Serum levels of BAFF are increased in bullous pemphigoid but not in pemphigus vulgaris

What is novel in the clinical management of pemphigus vulgaris?

INTRODUCTION

Pemphigus, an uncommon autoimmune blistering disorder affecting the skin and mucous membranes, currently with mortality primarily attributed to adverse reactions resulting from treatment protocols. Additionally, the existing treatments exhibit a notable recurrence rate. The high incidence of relapse and the considerable adverse effects associated with treatment underscore the imperative to explore safer and more effective therapeutic approaches. Numerous potential therapeutic targets have demonstrated promising outcomes in trials or preliminary research stages. These encompass anti-CD-20 agents, anti-CD-25 agents, TNF-α inhibition, FAS Ligand Inhibition, FcRn inhibition, BAFF inhibition, Bruton's tyrosine kinase (BTK) inhibition, CAAR T Cells, JAK inhibition, mTOR inhibition, abatacept, IL-4 inhibition, IL-17 inhibition, IL-6 inhibition, polyclonal Regulatory T Cells, and autologous hematopoietic stem cell transplantation.

AREAS COVERED

The most significant studies regarding the impact and efficacy of the mentioned treatments on pemphigus were meticulously curated through a comprehensive search conducted on the PubMed database. Moreover, the investigations of interest cited in these studies were also integrated.

EXPERT OPINION

The efficacy and safety profiles of the other treatments under discussion do not exhibit the same level of robustness as anti-CD20 therapy, which is anticipated to endure as a critical element in pemphigus treatment well into the foreseeable future.

Elevated serum BAFF in patients with ocular cicatricial pemphigoid

OBJECTIVE

The efficiency of B-cell depletion therapy for severe ocular cicatricial pemphigoid (OCP) highlights the key role of B lymphocytes in the immunopathogenesis of OCP. B-cell activating factor (BAFF) is a potent B-cell growth factor and costimulator of immunoglobulin production. Elevated serum BAFF is associated with systemic autoimmune diseases, such as systemic lupus erythematosus, rheumatoid arthritis and bullous pemphigoid. We hypothesize that serum BAFF levels are also increased in patients with OCP.

METHODS

Sera were collected from 30 patients with new-onset active OCP, 9 with disease in remission, 10 with OCP relapse, and 15 healthy control individuals. An enzyme-linked immunosorbent assay was performed to measure the concentration of serum BAFF.

RESULTS

BAFF was significantly higher in patients with new-onset active OCP (700.8 ± 181.8 pg/mL) than in healthy control individuals (564.1 ± 133.2 pg/mL; p = 0.014). No significant difference was found between patients with OCP in remission (585.4 ± 216.2 pg/mL) and healthy control individuals. Patients with disease relapse treated with rituximab had an extremely high concentration of BAFF (1721.9 ± 790.8 pg/mL). Longitudinal analysis of serum BAFF from 6 patients showed that BAFF decreased as the disease went from new onset (895.0 ± 240.8 pg/mL) to remission (625.4 ± 199.8 pg/mL; p = 0.003).

CONCLUSIONS

BAFF is involved in the active inflammation of OCP. Targeting BAFF with an antagonist may be therapeutically beneficial for patients with refractory OCP, especially those resistant to rituximab.

Targeting type 2 inflammation in bullous pemphigoid: current and emerging therapeutic approaches

Bullous pemphigoid (BP) is one of the most common autoimmune bullous diseases and mainly affects an elderly population with multi-morbidity. Due to the frailty of many BP patients, existing treatment options are limited. The blisters associated with BP result from IgG and IgE autoantibodies binding to the central components of hemidesmosome, BP180, and BP230, stimulating a destructive inflammatory process. The known characteristic features of BP, such as intense pruritus, urticarial prodrome, peripheral eosinophilia, elevated IgE, as well as recent expanding evidence from in vitro and in vivo studies implicate type 2 inflammation as an important driver of BP pathogenesis. Type 2 inflammation is an inflammatory pathway involving a subset of CD4+ T cells that secrete IL-4, IL-5, and IL-13, IgE-secreting B cells, and granulocytes, such as eosinophils, mast cells, and basophils. It is believed that effectors in type 2 inflammation may serve as novel and effective treatment targets for BP. This review focuses on recent understandings of BP pathogenesis with a particular emphasis on the role of type 2 inflammation. We summarize current clinical evidence of using rituximab (B-cell depletion), omalizumab (anti-IgE antibody), and dupilumab (anti-IL-4/13 antibody) in the treatment of BP. The latest advances in emerging targeted therapeutic approaches for BP treatment are also discussed.

Adaptive and innate immune pathogenesis of bullous pemphigoid: A review

Bullous pemphigoid (BP) is an autoimmune blistering disease that primarily affects elderly individuals. The presentation of BP is heterogeneous, typically manifesting as microscopic subepidermal separation with a mixed inflammatory infiltrate. The mechanism of pemphigoid development is unclear. B cells play a major role in pathogenic autoantibody production, and T cells, type II inflammatory cytokines, eosinophils, mast cells, neutrophils, and keratinocytes are also implicated in the pathogenesis of BP. Here, we review the roles of and crosstalk between innate and adaptive immune cells in BP.

