Decreases in the numbers of peripheral blood regulatory T cells, and increases in the levels of memory and activated B cells, in patients with active eosinophilic granulomatosis and polyangiitis

Refractory Eosinophilic Granulomatosis with Polyangiitis Complicated with IgG4-related Disease Showing Different Treatment Responses for Each Organ

We herein report a 75-year-old woman who presented with dyspnea and purpura. She was diagnosed with eosinophilic granulomatosis with polyangiitis (EGPA) based on axonal damage observed in the left tibial nerve and skin and lung pathologies. Lung pathology showed IgG4-positive plasma cells, considered a complication of IgG4-related disease (IgG4-RD). Computed tomography revealed thickening of the abdominal aorta and a poor contrast area in the left kidney, which was indicative of IgG4-RD. Steroid administration improved the IgG4-RD. However, the EGPA resisted treatment; therefore, immunosuppressive drugs and mepolizumab were administered. Refractory EGPA complicated with IgG4-RD showed different treatment responses for each organ.

Therapeutic Advances in Eosinophilic Granulomatosis with Polyangiitis

Eosinophilic granulomatosis with polyangiitis (EGPA) is an eosinophilic vasculitis that affects a variety of organ systems. Historically, glucocorticoids and a variety of other immunosuppressants were used to abrogate the inflammation and tissue injury associated with EGPA. The management of EGPA has evolved greatly during the last decade with the development of novel targeted therapeutics that have resulted in significantly improved outcomes for these patients, with many more novel targeted therapies emerging.

Long-term mepolizumab treatment reduces relapse rates in super-responders with eosinophilic granulomatosis with polyangiitis

BACKGROUND

The mainstay of treatment for eosinophilic granulomatosis with polyangiitis (EGPA) is systemic corticosteroid therapy; some patients also receive intravenous immunoglobulins, other immunosuppressive agents, and biologics. Mepolizumab, an anti-interleukin-5 monoclonal antibody, induces remission and decreases the daily corticosteroid dose; however, the clinical efficacy of mepolizumab in EGPA and the prognosis with long-term treatment with this drug are unknown.

METHODS

Seventy-one EGPA patients were treated at Hiratsuka City Hospital, Japan, between April 2018 and March 2022. We administered mepolizumab for a mean of 2.8 ± 1.7 years to 43 patients in whom remission could not be induced by conventional treatment. After excluding 18 patients who had received mepolizumab for less than 3 years, we classified 15 patients into a "super-responder group" (the daily dose of corticosteroids or other immunosuppressant could be decreased, or the interval between IVIG treatments could be prolonged) and 10 patients into a "responder group" (neither of these changes was achievable). Eosinophil numbers, serum IgG levels, daily doses of corticosteroids and other immunosuppressants, Birmingham Vasculitis Activity Score (BVAS), and relapse frequency before and after mepolizumab initiation were determined.

RESULTS

Blood eosinophil count at diagnosis and the lowest serum IgG level before mepolizumab treatment were significantly higher in super-responders than in responders (p < 0.05). In super-responders, the prednisolone dose at last visit on mepolizumab treatment was lower than that before treatment (p < 0.01) and lower than that at last visit in the responders (p < 0.01). In both groups, peripheral blood eosinophil numbers and BVAS were lower after starting mepolizumab than before (p < 0.01). BVAS before mepolizumab (p < 0.05) and at last visit (p < 0.01) were lower in super-responders than in responders. Relapse rates every year after the start of mepolizumab were lower in super-responders than in responder groups (p < 0.01). In super-responders, relapse rates were lower during the 3 years following mepolizumab initiation (p < 0.01) and at last visit (p < 0.01) were significantly lower than after 1 year of treatment.

CONCLUSION

Mepolizumab treatment of super-responders sustainably reduced the relapse rate.

Eosinophilic granulomatosis with polyangiitis - Advances in pathogenesis, diagnosis, and treatment

Eosinophilic granulomatosis with polyangiitis (EGPA) is a rare disease characterized by eosinophil-rich granulomatous inflammation and necrotizing vasculitis, pre-dominantly affecting small-to-medium-sized vessels. It is categorized as a primary antineutrophil cytoplasmic antibody (ANCA)-associated vasculitides (AAVs) but also shares features of hypereosinophilic syndrome (HES); therefore, both vessel inflammation and eosinophilic infiltration are suggested to cause organ damage. This dual nature of the disease causes variable clinical presentation. As a result, careful differentiation from mimicking conditions is needed, especially from HES, given the overlapping clinical, radiologic, and histologic features, and biomarker profile. EGPA also remains a diagnostic challenge, in part because of asthma, which may pre-dominate for years, and often requires chronic corticosteroids (CS), which can mask other disease features. The pathogenesis is still not fully understood, however, the interaction between eosinophils and lymphocytes B and T seems to play an important role. Furthermore, the role of ANCA is not clear, and only up to 40% of patients are ANCA-positive. Moreover, two ANCA-dependent clinically and genetically distinct subgroups have been identified. However, a gold standard test for establishing a diagnosis is not available. In practice, the disease is mainly diagnosed based on the clinical symptoms and results of non-invasive tests. The unmet needs include uniform diagnostic criteria and biomarkers to help distinguish EGPA from HESs. Despite its rarity, notable progress has been made in understanding the disease and in its management. A better understanding of the pathophysiology has provided new insights into the pathogenesis and therapeutic targets, which are reflected in novel biological agents. However, there remains an ongoing reliance on corticosteroid therapy. Therefore, there is a significant need for more effective and better-tolerated steroid-sparing treatment schemes.

