A functional inflammasome activation assay differentiates patients with pathogenic NLRP3 mutations and symptomatic patients with low penetrance variants

Pathogenic NLRP3 mutants form constitutively active inflammasomes resulting in immune-metabolic limitation of IL-1β production

Cryopyrin-associated periodic syndrome (CAPS) is an autoinflammatory condition resulting from monoallelic NLRP3 variants that facilitate IL-1β production. Although these are gain-of-function variants characterized by hypersensitivity to cell priming, patients with CAPS and animal models of the disease may present inflammatory flares without identifiable external triggers. Here we find that CAPS-associated NLRP3 variants are forming constitutively active inflammasome, which induce increased basal cleavage of gasdermin D, IL-18 release and pyroptosis, with a concurrent basal pro-inflammatory gene expression signature, including the induction of nuclear receptors 4 A. The constitutively active NLRP3-inflammasome of CAPS is responsive to the selective NLRP3 inhibitor MCC950 and its activation is regulated by deubiquitination. Despite their preactivated state, the CAPS inflammasomes are responsive to activation of the NF-κB pathway. NLRP3-inflammasomes with CAPS-associated variants affect the immunometabolism of the myeloid compartment, leading to disruptions in lipids and amino acid pathways and impaired glycolysis, limiting IL-1β production. In summary, NLRP3 variants causing CAPS form a constitutively active inflammasome inducing pyroptosis and IL-18 release without cell priming, which enables the host's innate defence against pathogens while also limiting IL-1β-dependent inflammatory episodes through immunometabolism modulation.

Hearing Loss as the Main Clinical Presentation in NLRP3-Associated Autoinflammatory Disease

The NLRP3 gene mutations are the cause of autosomal dominant autoinflammatory disorders (NLRP3-AID). Recently, hearing loss (HL) has been found to be the sole or major manifestation of NLRP3-AID. Here, we tested 110 autosomal dominant HL families with a custom panel of 237 HL genes and found one family carrying the NLRP3 c.1872C>G, p.Ser624Arg mutation. Functional studies revealed that this novel variant is a gain of function mutation, leading to increased activity of caspase-1 and subsequent oversecretion of proinflammatory interleukin-1β. Clinical reanalysis of the affected individuals, together with serological evidence of inflammation and pathological cochlear enhancement on FLAIR-MRI images, guided our diagnosis to atypical NLRP3-AID. The study highlights the role of genetic analysis in patients with progressive postlingual HL. This can help to identify individuals with hereditary HL as a consequence of NLRP3-AID and allow timely and effective treatment with interleukin-1-receptor antagonist.

Analysis of Activity and Expression of the NLRP3, AIM2, and NLRC4 Inflammasome in Whole Blood

Pro-inflammatory caspase-1 is a key player in innate immunity. Following activation in heterogenic protein complexes called the inflammasome , caspase-1 processes IL-1β and IL-18 to their mature forms and triggers pyroptosis. Here, we describe a small-volume whole blood assay facilitating the measurement of caspase-1 activity and inflammasome-related gene expression following specific stimulation of either the NLRP3, NLRC4, or AIM2 inflammasome .

Anti-Myelin Oligodendrocyte Glycoprotein Encephalomyelitis and Extensive Longitudinal Transverse Myelitis Associated with Compound Heterozygous NLRP3 Missense Mutations in a Young Child

Acute disseminated encephalomyelitis in association with extensive longitudinal transverse myelitis is reported in a young child with positive anti-myelin oligodendrocyte glycoprotein (MOG) antibody with heterozygous NLRP3 missense mutations; p.(Arg488Lys) and p.(Ser159Ile). This case may well present an exceptional coincidence, but may describe a yet unrecognized feature of the spectrum of childhood onset cryopyrinopathies that contribute to the understanding of the genetic basis for anti-MOG antibody positive encephalomyelitis. Based on this observation, a larger scale study investigating the role of NLRP3 and other inflammasomes in this entity would provide important pathophysiological insights and potentially novel avenues for treatment.

