Validation of chemiluminescent enzyme immunoassay in detection of autoantibodies in pemphigus and pemphigoid

B-cell targeted therapy of pemphigus

Pemphigus is an autoimmune disease that causes blistering and erosion of the skin and mucous membranes because of autoantibodies against desmoglein, which plays an important role in adhesion between epidermal keratinocytes. Treatment of pemphigus has long been centered on corticosteroids, and the guidelines for management of pemphigus have recommended high-dose systemic corticosteroids as the first-line treatment. While guideline-based treatment has been shown to be beneficial in patients with pemphigus, it has also become clear that this treatment is accompanied by significant burden and risk. The challenge for future pemphigus treatment is to maximize efficacy while minimizing risk during the course of the disease. In this regard, treatment targeting B cells is expected to become increasingly important as autoreactive B cells in pemphigus patients are thought to play a major role in the production of autoantibodies, which form the basis of the pathogenesis. The recent expansion of insurance coverage to rituximab, a monoclonal antibody against CD20, for refractory pemphigus in the USA, Europe, and Japan has opened up a new era of pemphigus treatment by enabling treatment strategies with drugs targeting B cells in patients. Here, we discuss the current status and future prospects of pemphigus treatment, focusing on rituximab and Bruton's tyrosine kinase inhibitors, which are expected to become essential drugs for pemphigus treatment in the future.

The pathogeneses of pemphigus and pemphigoid diseases

Autoimmune bullous diseases (AIBDs) are skin disorders which are mainly induced by autoantibodies against desmosomal or hemidesmosomal structural proteins. Previous studies using patients' samples and animal disease models identified target antigens and elucidated the mechanisms of blister formation. Pemphigus has been the subject of more active clinical and basic research than any other AIBD. These efforts have revealed the pathogenesis of pemphigus, which in turn has led to optimal diagnostic methods and novel therapies, such as rituximab. In bullous pemphigoid (BP), studies with passive-transfer mouse models using rabbit anti-mouse BP180 antibodies and studies with passive-transfer or active mouse models using autoantigen-humanized mice elucidated the immune reactions to BP180 in vivo. Recently, dipeptidyl peptidase-4 inhibitors have attracted attention as a trigger for BP. For epidermolysis bullosa acquisita (EBA), investigations using mouse models are actively under way and several molecules have been identified as targets for novel therapies. In this review, we give an overview and discussion of the recent progress in our understanding of the pathogenesis of pemphigus, BP, and EBA. Further studies on the breakdown of self-tolerance and on the identification of key molecules that are relevant to blister formation may expand our understanding of the etiology of AIBDs and lead to the development of novel therapeutic strategies.

Analysis of clinical characteristics, prognosis and antibody pathogenicity of pemphigus patients positive for anti-desmoglein IgG autoantibodies in remission: a retrospective cohort study

BACKGROUND

The detection of serum anti-desmoglein (Dsg) IgG autoantibodies has been reported to be useful for assessment of disease activity in pemphigus. However, previous studies have reported that anti-Dsg autoantibodies remain detectable in some patients without active pemphigus lesions.

OBJECTIVES

To investigate the clinical characteristics and antibody pathogenicity of pemphigus patients positive for anti-Dsg IgG autoantibodies in remission.

METHODS

We retrospectively investigated pemphigus patients with a history of clinical remission who visited the Department of Dermatology of Keio University during 2019 and 2020. The antibody pathogenicity was assessed by bead aggregation assay.

RESULTS

When patients were recognized as having entered remission (PDAI = 0 and PSL ≦ 10 mg/day for 2 months), serum autoantibodies against Dsg were detected in 72 of 132 patients (54.5%, positive group; PG), but were not detected in 60 patients (45.5%, negative group; NG). Anti-Dsg antibody titres in remission declined from the active phase in 33 patients in the PG for whom data were available. There were no differences in the chance of reducing PSL to 5 mg/day (P = 0.885) and rate of relapse (P = 0.279) between PG and NG, but fewer patients in PG discontinued corticosteroids (P = 0.004). The ability of patients' sera to block aggregation of Dsg/desmocollin beads was significantly reduced in remission compared to the active phase. However, our results revealed that whole sera in remission still had pathogenic activity in seven of nine patients, and the approximately equal amounts of anti-Dsg antibodies in active phase and remission showed similar pathogenicity.

CONCLUSIONS

This study will provide guidance in cases where autoantibodies are found to be positive in pemphigus patients during remission or steroid reduction.