New Insights into Pathogenesis and Treatment of ANCA-Associated Vasculitis: Autoantibodies and Beyond

Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis is a group of rare systemic diseases affecting small-caliber vessels. The damage caused by AAV mainly involves the lung and kidneys. AAV includes three different types: granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), and eosinophilic granulomatosis with polyangiitis (EGPA). Although the different phenotypic forms of AAV share common features, recent studies have shown that there are significant differences in terms of pathogenetic mechanisms involving both the adaptive and innate immune systems. Advances in our understanding of pathogenesis have enabled the development of immuno-targeted therapies. This review illustrates the characteristics of the various forms of AAV and the new therapies available for this disease that can have lethal consequences if left untreated.

EGPA Phenotyping: Not Only ANCA, but Also Eosinophils

Background: Eosinophilic Granulomatosis with Polyangiitis (EGPA) is a small-vessel necrotizing vasculitis. The anti-neutrophil cytoplasmic antibodies’ (ANCA) role in defining clinical EGPA phenotypes is well established. Although the role of eosinophils in disease pathogenesis has been clearly demonstrated, the value of blood eosinophil count (BEC) as a biomarker of disease phenotypes is currently uncertain. Methods: We retrospectively analyzed EGPA patients referred to our Immunology Clinic. Demographic, laboratory and clinical features were retrieved from clinical records, and a Logistic Regression was fitted to evaluate the predictive power of all baseline clinical and laboratory features to define EGPA phenotypes. Results: 168 patients were recruited. BEC ≤ 1500 cells/mL was predictive of a clinical involvement characterized by asthma, chronic rhinosinusitis with nasal polyps (CRSwNP) and lung opacities (OR 0.18, 95% CI 0.07–0.43; respiratory-limited phenotype); BEC > 3500/mL was predictive of extrapulmonary organ involvement (OR 3.5, 95% CI 1.7–7.1; systemic phenotype). BEC was also predictive of peripheral nervous system (PNS) involvement, with a positive trend with increasing BEC (<1500/mL: OR 0.17, 95%CI, 0.06–0.47; >3500/mL: OR 2.8, 95% CI, 1.5–5.28). ANCA positivity was also predictive of extrapulmonary involvement (OR 4.7, 95% CI 1.9–11.99). Conclusions: according to BEC and irrespective of the ANCA status, two EGPA phenotypes could be identified, named systemic and respiratory-limited phenotypes, with different organ involvement and possibly different prognoses.

Longitudinal monitoring of circulating immune cell phenotypes in anti-neutrophil cytoplasmic antibody-associated vasculitis

Anti-neutrophil cytoplasmic antibody-associated vasculitis (AAV) is a necrotizing multiorgan autoimmune disease that affects small- to medium-sized blood vessels. Despite the improvements in treatments, half of the patients with AAV still experience disease relapses. In this review, we focus on peripheral leukocyte properties and phenotypes in patients with AAV. In particular, we explore longitudinal changes in circulating immune cell phenotypes during the active phase of the disease and treatment. The numbers and phenotypes of leukocytes in peripheral blood were differs between AAV and healthy controls, AAV in active versus inactive phase, AAV in treatment responders versus non-responders, and AAV with and without severe infection. Therefore, biomarkers detected in peripheral blood immune cells may be useful for longitudinal monitoring of disease activity in AAV.

