Immunotherapy for antineutrophil cytoplasmic antibody–associated vasculitis: challenging the therapeutic status quo?

Infliximab therapy of relapsing tracheal stenosis in a pediatric patient with granulomatosis with polyangiitis: a case report

Background

Granulomatosis with polyangiitis is a granulomatous, necrotizing small-vessel vasculitis affecting both children and adults. However, subglottic tracheal stenosis appears more frequently in the pediatric cohort. To date, granulomatosis with polyangiitis is often treated with steroids, cyclophosphamide, azathioprine, or rituximab, but tumor-necrosis-factor-α-antagonistic drugs are increasingly gaining significance in treatment of refractory cases.

Case presentation

We report the case of a 15-year-old Caucasian male diagnosed with proteinase-3-positive granulomatosis with polyangiitis with acute shortness of breath. X-ray and magnet resonance imaging showed extensive subglottic narrowing. Forced expiratory volume in 1 s was reduced to 50% of age norm, with massively increased effective airway resistance. The patient initially responded very well to high-dose steroids and maintenance therapy with azathioprine. He was subsequently treated with four doses of rituximab, and levels of proteinase 3 antibodies normalized. After 6 months of clinical remission, the patient presented again with acute respiratory symptoms. Again, he was treated with high-dose steroids, but showed poor clinical response this time. Therefore, we decided to commence a tumor-necrosis-factor-α-antagonistic treatment with infliximab, under which our patient achieved clinical remission and normalization of lung function parameters.

Conclusions

The use of tumor-necrosis-factor-α-antagonistic agents might be a promising alternative for the treatment of refractory tracheal stenosis in pediatric patients with granulomatosis with polyangiitis.

Cellular targeting in autoimmunity

Many biologic agents that were first approved for the treatment of malignancies are now being actively investigated and used in a variety of autoimmune diseases such as rheumatoid arthritis (RA), antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis, systemic lupus erythematosus (SLE), and Sjogren's syndrome. The relatively recent advance of selective immune targeting has significantly changed the management of autoimmune disorders and in part can be attributed to the progress made in understanding effector cell function and their signaling pathways. In this review, we will discuss the recent FDA-approved biologic therapies that directly target immune cells as well as the most promising investigational drugs affecting immune cell function and signaling for the treatment of autoimmune disease.

Immune mediated diseases and immune modulation in the neurocritical care unit

This chapter will review the spectrum of immune-mediated diseases that affect the nervous system and may result in an admission to the neurological intensive care unit. Immunomodulatory strategies to treat acute exacerbations of neurological diseases caused by aberrant immune responses are discussed, but strategies for long-term immunosuppression are not presented. The recommendations for therapeutic intervention are based on a synthesis of the literature, and include recommendations by the Cochrane Collaborative, the American Academy of Neurology, and other key organizations. References from recent publications are provided for the disorders and therapies in which randomized clinical trials and large evidenced-based reviews do not exist. The chapter concludes with a brief review of the mechanisms of action, dosing, and side effects of commonly used immunosuppressive strategies in the neurocritical care unit.

B-cell depleting agents for ANCA vasculitides: a new therapeutic approach

Vasculitides associated with anti-neutrophil cytoplasmic antibody (ANCA) serum positivity affecting small and medium-sized vessels are defined as ANCA-associated vasculitis (AAV). Glomerulonephritis in AAV is characterized by focal necrosis, crescent formation, and few or no immunoglobulin deposits. In vitro and animal evidence suggests that ANCA play a pathogenic role in AAV. Specific gene expression signatures are reported to predict long-term prognosis in AAV, suggesting the possibility of individualizing therapy and identifying new therapeutic targets. Although immunosuppressants and glucocorticoids are the cornerstone of AAV therapy, results from two recent randomized controlled trials have shown the non-inferiority of rituximab, compared with cyclophosphamide, for the induction of remission in patients with severe AAV. In fact, in April 2011, the US Food and Drug Administration (FDA) approved rituximab, combined with glucocorticoids, as a front-line therapy for adult patients with granulomatosis with polyangiitis (GPA; Wegener's granulomatosis) or microscopic polyangiitis. This new indication for rituximab provided the first ever FDA-approved therapy for these two diseases and the first alternative to cyclophosphamide for the treatment of severe disease in almost 40years. However, issues regarding the use of maintenance therapy after rituximab, the concurrent use of cyclophosphamide and the toxicity of rituximab remain unanswered and should be clarified in ongoing and future randomized controlled trials.

Long-term effects of rituximab added to cyclophosphamide in refractory patients with vasculitis

BACKGROUND

Current therapies have changed systemic vasculitis from a disease with a high rate of mortality to a chronic curable condition. A limited percentage of patients either remains refractory to conventional treatment or experiences dose-limiting side effects.