The cytokine milieu of bullous pemphigoid: Current and novel therapeutic targets

Bullous pemphigoid (BP) is the most common autoimmune bullous disease, characterized by severe pruritus and skin blistering. The loss of tolerance against Collagen XVII, also referred to as BP180, is the main pathogenic event of BP, leading to production of IgG autoantibodies which mainly target the juxtamembranous extracellular non-collagenous 16th A (NC16A) domain of BP180. A complex inflammatory network is activated upon autoantibody binding to the basement membrane zone; this inflammatory loop involves the complement cascade and the release of several inflammatory cytokines, chemokines and proteases from keratinocytes, lymphocytes, mast cells and granulocytes. Collectively, these events disrupt the integrity of the dermal-epidermal junction, leading to subepidermal blistering. Recent advances have led to identify novel therapeutic targets for BP, whose management is mainly based on the long-term use of topical and systemic corticosteroids. As an example, targeting type-2 T-helper cell-associated cytokines, such as Interleukin-4 and interleukin-13 has shown meaningful clinical efficacy in case series and studies; targeting IL-17 and IL-23 has also been tried, owing to an important role of these cytokines in the chronic maintenance phase of BP. In this review article, we discuss the complex cytokine milieu that characterized BP inflammation, highlighting molecules, which are currently investigated as present and future therapeutic targets for this life-threatening disease.

Dipeptidyl Peptidase 4 Inhibitor‒Associated Bullous Pemphigoid Is Characterized by an Altered Expression of Cytokines in the Skin

Dipeptidyl peptidase 4 inhibitors (DPP4is), commonly used drugs for treatment of type 2 diabetes, increase the risk for bullous pemphigoid (BP). Currently, the mechanism leading to the loss of immunological tolerance of the cutaneous adhesion molecule BP180 as well as similarities and differences in disease progression between DPP4i-associated BP (DPP4i-BP) and DPP4i-independent regular BP are largely unknown. We analyzed the expression of 32 cytokines and two proteases by Luminex and ELISA assays in samples taken from lesional and nonlesional skin of patients with regular BP or DPP4i-BP and healthy controls. Cytokines mediating B-cell survival and targeting such as BAFF, CCL4, CXCL12, and IL-6 were expressed at a higher level in the lesional regular BP skin than the levels in the lesional DPP4i-BP skin. The DPP4i-BP samples had increased levels of eosinophilic cytokines CCL1, CCL17, CCL26, and IL-5, which correlated with the serum level of anti-BP180 NC16A IgG autoantibodies. The mRNA expression of BAFF, IL6, CCL1, CCL17, CCL26, and IL5 measured by qPCR correlated with the protein levels. Taken together, the cutaneous cytokine profiles were found to provide distinctive molecular fingerprints between regular BP and DPP4i-BP.

Increased gene expression of B cell-activating factor of tumor necrosis factor family, in remitting antineutrophil cytoplasmic antibody-associated vasculitis patients

AIM

To study the expression of B cell-activating factor of tumor necrosis factor family (BAFF) and A proliferation-inducing ligand (APRIL) genes in active and remitting patients with anti-neutrophil cytoplasmic antibody-associated vasculitis (AAV) and healthy controls and their correlation with disease activity.

METHODS

This was a prospective case-control study. Gene expressions of BAFF and APRIL were studied in 32 patients with AAV (16 each with active disease and in remission) and 30 healthy age and sex matched controls by real-time polymerase chain reaction.

RESULTS

Out of 32 AAV patients, 26 had granulomatosis with polyangiitis (GPA) and 6 had microscopic polyangiitis (MPA). Mean ages of patients in active (12 GPA and 4 MPA) and remission (14 GPA and 2 MPA) groups were 39.4 ± 17.2 and 44.6 ± 16.1 years, respectively. BAFF gene expression was significantly higher in both the active AAV group and remission AAV group compared to controls (P < .01). The BAFF expression was significantly higher in AAV patients in remission compared to active AAV patients (P = .003). In contrast, APRIL expression did not differ between AAV patients and controls (P = .829). However, APRIL had significantly higher expression in remission as compared to active patients (P = .048). There was no significant correlation of both BAFF and APRIL expression with disease activity markers (erythrocyte sedimentation rate, C-reactive protein, platelets and Birmingham Vasculitis Activity Score version 3).

CONCLUSION

BAFF gene is significantly expressed in patients with AAV. Among AAV patients, there is a significantly higher expression of BAFF and APRIL in remitting state of the disease as compared to active state. There is no significant change in APRIL gene expression in patients with AAV as compared to controls. This makes a case for anti-BAFF therapy in future for AAV patients in northern India.

Emerging Biomarkers and Therapeutic Strategies for Refractory Bullous Pemphigoid

Bullous pemphigoid (BP) is the most common autoimmune subepidermal blistering disorder in the elderly. Systemic and topical use of glucocorticoids and immunosuppressants has been shown to be effective in most patients. However, refractory BP patients are challenged to clinicians with severe clinical symptoms, resistance to treatment, and high relapse rate. How to predict and assess the refractory and severity of bullous pemphigoid is the key issue in clinical practice, and the urgent need for precision medicine in refractory patients is driving the search for biomarkers and biologics. Recently, some biomarkers, such as the level of specific autoantibodies and released cytokines, have been proposed as the potential parameters to reflect the disease severity and predict the treatment response and relapse of refractory BP. Moreover, new biologics targeting pathogenic antibodies, complement, Th2 axis, eosinophils, and Th17 axis have shown potent efficacy on refractory BP. Here, we review the literature and give an overview of emerging biomarkers and therapeutic strategies for refractory bullous pemphigoid to improve the prognosis of the patient.