Targeting immune checkpoints in anti-neutrophil cytoplasmic antibodies associated vasculitis: the potential therapeutic targets in the future

Anti-neutrophil cytoplasmic autoantibodies (ANCA) associated vasculitis (AAV) is a necrotizing vasculitis mainly involving small blood vessels. It is demonstrated that T cells are important in the pathogenesis of AAV, including regulatory T cells (Treg) and helper T cells (Th), especially Th2, Th17, and follicular Th cells (Tfh). In addition, the exhaustion of T cells predicted the favorable prognosis of AAV. The immune checkpoints (ICs) consist of a group of co-stimulatory and co-inhibitory molecules expressed on the surface of T cells, which maintains a balance between the activation and exhaustion of T cells. CD28, inducible T-cell co-stimulator (ICOS), OX40, CD40L, glucocorticoid induced tumor necrosis factor receptor (GITR), and CD137 are the common co-stimulatory molecules, while the programmed cell death 1 (PD-1), cytotoxic T lymphocyte-associated molecule 4 (CTLA-4), T cell immunoglobulin (Ig) and mucin domain-containing protein 3 (TIM-3), B and T lymphocyte attenuator (BTLA), V-domain Ig suppressor of T cell activation (VISTA), T-cell Ig and ITIM domain (TIGIT), CD200, and lymphocyte activation gene 3 (LAG-3) belong to co-inhibitory molecules. If this balance was disrupted and the activation of T cells was increased, autoimmune diseases (AIDs) might be induced. Even in the treatment of malignant tumors, activation of T cells by immune checkpoint inhibitors (ICIs) may result in AIDs known as rheumatic immune-related adverse events (Rh-irAEs), suggesting the importance of ICs in AIDs. In this review, we summarized the features of AAV induced by immunotherapy using ICIs in patients with malignant tumors, and then reviewed the biological characteristics of different ICs. Our aim was to explore potential targets in ICs for future treatment of AAV.

Baseline Eosinophil Count as a Potential Clinical Biomarker for Clinical Complexity in EGPA: A Real-Life Experience

Background: Eosinophilic granulomatosis with polyangiitis (EGPA) is a small-vessel necrotizing vasculitis with multiple organ involvement. Despite improvements in clinical management, biomarkers for organ involvement and disease prognosis are still an unmet need. Methods: EGPA patients referred to our immunology clinic were retrospectively reviewed. Demographic/clinical features, eosinophils, ANCA status, eosinophil cationic protein (ECP) and total serum IgE were evaluated at the baseline. Eosinophils, total serum IgE, ECP and ANCA were studied as possible biomarkers for lung and extrapulmonary disease. Results: In total, 167 EGPA patients were recruited for our study. A positive association between eosinophils and peripheral nervous system (PNS) involvement was demonstrated (p <0.001; chi-squared test). Receiver operating characteristic (ROC) curves using the eosinophil count or percentage as predictors of PNS involvement yielded AUC values of 0.75 and 0.67, respectively. ANCA positivity was associated with PNS involvement, while no correlations with clinical parameters were found for ECP and total serum IgE. Patients without extrapulmonary involvement had lower eosinophils (eosinophils: 2844.7 ± 1698 vs. 6373 ± 5468, p < 0.001; eosinophil percentage: 24.6 ± 10% vs. 36.2 ± 15.8, p < 0.001) and were less likely to be ANCA+ (p < 0.001, chi-squared test). Conclusion: Eosinophils in EGPA are an important biomarker and are associated with extrapulmonary involvement. These findings could strengthen the role of anti-eosinophilic drugs in improving extrapulmonary disease.

Neutrophils in ANCA-associated vasculitis: Mechanisms and implications for management

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a group of systemic autoimmune diseases, which is typified by inflammatory necrosis predominantly affecting the small vessels and often accompanied by positive ANCA. Clinically, AAV primarily includes microscopic polyangiitis (MPA), granulomatosis with polyangiitis (GPA), and eosinophilic granulomatosis with polyangiitis (EGPA). It has been found that in AAV pathogenesis, both innate and adaptive immunity are related to neutrophil function mutually. Many proteins, such as myeloperoxidase (MPO) and proteinase 3 (PR3), in neutrophil cytoplasm lead to the production of proteins such as MPO-ANCA and PR3-ANCA by activating adaptive immunity. In addition, through the process of neutrophil extracellular trap (NET) formation, activation of an alternative complement pathway and the respiratory burst can stimulate the neutrophils close to vascular endothelial cells and will participate the vessel inflammation. This review aims to reveal the potential mechanisms regulating the association between the neutrophils and various types of AAVs and to emphasize the results of recent findings on these interactions. Moreover, multiple underlying signaling pathways involved in the regulation of neutrophils during AAV processes have also been discussed. The ultimate goal of this review is to identify novel biomarkers and therapeutic targets for AAV management in the future.

