mouse epidermis. These results demonstrate the complexity of desmoglein gene expression and provide additional insights into the correlation between tissue expression patterns and disease phenotypes.

Are desmoglein autoantibodies essential for the immunopathogenesis of pemphigus vulgaris, or just ‘witnesses of disease'?

Pemphigus vulgaris (PV) is fascinating to dermatologists, epithelial biologists and immunologists alike, as its pathogenesis has been clarified to a much greater extent than that of most other organ-specific autoimmune diseases, and as it has provided abundant novel insights into desmoglein biology and pathology along the way. Historically, the most influential PV pathogenesis concept is that of Stanley and Amagai. This concept holds that autoantibodies against desmogleins are both essential and sufficient for epidermal blister formation (acantholysis) by impeding the normal functioning of these major adhesion proteins. However, as with most good theories, this landmark concept has left a number of intriguing and important questions open (or at least has not managed to answer these to everyone's satisfaction). Moreover, selected dissenting voices in the literature have increasingly called attention to what may or may not be construed as inconsistencies in this dominant PV pathogenesis paradigm of the recent past. The present debate feature therefore bravely rises to the challenge of re-examining the entire currently available evidence, as rationally and as undogmatically as possible, by provocatively asking a carefully selected congregation of experts (who have never before jointly published on this controversial topic!) to discuss how essential anti-desmoglein autoantibodies really are in the immunopathogenesis of PV. Not surprisingly, some of our expert "witnesses" in this animated debate propose diametrically opposed answers to this question. While doing so, incisive additional questions are raised that relate to the central one posed, and our attention is called to facts that may deserve more careful consideration than they have received so far. Together with the intriguing (often still very speculative) complementary or alternative pathogenesis scenarios proposed in the following pages, this offers welcome "food for thought" as well as very specific suggestions for important future research directions--within and beyond the camp of PV aficionados. The editors trust that this attempt at a rational public debate of the full evidence that is currently at hand will constructively contribute to further dissecting the exciting--and clinically very relevant!--immunopathogenesis of PV in all its complexity.

Autoimmunity and Cytokine Imbalance in Inherited Epidermolysis Bullosa

In order to evaluate the serum anti-skin autoantibodies and cytokine concentrations in patients with different epidermolysis bullosa (EB) types and severity, 42 EB patients and 38 controls were enrolled. Serum anti-skin antibodies were significantly higher in the patients than in the controls (p = 0.008, p < 0.001, p < 0.001, p < 0.001 and p < 0.001 for desmoglein 1 (DSG1) desmoglein 3 (DSG3), bullous pemphigoid 180 (BP180), BP230 and type VII collagen (COL7), respectively). The same trend was observed for interleukin (IL)-1β, IL-2, IL-6, IL-10, tumor necrosis factor-β, and interferon-γ (p < 0.001, p < 0.001, p < 0.001, p = 0.008, p < 0.001 and p = 0.002, respectively). Increases in anti-skin antibodies and cytokine concentrations were higher in patients with recessive dystrophic EB than in those with different types of EB, in generalized cases than in localized ones, and in patients with higher Birmingham Epidermolysis Bullosa Severity (BEBS) scores than in those with a lower score. The BEBS score was directly correlated with BP180, BP230, COL7 (p = 0.015, p = 0.008 and p < 0.001, respectively) and IL-6 (p = 0.03), whereas IL-6 appeared significantly associated with DSG1, DSG3, BP180, BP230 and COL7 (p = 0.015, p = 0.023, p = 0.023, p = 0.015 and p = 0.005, respectively). This study showed that autoimmunity and inflammatory responses are frequently activated in EB, mainly in severe forms, suggesting the use of immunosuppressive drugs or biologicals that are active against pro-inflammatory cytokines to reduce clinical signs and symptoms of disease.

Evaluation of desmoglein enzyme-linked immunosorbent assay (ELISA) in Indian patients with pemphigus vulgaris

OBJECTIVE

To evaluate the role of the enzyme-linked immunosorbent assay (ELISA) test for the detection of antibodies to desmoglein 1 (dsg1) and desmoglein 3 (dsg3) in the diagnosis of pemphigus vulgaris (PV), and its correlation with disease severity and clinical presentation (mucosal PV, cutaneous PV, mucocutaneous PV).