Analysis of the Specificity of Auto-Reactive Antibodies to Individual Fragments of the Extracellular Domain of Desmoglein 3 in Patients with Pemphigus Vulgaris

A method for the analysis of the epitope specificity of auto-reactive antibodies to desmoglein 3 (Dsg3) using competitive ELISA has been developed. It is based on a two-stage solid-phase ELISA with initial "depletion" of auto-reactive antibodies against the studied epitope and subsequent quantitative assessment of antibodies against full-length extracellular domain Dsg3. The proposed approach for assessing the specificity of the autoimmune response in patients with pemphigus vulgaris can provide in the future the possibility to personalize the therapy using plasmapheresis by preliminary selection of the antigenic composition of the extracorporeal immunosorbent.

Clinical characteristics and outcomes of bullous pemphigoid patients with versus without oral prednisolone treatment

Bullous pemphigoid (BP) varies in severity and stratified treatments are needed. However, there are no definitive standards for choosing appropriate treatments. To elucidate the factors involved in choosing treatments and the clinical outcomes of BP, we retrospectively reviewed the clinical records of 78 BP patients at a single center. Of the 78 patients, 49 (62.8%) were treated with oral prednisolone (PSL) and 29 (37.2%) were treated without PSL. The patients with older age, lower Bullous Pemphigoid Disease Area Index (BPDAI), and/or lower anti-BP180NC16a antibody titer at onset tended to be treated without oral PSL. Notably, only 9.1% patients without PSL experienced relapse, whereas 36.7% patients with oral PSL experienced relapse when the PSL was around 0.1 mg/kg. It suggests that the patients with mild disease severity could be well controlled without oral PSL. Receiver-operator curve analysis demonstrated that the cut-off value for the use of oral PSL was 31 for total BPDAI and was 7 for BPDAI skin urticaria/erythema, with a high (>0.9) area under the curve. Notably, none of the patients who were negative for the anti-BP180NC16a antibody at onset experienced relapse even though they were treated without PSL. In conclusion, in BP patients who were negative for anti-BP180NC16a antibody at onset, with a total BPDAI score of less than 31 or with an urticaria/erythema score of less than 7 can be treated without PSL. When the PSL is tapered to around 0.1 mg/kg, we should carefully monitor the patients to detect relapse.

Advances in the diagnosis of autoimmune bullous dermatoses

Autoimmune bullous dermatoses are defined by autoantibodies directed against adhesion proteins in the epidermis or basement membrane zone, resulting in blister formation on the skin and mucosa. Diagnosis depends on lesional biopsy for histopathology and perilesional biopsy for direct immunofluorescence. Additional diagnostic methods include indirect immunofluorescence, enzyme-linked immunosorbent assay, and immunoblot (Western blot), which may be selected in specific clinical scenarios due to improved sensitivity and/or specificity. This contribution reviews the available evidence supporting the use of each method to provide a practical reference for clinicians when diagnosing autoimmune bullous disorders. Techniques and cost are reviewed, and newer diagnostic techniques with potential for clinical application are.

Clinical and immunological features of pemphigus relapse

BACKGROUND

More than half of patients with pemphigus experience relapse during the disease course. The risk factors and clinical and immunological characteristics of relapse remain largely unclear.

OBJECTIVES

To elucidate the risk factors and clinical features of pemphigus relapse.

METHODS

We carried out a retrospective review of the clinical records of 42 cases of pemphigus at a single centre.

RESULTS

Sixty-two per cent of patients experienced relapse, usually when oral prednisolone was tapered to around 0·1 mg kg^-1 . In mucocutaneous pemphigus vulgaris (mcPV), the initial doses (mean ± SD) of prednisolone were significantly lower in patients with relapse (0·78 ± 0·24 mg kg^-1 ) than in those without relapse (1·01 ± 0·01 mg kg^-1 ). At relapse, mcPV shifted to mucosal dominant PV (mPV; 40%), pemphigus foliaceus (PF) (20%) or 'other' (20%). In contrast, relapsing mPV and PF had the same clinical phenotypes as the initial phenotypes. Patients with both anti-desmoglein (Dsg)1 and anti-Dsg3 antibodies at onset had recurrence with anti-Dsg3 antibodies alone (40%), with both anti-Dsg1 and anti-Dsg3 antibodies (30%), with anti-Dsg1 antibody alone (20%) or were subthreshold (10%).

CONCLUSIONS

mcPV shows transitions in clinical phenotype and autoantibody profile at relapse. At least 1 mg kg^-1 daily of prednisolone, especially for patients with mcPV, and prudent tapering around 0·1 mg kg^-1 may lead to better outcomes.