Regulatory T Cells in Autoimmune Vasculitis

Blood vessels are indispensable for host survival and are protected from inappropriate inflammation by immune privilege. This protection is lost in patients with autoimmune vasculitides, a heterogeneous group of diseases causing damage to arteries, arterioles, and capillaries. Vasculitis leads to vascular wall destruction and/or luminal occlusion, resulting in hemorrhage and tissue ischemia. Failure in the quantity and quality of immunosuppressive regulatory T cells (Treg) has been implicated in the breakdown of the vascular immune privilege. Emerging data suggest that Treg deficiencies are disease-specific, affecting distinct pathways in distinct vasculitides. Mechanistic studies have identified faulty CD8+ Tregs in Giant Cell Arteritis (GCA), a vasculitis of the aorta and the large aortic branch vessels. Specifically, aberrant signaling through the NOTCH4 receptor expressed on CD8+ Treg cells leads to rerouting of intracellular vesicle trafficking and failure in the release of immunosuppressive exosomes, ultimately boosting inflammatory attack to medium and large arteries. In Kawasaki’s disease, a medium vessel vasculitis targeting the coronary arteries, aberrant expression of miR-155 and dysregulated STAT5 signaling have been implicated in undermining CD4+ Treg function. Explorations of mechanisms leading to insufficient immunosuppression and uncontrolled vascular inflammation hold the promise to discover novel therapeutic interventions that could potentially restore the immune privilege of blood vessels and pave the way for urgently needed innovations in vasculitis management.

Rituximab and dupilumab improve eosinophilic granulomatosis with polyangiitis with multiple pulmonary thrombi

Background

Eosinophilic granulomatosis with polyangiitis (EGPA) is characterized by a necrotizing vasculitis with tissue and peripheral blood eosinophilia affecting small and medium-sized arteries, capillaries, and veins. Venous thromboembolic events are uncommon in EGPA. Moreover, there are only a few reported cases of EGPA complicated by pulmonary embolism or infarction.

Case presentation

We report the case of a 43-year-old woman with eosinophilic granulomatosis with polyangiitis and acute respiratory and heart failure due to bilateral pulmonary artery thrombosis and left femoral vein thrombosis 12 years after disease onset. She also had cardiac involvement (myocarditis, pericardial effusion, and diastolic dysfunction), gastrointestinal symptoms, and peripheral neuropathy. The condition was refractory to treatment with systemic corticosteroids, intravenous cyclophosphamide, and mepolizumab, but the thrombosis and associated acute cardiac failure, as well as the cardiac and gastrointestinal symptoms and multiple polyneuropathy, improved after a switch to rituximab. However, the heart failure did not improve sufficiently and the patient continued to need inhaled oxygen at 1 L/min and asthma exacerbations occurred. We then swapped the patient’s mepolizumab treatment for dupilumab. Not only did she have no further asthma attacks after switching to dupilumab, but also her vasculitis symptoms improved. Oxygen therapy was discontinued as the heart failure improved 5 months after starting the dupilumab.

Conclusions

This may be the first case report of the successful treatment by rituximab of pulmonary thromboembolism associated with EGPA. In addition, in this patient, treatment with dupilumab was effective not only for the asthma symptoms but also for the symptoms of vasculitis and heart failure.

Switching from omalizumab to mepolizumab therapy improved extra-pulmonary abdominal and cutaneous vasculitis symptoms in a patient with eosinophilic granulomatosis with polyangiitis

Eosinophilic granulomatosis with polyangiitis (EGPA) is a systemic vasculitis of small-to-medium-sized vessels. Both eosinophilic infiltration and vasculitis are thought to contribute to multi-organ damage. Some biologics have been used to reduce the required dose of corticosteroids in EGPA, but no single agent can ensure a complete control of this disease. Here, we describe a patient with anti-neutrophil cytoplasmic antibodies-negative relapsing EGPA whose asthma control was improved by omalizumab, but she continued to develop flares of abdominal and cutaneous vasculitis symptoms. After switching to mepolizumab therapy, her blood hypereosinophilia and extra-pulmonary symptoms were significantly improved. Moreover, the dose of daily maintenance corticosteroid could be tapered off. The experience from our case suggests that biologics targeting interleukin-5 may be more effective than omalizumab in the management of extra-thoracic manifestations in EGPA.

Novel Targets for Drug Use in Eosinophilic Granulomatosis With Polyangiitis

Eosinophilic Granulomatosis with Polyangiitis (EGPA) is a rare autoimmune disease characterized by medium and small vessels inflammation. Cardiac vasculitic involvement is one of the most severe manifestations with a significant impact on patients' long-term prognosis: anyway, a specific therapeutic approach for heart involvement in EGPA has not been explored yet. Current regimen consists of a long-term therapy with high dose of glucocorticoids, causing the well-known related-adverse events; immunosuppressive drugs are used in patients with severe manifestations, with some limitations. New therapeutic approaches are needed for patients with refractory disease or contraindications to conventional therapies. The quest for the ideal therapy is going toward a more and more personalized approach: on the one hand, efforts are made to use already existing therapies in the most appropriate way; on the other hand, new insights into EGPA pathogenesis allow the discovery of new targets, as demonstrated by mepolizumab and rituximab, targeting eosinophils, and B-cell compartments. This review summarizes the emerging therapies used in EGPA, focusing on the most recent studies on biologics and analyzing their efficacy and safety.