METHODS

Twenty-seven active PV patients and 26 controls with other dermatologic disorders were included in the study. The severity of oral and cutaneous involvement was assessed and recorded. ELISA test for the measurement of anti-dsg1 and anti-dsg3 antibodies was performed (Medical and Biological Laboratories Co. Ltd., Nagoya, Japan). The cut-off ELISA value for both anti-dsg1 and anti-dsg3 was taken as 20.

RESULTS

Of the 27 patients, 26 were ELISA positive for anti-dsg1 antibodies and 23 for anti-dsg3 antibodies. Of the controls, two were positive for anti-dsg1 and none for anti-dsg3 antibodies. The sensitivity and specificity of ELISA for anti-dsg1 in the diagnosis of PV were 96.3% and 92.3%, respectively. For anti-dsg3, they were 85.2% and 100%, respectively. The different morphologic types of PV could not be differentiated on the basis of antibody profile; however, a direct correlation between anti-dsg3 titers and the severity of oral disease was noted, and also between anti-dsg1 titers and the severity of cutaneous disease.

CONCLUSIONS

ELISA (dsg1 and dsg3) is an efficient tool for confirming the diagnosis of PV. Specific antibody titers correlate with disease severity; however, desmoglein testing cannot differentiate between the various morphologic subtypes of PV.

Pathogenic epitopes of autoantibodies in pemphigus reside in the amino-terminal adhesive region of desmogleins which are unmasked by proteolytic processing of prosequence

Pemphigus targets desmogleins (Dsgs), which are thought to be synthesized as inactive precursor proteins with prosequences that are cleaved by substilisin-like proprotein convertases, such as furin, to yield mature adhesive molecules. We hypothesized that some pemphigus pathogenic antibodies (Abs), which presumably interfere with adhesion, only bind the mature form. A pathogenic and three non-pathogenic anti-Dsg1 monoclonal Abs (mAbs) isolated from a pemphigus foliaceus (PF) patient, were used for immunoprecipitation and ELISA of recombinant precursor and mature Dsg1. The pathogenic Ab binds mature Dsg1, whereas non-pathogenic Abs bind either only the precursor or both the precursor and mature Dsg1. Competition ELISA showed that the majority of PF sera target the same or nearby epitopes defined by the pathogenic anti-Dsg1 mAb that blocked >20% binding of 29 out of 40 PF sera. Furthermore, the immunoreactivity of 45 PF sera against the mature Dsg1 was 3.2 fold stronger than that against the precursor Dsg1 by ELISA. Similar results were observed in anti-Dsg3 Abs in 47 pemphigus vulgaris sera, suggesting that most pemphigus sera target epitopes that are unmasked by proteolytic processing. These findings support the idea that at least some pathogenic pemphigus autoantibodies induce the loss of cell adhesion by directly binding the trans-interaction site of Dsgs.

Prolonged Clinical Remission of Patients with Severe Pemphigus upon Rapid Removal of Desmoglein-Reactive Autoantibodies by Immunoadsorption

BACKGROUND

In pemphigus, loss of epidermal adhesion is induced by binding of circulating autoantibodies to the desmosomal cadherins desmoglein 3 (Dsg3) in pemphigus vulgaris (PV) and desmoglein 1 (Dsg1) in pemphigus foliaceus (PF), respectively. Therapeutic removal of Dsg-reactive autoantibodies by immunoadsorption (IA) has been demonstrated to exert clinical remission of the disease.

OBJECTIVES

The aim of this intervention study was to evaluate the efficacy and safety of the peptide-based Globaffin adsorber system in the treatment of severe pemphigus cases.

PATIENTS AND METHODS

We applied IA in 4 PV and 2 PF patients with severe chronic disease resistant to conventional immunosuppressive therapy. IA was performed on 4 consecutive days, representing 1 treatment cycle, followed by a 4-week treatment-free interval. Serum samples for determining serum IgG and anti-Dsg1/Dsg3 IgG autoantibodies were drawn daily before and after IA, respectively. During follow-up, patients were examined carefully, and laboratory parameters were controlled monthly for up to 1 year.