Biologics in autoimmune bullous diseases: Current scenario

Autoimmune bullous diseases can be intraepidermal (pemphigus group of disorders) or subepidermal (pemphigoid group of disorders). The treatment of these disorders chiefly comprises corticosteroids and immunosuppressant adjuvants like azathioprine and mycophenolate mofetil. Autoantibodies are the main mediators of these diseases. Rituximab, a chimeric anti-CD20 monoclonal antibody targeting B-cells, has emerged as an excellent treatment option for refractory pemphigus vulgaris in the last decade. Since then, many new biologics have been proposed/explored for managing autoimmune bullous diseases. These hold potential for greater efficacy and lesser adverse effects than conventional immunosuppressants. In this review, we discuss the role of various biologics in the treatment of autoimmune bullous diseases, followed by a brief discussion on the drawbacks to their use and new developments in this area.

Modifications of the BAFF/BAFF-Receptor Axis in Patients With Pemphigus Treated With Rituximab Versus Standard Corticosteroid Regimen

The efficacy of the B-cell-depleting agent rituximab has been reported in immune diseases but relapses are frequent, suggesting the need for repeated infusions. The B-cell activating factor (BAFF) is an important factor for B cell survival, class switch recombination and selection of autoreactive B cells, as well as maintaining long-lived plasma cells. It has been hypothesized that relapses after rituximab might be due to the increase of serum BAFF levels. From the Ritux3 trial, we showed that baseline serum BAFF levels were higher in pemphigus patients than in healthy donors (308 ± 13 pg/mL versus 252 ± 28 pg/mL, p=0.037) and in patients with early relapse compared who didn't (368 ± 92 vs 297 ± 118 pg/mL, p=0.036). Rituximab and high doses of CS alone have different effects on the BAFF/BAFF-R axis. Rituximab led to an increase of BAFF levels associated to a decreased mRNA (Day 0: 12.3 ± 7.6 AU vs Month 36: 3.3 ± 4.3 AU, p=0.01) and mean fluorescence intensity of BAFF-R in non-autoreactive (Day 0: 3232 vs Month 36: 1527, mean difference: 1705, 95%CI: 624 to 2786; p=0.002) as well as on reappearing autoreactive DSG-specific B cells (Day 0: 3873 vs Month 36: 2688, mean difference: 1185, 95%CI: -380 to 2750; p=0.20). Starting high doses of corticosteroids allowed a transitory decrease of serum BAFF levels that re-increased after doses tapering whereas it did not modify BAFF-R expression in autoreactive and non-autoreactive B cells. Our results suggest that the activation of autoreactive B cells at the onset of pemphigus is likely to be related to the presence of high BAFF serum levels and that the decreased BAFF-R expression after rituximab might be responsible for the delayed generation of memory B cells, resulting in a rather long period of mild pemphigus activity after rituximab therapy. Conversely, the incomplete B cell depletion and persistent BAFF-R expression associated with high BAFF serum levels might explain the high number of relapses in patients treated with CS alone.

Novel Therapies for Pemphigus Vulgaris

Pemphigus vulgaris (PV) is a severe chronic autoimmune blistering disease that affects the skin and mucous membranes. It is characterized by suprabasal acantholysis due to disruption of desmosomal connections between keratinocytes. Autoantibodies against desmosomal cadherins, desmoglein 3 and 1, have been shown to induce disease. Certain human leukocyte antigen (HLA) types and non-HLA foci confer genetic susceptibility. Until the discovery of corticosteroids in the 1950s, PV was 75% fatal. Since then, multiple PV treatments, such as systemic corticosteroids and adjunctive therapy with immunosuppressive medications (mycophenolate mofetil, azathioprine, cyclophosphamide, cyclosporine, methotrexate, gold, and others) have been introduced; however, none have led to long-term remissions and many have undesired adverse effects. Our growing understanding of the pathophysiologic mechanisms in PV is leading to development of new targeted therapies, such as intravenous immunoglobulin, anti-CD20 monoclonal antibodies, inhibitors of Bruton tyrosine kinase and neonatal Fc receptors, and adoptive cellular transfer, that may result in lasting control of this life-threatening disease.

B-cell targeted therapies in pemphigus

Pemphigus is a rare autoimmune disease of the skin, characterized by autoantibodies targeting adhesion proteins of the epidermis, in particular desmoglein 3 and desmoglein 1, that cause the loss of cell-cell adhesion and the formation of intraepidermal blisters. Given that these autoantibodies are both necessary and sufficient for pemphigus to occur, the goal of pemphigus therapy is the elimination of autoreactive B-cells responsible for autoantibody production. Rituximab, an anti-CD20 monoclonal antibody, was the first targeted B-cell therapy approved for use in pemphigus and is now considered the frontline therapy for new onset disease. One limitation of this treatment is that it targets both autoreactive and non -autoreactive B-cells, which accounts for the increased risk of serious infections in treated patients. In addition, most rituximab-treated patients experience disease relapse, highlighting the need of new therapeutic options. This review provides a concise overview of rituximab use in pemphigus and discusses new B-cell and antibody-directed therapies undergoing investigation in clinical studies.

