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.

Review of guideline for the management of ANCA-associated vasculitis, presented in 2021 by the American College of Rheumatology/Vasculitis Foundation

The anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitides (AAVs) are a group of severe life-threatening autoimmune diseases, and one of the most important problems in practical rheumatology. This article discusses 2021 American College of Rheumatology/Vasculitis Foundation guideline for the management of AAVs, including granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), and eosinophilic granulomatosis with polyangiitis (EGPA). The guideline features 26 recommendations and 5 upgraded position statements for GPA/ MPA, as well as 15 recommendations and 5 upgraded position statements for EGPA, which became the basis for the proposed algorithms for the treatment of patients with GPA/MPA and EGPA. Particular attention has been paid to the use of biologics.

Eosinophilic Granulomatosis with Polyangiitis Relapse after COVID-19 Vaccination: A Case Report

Background: We here describe the case of a 71-year-old Caucasian woman previously diagnosed with Eosinophilic Granulomatosis with Polyangiitis (EGPA) that had been treated with Mepolizumab, an anti-IL5 monoclonal antibody, since 2019 with a good clinical response. Methods: She had a mild COVID-19 in December 2020 and she tested negative for SARS-CoV-2 infection in only late January 2021. In April 2021 she received the first dose of mRNA BNT162b2 vaccine. Ten days later she developed myalgia, dyspnea and numbness of the limbs due to a relapse of EGPA that occurred during Mepolizumab treatment.

Influence of Genetic Factors on Immunopathogenesis and Clinical Phenotypes of ANCA-associated Vasculitis

The review presents the recent data on assumed risk factors for the development of ANCA-associated vasculitis (AAV), among which environmental factors, such as climatic, chemical, etc., are of particular interest of researchers. Controversial opinions of various authors on the role of individual causative agents of infectious diseases in the development of AAV are analyzed. The review pays special attention to scientific data on the influence of variants of the structure of genes encoding various components of the immune system on the development of the pathogenetic process of AAV. Up-to-date information on the association of single-nucleotide polymorphisms (SNPs) with the course, risk of development and the likelihood of AAV recurrence is indicated, the most associated of which are genes encoding proteins of the main histocompatibility complex (HLA), a toll-like receptors (TLR`s), as well as an inhibitor of serine proteinases-alpha-antitrypsin (AAT). The analysis of scientific publications describing the molecular mechanism of the development of a pathological focus that forms the conditions for the synthesis of PR3ANCA and MPOANCA complexes characteristic of AAV has been carried out. The data of a number of foreign studies on the relationship of individual SNPs associated with the features of the course of granulomatosis with polyangiitis, microscopic polyangiitis, as well as eosinophilic granulomatosis with polyangiitis are presented and summarized. The review presents current AAV treatment regimens and promising directions for the development of medical care for patients.