RESULTS

IA led to excellent clinical responses. Skin and mucosal lesions cleared almost completely within weeks. One IA cycle reduced anti-Dsg1 and anti-Dsg3 autoantibodies by an average of 50-70% as determined by ELISA.

CONCLUSIONS

Using the Globaffin adsorber system, IA represents an effective and safe treatment opportunity in severe and therapy-resistant pemphigus.

Translational implications of Th17-skewed inflammation due to genetic deficiency of a cadherin stress sensor

Desmoglein 1 (Dsg1) is a cadherin restricted to stratified tissues of terrestrial vertebrates, which serve as essential physical and immune barriers. Dsg1 loss-of-function mutations in humans result in skin lesions and multiple allergies, and isolated patient keratinocytes exhibit increased proallergic cytokine expression. However, the mechanism by which genetic deficiency of Dsg1 causes chronic inflammation is unknown. To determine the systemic response to Dsg1 loss, we deleted the 3 tandem Dsg1 genes in mice. Whole transcriptome analysis of embryonic Dsg1-/- skin showed a delay in expression of adhesion/differentiation/keratinization genes at E17.5, a subset of which recovered or increased by E18.5. Comparing epidermal transcriptomes from Dsg1-deficient mice and humans revealed a shared IL-17-skewed inflammatory signature. Although the impaired intercellular adhesion observed in Dsg1-/- mice resembles that resulting from anti-Dsg1 pemphigus foliaceus antibodies, pemphigus skin lesions exhibit a weaker IL-17 signature. Consistent with the clinical importance of these findings, treatment of 2 Dsg1-deficient patients with an IL-12/IL-23 antagonist originally developed for psoriasis resulted in improvement of skin lesions. Thus, beyond impairing the physical barrier, loss of Dsg1 function through gene mutation results in a psoriatic-like inflammatory signature before birth, and treatment with a targeted therapy significantly improved skin lesions in patients.

Coexistence of IgA antibodies to desmogleins 1 and 3 in pemphigus vulgaris, pemphigus foliaceus and paraneoplastic pemphigus

BACKGROUND

Pemphigus is a bullous mucocutaneous autoimmune disease characterized by IgG autoantibodies to desmoglein (Dsg) 1 and/or Dsg3. Occasionally direct immunofluorescence of pemphigus skin reveals IgA depositions with an intraepidermal intercellular pattern in addition to the IgG deposition.

OBJECTIVES

To investigate if pemphigus patients, in addition to having IgG autoantibodies, also generate IgA antibodies to Dsg1 and/or Dsg3.

PATIENTS/METHODS

Sera of 100 pemphigus patients and 36 bullous pemphigoid controls were tested by IgA enzyme-linked immunosorbent assay (ELISA) to the recombinant extracellular domains of Dsg1 and Dsg3. The patients were selected on clinical grounds and positive IgG ELISA index values for Dsg1 and/or Dsg3. They were divided into four groups: patients having IgG to only Dsg1 (n=34), patients having IgG to both Dsg1 and Dsg3 (n=31), patients having IgG to only Dsg3 (n=27) and patients who had paraneoplastic pemphigus (PNP) (n=8).

RESULTS

IgA antibodies to Dsg1 were found in 13 (38%) of the patients with IgG to Dsg1, in five (16%) of the patients with IgG to both Dsg1 and Dsg3, in four (15%) of the patients with IgG to Dsg3 and in none of the PNP patients. IgA antibodies to Dsg3 were found in one (3%) of the patients with IgG to Dsg1, in 18 (58%) of the patients with IgG to both Dsg1 and 3, in 18 (67%) of the patients with IgG to Dsg3, and in four (50%) of the PNP patients. Immunofluorescence analysis demonstrated intraepidermal intercellular staining IgA antibodies in serum and intercellular IgA deposits in skin of IgA ELISA-positive patients, although to a lesser extent than by ELISA.