Role of B cells in immune-mediated dermatoses

Although T cells are considered as the central component in immune-mediated diseases, supportive evidence has demonstrated that B cells also contribute to the progression of these diseases. B cells are divided into various subsets according to their secreted cytokines. Different B cell subsets play diverse roles in immune-mediated dermatoses. Regulatory B cells (Bregs) are defined functionally by their ability to secrete IL-10, which has been revealed to contribute to immunological tolerance. Drugs that deplete B cells, such as rituximab, are now used for the treatment of several immune-mediated dermatoses. In this review, we present and discuss the current knowledge on the roles of B cells in several immune-mediate dermatoses including psoriasis, pemphigus, bullous pemphigoid, and dermatomyositis, atopic dermatitis.

Beyond the HLA polymorphism: A complex pattern of genetic susceptibility to pemphigus

Pemphigus is a group of autoimmune bullous skin diseases that result in significant morbidity. As for other multifactorial autoimmune disorders, environmental factors may trigger the disease in genetically susceptible individuals. The goals of this review are to summarize the state of knowledge about the genetic variation that may affect the susceptibility and pathogenesis of pemphigus vulgaris and pemphigus foliaceus – both the endemic and the sporadic forms –, to compare and discuss the possible meaning of the associations reported, and to propose recommendations for new research initiatives. Understanding how genetic variants translate into pathogenic mechanisms and phenotypes remains a mystery for most of the polymorphisms that contribute to disease susceptibility. However, genetic studies provide a strong foundation for further developments in this field by generating testable hypotheses. Currently, results still have limited influence on disease prevention and prognosis, drug development, and clinical practice, although the perspectives for future applications for the benefit of patients are encouraging. Recommendations for the continued advancement of our understanding as to the impact of genetic variation on pemphigus include these partially overlapping goals: (1) Querying the functional effect of genetic variants on the regulation of gene expression through their impact on the nucleotide sequence of cis regulatory DNA elements such as promoters and enhancers, the splicing of RNA, the structure of regulatory RNAs and proteins, binding of these regulatory molecules to regulatory DNA elements, and alteration of epigenetic marks; (2) identifying key cell types and cell states that are implicated in pemphigus pathogenesis and explore their functional genomes; (3) integrating structural and functional genomics data; (4) performing disease-progression longitudinal studies to disclose the causal relationships between genetic and epigenetic variation and intermediate disease phenotypes; (5) understanding the influence of genetic and epigenetic variation in the response to treatment and the severity of the disease; (6) exploring gene-gene and genotype-environment interactions; (7) developing improved pemphigus-prone and non-prone animal models that are appropriate for research about the mechanisms that link genotypes to pemphigus. Achieving these goals will demand larger samples of patients and controls and multisite collaborations.

BAFF serum and CSF levels in patients with multiple sclerosis and infectious nervous system diseases

Purpose: Multiple sclerosis (MS) is the most common immune-mediated CNS disease, characterised by demyelination and progressive neurological disability. The B-cell activating factor BAFF has been described as one important factor in the pathophysiology of different autoimmune diseases.Methods: We measured BAFF levels in the serum and cerebrospinal fluid (CSF) in 50 consecutive patients with MS and 35 patients with infectious CNS disease (ID). 52 patients with other, non-inflammatory disorders (OND), served as controls.Results: BAFF-serum levels in ID patients were higher than in patients diagnosed with MS (ID 0.55 ± 0.24 ng/ml, MS 0.43 ± 0.14 ng/ml, OND 0.45 ± 0.24 ng/ml; p = 0.09). Interestingly, MS patients had lower BAFF CSF levels compared to the controls and ID patients, and the CSF levels in the latter were elevated compared to those of the controls (MS 0.17 ± 0.11 ng/ml, OND 0.25 ± 0.14 ng/ml, ID 0.97 ± 0.78 ng/ml; p < 0.001).Conclusions: The ID patients' having higher absolute BAFF levels in the CSF than in the serum indicates that the increased BAFF CSF levels were caused by intrathecal synthesis rather than passive transfer via a disturbed blood-brain-barrier. The significantly decreased BAFF CSF levels in MS patients were a surprising result of our study. Although it has been reported that astrocytes in active MS lesions can express BAFF, the soluble form was not increased in the CSF of MS patients. It remains unclear whether the inflammatory features of active MS plaques are truly represented by the CSF compartment.