Interleukin-2 and regulatory T cells in rheumatic diseases

Failure of regulatory T (T_reg) cells to properly control immune responses leads invariably to autoimmunity and organ damage. Decreased numbers or impaired function of T_reg cells, especially in the context of inflammation, has been documented in many human autoimmune diseases. Restoration of T_reg cell fitness and/or expansion of their numbers using low-dose natural IL-2, the main cytokine driving T_reg cell survival and function, has demonstrated clinical efficacy in early clinical trials. Genetically modified IL-2 with an extended half-life and increased selectivity for T_reg cells is now in clinical development. Administration of IL-2 combined with therapies targeting other pathways involved in the expression of autoimmune diseases should further enhance its therapeutic potential. Ongoing clinical efforts that capitalize on the early clinical success of IL-2 treatment should bring the use of this cytokine to the forefront of biological treatments for autoimmune diseases.

Immune Cells Profiling in ANCA-Associated Vasculitis Patients-Relation to Disease Activity

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitides (AAV) are a group of necrotizing multiorgan autoimmune vasculitides that predominantly affect small blood vessels and are associated with the presence of ANCAs. The aim was to assess regulatory and effector cell populations accompanied by the suPAR biomarker level and link the so-defined immune state to the AAV disease activity. The research involved a multicomponent description of an immune state encompassing a range of B and T cell subsets such as transitional/regulatory B cells (CD19+CD24++CD38++), naïve B cells (CD19+CD24INTCD38INT), Th17 cells, T regulatory cells (CD4+CD25+FoxP3+) and cytotoxic CD4+CD28- cells by flow cytometry. The suPAR plasma level was measured by ELISA. The results indicate that AAV is associated with an increased suPAR plasma level and immune fingerprint characterized by an expansion of Th17 cells and T cells lacking the costimulatory molecule CD28, accompanied by a decrease of regulatory populations (Tregs and transitional B cells) and NK cells. Decreased numbers of regulatory T cells and transitional B cells were shown to be linked to activation of the AAV disease while the increased suPAR plasma level-to AAV-related deterioration of kidney function. The observed immune fingerprint might be a reflection of peripheral tolerance failure responsible for development and progression of ANCA-associated vasculitides.

Systemic hypereosinophilic syndromes: when autoimmunity is Th2 mediated

PURPOSE OF REVIEW

Clinical conditions associated with hypereosinophilia represent a field of particular interest, taking into account the epidemiological impact of the different primary and secondary forms. In addition to a classical Th1 response, also Th2 cells can be involved in the pathogenesis of autoimmune diseases, among them eosinophilic forms such as eosinophilic granulomatosis with polyangiitis.

RECENT FINDINGS

In patients with severe asthma, recent evidence highlights the role of pathogenic autoantibodies against autologous eosinophil proteins (e.g. eosinophil peroxidase) suggest the role of autoimmune mechanisms, particularly in patients in which asthma is included in eosinophilic vasculitis with antineutrophilic autoantibody positivity. Is now evident that in addition to Th2 cells, also type 2 innate lymphoid cells and Th1/Th17 cells play a central role in the pathogenesis of hypereosinophilic syndrome.

SUMMARY

The definition of cellular and molecular mechanisms and the critical role of specific cytokines involved in the pathogenesis of hypereosinophilic syndrome open the way to new therapeutic strategies by using biological agents targeting these specific factors.

Clinical Features of Patients with Active Eosinophilic Granulomatosis with Polyangiitis Successfully Treated with Mepolizumab

BACKGROUND

In some patients with eosinophilic granulomatosis with polyangiitis (EGPA), remission cannot be induced, despite treatment with corticosteroids and immunosuppressants. We evaluated the clinical features of patients with EGPA in whom mepolizumab was effective.

METHODS

There were 59 EGPA patients treated at Hiratsuka City Hospital, Japan, between April 2018 and September 2020, and 30 of them received mepolizumab. Twenty (66.7%) experienced a "marked effect" (the daily dose of corticosteroid or immunosuppressant could be decreased, or the interval between intravenous immunoglobulin (IVIG) treatments could be prolonged) and 10 (33.3%) experienced a "weak effect" (these measures were not achieved). Eosinophil numbers, serum IgG levels, daily doses of corticosteroids and immunosuppressants, and the interval between IVIG treatments at diagnosis and before and after mepolizumab initiation were determined.

