Genetics and pathophysiology of granulomatosis with polyangiitis (GPA) and its main autoantigen proteinase 3

Genetic and epigenetic dysregulation of innate immune mechanisms in autoinflammatory diseases

Dysregulation and hyperactivation of innate immune responses can lead to the onset of systemic autoinflammatory diseases. Monogenic autoinflammatory diseases are caused by inborn genetic errors and based on molecular mechanisms at play, can be divided into inflammasomopathies, interferonopathies, relopathies, protein misfolding, and endogenous antagonist deficiencies. On the other hand, more common autoinflammatory diseases are multifactorial, with both genetic and non-genetic factors playing an important role. During the last decade, long-term memory characteristics of innate immune responses have been described (also called trained immunity) that in physiological conditions provide enhanced host protection from pathogenic re-infection. However, if dysregulated, induction of trained immunity can become maladaptive, perpetuating chronic inflammatory activation. Here, we describe the mechanisms of genetic and epigenetic dysregulation of the innate immune system and maladaptive trained immunity that leads to the onset and perpetuation of the most common and recently described systemic autoinflammatory diseases.

Granulomatosis With Polyangiitis: The Complexity of Clinical Manifestations, Therapeutic Challenges, and Complications of a Severe Multisystemic Case

We report a case of a 34-year-old male with severe multisystemic involvement (including the testis, musculoskeletal system, skin, upper respiratory tract, ocular system, peripheral nerves, abdomen, and kidney) due to granulomatosis with polyangiitis (GPA) and a high proteinase 3 (PR3)-antineutrophil cytoplasmic antibodies (PR3ANCA) titer. A renal biopsy showed pauci-immune glomerulonephritis (GN). Systemic corticotherapy combined with cyclophosphamide was chosen for induction therapy. During the induction phase, clinical deterioration occurred in the form of severe alveolar hemorrhage, leading to admission to the intensive care unit (ICU). Influenza A (H1N1) was detected in the respiratory tract. Furthermore, blood sampling revealed an invasive Klebsiella pneumoniae infection that persisted despite multiple antibiotic regimens. A CT scan showed splenic vascular compromise, assumed to be the primary source of the infection, with sustained improvement after splenectomy. Maintenance therapy included a tapering dose of corticotherapy for 36 months and azathioprine 100mg daily for five years, which achieved full and sustained remission. The patient has been in full remission for nine years, with mild renal sequelae, including proteinuria and secondary hypertension.

Familial Association of Granulomatosis With Polyangiitis: A Case-Based Review of Literature

Anti-neutrophil cytoplasm antibody (ANCA)-associated vasculitis (AAV) is a class of small vessel vasculitis that includes granulomatosis with polyangiitis (GPA), eosinophilic GPA (EGPA), and microscopic polyangiitis (MPA). Despite extensive research, the mechanisms behind AAV etiology remain obscure. The genetics of AAV is a complex area of investigation because of the rarity of familial cases. However, recent multi-center genome-wide association studies (GWAS) have greatly contributed to our understanding of the genetic basis of AAV. In this study, we report a rare occurrence of GPA in two Caucasian family members who presented with similar clinical symptoms and performed a comprehensive review to study the present literature available regarding the heritability of this disease.

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.

Meta-analysis confirmed genetic susceptibility conferred by multiple risk variants from CTLA4 and SERPINA1 in granulomatosis with polyangiitis

BACKGROUND

Granulomatosis with polyangiitis (GPA) is a rare systemic autoimmune disease. Smaller sample size and complex nature of the disease pathogenesis has made it challenging to perform well-powered genetic investigations. We performed a systematic review based meta-analysis in GPA to investigate the genetic susceptibility conferred by non-human leukocyte antigen (non-HLA) candidate genes.

METHODS

A systematic review was performed using web-based literature search and eligible studies were included following inclusion-exclusion criteria. Studies were evaluated for their quality of evidence and study outcome was assessed using the Newcastle-Ottawa Scale and Grades of Research, Assessment, Development and Evaluation tools. Reviewer's agreement was accessed through Cohen's κ value. Meta-analyses were performed using RevMan 5 tool. Meta-odds ratio (meta-OR) and Z test P value were evaluated to estimate the genetic susceptibility for each of the variants.