Autoreactive IgG and IgA B Cells Evolve through Distinct Subclass Switch Pathways in the Autoimmune Disease Pemphigus Vulgaris

Lineage analysis of autoreactive B cells can reveal the origins of autoimmunity. In the autoimmune disease pemphigus vulgaris (PV), desmoglein 3 (DSG3) and DSG1 autoantibodies are predominantly of the IgG4 subclass and less frequently of IgG1 and IgA subclasses, prompting us to investigate whether anti-DSG IgG4 B cells share lineages with IgG1, IgA1, and IgA2. Combining subclass-specific B cell deep sequencing with high-throughput antibody screening, we identified 80 DSG-reactive lineages from 4 PV patients. Most anti-DSG IgG4 B cells lacked clonal relationships to other subclasses and preferentially targeted DSG adhesion domains, whereas anti-DSG IgA frequently evolved from or to other subclasses and recognized a broader range of epitopes. Our findings suggest that anti-DSG IgG4 B cells predominantly evolve independently or diverge early from other subclasses and that IgA is most often not the origin of IgG autoreactivity in PV. These data provide insight into how autoreactivity diversifies across B cell subclasses.

Ellebrecht et al. use next-generation sequencing to identify clonal relationships among antigen-specific B cells in the autoimmune disease pemphigus vulgaris. They find that autoreactive IgG4 B cells are largely clonally distinct from autoreactive IgG1 and IgA, thus elucidating the class-switch pathways that diversify and modify an autoimmune response in humans.

Updates on diagnosis and management of autoimmune blistering diseases

Over the last several decades, advances in the understanding of the pathogenesis of autoimmune blistering diseases has resulted in significant improvements in diagnosis and management. These improvements include new diagnostic assays and therapies targeted at specific disease mediators. Furthermore, the abundance of new therapies in clinic trials for autoimmune blistering diseases will translate to an enhanced therapeutic armamentarium for clinicians. The aim of this article is to review new developments in the understanding of autoimmune blistering diseases and to summarize advancements in their diagnosis and management.

Treatment of pemphigus vulgaris: part 2 - emerging therapies

Introduction: Corticosteroids and immunosuppressive agents have been the mainstay for the treatment of pemphigus vulgaris (PV). While they have benefited patients, they have been associated with the risks of prolonged immune suppression and a high incidence of significant and catastrophic side effects. Relapses are common. Novel agents promising targeted therapies, that may provide better outcomes, are being studied. Areas covered: Recently rituximab with corticosteroids has been recommended as the first-line treatment for PV. A number of known and new therapeutic agents currently investigated are BAFF, P13K, BTK inhibitors along with the use of IVIg and CAR-T therapy. The possible role of these therapeutic targets in the pathophysiology appears to be the rationale for the treatment of this potentially fatal disease. Expert opinion: While there is significant enthusiasm for these therapies, certain concerns and consequences are being under-discussed. None of the current clinical trials in progress are specific for PV, except possibly CAR-T therapy. The major issue(s) that are unclear is whether these therapies would be successful in providing long-term clinical remissions. Will these therapies require additional agents to be effective? Will the benefits be limited in duration? The answers to many questions will determine their final place in the algorithm for the treatment of PV.

Targeted Therapies for Autoimmune Bullous Diseases: Current Status

Autoimmune bullous skin disorders are rare but meaningful chronic inflammatory diseases, many of which had a poor or devastating prognosis prior to the advent of immunosuppressive drugs such as systemic corticosteroids, which down-regulate the immune pathogenesis in these disorders. Glucocorticoids and adjuvant immunosuppressive drugs have been of major benefit for the fast control of most of these disorders, but their long-term use is limited by major side effects such as blood cytopenia, osteoporosis, diabetes mellitus, hypertension, and gastrointestinal ulcers. In recent years, major efforts were made to identify key elements in the pathogenesis of autoimmune bullous disorders, leading to the identification of their autoantigens, which are mainly located in desmosomes (pemphigus) and the basement membrane zone (pemphigoids). In the majority of cases, immunoglobulin G, and to a lesser extent, immunoglobulin A autoantibodies directed against distinct cutaneous adhesion molecules are directly responsible for the loss of cell-cell and cell-basement membrane adhesion, which is clinically related to the formation of blisters and/or erosions of the skin and mucous membranes. We describe and discuss novel therapeutic strategies that directly interfere with the production and regulation of pathogenic autoantibodies (rituximab), their catabolism (intravenous immunoglobulins), and their presence in the circulation and extravascular tissues such as the skin (immunoadsorption), leading to a significant amelioration of disease. Moreover, we show that these novel therapies have pleiotropic effects on various proinflammatory cells and cytokines. Recent studies in bullous pemphigoid suggest that targeting of immunoglobulin E autoantibodies (omalizumab) may be also beneficial. In summary, the introduction of targeted therapies in pemphigus and pemphigoid holds major promise because of the high efficacy and fewer side effects compared with conventional global immunosuppressive therapy.

Pharmacological advances in pemphigus

This is an updated review of the literature on the emerging therapeutic options for the treatment of pemphigus to provide better care for patients. There is an increasing range of molecules targeted for pemphigus therapy against CD20, Bruton tyrosine kinase, chimeric antigen receptor, T-cell immune components, B-cell activating factor, proliferation-inducing ligand (APRIL), CD25, p38 mitogen-activated protein kinase (p38MAPK) and cytokine modulation therapies (anti-IL-4, anti-IL-6). The main aim of the current new therapies is to provide specific pathology-focused therapeutic options which have long-term sustainable therapeutic effects on disease progress, cause less side effects without systemic immunosuppression, and have less risk of getting antibodies against the medication during treatment.