Lipopolysaccharide stimulation test on cultured PBMCs assists the discrimination of cryopyrin-associated periodic syndrome from systemic juvenile idiopathic arthritis

Systemic juvenile idiopathic arthritis (sJIA) and cryopyrin-associated periodic syndrome (CAPS) share many common manifestations. We aim to identify an applicable method to assist disease discrimination. Inflammatory cytokines were measured in the plasma of patients with CAPS, sJIA with persistent disease course and healthy controls. Supernatants collected from non-stimulated peripheral blood mononuclear cells (PBMCs) and those undergone inflammasome stimulation tests utilizing lipopolysaccharide (LPS) with and without adenosine triphosphate (ATP) were investigated. Inflammatory cytokines in patient plasma fail to differentiate sJIA from CAPS. PBMCs from sJIA secrets higher amount of IL-1β and IL-18 while CAPS PBMCs produces more caspase-1 without stimulation. IL-1β, IL-18, and caspase-1 were significantly elevated among CAPS PBMCs (all p < 0.05) upon LPS stimulation, but not when additional ATPs were provided. Levels of cytokines and PBMC responses to the stimulation assays were similar among all sJIA patients regardless of their history of macrophage activation syndrome. Unstimulated PBMC activities and the LPS inflammasome stimulation assay without exogenic ATPs can assist the differentiation of CAPS from sJIA with persistent disease course.

Drug survival of anakinra and canakinumab in monogenic autoinflammatory diseases: observational study from the International AIDA Registry

OBJECTIVES

To investigate survival of interleukin (IL)-1 inhibitors in monogenic autoinflammatory disorders (mAID) through drug retention rate (DRR) and identify potential predictive factors of drug survival from a real-life perspective.

PATIENTS AND METHODS

Multicentre retrospective study analyzing patients affected by the most common mAID treated with anakinra or canakinumab. Survival curves were analyzed with the Kaplan-Meier method. Statistical analysis included a Cox-proportional hazard model to detect factors responsible for drug discontinuation.

RESULTS

Seventy-eight patients for a total of 102 treatment regimens were enrolled. The mean treatment duration was 29.59 months. The estimated DRR of IL-1 inhibitors at 12, 24, and 48 months of follow-up was 75.8%, 69.7% and 51.1%, respectively. Patients experiencing an adverse event had a significantly lower DRR (p = 0.019). In contrast, no significant differences were observed between biologic-naïve patients and those previously treated with biologic drugs (p = 0.985) Patients carrying high-penetrance mutations exhibited a significantly higher DRR compared with those with low-penetrance variants (p = 0.015). Adverse events were the only variable associated with a higher hazard of treatment withdrawal (HR 2.573 [CI: 1.223-5.411], p = 0.013) on regression analysis. A significant glucorticoid-sparing effect was observed (p < 0.0001).

CONCLUSIONS

IL-1 inhibitors display an excellent long-term effectiveness in terms of DRR, and their survival is not influenced by the biologic line of treatment. They display a favorable safety profile, that deserves however a close monitoring given its impact on treatment continuation. Special attention should be paid to molecular diagnosis and mutation penetrance, as patients carrying low-penetrance variants are more likely to interrupt treatment.

