Natural Killer Cells in Anti-Neutrophil Cytoplasmic Antibody-Associated Vasculitis - A Review of the Literature

Anti-neutrophil cytoplasmic antibody (ANCA)- associated vasculitis (AAV) is a group of systemic autoimmune diseases characterized by inflammation of small- and medium-sized vessels. The three main types of AAV are granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA) and eosinophilic granulomatosis with polyangiitis (EGPA). A growing number of studies focus on natural killer (NK) cells in AAV. NK cells are innate lymphoid cells with important roles in anti-viral and anti-tumor defense, but their roles in the pathogenesis of autoimmunity is less well established. In this review, we will present a summary of what is known about the number, phenotype and function of NK cells in patients with AAV. We review the literature on NK cells in the circulation of AAV patients, studies on tissue resident NK cells and how the treatment affects NK cells.

ANCA-Associated Vasculitis with Cardiac Valve Vegetations in Two Teenage Males: A Case Report and Literature Review

Background: Anti-neutrophil cytoplasm antibody (ANCA)-associated vasculitis is a term used to describe systemic vasculitides that affect small and medium-sized blood vessels. The three types of ANCA-associated vasculitis (AAV) are Granulomatosis with Polyangiitis (GPA), formerly Wegener’s granulomatosis , Microscopic Polyangiitis (MPA), and Eosinophilic Granulomatosis with Polyangiitis (EGPA), formerly Churg-Strauss, with clinical presentation most frequently involving the respiratory tract, the kidney, the skin and the joints. ANCA-associated vasculitis is rare in children, with estimated prevalence of 3-4 per million, and even more rare is the manifestation of cardiac abnormalities secondary to ANCA-associated vasculitis in the pediatric population. Case Presentation: We present the cases of two teenage males who presented with cardiac valvular lesions secondary to Granulomatosis with Polyangiitis in addition to sinus, pulmonary, renal, and cutaneous involvement. These findings of cardiac valvular abnormalities in GPA have rarely been described in the literature in pediatrics. Both patients were treated with rituximab, high-dose methylprednisolone, and plasma exchange (PLEX) and showed improvement in their disease manifestations. Conclusions: A review of the literature revealed only five pediatric cases of ANCA-associated vasculitis with cardiac manifestations, and interestingly, three of the five had valvular involvement. Subsequent valvular involvement makes obtaining the diagnosis of ANCA-Associated Vasculitis very difficult due to concern for underlying infectious endocarditis and can lead to misdiagnosis given the rarity of cardiac involvement in ANCA-associated vasculitis. Routine echocardiogram is not always completed in newly diagnosed GPA, yet cardiac involvement can lead to severe consequences as was seen with our first patient in the form of thromboembolic stroke. We discuss the importance of keeping AAV on the differential when cardiac lesions are present as well as the importance of regular cardiac screening in newly diagnosed patients with AAV, as it is a major factor of cardiac morbidity and mortality in the adult population and can contribute substantially to management decisions.

Increased Circulating Cell-Free DNA in Eosinophilic Granulomatosis With Polyangiitis: Implications for Eosinophil Extracellular Traps and Immunothrombosis

BackgroundEndogenous DNA derived from nuclei or mitochondria is released into the blood circulation as cell-free DNA (cfDNA) following cell damage or death. cfDNA is associated with various pathological conditions; however, its clinical significance in antineutrophil cytoplasmic antibody-associated vasculitis (AAV) remains unclear. This study aimed to evaluate the clinical significance of cfDNA in AAV.MethodsWe enrolled 35 patients with AAV, including 10 with eosinophilic granulomatosis with polyangiitis (EGPA), 13 with microscopic polyangiitis, and 12 with granulomatosis with polyangiitis. Serum cf-nuclear DNA (cf-nDNA) and cf-mitochondrial DNA (cf-mtDNA) levels were measured by quantitative polymerase chain reaction before and after the initiation of immunosuppressive therapy. Tissue samples from EGPA patients were examined by immunofluorescence and transmission electron microscopy. The structure of eosinophil extracellular traps (EETs) and neutrophil extracellular traps (NETs) and stability against DNase were assessed in vitro. Platelet adhesion of EETs were also assessed.ResultsSerum cf-nDNA and cf-mtDNA levels were significantly higher in AAV than in healthy controls, with the highest levels in EGPA; however, serum DNase activities were comparable among all groups. cf-nDNA and cf-mtDNA decreased after treatment and were associated with disease activity only in EGPA. Blood eosinophil count and plasma D-dimer levels were significantly correlated with cf-nDNA in EGPA and cf-mtDNA. EGPA tissue samples showed lytic eosinophils and EETs in small-vessel thrombi. The structure of EETs showed bolder net-like chromatin threads in vitro and EETs showed greater stability against DNase than NETs. EETs provided a scaffold for platelet adhesion.ConclusioncfDNA was increased in EGPA, associated with disease activity. The presence of DNase-resistant EETs in small-vessel thrombi might contribute to higher concentration of cfDNA and the occurrence of immunothrombosis in EGPA.