RESULTS

Eosinophil numbers at diagnosis were significantly higher in the marked-effect group than in the weak-effect group (p < 0.05) but not before mepolizumab initiation or at the last visit. Birmingham Vasculitis Activity Scores (BVASs) before mepolizumab initiation (p < 0.05) and at last visit (p < 0.01), and frequency of relapse before treatment initiation (p < 0.05) were significantly higher, and the serum IgG level before mepolizumab treatment was significantly lower in the weak-effect group than in the marked-effect group. The weak-effect group received higher doses of corticosteroids, even if the corticosteroid dose could be reduced for a while after mepolizumab initiation.

CONCLUSION

High peripheral blood eosinophil numbers at EGPA diagnosis were suggestive of a positive clinical response to mepolizumab.

Eosinophilic Granulomatosis With Polyangiitis: Dissecting the Pathophysiology

Eosinophilic Granulomatosis with Polyangiitis (EGPA) is a rare multisystemic disease classified both amongst hypereosinophilic disorders and ANCA-associated vasculitis. Vessel inflammation and eosinophilic proliferation are the hallmarks of the disease and main effectors of organ damage. Two distinct disease phenotypes have classically been described according to ANCA-status: the ANCA-negative subset with eosinophil-driven manifestation and the ANCA-positive one with vasculitic manifestations. An analogous dichotomization has also been backed by histological findings and a distinct genetic background. EGPA is typically consider a Th2-mediated disease and blood and tissue eosinophilia represent the cornerstone of diagnosis. Besides, ANCA are known for inducing endothelial injury and vascular inflammation by activating the circulating neutrophils. Thus, the pathogenesis of EGPA seems to be mediated by two coexisting mechanisms. However, the verbatim application of this strict dualism cannot always be translated into routine clinical practice. In the present review we describe the current knowledge on the eosinophilic and ANCA-mediated aspects of EGPA pathogenesis. Finally, we review the rationale of the currently proposed EGPA dichotomy and future research perspectives.

Pulmonary Eosinophilic Granulomatosis with Polyangiitis Has IgG4 Plasma Cells and Immunoregulatory Features

The immunologic mechanisms promoting eosinophilic granulomatosis with polyangiitis (EGPA) are unclear. To characterize the mechanisms underlying pulmonary EGPA, we examined and compared EGPA paraffin-embedded lung biopsies with normal lung biopsies, using immunostaining, RNA sequencing, and RT-PCR. The results revealed novel type 2 as well as immuneregulatory features. These features included basophils and increased mast cell contents; increased immunostaining for tumor necrosis factor ligand superfamily member 14; sparse mast cell degranulation; numerous forkhead box protein P3 (FoxP3)+ regulatory T cells and IgG4 plasma cells; and abundant arachidonate 15-lipoxygenase and 25-hydroxyvitamin D-1 α hydroxylase, mitochondrial. Significantly decreased 15-hydroxyprostaglandin dehydrogenase [NAD(⁺)], which degrades eicosanoids, was observed in EGPA samples. In addition, there was significantly increased mRNA for chemokine (C-C motif) ligands 18 and 13 and major collagen genes, IgG4-rich immune complexes coating alveolar macrophages, and increased immunostaining for phosphorylated mothers against decapentaplegic homolog 2/SMAD2, suggesting transforming growth factor-β activation. These findings suggest a novel self-promoting mechanism of activation of alveolar macrophages by arachidonate 15-lipoxygenase-derived eicosanoids to express chemokines that recruit a combined type 2/immunoregulatory immune response, which produces these eicosanoids. These results suggest that the pulmonary EGPA immune response resembles the immune response to a tissue-invasive parasite infection.

Mepolizumab for the treatment of eosinophilic granulomatosis with polyangiitis

INTRODUCTION

Eosinophilic granulomatosis with polyangiitis (EGPA) is a rare antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis characterized by asthma, hypereosinophilia, and progressive multiorgan involvement. Although not fully elucidated, advancement in our understanding of the pathophysiology of EGPA has led to the development of multiple new treatment targets.

AREAS COVERED

Herein we review the epidemiology, clinical manifestations, pathophysiology, treatments, and ongoing research in the management of EGPA. The central role of Interleukin-5 (IL-5) in the development and maintenance of hypereosinophilia will be discussed. The value of mepolizumab, an anti-IL-5 monoclonal antibody, in the treatment of EGPA is reviewed in detail.

EXPERT OPINION

The available literature supports the use of mepolizumab for the induction and maintenance of remission of refractory, relapsing, or glucocorticoid-dependent EGPA with potentially greater benefit in those who are ANCA-positive or those with greater eosinophilia ( ≥ 150 cells/ μ L). Despite these positive results, relapses remain frequent, and the need for both short- and long-term glucocorticoid use remains common. More research is needed to address these needs and determine the precise role of mepolizumab.