Management of Monogenic IL-1 Mediated Autoinflammatory Diseases in Childhood

Monogenic Interleukin 1 (IL-1) mediated autoinflammatory diseases (AID) are rare, often severe illnesses of the innate immune system associated with constitutively increased secretion of pro-inflammatory cytokines. Clinical characteristics include recurrent fevers, inflammation of joints, skin, and serous membranes. CNS and eye inflammation can be seen. Characteristically, clinical symptoms are coupled with elevated inflammatory markers, such as C-reactive protein (CRP) and serum amyloid A (SAA). Typically, AID affect infants and children, but late-onset and atypical phenotypes are described. An in-depth understanding of autoinflammatory pathways and progress in molecular genetics has expanded the spectrum of AID. Increasing numbers of genetic variants with undetermined pathogenicity, somatic mosaicisms and phenotype variability make the diagnosis of AID challenging. AID should be diagnosed as early as possible to prevent organ damage. The diagnostic approach includes patient/family history, ethnicity, physical examination, specific functional testing and inflammatory markers (SAA, CRP) during, and in between flares. Genetic testing should be performed, when an AID is suspected. The selection of genetic tests is guided by clinical findings. Targeted and rapid treatment is crucial to reduce morbidity, mortality and psychosocial burden after an AID diagnosis. Management includes effective treat-to-target therapy and standardized, partnered monitoring of disease activity (e.g., AIDAI), organ damage (e.g., ADDI), patient/physician global assessment and health related quality of life. Optimal AID care in childhood mandates an interdisciplinary team approach. This review will summarize the current evidence of diagnosing and managing children with common monogenic IL-1 mediated AID.

Diagnosis and Management of the Cryopyrin-Associated Periodic Syndromes (CAPS): What Do We Know Today?

The cryopyrin-associated periodic syndromes (CAPS) are usually caused by heterozygous NLRP3 gene variants, resulting in excessive inflammasome activation with subsequent overproduction of interleukin (IL)-1β. The CAPS spectrum includes mild, moderate, and severe phenotypes. The mild phenotype is called familial cold autoinflammatory syndrome (FCAS), the moderate phenotype is also known as Muckle-Wells syndrome (MWS), and the neonatal-onset multisystem inflammatory disease (NOMID)/chronic infantile neurologic cutaneous articular syndrome (CINCA) describes the severe phenotype. The CAPS phenotypes display unspecific and unique clinical signs. Dermatologic, musculoskeletal, ocular, otologic, and neurologic disease symptoms combined with chronic systemic inflammation are characteristic. Nevertheless, making the CAPS diagnosis is challenging as several patients show a heterogeneous multi-system clinical presentation and the spectrum of genetic variants is growing. Somatic mosaicisms and low-penetrance variants lead to atypical clinical symptoms and disease courses. To avoid morbidity and to reduce mortality, early diagnosis is crucial, and a targeted anti-IL-1 therapy should be started as soon as possible. Furthermore, continuous and precise monitoring of disease activity, organ damage, and health-related quality of life is important. This review summarizes the current evidence in diagnosis and management of patients with CAPS.

A Novel DSP Truncating Variant in a Family with Episodic Myocardial Injury in the Course of Arrhythmogenic Cardiomyopathy-A Possible Role of a Low Penetrance NLRP3 Variant

Mono-allelic dominant mutations in the desmoplakin gene (DSP) have been linked to known cardiac disorders, such as arrhythmogenic right ventricular cardiomyopathy and dilated cardiomyopathy. During the course of DSP cardiomyopathy, episodes of acute myocardial injury may occur. While their mechanisms remain unclear, myocarditis has been postulated as an underlying cause. We report on an adolescent girl with arrhythmogenic biventricular cardiomyopathy and three acute myocarditis-like episodes in whom we found a novel truncating DSP variant accompanied by a known low penetrance R490K variant in the NLRP3. Upon family screening, other carriers of the DSP variant have been identified in whom only mild cardiac abnormalities were found. We hypothesized that the uncommon course of cardiomyopathy in the proband as well as striking discrepancies in the phenotype observed in her family may be explained by the co-existence of her low penetrance genetic autoinflammatory predisposition.