CONCLUSIONS

This study shows that in a considerable number of supposedly IgG-mediated pemphigus patients IgA to Dsg1 and Dsg3 is also present. In most cases the antigen specificity of the IgA follows the antigen specificity of the IgG, although in a small number of cases IgA is present against the Dsg not recognized by IgG.

Anti-skin specific autoantibodies detected by a new immunofluorescence multiplex biochip method in patients with autoimmune bullous diseases

BACKGROUND

Autoimmune blistering skin diseases are a heterogeneous group of diseases characterized by autoantibodies against structural components of the skin. In pemphigus vulgaris (PV) autoantibodies react mainly with desmoglein 3 (Dsg3) alone and/or in combination with desmoglein 1 (Dsg1). In bullous pemphigoid (BP) autoantibodies target two hemidesmosomal proteins, BP180 and BP230.

OBJECTIVE

To evaluate the diagnostic accuracy of a new indirect immunofluorescence (IIF) multiplex biochip method for the detection of anti-skin specific autoantibodies.

METHODS

Sera from 36 patients with PV and from 40 patients with BP were collected. The control group included 54 patients with other skin diseases and 40 healthy subjects. The detection of circulating autoantibodies to Dsg1, Dsg3, BP230 and BP180 was performed with a new IIF multiplex biochip method and with two currently commercially available ELISA methods.

RESULTS

The multiplex IIF method showed a high diagnostic sensitivity (100%) for PV on cells transfected with Dsg3. In patients with BP, the positivity to the BP180 antigen was higher (90%) than that on monkey esophagus (50%) and on cells transfected with BP230 (40%). A good rate of agreement was observed among methods (IIF vs. ELISA) and among ELISA systems.

CONCLUSIONS

The new multiplex biochip IIF method has a high diagnostic accuracy for the diagnosis of PV and BP, comparable to ELISA methods, and is able to screen autoimmune bullous diseases.

Prevalence of Anti-Desmoglein-3 Antibodies in Endemic Regions of Fogo Selvagem in Brazil

Fogo selvagem (FS), the endemic form of pemphigus foliaceus (PF), is an autoimmune blistering disease characterized by autoantibodies against desmoglein 1. The Terena reservation of Limao Verde in Mato Grosso do Sul, Brazil, is a previously identified focus of disease. Autoantibodies against desmoglein 3 (Dsg3) have also been detected in sera from patients with FS. In an effort to further characterize the serological, geographical, and clinical epidemiology of the disease, we sought to determine the prevalence of anti-Dsg3 autoantibodies in sera from normal subjects living outside of and in an endemic area using an ELISA. Anti-Dsg3 antibodies were detected in 53 of 146 normal subjects from Limao Verde (36%), and in eight of 140 normal subjects from surrounding areas (6%). A significant trend was observed in the proportion of positive tests relative to distance from the endemic area (P < 0.001). Our seroepidemiological observations support the concept that the likely environmental trigger of the antibody response in FS is located in this endemic area, and that the population at risk to develop FS may also be at risk to develop an endemic form of pemphigus vulgaris as reported by our co-investigators from Brasilia.

Desmoglein-1 is a minor autoantigen in dogs with pemphigus foliaceus

The majority of human patients with pemphigus foliaceus (PF) have circulating IgG autoantibodies that target conformational epitopes on the desmosomal cadherin desmoglein-1 (dsg1). Limited studies using immunoblot techniques suggested that the principal autoantigen in dogs with PF might also be dsg1. It was the objective of this study to test this hypothesis. A comprehensive survey of canine PF sera was conducted using a novel screening strategy that detects conformational epitopes. This method consists of the ectopic expression of canine dsg1 at the surface of human 293T epithelial kidney cells and their live screening, i.e. prior to fixation. Out of seven control human PF sera that bound to canine epidermis, three (57%) contained IgG autoantibodies that recognized ectopically expressed canine dsg1 with a membrane and punctate pattern. Out of 83 canine PF sera only five (6%) contained IgG that recognized canine dsg1. Consistent with findings for human PF sera obtained in this study, autoantibody binding was conformation- and glycosylation-dependent as demonstrated by calcium chelation with EDTA and tunicamycin or wheat germ agglutinin treatment, respectively. In conclusion, these studies establish canine dsg1 as a minor autoantigen for canine PF. Antigenic epitopes appear to be conformation- and glycosylation-dependent.