Treatment of Eosinophilic Granulomatosis with Polyangiitis: A Review

Eosinophilic granulomatosis with polyangiitis (formerly Churg-Strauss syndrome) is a rare type of anti-neutrophil cytoplasm antibody-associated vasculitis. Nevertheless, eosinophilic granulomatosis with polyangiitis stands apart because it has features of vasculitis and eosinophilic disorders that require targeted therapies somewhat different from those used for other anti-neutrophil cytoplasm antibody-associated vasculitides. Considerable advances have been made in understanding the underlying pathophysiology of eosinophilic granulomatosis with polyangiitis that have highlighted the key role of eosinophils and opened new therapeutic opportunities. Its conventional treatment relies mainly on agents that decrease inflammation: corticosteroids and immunosuppressant adjunction for severe manifestations. New therapeutic approaches are needed for refractory disease, relapses and issues associated with corticosteroid dependence, especially for asthma manifestations. Drugs under evaluation mostly target eosinophils and B cells. Results of low-evidence-based trials suggested possible efficacies of biologicals: B-cell-blocking rituximab and anti-immunoglobulin E omalizumab. Recently, the first large-scale randomised controlled trial on eosinophilic granulomatosis with polyangiitis proved the efficacy of anti-interleukin-5 mepolizumab. That finding opens a new era in eosinophilic granulomatosis with polyangiitis management, with mepolizumab approval but also in future drug evaluations and trial designs for eosinophilic granulomatosis with polyangiitis. Additional studies are needed to determine which patients would benefit most from targeted therapies and achieve personalised treatment for patients with eosinophilic granulomatosis with polyangiitis. Herein, we review eosinophilic granulomatosis with polyangiitis characteristics and provide an overview of established and novel pharmacological agents.

New insights into immune cells cross-talk during IgG4-related disease

Immunoglobulin G4-related disease (IgG4-RD) is a newly acknowledged entity, characterized by an immune-mediated fibro-inflammatory process affecting virtually all organs, with infiltration of IgG4⁺ bearing plasma cells. Until today the pathogenesis of IgG4-RD remains unknown. Treatment with anti-CD20 monoclonal antibodies efficiently induced remission and attenuated the secretory phenotype of myofibroblasts responsible of uncontrolled collagen deposition. This supports the pathogenic role of the adaptive immunity, particularly B cell compartment and B cell/T cell interaction. Latest studies have also highlighted the importance of innate immune system that has been underestimated before and the key role of a specific T cell subset, T follicular helper cells that are involved in IgG4-class-switching and plasmablast differentiation. In this review, we aim to review the most recent knowledge of innate immunity, T and B cells involvement in IgG4-RD, and introduce tertiary lymphoid organs (TLO) as a potential marker of relapse in this condition.

Innate immune response reflects disease activity in eosinophilic granulomatosis with polyangiitis

BACKGROUND

Eosinophilic granulomatosis with polyangiitis (EGPA) is a disease characterized by allergic granulomatosis, necrotizing vasculitis, and peripheral blood eosinophilia. Interleukin (IL)-33, thymic stromal lymphopoietin (TSLP), and type 2 innate lymphoid cells (ILC2) are involved in the innate and type 2 immune responses in EGPA. However, the relationships among these molecules and the mechanisms underlying the development of EGPA remain unknown.

OBJECTIVE

We investigated the relationships among peripheral blood eosinophil count, serum IL-33 and TSLP concentration, and peripheral blood ILC2 count in patients with EGPA, chronic eosinophilic pneumonia (CEP), or bronchial asthma (BA).

METHODS

We recruited 86 patients with EGPA in three groups (remission, relapse, and onset), 25 patients with CEP at active or inactive stages of disease, and 11 patients with BA. In patients with EGPA, CEP, or BA, serum IL-33, sST2, and TSLP concentrations were determined using ELISA and peripheral blood ILC2 counts (as Lin-1^- CD127⁺ CRTH2⁺ cells) were determined using flow cytometry.

RESULTS

Peripheral blood eosinophil count or ILC2 count, and serum sST2 or TSLP concentration were higher in patients with EGPA at onset than in those with EGPA at relapse or remission, or in those with BA or CEP. Serum IL-33 concentration was higher in patients with EGPA at relapse than in those with EGPA at onset or remission, or in those with BA or CEP. In a logistic regression model, EGPA disease activity was correlated with serum IL-33 concentration and peripheral blood ILC2 count, but not daily systemic and inhaled corticosteroid dose or immunosuppressant use. Eosinophil count was correlated with peripheral blood ILC2 count and serum TSLP concentration, but not serum IL-33 concentration.

CONCLUSIONS

Increased peripheral blood ILC2 count and serum IL-33 concentration were associated with disease activity in EGPA. Increases in serum IL-33 concentration may indicate the presence of active vasculitis rather than peripheral or tissue eosinophilia.