Increased Prevalence of NLRP3 Q703K Variant Among Patients With Autoinflammatory Diseases: An International Multicentric Study

Background: The NLRP3 inflammasome has been recognized as one of the key components of innate immunity. Gain-of-function mutations in the exon 3 of NLRP3 gene have been implicated in inflammatory diseases suggesting the presence of functionally important sites in this region. Q703K (c.2107C>A, p.Gln703Lys, also known in the literature as Q705K) is a common variant of NLRP3, that has been considered to be both clinically unremarkable or disease-causing with a reduced penetrance. Objectives: We aimed to investigate the potential genetic impact of the NLRP3 variant Q703K in patients with recurrent fever presenting with two autoinflammatory diseases: PFAPA (periodic fever, aphthous stomatitis, pharyngitis and cervical adenitis) and CAPS (cryopyrin-associated periodic syndrome), as well as with undefined autoinflammatory disease (uAID). Methods: This is an international multicentric observational retrospective study characterizing the clinical phenotype of patients presenting with recurrent fever suspected to be of auto-inflammatory origin and where the Q703K NLRP3 variant was found. Monocytes of parents of 6 Q703K+ PFAPA patients were studied and levels of pro-inflammatory cytokines produced by monocytes of Q703K+ and Q703K- parents have been compared by ELISA. Results: We report 42 patients with the Q703K NLRP3 genetic variant: 21 were PFAPA patients, 6 had a CAPS phenotype, and 15 had an uAID. The phenotypes of PFAPA, CAPS and uAID were quite similar between Q703K positive and negative patients with the exception of increased prevalence of pharyngitis in the Q703K positive CAPS population compared to the negative one. The in vitro production of IL-1β was not significantly different between Q703K+ and Q703K- monocytes from asymptomatic parents. Conclusion: The evidence we report in our study shows an increased prevalence of NLRP3 Q703K in patients with autoinflammatory diseases, suggesting an association between the Q703K variant and the risk of PFAPA, CAPS and uAID syndromes. However, we did not show a functional effect of this mutation on the inflammasome basal activity.

Putative link between Polo-like kinases (PLKs) and Toll-like receptor (TLR) signaling in transformed and primary human immune cells

Toll-like receptors (TLRs) are important sentinels of bacterial and viral infection and thus fulfil a critical sensory role in innate immunity. Polo-like kinases (PLKs), a five membered family of Ser/Thr protein kinases, have long been studied for their role in mitosis and thus represent attractive therapeutic targets in cancer therapy. Recently, PLKs were implicated in TLR signaling in mice but the role of PLKs in TLR signaling in untransformed primary immune cells has not been addressed, even though PLK inhibitors are in clinical trials. We here identified several phospho-serine and phospho-threonine residues in the known TLR pathway kinases, Interleukin-1 receptor-associated kinase (IRAK) 2 and IRAK4. These sites lie in canonical polo-box motifs (PBM), sequence motifs known to direct recruitment of PLKs to client proteins. Interestingly, PLK1 was phosphorylated and PLK 2 and 3 mRNA induced upon TLR stimulation in primary immune cells, respectively. In whole blood, PLK inhibition disparately affected TLR mediated cytokine responses in a donor- and inhibitor-dependent fashion. Collectively, PLKs may thus potentially interface with TLR signaling in humans. We propose that temporary PLK inhibitor-mediated blockade of TLR-signaling in certain patients receiving such inhibitors during cancer treatment may cause adverse effects such as an increased risk of infections due to a then compromised ability of the TLR recognition system to sense and initiate cytokine responses to invading microbes.

An optimized whole blood assay measuring expression and activity of NLRP3, NLRC4 and AIM2 inflammasomes

The proinflammatory protease caspase-1 plays pivotal roles in central pathways of innate immunity, thereby contributing to pathogen clearance. Beside its physiological role, dysregulated activity of caspase-1 is known to contribute to an increasing number of diseases. In this study, we optimized and validated a low-volume human whole blood assay facilitating the measurement of caspase-1 activation and inflammasome-related gene expression upon stimulation of the NLRP3, NLRC4 or AIM2 inflammasome. Using the NLRP3 inflammasome specific inhibitor MCC950, we were able to measure the activity of canonical or alternative NLRP3 pathways, AIM2 and NLRC4 inflammasomes in whole blood. Based on our data we assume a superposition of NLRP3 and NLRC4 inflammasome activities in human whole blood following stimulation with S. typhimurium. The optimized whole blood assay may be suitable for diagnostic and research purposes for pediatric patients who can only donate small amounts of blood.