RESULTS

Eighteen studies were found eligible and 7 genetic variants from only 4 genes, namely CTLA4, PRTN3, SERPINA1 and PTPN22 could be studied for meta-analysis. rs231775-G (49-G) (Meta-OR = 1.42 [1.14-1.76]; P = .001) of CTLA4 and rs7151526-A (Meta-OR = 2.70 [1.51-4.85]; P = .0008) of SERPINA1 were confirmed to be predisposing alleles, and rs5742909-C (318-C) (Meta-OR = 0.65 [0.44-0.97]; P =.03) of CTLA4 was found to be protective for GPA. In concordance with the genetic association of rs7151526-A, serological marker for the same variant "Z" allele of SERPINA1 was found to be predisposing (Meta-OR = 12.60 [5.01-31.68]; P < .00001) for GPA.

CONCLUSION

Genetic variants confirmed in this study play critical roles in T-cell mediated immune function and could be significantly implicated in GPA. Molecular pathology studies are warranted to confirm their role. These markers could be used for efficient patient classification and disease management.

Anti-Proteinase 3 Antibodies as a Biomarker for Ulcerative Colitis and Primary Sclerosing Cholangitis in Children

OBJECTIVES

Anti-neutrophil cytoplasmic antibody (ANCA) directed against proteinase 3 (PR3) is a marker for granulomatosis with polyangiitis, but is also found in patients with inflammatory bowel disease (IBD), mainly ulcerative colitis (UC). The aim of our study was to investigate ANCA and PR3-ANCA in paediatric IBD.

METHODS

We tested 326 paediatric IBD patients and 164 controls for anti-Saccharomyces cerevisiae antibodies (ASCA), ANCA (indirect immunofluorescence, IIF) and PR3-ANCA (chemiluminescence immunoassay). We applied the Paris classification for paediatric IBD and documented liver manifestations such as primary sclerosing cholangitis (PSC) and autoimmune hepatitis (AIH).

RESULTS

We found PR3-ANCA in 49/121 (40%) of UC, 20/187 (11%) of Crohn disease (CD) and 2/18 (11%) of IBD-unclassified (IBD-U) patients but in none of the controls. 54% UC and 12% CD patients were positive for ANCA (IIF). PR3-ANCA positive UC patients were characterised by more extensive disease (P = .070). Fourteen of 21 (67%) of UC patients with backwash ileitis were anti-PR3 ANCA-positive (P = .011). We diagnosed PSC or PSC/AIH in 19 UC and 3 IBD-U patients. Fifteen of 22 (68%) patients with PSC or PSC/AIH were anti-PR3-ANCA positive in contrast to 36 of 117 (32%) patients without PSC (P = .001). PR3-ANCA positive patients showed higher levels of gamma-glutamyl transferase, alanine transaminase and aspartate transferase (P < 0.001, 0.001, 0.006, respectively). Forty-seven percent of CD and 6% of UC patients were ASCA-IgA positive. PR3-ANCA-positive and -negative patients showed no significant differences concerning age at diagnosis, disease activity, need for drugs, and number of hospitalisations.

CONCLUSIONS

Our study provides data for PR3-ANCA as a potential serological marker for paediatric UC and PSC.

Cardiac imaging of a patient with unusual presentation of granulomatosis with polyangiitis: A case report and review of the literature

BACKGROUND

Recent evidence suggests that cardiac involvement in patients with granulomatosis with polyangiitis (GPA) occurs more frequently than previously reported. Multimodality cardiac imaging is gaining attention in the diagnosis, prognostication, and follow-up of such patients; however, the data remain scarce.

RESULTS

2D-TTE was useful for initial screening; while both cardiac magnetic resonance imaging and 18F-fluoro-2-deoxyglucose positron emission tomography/computed tomography (18FDG-PET/CT) metabolic imaging with rubidium-82 PET perfusion imaging were useful for characterization of myocardial disease. 18FDG-PET/CT was very useful for the follow-up of cardiac disease activity following treatment.

CONCLUSION

18FDG-PET/CT is sensitive for the detection of cardiac involvement by GPA and is useful for the tissue characterization and follow-up of disease activity following treatment.

Role of Neutrophils in Systemic Vasculitides

Neutrophils and neutrophil extracellular traps (NETs) contribute to the pathogenesis of many autoimmune diseases, including vasculitis. Though neutrophils, and NETs, can break self-tolerance by being a source of autoantigens for autoantibodies in anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis, playing a key role in driving the autoimmune response, the role of neutrophils and NETs in large vessel vasculitis, including giant cell arteritis (GCA), is not well understood. In this review, we summarize the current insight into molecular mechanisms contributing to neutrophil-mediated pathology in small and medium vessel vasculitis, as well as provide potential translational perspectives on how neutrophils, and NETs, may partake in large vessel vasculitis, a rare disease entity of unclear pathogenesis.