Synergy among non-desmoglein antibodies contributes to the immunopathology of desmoglein antibody-negative pemphigus vulgaris

Pemphigus vulgaris (PV) is a potentially lethal mucocutaneous blistering disease characterized by IgG autoantibodies (AuAbs) binding to epidermal keratinocytes and inducing this devastating disease. Here, we observed that non-desmoglein (Dsg) AuAbs in the sera of patients with Dsg1/3 AuAb-negative acute PV are pathogenic, because IgGs from these individuals induced skin blistering in neonatal mice caused by suprabasal acantholysis. Serum levels of AuAbs to desmocollin 3 (Dsc3), M3 muscarinic acetylcholine receptor (M3AR), and secretory pathway Ca2+/Mn2+-ATPase isoform 1 (SPCA1) correlated with the disease stage of PV. Moreover, AuAb absorption on recombinant Dsc3, M3AR, or SPCA1 both prevented skin blistering in the passive transfer of AuAbs model of PV in BALB/c mice and significantly decreased the extent of acantholysis in a neonatal mouse skin explant model. Although acantholytic activities of each of these immunoaffinity-purified AuAbs could not induce a PV-like phenotype, their mixture produced a synergistic effect manifested by a positive Nikolskiy sign in the skin of neonatal mice. The downstream signaling of all pathogenic non-Dsg AuAbs involved p38 mitogen-activated protein kinase (MAPK)-mediated phosphorylation and elevation of cytochrome c release and caspase 9 activity. Anti-Dsc3 and anti-SPCA1 AuAbs also activated SRC proto-oncogene, nonreceptor tyrosine kinase (SRC). Of note, although a constellation of non-Dsg AuAbs apparently disrupted epidermal integrity, elimination of a single pathogenic AuAb could prevent keratinocyte detachment and blistering. Therefore, anti-Dsg1/3 AuAb-free PV can be a model for elucidating the roles of non-Dsg antigen-specific AuAbs in the physiological regulation of keratinocyte cell-cell adhesion and blister development.

Antidesmoplakin antibodies in pemphigus vulgaris

BACKGROUND

Besides being present in paraneoplastic pemphigus (PNP), circulating antidesmoplakin (DP) antibodies have been found anecdotally in other bullous diseases, including pemphigus foliaceus and pemphigus vulgaris.

OBJECTIVES

To verify how frequent anti-DP antibodies are in pemphigus vulgaris.

METHODS

We studied 48 sera from patients with proven pemphigus vulgaris (29 mucosal dominant pemphigus and 19 mucocutaneous pemphigus) by indirect immunofluorescence (IIF) with rat bladder epithelium (RBE) as a substrate and by immunoblotting (IB) on human keratinocyte cultures enriched in DP.

RESULTS

Ten sera (21%) were positive in IIF on RBE. By IB, eight sera proved to have antibodies to both DP I (250 kDa) and DP II (210 kDa), one serum had antibodies directed to DP I only, and two sera to DP II only.

CONCLUSIONS

Our data confirm that RBE is not a specific IIF substrate for the serological diagnosis of PNP. It remains a sensitive and specific substrate for the detection of anti-DP antibodies, which, in patients with pemphigus vulgaris, are probably caused by an epitope-spreading phenomenon.