METHODS

11 patients (4 affected by idiopathic systemic microscopic polyangiitis, 5 by Wegener's granulomatosis, and 2 by Churg-Strauss syndrome) intolerant or refractory to conventional therapies including cyclophosphamide were enrolled. All patients received rituximab as a rescue therapy and were followed for 30-54 months. Following rituximab administration, immunosuppressive drugs were rapidly tapered and no immunosuppressive maintenance therapy was given.

RESULTS

Significant decreases in levels of serum creatinine, proteinuria, erythrocyte sedimentation rate, C-reactive protein, and ANCA titers were observed during the follow-up (at least 30 months after rituximab administration). Arthralgia and weakness rapidly disappeared in all patients. Out of 7 patients, 5 reported a decrease in the degree of paresthesia and in the electrophysiologic parameters. Six months after rituximab administration the mean dose of prednisone was 5.5 mg/day.

CONCLUSION

In this sample of patients with systemic vasculitis who were refractory or intolerant to more conventional treatment, rituximab proved to be safe and effective in a long-term follow-up, and showed steroid- and immunosuppressive-sparing effects allowing the persistence of long-lasting remissions without maintenance therapy.

Therapeutic targeting of B cells for rheumatic autoimmune diseases

Autoreactive B cells are characterized by their ability to secrete autoantibodies directed against self-peptides. During the last decade, it has become increasingly apparent that B lymphocytes not only produce autoantibodies but also exert important regulatory roles independent of their function as antibody-producing cells. This is especially relevant in the context of autoimmunity, because autoreactive B cells have been shown to possess the ability to activate pathogenic T cells, to produce pro-inflammatory cytokines, and to promote the formation of tertiary lymphoid tissue in target organs. The production of monoclonal antibodies against B-cell-surface molecules has facilitated the characterization of several distinct B lymphocyte subsets. These cell-surface molecules have not only served as useful cell differentiation markers but have also helped to unravel the important biological functions of these cells. Some of these molecules, all of which are expressed on the cell surface, have proven to be effective therapeutic targets. In both animal models and in clinical assays, the efficient elimination of B lymphocytes has been shown to be useful in the treatment of rheumatoid arthritis and other autoimmune diseases. The treatment of most rheumatic autoimmune diseases relies mainly on the use of cytotoxic immunosuppressants and corticosteroids. Although this has resulted in improved disease survival, patients may nonetheless suffer severe adverse events and, in some cases, their relapse rate remains high. The increasing need for safer and more effective drugs along with burgeoning new insights into the pathogenesis of these disorders has fueled interest in biological agents; clinical trials involving the B-cell depletion agent rituximab have been especially promising. This article reviews the current knowledge of B-cell biology and pathogenesis as well as the modern therapeutic approaches for rheumatic autoimmune diseases focusing in particular on the targeting of B-cell-specific surface molecules and on the blocking of B-cell activation and survival.

Anti-neutrophil cytoplasmic antibody pathogenesis in small-vessel vasculitis: an update

Vasculitides associated with serum positivity for anti-neutrophil cytoplasmic antibodies (ANCAs) that affect small- to medium-sized vessels are commonly known as ANCA-associated vasculitis (AAV) and include Wegener's granulomatosis, microscopic polyangiitis, and Churg-Strauss syndrome. Evidence derived from both in vitro studies and recent animal models points to a pathogenic role of ANCAs in AAV. In 2002, the first in vivo breakthrough in the pathogenesis of ANCAs showed that mouse ANCAs against myeloperoxidase (MPO) led to intrinsic pauci-immune renal vasculitis in mice. In 2004, a report using both in vitro and in vivo studies proposed that proteinase 3 (PR3)-directed autoimmunity involved the complementary peptide of PR3 (cPR3), which is encoded by the antisense strand of the PR3 gene. The last breakthrough came in October 2008 with a previously undescribed molecular explanation for the origin and development of injury in pauci-immune renal vasculitis, with potential clinical implications. This report showed that infection by fimbriated bacteria may trigger cross-reactive autoimmunity to a previously characterized ANCA antigen, lysosomal membrane protein-2, which is contained in the same vesicles that harbor MPO and PR3. Infection by fimbriated bacteria resulted in the production of autoantibodies, which activated neutrophils and killed human microvascular endothelium in vitro and caused renal vasculitis in rats. Although the evidence for a pathogenic role of ANCAs, mainly MPO-ANCAs, is striking, various questions remain unanswered. Understanding the key pathogenic mechanisms of AAV may provide a safer, more rational therapeutic approach than the traditional (ie, corticosteroids and immunosuppressants) treatment strategy.

Vasculitis syndromes: LAMP-2 illuminates pathogenesis of ANCA glomerulonephritis

The discovery that antibodies to a bacterial antigen can cross-react with a mammalian protein to cause pauci-immune necrotizing and crescentic glomerulonephritis opens up new possibilities for the diagnosis and treatment of this condition.