Secretory Leukocyte Protease Inhibitor Is Present in Circulating and Tissue-Recruited Human Eosinophils and Regulates Their Migratory Function

Eosinophils and secretory leukocyte protease inhibitor (SLPI) are both associated with Th2 immune responses and allergic diseases, but whether the fact that they are both implicated in these conditions is pathophysiologically related remains unknown. Here we demonstrate that human eosinophils derived from normal individuals are one of the major sources of SLPI among circulating leukocytes. SLPI was found to be stored in the crystalline core of eosinophil granules, and its dislocation/rearrangement in the crystalline core likely resulted in changes in immunostaining for SLPI in these cells. High levels of SLPI were also detected in blood eosinophils from patients with allergy-associated diseases marked by eosinophilia. These include individuals with eosinophilic granulomatosis with polyangiitis (EGPA) and atopic dermatitis (AD), who were also found to have elevated SLPI levels in their plasma. In addition to the circulating eosinophils, diseased skin of AD patients also contained SLPI-positive eosinophils. Exogenous, recombinant SLPI increased numbers of migratory eosinophils and supported their chemotactic response to CCL11, one of the key chemokines that regulate eosinophil migratory cues. Together, these findings suggest a role for SLPI in controlling Th2 pathophysiologic processes via its impact on and/or from eosinophils.

Mepolizumab -- therapeutic strategy for a paediatric patient with eosinophilic granulomatosis with polyangiitis

Eosinophilic granulomatosis with polyangiitis (EGPA; formerly known as Churg-Strauss syndrome) is classified as an anti-neutrophil cytoplasmic antibody (ANCA)-associated small vessel vasculitis. It is a multisystem disorder and can affect every organ system. EGPA is a rare disease, with an estimated prevalence of 1/70,000–100,000 in Europe. As its onset usually occurs in adulthood, data from paediatric patients are limited. We present here a very rare practical EGPA clinical case involving a paediatric patient. Presently, data on mepolizumab usage in paediatric patients are limited, with only a few case reports published.

Right atrial myxoma as the first manifestation of granulomatosis with polyangiitis, and a possible association with vascular endothelial growth factor (VEGF) and interleukin 6 (IL-6): a case report and review of the literature

Background Granulomatosis with polyangiitis and myxomas are rare conditions previously described to co-exist. Cardiac masses are often presumed to be myxomas rather than lesions of granulomatosis with polyangiitis. Case presentation We present a review of the symptoms for the two diagnoses along with the first verified case. Conclusions Two possible risk factors for developing myxomas (VEGF and IL-6) are explored and discussed.

Avacopan, a Selective C5a Receptor Antagonist, for Anti-Neutrophil Cytoplasmic Antibody-Associated Vasculitis

Avacopan, an orally administered C5a receptor (C5aR) antagonist, has been approved for the treatment of microscopic polyangiitis (MPA) and granulomatosis with polyangiitis (GPA) in Japan and the United States. In ADVOCATE Phase III clinical trial, patients with active MPA or GPA received either 30 mg avacopan twice daily or prednisone on a tapering schedule in combination with rituximab or cyclophosphamide (followed by azathioprine). The trial met its two primary endpoints: avacopan showed non-inferiority to prednisone for achieving remission at week 26 (avacopan, 72.3%; prednisone, 70.1%; p < 0.001 for non-inferiority and p = 0.24 for superiority) and superiority for maintaining remission at week 52 (65.7% for avacopan, 54.9% prednisone, p < 0.001 for non-inferiority and p = 0.007 for superiority). Of several key secondary endpoints tested, the glucocorticoid toxicity index (GTI)-cumulative worsening score and GTI-aggregate improvement score were significantly lower in the avacopan group than in the prednisone group at both weeks 26 and 52. Serious adverse events related and unrelated to the worsening vasculitis were reported at 10.2% and 37.3% in the avacopan group and at 14.0% and 39.0% in the prednisone group, respectively. Avacopan has set the stage for the semi-glucocorticoid-free or glucocorticoid-free treatment of MPA and GPA.