Changes in desmoglein 1 expression and subcellular localization in cultured keratinocytes subjected to anti-desmoglein 1 pemphigus autoimmunity

The complexity of pemphigus acantholysis together with the weak expression of desmoglein 1 (Dsg1) in cultured keratinocytes have made the study on the pathogenic action of anti-Dsg1 antibodies quite difficult. The pathophysiology of the acantholytic phenomenon could depend on the reduction of Dsg1 adhesion function occurring after its massive internalization or decrease of its synthesis. Here, we have investigated this hypothesis by using sera of patients having antibodies against Dsg1 or monoclonal anti-Dsg1 antibodies to simulate pemphigus autoimmunity in Dsg1-rich keratinocytes. Similar to pemphigus foliaceus (PF) and vulgaris (PV) sera, monoclonal anti-Dsg1 antibodies induced transient internalization of Dsg1 and reduced the adhesion strength among keratinocytes. However, binding of IgG to Dsg1 did not determine its early depletion from the adhesion complexes but reduced the amount of Dsg1 found in the Triton X-100 soluble pool of proteins. Taken together, our results represent the first demonstration that anti-Dsg1 antibodies induce similar alterations on the subcellular distribution of Dsg1 irrespective of the disease where they come from. Furthermore, the present study provides insight into the mechanisms underlying epithelial blistering observed in the skin type of pemphigus.

Endemic Pemphigus Vulgaris

BACKGROUND

Investigators from Brasilia, Brazil, observed several patients with a mucocutaneous disease that resembles pemphigus vulgaris clinically and histologically but with epidemiological features of fogo selvagem. Our objective was to characterize antidesmoglein 3 and antidesmoglein 1 autoantibody profiles in these unique patients who reside in Goiânia and Brasilia, Brazil, known endemic regions of fogo selvagem.

OBSERVATIONS

We performed serological evaluation of 8 patients with a mucocutaneous disease clinically and histologically consistent with pemphigus vulgaris, as well as 27 healthy relatives of patients with fogo selvagem who reside in these endemic areas. Serum samples from all 8 patients bound desmoglein 3 by cold immunoprecipitation and from 6 patients by enzyme-linked immunosorbent assay, while serum samples from 4 patients bound desmoglein 1 by cold immunoprecipitation and by enzyme-linked immunosorbent assay. Antidesmoglein 3 autoantibodies were detected in 4 of 27 healthy donors by cold immunoprecipitation and by enzyme-linked immunosorbent assay, whereas antidesmoglein 1 autoantibodies were detected in 6 individuals by cold immunoprecipitation and in 3 individuals by enzyme-linked immunosorbent assay.

CONCLUSION

These findings provide serological evidence of a new endemic variant of pemphigus vulgaris.

Targeting Pemphigus Autoantibodies through their Heavy-Chain Variable Region Genes

Pemphigus vulgaris (PV) is a potentially fatal blistering disease characterized by autoantibodies against cell surface adhesion proteins desmoglein (Dsg) 3 and Dsg1. Previous studies using phage display to clone Dsg-reactive monoclonal antibodies from a PV patient demonstrated that a limited number of antibody variable region genes encode the autoantibody repertoire, with different genes for pathogenic and non-pathogenic mAbs. Here, we investigated the feasibility of specific autoantibody targeting in pemphigus. We produced rabbit anti-idiotypic antibodies against two pathogenic and two non-pathogenic PV mAbs. Antisera inhibited binding of the immunizing mAb to Dsgs by ELISA as well as pathogenicity against cultured human keratinocytes. Antisera also inhibited other mAbs using the same variable region heavy chain (V(H)) genes, despite different light chains or somatic mutations. Additionally, peptide phage display identified peptide sequences that bound PV mAbs in a V(H)-specific manner. To evaluate the therapeutic potential of V(H) gene-targeted reagents, preimmune sera and antisera were used to adsorb pathogenic antibodies from PV sera. Pooled antisera significantly reduced pathogenic activity from the original PV patient's serum and bound pathogenic antibodies from two other PV sera, suggesting shared autoantibody V(H) gene usage among PV patients. Together, these data suggest novel V(H) gene-targeted approaches toward PV treatment.

Circulating pemphigus autoantibodies in healthy relatives of pemphigus patients: coincidental phenomenon with a risk of disease development?