Biological therapy of autoimmune blistering diseases

INTRODUCTION

Autoimmune blistering skin diseases are a group of disorders subdivided according to the location of blister formation: intraepidermal blistering in the pemphigus group and subepidermal in the pemphigoid group. These conditions are clinically heterogeneous and are treated with systemic corticosteroids and/or other forms of immunosuppression on the basis of clinical subtype and disease severity. These approaches may not be effective for the induction and maintenance of clinical response or need to be stopped because of intolerable side effects.

AREAS COVERED

Biological therapies can represent a valid alternative strategy in various autoimmune blistering disorders and this review article will address this issue with a special focus on pemphigus vulgaris and bullous pemphigoid. These biological approaches are designed to target B cells, autoantibodies, complement proteins, and several cytokines.

EXPERT OPINION

Innovative strategies for the treatment of autoimmune blistering conditions primarily depend on the use of drugs with a high degree of specificity targeting crucial steps in the immunopathology of these disorders. Novel biological agents offer treatment alternatives to patients with autoimmune blistering conditions by targeting B cells, pathogenic autoantibodies, complement and cytokines.

The Role of Eosinophils in Bullous Pemphigoid: A Developing Model of Eosinophil Pathogenicity in Mucocutaneous Disease

Bullous pemphigoid (BP) is an autoimmune blistering disease which carries a significant mortality and morbidity. While historically BP has been characterized as an IgG driven disease mediated by anti-BP180 and BP230 IgG autoantibodies, developments in recent years have further elucidated the role of eosinophils and IgE autoantibodies. In fact, eosinophil infiltration and eosinophilic spongiosis are prominent features in BP. Several observations support a pathogenic role of eosinophils in BP: IL-5, eotaxin, and eosinophil-colony stimulating factor are present in blister fluid; eosinophils line the dermo-epidermal junction (DEJ) in the presence of BP serum, metalloprotease-9 is released by eosinophils at the site of blisters; eosinophil degranulation proteins are found on the affected basement membrane zone as well as in serum corresponding with clinical disease; eosinophil extracellular DNA traps directed against the basement membrane zone are present, IL-5 activated eosinophils cause separation of the DEJ in the presence of BP serum; and eosinophils are the necessary cell required to drive anti-BP180 IgE mediated skin blistering. Still, it is likely that eosinophils contribute to the pathogenesis of BP in numerous other ways that have yet to be explored based on the known biology of eosinophils. We herein will review the role of eosinophils in BP and provide a framework for understanding eosinophil pathogenic mechanisms in mucocutaneous disease.

Emerging treatment options for the management of pemphigus vulgaris

Pemphigus vulgaris (PV) is a life-threatening disease belonging to the pemphigus group of autoimmune intra-epidermal bullous diseases of the skin and mucosae. The therapeutic management of PV remains challenging and, in some cases, conventional therapy is not adequate to induce clinical remission. The cornerstone of PV treatment remains systemic corticosteroids. Although very effective, long-term corticosteroid administration is characterized by substantial adverse effects. Corticosteroid-sparing adjuvant therapies have been employed in the treatment of PV, aiming to reduce the necessary cumulative dose of corticosteroids. Specifically, immunosuppressive agents such as azathioprine and mycophenolate mofetil are widely used in PV. More recently, high-dose intravenous immunoglobulins, immunoadsorption, and rituximab have been established as additional successful therapeutic options. This review covers both conventional and emerging therapies in PV. In addition, it sheds light on potential future treatment strategies for this disease.

Glucocorticoids: The mode of action in bullous pemphigoid

Bullous pemphigoid (BP) is the most common of pemphigoid diseases caused by autoantibodies against the structures of dermoepidermal junction followed by complement activation, innate immune cell infiltration, neutrophil proteinase secretion and subepidermal blister formation. The first-line treatment of BP is topical and systemic glucocorticoids (GC). Regulation of the immune system and inflammatory cells is the main target of GC actions. GCs act through genomic and non-genomic mechanisms. The human glucocorticoid receptor (GR) mediates most of the biologic effects of GC: cytosolic GR binds GCs and is capable to bind to glucocorticoid response elements in DNA and either transactivate or transrepress genes depending on the tissue and cell type. In addition, GR exerts rapid, non-genomic effects possibly mediated by membrane-localized receptors or by translocation to mitochondria. GCs can also interact directly with several enzymes and cytokines. As a target treatment for BP, the production of autoantibodies should be discontinued. GCs, in spite of their wide immunosuppressive actions, are weak to stop immunoglobulin G (IgG) autoantibody formation. However, both systemic and topical GCs are able to reduce the clinical symptoms of BP. GCs are used to inhibit the secondary inflammation and symptoms, such as blistering and pruritus, and it is shown that GC treatment will gradually decrease also the autoantibody formation. Our review article analyses the mode of action of GC treatment in BP, as far it is possible due to paucity of modern immunological studies.