Evidence for genetic overlap between adult onset Still's disease and hereditary periodic fever syndromes

OBJECTIVE

Adult onset Still's disease (AOSD) is a severe, autoimmune disease that can be challenging to treat with conventional therapeutics and biologicals in a considerable number of cases. Therefore, there is a high need to understand its pathogenesis better. As major clinical symptoms overlap between AOSD and hereditary periodic fever syndromes (HPFS), we analysed four known HPFS genes in AOSD.

METHODS

We performed Sanger sequencing and quantitative analysis of all coding regions of MEFV, TNFRSF1A, MVK and NLRP3 in 40 AOSD patients. All rare coding variants (n = 6) were evaluated for several aspects to classify them as benign to pathogenic variants. Statistical analysis was performed to analyse whether variants classified as (likely) pathogenic were associated with AOSD.

RESULTS

We identified three rare variants in MEFV, one previously not described. Association to the three likely pathogenic MEFV variants was significant (p _c = 2.34E- 03), and two of the three carriers had a severe course of disease. We observed strong evidence for significant association to mutations in TNFRSF1A (p _c = 2.40E- 04), as 5% of patients (2/40) carried a (likely) pathogenic variant in this gene. Both of them received a biological for treatment.

CONCLUSION

Our results indicate TNFRSF1A as a relevant gene in AOSD, especially in patients with a more challenging course of disease, while causal variants remain to be identified in the majority of patients.

A web-based collection of genotype-phenotype associations in hereditary recurrent fevers from the Eurofever registry

Background

Hereditary recurrent fevers (HRF) are a group of rare monogenic diseases leading to recurrent inflammatory flares. A large number of variants has been described for the four genes associated with the best known HRF, namely MEFV, NLRP3, MVK, TNFRSF1A. The Infevers database (http://fmf.igh.cnrs.fr/ISSAID/infevers) is a large international registry collecting variants reported in these genes. However, no genotype-phenotype associations are provided, but only the clinical phenotype of the first patient(s) described for each mutation. The aim of this study is to develop a registry of genotype-phenotype associations observed in patients with HRF, enrolled and validated in the Eurofever registry.

Results

Genotype-phenotype associations observed in all the patients with HRF enrolled in the Eurofever registry were retrospectively analyzed. For autosomal dominant diseases (CAPS and TRAPS), all mutations were individually analyzed. For autosomal recessive diseases (FMF and MKD), homozygous and heterozygous combinations were described. Mean age of onset, disease course (recurrent or chronic), mean duration of fever episodes, clinical manifestations associated with fever episodes, atypical manifestations, complications and response to treatment were also studied.

Data observed in 751 patients (346 FMF, 133 CAPS, 114 MKD, 158 TRAPS) included in the Eurofever registry and validated by experts were summarized in Tables. A total of 149 variants were described: 46 TNFRSF1A and 27 NLRP3 variants, as well as various combinations of 48 MVK and 28 MEFV variants were available.

Conclusions

We provide a potentially useful tool for physicians dealing with HRF, namely a registry of genotype-phenotype associations for patients enrolled in the Eurofever registry. This tool is complementary to the Infevers database and will be available at the Eurofever and Infevers websites.