Proteinase 3 Autoreactivity in Anti-Neutrophil Cytoplasmic Antibody-associated vasculitis-Immunological versus clinical features

ANCA-associated vasculitis (AAV) is a group of chronic inflammatory diseases of small- and medium-sized vessels, which are broadly subdivided based on organ manifestations and disease-specific autoantibodies. The so called anti-neutrophil cytoplasmic antibodies (ANCA) mostly target one of the enzymes, proteinase 3 (PR3) or myeloperoxidase (MPO). Accumulating genetic data demonstrates that these two autoantibodies discriminate two distinct disease entities, more so than the clinical subdivision which is mainly criteria-based. Treatment of AAV includes heavy immunosuppression and is guided by which organs that are involved. Generally, patients with PR3-ANCA display higher risk for disease relapse than patients with MPO-ANCA. In this review, we will focus on the autoimmune features of PR3+ AAV and our current understanding of its triggers and the potential translation into clinical practice.

Current insights in the pathogenesis of scleritis

Scleritis is a sight-threatening inflammation characterized by severe pain and redness of the eye. It can cause blindness by severe complications like scleral and corneal necrosis, keratitis, and uveitis. The pathogenesis of scleritis is largely unknown due to a combination of the rarity of the disease, the little available human tissue-based research material, and the lack of animal models. The immune system is assumed to play a crucial role in the pathogenesis of scleritis. Multiple clues indicate probable antigenic stimuli in scleritis, and the involvement of matrix metalloproteinases in the destruction of scleral tissue. In this article we review the current insights into the pathogenesis of scleritis, and we suggest new hypotheses by implementing knowledge of systemic autoimmune disease pathogenesis. Understanding the pathogenesis of scleritis is crucial to improve the clinical management, as well as to find novel treatment modalities.

Temporal and Cartographic Analyses of the Distribution within Spain of Mortality Due to Granulomatosis with Polyangiitis (1984⁻2016)

The aim is to conduct a descriptive, population-based study in order to assess temporal and spatial changes in mortality due to granulomatosis with polyangiitis (GPA) in Spain from 1984 to 2016. Mortality data were obtained from the Spanish Annual Death Registry. Deaths in which GPA was the underlying cause were selected using the 446.4 and M31.3 codes from the International Classification of Diseases, 9th and 10th revision. Annual average age at death and age-adjusted mortality rates were calculated. Geographic analysis was performed at municipality and district level. Variations in mortality according to the type of municipality (urban, agro-urban or rural), district and geographic location (degrees of latitude) were assessed using standardized mortality ratios (SMRs) and smoothed-SMRs. Over the whole period, 620 deaths due to GPA were identified. Age at death increased at an average annual rate of 0.78% over the period 1987–2016 (p < 0.05). Age-adjusted mortality rates increased by an annual average of 20.58% from 1984 to 1992, after which they fell by 1.91% a year (p < 0.05). The agro-urban category had the highest percentage (4.57%) of municipalities with a significantly higher GPA mortality rate than expected. Geographic analysis revealed four districts with a higher risk of death due to GPA, two in the North of Spain and two in the South. This population-based study revealed an increase in the age at death attributed to GPA. Age-adjusted mortality rates went up sharply until 1992, after which they started to decline until the end of the study period. Geographic differences in mortality risk were identified but further studies will be necessary to ascertain the reasons for the distribution of GPA disease.

Genetic Variants in Antineutrophil Cytoplasmic Antibody-Associated Vasculitis: A Bayesian Approach and Systematic Review

A number of genome-wide association studies (GWASs) and meta-analyses of genetic variants have been performed in antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis. We reinterpreted previous studies using false-positive report probability (FPRP) and Bayesian false discovery probability (BFDP). This study searched publications in PubMed and Excerpta Medica Database (EMBASE) up to February 2018. Identification of noteworthy associations were analyzed using FPRP and BFDP, and data (i.e., odds ratio (OR), 95% confidence interval (CI), p-value) related to significant associations were separately extracted. Using filtered gene variants, gene ontology (GO) enrichment analysis and protein⁻protein interaction (PPI) networks were performed. Overall, 241 articles were identified, and 7 were selected for analysis. Single nucleotide polymorphisms (SNPs) discovered by GWASs were shown to be noteworthy, whereas only 27% of significant results from meta-analyses of observational studies were noteworthy. Eighty-five percent of SNPs with borderline p-values (5.0 × 10-8 < p < 0.05) in GWASs were found to be noteworthy. No overlapping SNPs were found between PR3-ANCA and MPO-ANCA vasculitis. GO analysis revealed immune-related GO terms, including "antigen processing and presentation of peptide or polysaccharide antigen via major histocompatibility complex (MHC) class II", "interferon-gamma-mediated (IFN-γ) signaling pathway". By using FPRP and BFDP, network analysis of noteworthy genetic variants discovered genetic risk factors associated with the IFN-γ pathway as novel mechanisms potentially implicated in the complex pathogenesis of ANCA-associated vasculitis.