The Diagnosis and Blistering Mechanisms of Mucous Membrane Pemphigoid

Mucous membrane pemphigoid (MMP) is a mucous membrane-dominated autoimmune subepithelial blistering disease that is caused by autoantibodies against various autoantigens in basement membrane zone (BMZ) proteins, including collagen XVII (COL17). Clinicians face diagnostic problems in detecting circulating antibodies and targeted antigens in MMP. The diagnostic difficulties are mainly attributed to the low titers of MMP autoantibodies in sera and to heterogeneous autoantigens. Additionally, no unanimous diagnostic criteria have been drawn for MMP, which can result in delayed diagnoses or misdiagnoses. This review aims to integrate and present currently available data to clarify diagnostic strategies and to present diagnostic criteria for MMP. The ultimate blistering mechanism in MMP has not been elucidated, and such mechanism is especially obscure in COL17-type MMP. In bullous pemphigoid (BP), which is the most common autoimmune subepidermal blistering disease, some patients show oral lesion as well as predominant skin lesions. However, there is no fundamental explanation for the onset of oral lesions in BP. This article summarizes innovative research perspectives on the pathogenesis of oral lesions in pemphigoid. Finally, we propose a potential pathogenesis for COL17-type MMP.

High Index Values of Enzyme-Linked Immunosorbent Assay for BP180 at Baseline Predict Relapse in Patients With Bullous Pemphigoid

Bullous pemphigoid (BP) presenting with erythema plaques and tense blisters is the most frequent autoimmune bullous disease. Immunologically, BP is characterized by the presence of circulating anti-epidermal basement membrane zone (BMZ) antibodies. The autoantigens in BMZs targeted by patient's antibodies are mainly BP180 (type XVII collagen) and BP230. Previous reports have indicated that IgG to the immunodominant region of BP180 in BP, 16th non-collagenous domain (NC16A), and anti-BP180NC16A IgE are related to disease activity. In the cytokine profile, serum levels of IL-6, TNF-α, IL-15, and CCL18 were associated with the severity or activity of the disease. Blood eosinophilia is seen frequently, especially in severe cases. These biomarkers are helpful to evaluate efficacy of treatment and disease severity. Due to the high frequency of disease relapse, prediction of relapse at initiation of treatment (baseline) must be beneficial for clinicians. Therefore, we evaluated biomarkers anti-BP180 IgG (BP180 ELISA), anti-BP230 IgG (BP230 ELISA), peripheral eosinophils, and serum IgE at baseline between BP patients with (n = 16) and without (n = 31) relapse. We found significantly higher index values of BP180 ELISA in the relapse group, whereas no significant difference was found in BP230 ELISA, peripheral eosinophils, and serum IgE. This study indicated that a high index value of BP180 ELISA (cutoff value, 53.09 U/mL; sensitivity, 81.3%; specificity, 48.4%) at baseline may predict relapse in patients with BP. This may help clinicians treating BP patients in decision-making regarding duration and intensity of treatment.

Clinical and Immunological Profiles of 14 Patients With Bullous Pemphigoid Without IgG Autoantibodies to the BP180 NC16A Domain

Importance

Enzyme-linked immunosorbent assay (ELISA) and/or chemiluminescent enzyme immunoassay (CLEIA) for BP180 noncollagenous 16A (NC16A) extracellular domain is a sensitive diagnostic tool for bullous pemphigoid (BP). However, some patients with BP have negative results for these assays.

Objective

To elucidate the clinical and immunological features of patients with BP without antibodies that react to BP180 NC16A.

Design, Setting, and Participants

This retrospective case series study included 152 patients who were diagnosed with BP and followed up at the Kurume University Hospital in Japan from 2007 to 2016. The diagnosis was made using clinical, histological, and immunological findings.

Main Outcomes and Measures

Clinical and immunological features of patients with BP who had negative results for BP180 NC16A using ELISA and/or CLEIA.

Results

Of the 152 patients, 69 (45.4%) were men and 83 (54.6%) were women. The mean (SD) age of participants was 75.2 (14.4) years. Of the 152 patients with BP, 14 (9.2%) had negative results for BP180 NC16A on ELISA and/or CLEIA; most of these patients exhibited no erythema and had relatively mild phenotypes. Two (14%) of the 14 patients had positive results for intact BP180 in epidermal extracts, 10 (71%) had positive results for a 120-kD fragment of BP180 (LAD-1) and 3 (21%) had positive results for BP180 C-terminal domain. Seven (50%) patients tested positive in BP230 ELISA. Five (36%) patients did not require oral prednisolone treatment, whereas the others required a dose of prednisolone at less than 30 mg per day. Three (21%) patients were administered a dipeptidyl peptidase-4 inhibitor (DPP4i) before disease onset. This ratio was not significantly higher than that in patients with BP who tested positive for BP180 NC16A ELISA and/or CLEIA (19 [14%] of 138 patients). Our follow-up study (mean [SD], 31.9 [33.2] weeks; range, 0-108 weeks) revealed that patients with BP tested negative for BP180 NC16A ELISA and/or CLEIA during the later stages of the disease.

Conclusions and Relevance

This study indicates that patients with BP negative for BP180 NC16A ELISA and/or CLEIA had milder phenotypes, fewer erythemas, and required less extensive treatments.