Longterm Prognosis of 121 Patients with Eosinophilic Granulomatosis with Polyangiitis in Japan

OBJECTIVE

We investigated the risk factors for relapse or prognosis of eosinophilic granulomatosis with polyangiitis (EGPA) in Japanese patients presenting to our hospital.

METHODS

From June 1999 through March 2015, we retrospectively recruited 121 patients with EGPA according to the American College of Rheumatology criteria. Frequent relapse was defined as disease occurrence at least once every 2 years after a period of initial remission. The study endpoint was the last examination performed. We used multiple logistic regression to analyze risk factors for relapse or survival in EGPA.

RESULTS

Gastrointestinal (GI) involvement with both abnormalities on endoscopy and biopsy (p < 0.01) and symptoms; myocardial involvement with both abnormalities on 1 or more cardiac investigations and symptoms (p < 0.01); and treatment at initial or maintenance with immunosuppressants (p < 0.01) or administration of intravenous immunoglobulin (IVIG; p < 0.01) were associated significantly more often with frequent relapse than with infrequent. Overall 5-, 10-, and 20-year survival rates were 91.1%, 83.7%, and 68.6%, respectively. Survival in EGPA was associated with age of onset < 65 years. Age at onset of EGPA was the only significant predictor of survival (p < 0.01). Myocardial or GI tract involvement did not affect mortality risk.

CONCLUSION

Patients with myocardial or GI tract involvement had frequent relapses, but these conditions were not reflected in increased mortality. Treatment with immunosuppressants or IVIG in addition to corticosteroids might have improved the prognosis in Japanese patients with EGPA.

An increase of CD83+ dendritic cells ex vivo correlates with increased regulatory T cells in patients with active eosinophilic granulomatosis and polyangiitis

BACKGROUND

Eosinophilic granulomatosis with polyangiitis (EGPA) is a rare disease characterized by the presence of allergic granulomatosis and necrotizing vasculitis with eosinophilic infiltration. The etiology of EGPA is unknown. Dendritic cells (DCs) are not only critical for the induction of primary immune responses; they may also be important for the induction of immunological tolerance and the regulation of the type of T-cell-mediated immune response. To investigate whether DC maturation is associated with EGPA disease status, we examined the relationship between the maturation of DCs and the differentiation of regulatory T (Treg) cells in EGPA patients. We exposed the CD14+ blood monocytes of 19 patients with EGPA in remission or relapse to stimulation with GM-CSF and IL-4 for 6 d and lipopolysaccharide for 24 h to obtain mature CD83+ DCs and immature CD206+ DCs. Using immunohistochemistry, we examined four patients for the presence of CD83+ and CD206+ DCs in the lung at the onset of EGPA.

RESULTS

The percentage of CD83+ cells among DCs differentiated from CD14+ monocytes was lower for EGPA patients in relapse than in remission. The percentage of CD83+ DCs was inversely correlated with the percentage of CD206+ DCs and was significantly correlated with the numbers of naturally occurring CD4+ regulatory Treg (nTreg; FOXP3+CD4+) cells and inducible Treg (iTreg; CD4+CD25+ T cells producing IL-10 or TGF-β) cells but not the number of eosinophils. The percentage of CD206+ DCs was significantly inversely correlated with the percentages of nTreg and iTreg cells but not the number of eosinophils. Immunohistochemistry revealed both CD206+ DCs and CD83+ DCs in alveoli and interstitial spaces at the onset of EGPA.

CONCLUSION

The maturation of DCs from monocytes was related to disease activity in patients with EGPA. Increased CD83+ DCs in EGPA patients may induce the differentiation of iTreg and nTreg cells, thereby suppressing inflammation and disease activity.

Eosinophils in vasculitis: characteristics and roles in pathogenesis

Eosinophils are multifunctional granular leukocytes that are implicated in the pathogenesis of a wide variety of disorders, including asthma, helminth infection, and rare hypereosinophilic syndromes. Although peripheral and tissue eosinophilia can be a feature of many types of small-vessel and medium-vessel vasculitis, the role of eosinophils has been best studied in eosinophilic granulomatosis with polyangiitis (EGPA), where eosinophils are a characteristic finding in all three clinical stages of the disorder. Whereas numerous studies have demonstrated an association between the presence of eosinophils and markers of eosinophil activation in the blood and tissues of patients with EGPA, the precise role of eosinophils in disease pathogenesis has been difficult to ascertain owing to the complexity of the disease process. In this regard, results of clinical trials using novel agents that specifically target eosinophils are providing the first direct evidence of a central role of eosinophils in EGPA. This Review focuses on the aspects of eosinophil biology most relevant to the pathogenesis of vasculitis and provides an update of current knowledge regarding the role of eosinophils in EGPA and other vasculitides.