Extrahepatic autoimmune diseases in patients with autoimmune hepatitis and their relatives: A Danish nationwide cohort study

BACKGROUND & AIMS

It is widely accepted that patients with autoimmune hepatitis have an increased prevalence of extrahepatic autoimmune diseases. It is believed that the patients' relatives share this trait, but it has not been studied in a satisfactory setting. We conducted a nationwide registry-based cohort study on this issue.

METHODS

From Danish healthcare registries 1994-2015, we included 2745 patients with autoimmune hepatitis, 17 812 of their first- and second-degree relatives and 27 450 general population controls matched with the patients for sex and age. We compared the sex- and age-specific prevalence of extrahepatic autoimmune diseases between the patients with autoimmune hepatitis, their relatives and the controls. We computed the prevalence ratio as a measure of the relative prevalence, using the controls as reference group.

RESULTS

In the patients with autoimmune hepatitis, the prevalence ratio of extrahepatic autoimmune diseases ranged from 7 to 10 until age 30 years (prevalence ratio at age 20 = 9.92; 95% confidence interval 6.21-15.83), after which it gradually decreased to about 2 (prevalence ratio at age 80 = 2.37; 95% confidence interval 1.89-3.00). Neither first- nor second-degree relatives had an increased prevalence of extrahepatic autoimmune diseases (prevalence ratio for relatives at age 20 = 1.11; 95% confidence interval 0.72-1.70; prevalence ratio at age 80 = 0.96; 95% confidence interval 0.70-1.31).

CONCLUSIONS

Danish patients with autoimmune hepatitis were highly prone to extrahepatic autoimmune diseases, but their relatives were not.

Is granulomatosis with polyangiitis in Asia different from the West?

The incidence and clinical features of antineutrophil cytoplasmic antibody (ANCA) associated vasculitis (AAV) have been shown to vary according to geographical areas, with granulomatosis with polyangiitis (GPA) being more common in northern Europe and microscopic polyangiitis (MPA) being more common in Asian countries. The annual incidence of GPA among Asians varies between 0.37/million to 2.1/million population. The prevalence of GPA has been estimated to be 1.94/100 000 in a Chinese population. Polymorphisms in class II major histocompatibility genes and ETS1 proto-oncogene has been shown in Asian patients with GPA. There is a difference in mean age at onset and proteinase 3 (PR3) or myeloperoxidase (MPO) positivity in GPA patients from different Asian countries. Those from India had mean age of 40 years and those from Japan had mean age of 65 years. Sixty percent of GPA patients from China and Japan were MPO ANCA positive while the majority of patients from India and Korea were PR3 positive. Geographical variation with lower frequency of renal involvement in Indian studies and higher frequency in Chinese patients has also been noted. Treatment outcomes have been similar to those reported from other parts of the world. Remission was achieved in about two-thirds of patients while relapses were noted in one-third to half of the patients. Apart from minor differences in the organ systems involved, MPO-ANCA GPA and PR3-ANCA GPA had similar rates of remission and relapses.

Extended Cleavage Specificity of Human Neutrophil Elastase, Human Proteinase 3, and Their Distant Ortholog Clawed Frog PR3-Three Elastases With Similar Primary but Different Extended Specificities and Stability

Serine proteases are major granule constituents of several of the human hematopoietic cell lineages. Four proteolytically active such proteases have been identified in human neutrophils: cathepsin G (hCG), N-elastase (hNE), proteinase 3 (hPR-3), and neutrophil serine protease 4 (hNSP-4). Here we present the extended cleavage specificity of two of the most potent and most abundant of these enzymes, hNE and hPR-3. Their extended specificities were determined by phage display and by the analysis of a panel of chromogenic and recombinant substrates. hNE is an elastase with a relatively broad specificity showing a preference for regions containing several aliphatic amino acids. The protease shows self-cleaving activity, which results in the loss of activity during storage even at +4°C. Here we also present the extended cleavage specificity of hPR-3. Compared with hNE, it shows considerably lower proteolytic activity. However, it is very stable, shows no self-cleaving activity and is actually more active in the presence of SDS, possibly by enhancing the accessibility of the target substrate. This enables specific analysis of hPR-3 activity even in the presence of all the other neutrophil enzymes with addition of 1% SDS. Neutrophils are the most abundant white blood cell in humans and one of the key players in our innate immune defense. The neutrophil serine proteases are very important for the function of the neutrophils and therefore also interesting from an evolutionary perspective. In order to study the origin and functional conservation of these neutrophil proteases we have identified and cloned an amphibian ortholog, Xenopus PR-3 (xPR-3). This enzyme was found to have a specificity very similar to hPR-3 but did not show the high stability in the presence of SDS. The presence of an elastase in Xenopus closely related to hPR-3 indicates a relatively early appearance of these enzymes during vertebrate evolution.