Human NACHT, LRR, and PYD domain-containing protein 3 (NLRP3) inflammasome activity is regulated by and potentially targetable through Bruton tyrosine kinase

BACKGROUND

The Nod-like receptor NACHT, LRR, and PYD domain-containing protein 3 (NLRP3) and Bruton tyrosine kinase (BTK) are protagonists in innate and adaptive immunity, respectively. NLRP3 senses exogenous and endogenous insults, leading to inflammasome activation, which occurs spontaneously in patients with Muckle-Wells syndrome; BTK mutations cause the genetic immunodeficiency X-linked agammaglobulinemia (XLA). However, to date, few proteins that regulate NLRP3 inflammasome activity in human primary immune cells have been identified, and clinically promising pharmacologic targeting strategies remain elusive.

OBJECTIVE

We sought to identify novel regulators of the NLRP3 inflammasome in human cells with a view to exploring interference with inflammasome activity at the level of such regulators.

METHODS

After proteome-wide phosphoproteomics, the identified novel regulator BTK was studied in human and murine cells by using pharmacologic and genetic BTK ablation.

RESULTS

Here we show that BTK is a critical regulator of NLRP3 inflammasome activation: pharmacologic (using the US Food and Drug Administration-approved inhibitor ibrutinib) and genetic (in patients with XLA and Btk knockout mice) BTK ablation in primary immune cells led to reduced IL-1β processing and secretion in response to nigericin and the Staphylococcus aureus toxin leukocidin AB (LukAB). BTK affected apoptosis-associated speck-like protein containing a CARD (ASC) speck formation and caspase-1 cleavage and interacted with NLRP3 and ASC. S aureus infection control in vivo and IL-1β release from cells of patients with Muckle-Wells syndrome were impaired by ibrutinib. Notably, IL-1β processing and release from immune cells isolated from patients with cancer receiving ibrutinib therapy were reduced.

CONCLUSION

Our data suggest that XLA might result in part from genetic inflammasome deficiency and that NLRP3 inflammasome-linked inflammation could potentially be targeted pharmacologically through BTK.

Correlation of Secretory Activity of Neutrophils With Genotype in Patients With Familial Mediterranean Fever

OBJECTIVE

Familial Mediterranean fever (FMF) is an autoinflammatory disorder caused by pyrin-encoding MEFV mutations. Patients present with recurrent but self-limiting episodes of acute inflammation and often have persistent subclinical inflammation. The pathophysiology is only partially understood, but neutrophil overactivation is a hallmark of the disease. S100A12 is a neutrophil-derived proinflammatory danger signal that is strongly elevated in active FMF. This study was undertaken to characterize the secretory activity of neutrophils in vitro and investigate the association of S100A12 with disease activity and genotype in patients with FMF.

METHODS

Neutrophils from FMF patients carrying the p.M694V mutation (1 compound heterozygous and 5 homozygous) and neutrophils from 4 healthy control subjects were purified and stimulated in vitro. Neutrophil secretion of S100A12, interleukin-18 (IL-18), IL-1β, and caspase 1 was determined. Based on these in vitro analyses, serum concentrations of S100A12, IL-18, and IL-1β were also analyzed in 128 clinically and genetically characterized patients with FMF.

RESULTS

In vitro, unstimulated neutrophils from p.M694V-positive patients spontaneously secreted more S100A12, IL-18, and caspase 1 compared to neutrophils from healthy controls. Serum concentrations of S100A12 correlated with disease activity and genotype, with the levels being highest in homozygous patients and with compound heterozygotes displaying higher levels than heterozygotes. Compared to individuals negative for the p.M694V mutation, heterozygous, compound heterozygous, or homozygous p.M694V-positive patients had higher serum levels of S100A12 and IL-18 during inactive and subclinical disease.

CONCLUSION

The FMF phenotype is known to be more severe in patients carrying the p.M694V mutation. This report describes 2 molecules secreted by unconventional secretory pathways, S100A12 and IL-18, whose concentrations correlated with clinical disease activity and genotype in patients with FMF. In this clinically and genetically heterogeneous disease, management of these surrogate markers might help to improve patient care and outcomes.