B-cell-activating factor, a proliferation inducing ligand and co-stimulatory molecules in the pathogenesis of immune thrombocytopenia in childhood

The aim of this study was to measure the levels of B-cell-activating factor (BAFF), a proliferation-inducing ligand (APRIL), and co-stimulatory molecules in immune thrombocytopenia (ITP) of childhood to investigate the interaction between T and B lymphocytes and the impact of proliferation of B lymphocytes in the pathogenesis. Twenty newly diagnosed ITPs, 20 chronic ITPs, and 20 healthy controls between 2 and 18 years were enrolled in this study. Hemogram, BAFF, APRIL, interleukin-4, and interferon (IFN)-γ levels in sera and expressions of CD19, CD 3, CD21, CD40, and CD 154 on leukocytes were measured by ELISA and flow cytometry. Mean BAFF level in newly diagnosed ITP group was higher than the mean BAFF level in other groups. BAFF levels were significantly decreased after the treatment in newly diagnosed ITP group. APRIL, interleukin-4, and IFN-γ in newly diagnosed ITP group and BAFF, APRIL, interleukin-4, and IFN-γ in chronic ITP group were similar before and after treatment. There was no statistical difference for expressions of CD 19 and CD3 on lymphocytes, CD40 on leukocytes, CD154 on T cells, and for percentages of CD21/CD40, CD21/CD40, CD21/CD40 B cells, and CD19/CD3 lymphocytes for pretreatment and posttreatment levels in both ITP groups. In conclusion, our study strongly demonstrated that BAFF has an important role in the pathogenesis of newly diagnosed childhood ITP. It may be important in the follow-up and in novel therapy modalities of these patients.

Immune thrombocytopenia and B-cell-activating factor/a proliferation-inducing ligand

Primary immune thrombocytopenia (ITP) is an organ-specific autoimmune disorder characterized by autoantibody-mediated enhanced platelet destruction and dysmegakaryocytopoiesis. B cells have been demonstrated to play critical roles in the pathophysiology of ITP. B-cell-activating factor (BAFF) and a proliferation-inducing ligand (APRIL) are crucial cytokines supporting survival and differentiation of B cells, and dysregulation of BAFF/APRIL is involved in the pathogenesis of B-cell related autoimmune diseases including ITP. Currently ongoing clinical trials using BAFF and/or APRIL-blocking agents have yielded positive results in human systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA), further confirming the pathological role of BAFF/APRIL in autoimmunity. This review will describe the function of BAFF/APRIL and address the feasibility of BAFF/APRIL inhibition in the management of ITP.

Functional and clinical aspects of the B-cell-activating factor (BAFF): a narrative review

B-cell-activating factor (BAFF) influences peripheral B-cell survival, maturation and immunoglobulin class-switch recombination and has a range of potential clinical implications. Biological functions of BAFF and its relevance in various clinical disorders including currently investigated BAFF-targeting therapies are reviewed and discussed based on PubMed search of relevant articles. Serum levels of BAFF are increased in autoimmune diseases including autoimmune hepatitis and primary biliary cirrhosis where BAFF concentrations are related to titres of autoantibodies and disease progression. Increased BAFF levels are found in synovial, bronchoalveolar and gut lavage fluids, suggesting local class switching and immunoglobulin production. Clinical relevance and diagnostic potential of BAFF are also noted in patients with allergic diseases, malignancies and infections including hepatitis C virus. BAFF antagonists are promising new therapeutic agents, currently being tried in B-cell-related autoimmune diseases. Serum level of BAFF may indicate disease mechanisms and the degree of activity. Determination of BAFF in different body compartments like synovium, airways and gut may also have clinical implications. Results of ongoing clinical trials with BAFF antagonists are eagerly awaited.

Rituximab mediates a strong elevation of B-cell-activating factor associated with increased pathogen-specific IgG but not autoantibodies in pemphigus vulgaris

Pemphigus vulgaris (PV) is a severe autoimmune disease affecting the skin and mucous membranes, characterized by autoantibodies mainly against desmoglein 3 (dsg3). This study investigated the effects of different treatment options on two B-cell mediators, B-cell-activating factor (BAFF) and a proliferation-inducing ligand (APRIL), in 19 PV patients on immunosuppressive drugs alone or in combination with immunoadsorption and anti-CD20 antibody, respectively. Serum BAFF and APRIL levels, circulating desmoglein-reactive autoantibodies, and serum IgG specific for varicella-zoster virus (VZV) and Epstein-Barr virus (EBV) were determined by ELISA before and at different time points after initiation of the respective therapy. In contrast to immunosuppressive therapy alone and in combination with adjuvant immunoadsorption, respectively, rituximab treatment led to a strong and significant elevation of BAFF, but not of APRIL levels, which normalized upon recovery of peripheral CD19(+) B cells. Moreover, rituximab treatment led to a statistically significant increase of anti-VZV-IgG and anti-EBV-IgG titers, whereas anti-dsg1 and -3 specific autoantibody titers decreased significantly. Our results suggest that elevated BAFF levels might exert a differential effect on the induction of autoreactive versus pathogen-specific IgG antibody production in PV patients, possibly due to promotion of antibody release of pathogen-specific long-lived plasma cells.