Clinical Significance of Neutrophil/lymphocyte Ratio in Patients With Granulomatosis With Polyangiitis

OBJECTIVE

To determine to neutrophil-to-lymphocyte ratio (NLR) in granulomatosis with polyangiitis (GPA) patients and to study its relation to disease manifestations and activity.

METHODS

The study included 44 GPA patients and 44 matched age and sex controls. Full history taking, thorough clinical examination with more attention to ocular examination, laboratory and radiological investigations were considered. Disease activity was assessed using the Birmingham Vasculitis Activity Score (BVAS).

RESULTS

The patients (21 males and 23 females) had a mean age of 45.66±7.24 years, disease duration 6.8±3.6 years and BVAS 50.1±14.3. All patients had a positive cytoplasmic anti-neutrophil cytoplasmic antibody (c-ANCA) while only 5 had a positive p-ANCA. The NLR was significantly increased in the GPA patients (5.1±2.4) compared to the control (1.5±0.8) (P<.0001). Ten patients with uveitis had a significantly higher NLR (6.5±1.9) compared to those without (4.7±2.4) (0.03) while those with proptosis (n=10), cutaneous manifestations (n=17) or ischemic heart disease (n=9) had a significantly lower NLR than those without (P=.0001, P=.017 and P=.046 respectively). The NLR did not significantly correlate with any of the patients' characteristics. The NLR inversely yet insignificantly correlated with the disease activity (r=-0.02, P=.93).

CONCLUSION

The NLR may have a significant role in the pathogenesis of GPA, the development of uveitis or proptosis, cutaneous manifestations and ischemic heart disease. NLR may serve as a future potential companion to c-ANCA positivity in diagnosing and evaluating GPA and may play a role in the tissue-specific and clinical characteristics.

Th17 and Treg lymphocytes as cellular biomarkers of disease activity in Granulomatosis with Polyangiitis

Granulomatosis with Polyangiitis (GPA) (formerly known as Wegener's granulomatosis) is a vasculitis of unknown etiology affecting predominantly small- to medium-sized vessels, usually involving the upper and lower respiratory tract and kidneys. Anti-neutrophil cytoplasmic autoantibodies are probably the initial cause of the inflammatory process that leads to the typical necrotizing lesions. In this issue of the European Journal of Immunology, Szczeklik et al. [Eur. J. Immunol. 2017. 47: 724-733] report some interesting findings on the possible involvement of T-cell subsets in the pathogenesis of the disease. This prospective study, performed on a large cohort of patients, identifies Th17 lymphocytes as the possible pathogenic subset of GPA, and Treg cells as the possible suppressors of the inflammatory process. These two subsets in peripheral blood could be used as cellular biomarkers of disease activity, and this would result particularly useful in the follow-up of patients once the immunosuppressive treatment has been initiated.

Therapeutic Complement Targeting in ANCA-Associated Vasculitides and Thrombotic Microangiopathy

Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitides (AAVs) are a group of systemic autoimmune disorders characterized by necrotizing inflammation of medium-to-small vessels, a relative paucity of immune deposits, and an association with detectable circulating ANCAs. AAVs include granulomatosis with polyangiitis (renamed from Wegener's granulomatosis), microscopic polyangiitis, and eosinophilic granulomatosis with polyangiitis (Churg-Strauss syndrome). Until recently, AAVs have not been viewed as complement-mediated disorders. However, recent findings predominantly from animal studies demonstrated a crucial role of the complement system in the pathogenesis of AAVs. Complement activation or defects in its regulation have been described in an increasing number of acquired or genetically driven forms of thrombotic microangiopathy. Coinciding with this expanding spectrum of complement-mediated diseases, the question arises as to which AAV patients might benefit from a complement-targeted therapy. Therapies directed against the complement system point to the necessity of a genetic workup of genes of complement components and regulators in patients with AAV. Genetic testing together with pluripotent stem cells and bioinformatics tools may broaden our approach to the treatment of patients with aggressive forms of AAV.