Pemphigus is a severe autoimmune disease characterized by circulating and bound in vivo pemphigus autoantibodies. It was revealed that the autoantibodies occur in healthy first-degree relatives of pemphigus patients; however, their significance is not fully elucidated. Thus, the aim of the study was to assess the frequency of circulating IgG pemphigus autoantibodies in the healthy relatives of pemphigus patients and of their ability to bind in vivo in the epidermis. We also analyzed IgG subclasses distribution, both in the serum-positive relatives and in the patients. Our study included 67 healthy relatives, 50 healthy normal controls and 33 patients (25 at an active stage of the disease, 8 in clinical remission). To detect circulating pemphigus antibodies we applied indirect immunofluorescence and anti-desmoglein ELISA. Monoclonal anti-human IgG1, IgG2, IgG3, IgG4 antibodies were used to assess subclass distribution. The frequency of circulating pemphigus autoantibodies in the relatives, detected by IIF (30/67) was statistically higher (P < 0.001) than in the control group (0/50). ELISA revealed anti-desmoglein 1 and/or 3 antibodies in 13 out of 67 relatives. Direct immunofluorescence performed in 25 out of 32 seropositive relatives did not show intercellular bound in vivo IgG and/or C3 in the epidermis in any cases. Circulating IgG2 subclass was observed in 60% of the examined relatives and IgG4 was detected in 23.3% of them. In the patients at an active stage of pemphigus IgG4 and IgG1 were the dominant subclasses (96 and 76% relatively) while in clinical remission antibodies predominantly belonged to the IgG2 (75%) and IgG4 (37.5%) subclass. The obtained results confirmed polyclonal production of pemphigus autoantibodies and their different distributions dependent on the disease activity. Statistical analysis showed that the frequency of IgG1 and IgG4 subclasses was significantly higher in the patients at an active stage of the disease when compared to the patients in clinical remission (P < 0.001) or with seropositive healthy relatives (P < 0.001). The relevance of the presence of IgG4 autoantibodies in the healthy relatives' sera requires further studies that focus on their potential pathogenicity.

Study of desmoglein 1 and 3 antibody levels in relation to disease severity in Indian patients with pemphigus

OBJECTIVES

To conduct a cross-sectional study to compare Dsg1 and Dsg3 antibody levels independently with severity of disease activity in pemphigus vulgaris (PV) and pemphigus foliaceus (PF).

METHODS

Blood samples from 44 patients with pemphigus (PV-38, PF-6) were analyzed using ELISA. The severity of skin and mucosal disease was graded using a score from 0 to 3.

RESULTS

A statistically significant correlation between increase in Dsg 3 antibody titres with severity of oral involvement and Dsg 1 titres with severity of skin involvement was found in both PV and PF patients (p < 0.01). However, we were unable to demonstrate a relationship between increased titres of Dsg1 and Dsg 3 antibodies with oral and skin involvement respectively.

CONCLUSION

This study suggests that the severity of skin and oral disease in pemphigus is determined by the quantities of Dsg1 and Dsg3 antibodies respectively.

Antigen selection of anti-DSG1 autoantibodies during and before the onset of endemic pemphigus foliaceus

Fogo selvagem (FS), the endemic form of pemphigus foliaceus (PF), is characterized by pathogenic anti-desmoglein 1 (DSG1) autoantibodies. To study the etiology of FS, hybridomas that secrete either IgM or IgG (predominantly IgG1 subclass) autoantibodies were generated from the B cells of eight FS patients and one individual 4 years before FS onset, and the H and L chain V genes of anti-DSG1 autoantibodies were analyzed. Multiple lines of evidence suggest that these anti-DSG1 autoantibodies are antigen selected. First, clonally related sets of anti-DSG1 hybridomas characterize the response in individual FS patients. Second, H and L chain V gene use seems to be biased, particularly among IgG hybridomas, and third, most hybridomas are mutants and exhibit a bias in favor of CDR (complementary determining region) amino acid replacement (R) mutations. Strikingly, pre-FS hybridomas also exhibit evidence of antigen selection, including an overlap in V(H) gene use and shared multiple R mutations with anti-DSG1 FS hybridomas, suggesting selection by the same or a similar antigen. We conclude that the anti-DSG1 response in FS is antigen driven and that selection for mutant anti-DSG1 B cells begins well before the onset of disease.