B-cell-directed therapy for inflammatory skin diseases

The basic understanding of inflammatory dermatoses and autoimmune-mediated skin disorders has greatly advanced and broadened our understanding of underlying immune mechanisms that shape the complex network of chronic inflammation and autoimmunity. The new treatment options for psoriasis exemplify how new insights into (auto)immune responses, especially the role and function of various immune cells and proinflammatory cytokines, may lead to new therapeutic strategies. The concept of targeting B cells in autoimmune-mediated disorders is closely related to the discovery of autoantibodies and their cellular origin. However, the appreciation of B cells in autoimmunity has significantly changed and is not limited to their role as progenitors of autoantibody secreting plasma cells. Recent investigations of various inflammatory skin diseases, that is, autoimmune blistering disorders, collagen vascular diseases, and atopic dermatitis, actually support the concept that B cells might be as important as T cells in the etiopathogenesis of these disorders. The striking clinical improvement seen in patients with rheumatoid arthritis following B-cell depletion with the anti-CD20 mAb rituximab has tremendously catalyzed the interest in B-cell-targeted therapies in different autoimmune diseases. Future translational and clinical investigations are mandatory to precisely define the role and the contribution of impaired B-cell function in (auto)immune-mediated skin diseases.

Blistering skin disorders: an evidence-based update. Conference report

Evidence-based update meetings are held annually by the Centre of Evidence Based Dermatology, University of Nottingham. Past topics have included important themes such as eczema, psoriasis, hair disorders and skin cancers. This year, the seventh Evidence Based Update meeting focused on blistering disorders and took place in Loughborough University on 5 June 2008. The latest data on incidence and mortality, therapeutic trials and management of bullous pemphigoid, pemphigus and epidermolysis bullosa (EB) were presented by an international panel of renowned speakers. The highlights of the meeting included an informal atmosphere, an international perspective, a practical question and answer session and hearing first-hand a patient and carer's perspective of living with EB.

[B-cell-depleting antibodies in skin diseases]

Basic insight into immune mechanisms, particularly the role and function of various immune cells and proinflammatory cytokines in the etiopathogenesis of inflammatory dermatoses and autoimmune skin disorders, has made possible the development of novel therapeutic strategies. Because of their properties as antigen presenting cells and progenitors of autoantibody-secreting plasma cells, B cells have a major impact in different autoimmune diseases and represent an important therapeutic target. The remarkable clinical improvement seen in patients with rheumatoid arthritis after treatment with the monoclonal anti-CD20 antibody, rituximab, has strongly augmented the interest in B-cell-targeted therapies in different autoimmune diseases. Future clinical and immunological investigations are mandatory to precisely define the contribution of impaired B-cell function in development and progression of autoimmune mediated skin disorders.

Dexamethasone inhibits BAFF expression in fibroblast-like synoviocytes from patients with rheumatoid arthritis

Fibroblast-like synoviocytes (FLS) play a major role in the pathogenesis of rheumatoid arthritis (RA). FLS isolated from patients with RA (FLS-RA) express B cell-activating factor belonging to the TNF family (BAFF), a cytokine that has been associated with the onset and progression of RA. Glucocorticoids are powerful anti-inflammatory drugs used in the treatment of RA. In the present study, we examined the effect of dexamethasone (Dex) on constitutive and TNF-alpha- and IFN-gamma-induced BAFF expression in FLS-RA. BAFF mRNA expression and soluble BAFF were determined by RT-PCR and ELISA, respectively. The results showed that constitutive BAFF mRNA expression was inhibited by Dex in a dose- and time-dependent manner. Also, Dex inhibited the secretion of BAFF in a time-dependent manner reaching 76% of inhibition 72 h after treatment. Moreover, Dex suppressed both mRNA and protein BAFF expression induced by TNF-alpha but had no effect on IFN-gamma-induced BAFF expression. In comparison with B cells cultured alone, B cells co-cultured with FLS-RA exhibited a higher survival, which was inhibited when FLS-RA were pretreated with Dex. However, the enhanced B cell survival was reestablished by the addition of rhBAFF. Therefore, Dex is a potent inhibitor of constitutive and TNF-alpha-induced BAFF expression in FLS-RA.

Increased serum levels of a proliferation-inducing ligand in patients with bullous pemphigoid

BACKGROUND

B cells have been demonstrated to have critical roles in developing autoimmune bullous diseases. Recently identified tumor necrosis factor-like molecules, B cell-activating factor of the TNF family (BAFF) and a proliferation-inducing ligand (APRIL) are essential molecules for B cell development, survival, and proliferation. Although the functions of APRIL have not been fully evaluated, recent studies suggest that circulating levels of APRIL are increased in various autoimmune diseases, including systemic lupus erythematosus and rheumatoid arthritis.

OBJECTIVES

To determine serum APRIL levels in patients with pemphigus vulgaris (PV) and bullous pemphigoid (BP), and compare those with clinical findings and laboratory findings.

PATIENTS/METHODS

Sera from 15 PV patients, 43 BP patients, and 15 normal controls were subjected to ELISA assays to measure serum APRIL, BAFF, Dsg3, and BP180 levels.

RESULTS AND CONCLUSIONS

Circulating APRIL levels were significantly elevated in BP patients but not in PV patients, and correlated with serum BAFF levels. Our study revealed that serum APRIL levels tended to be increased in the quite early stage of disease. In conclusion, circulating APRIL levels may be a useful marker for early activation of autoimmune diathesis, and furthermore, an effective therapeutic target molecule in patients with BP.