Monogenic Autoinflammatory Diseases with Mendelian Inheritance: Genes, Mutations, and Genotype/Phenotype Correlations

Autoinflammatory diseases (AIDs) are a genetically heterogeneous group of diseases caused by mutations of genes encoding proteins, which play a pivotal role in the regulation of the inflammatory response. In the pathogenesis of AIDs, the role of the genetic background is triggered by environmental factors through the modulation of the innate immune system. Monogenic AIDs are characterized by Mendelian inheritance and are caused by highly penetrant genetic variants in single genes. During the last years, remarkable progress has been made in the identification of disease-associated genes by using new technologies, such as next-generation sequencing, which has allowed the genetic characterization in undiagnosed patients and in sporadic cases by means of targeted resequencing of a gene panel and whole exome sequencing. In this review, we delineate the genetics of the monogenic AIDs, report the role of the most common gene mutations, and describe the evidences of the most sound genotype/phenotype correlations in AID.

Periodic Fever with Aphthous Stomatitis, Pharyngitis, and Cervical Adenitis Syndrome Is Associated with a CARD8 Variant Unable To Bind the NLRP3 Inflammasome

Periodic fever with aphthous stomatitis, pharyngitis, and cervical adenitis (PFAPA) is a relatively common autoinflammatory condition that primarily affects children. Although tendencies were reported for this syndrome, genetic variations influencing risk and disease progression are poorly understood. In this study, we performed next-generation sequencing for 82 unrelated PFAPA patients and identified a frameshift variant in the CARD8 gene (CARD8-FS). Subsequently, we compared the frequency of CARD8-FS carriers in our PFAPA cohort (13.9%) with a healthy local population group (3.2%) and found a significant association between the CARD8-FS polymorphism and risk for PFAPA syndrome (p = 0.012; odds ratio: 4.96 [95% confidence interval, 1.33-18.47]). Moreover, CARD8-FS carriers display a distinct PFAPA phenotype that is characterized by a higher prevalence of symptoms out of flares and oral aphthosis (both p = 0.02 compared with PFAPA patients without the frameshift variant). CARD8 encodes a protein component of the NLRP3 inflammasome, which plays an important role in inflammation and contributes to the pathology of various autoinflammatory diseases. We found that the CARD8-FS variant led to a truncated CARD8 protein lacking the FIIND and CARD domains. As a result, the mutant CARD8 protein lost the ability to interact with the NOD domain of NLRP3. In summary, these results identify a new CARD8 variant associated with PFAPA and further suggest that disruption of the interaction between CARD8 and NLRP3 can regulate autoinflammation in patients.

Induction of Myeloid-Derived Suppressor Cells in Cryopyrin-Associated Periodic Syndromes

Cryopyrin-associated periodic syndromes (CAPS) are caused by mutations in the NLRP3 gene leading to overproduction of IL-1β and other NLRP3 inflammasome products. Myeloid-derived suppressor cells (MDSCs) represent a novel innate immune cell subset capable of suppressing T-cell responses. As inflammasome products were previously found to induce MDSCs, we hypothesized that NLRP3 inflammasome-dependent factors induce the generation of MDSCs in CAPS. We studied neutrophilic MDSCs, their clinical relevance, and MDSC-inducing factors in a unique cohort of CAPS patients under anti-IL-1 therapy. Despite anti-IL-1 therapy and low clinical disease activity, CAPS patients showed significantly elevated MDSCs compared to healthy controls. MDSCs were functionally competent, as they suppressed polyclonal T-cell proliferation, as well as Th1 and Th17 responses. In addition, MDSCs decreased monocytic IL-1β secretion. Multiplex assays revealed a distinct pattern of MDSC-inducing cytokines, chemokines, and growth factors. Experimental analyses demonstrated that IL-1 cytokine family members and autoinflammation-associated alarmins differentially induced human MDSCs. Increased MDSCs might represent a novel autologous anti-inflammatory mechanism in autoinflammatory conditions and may serve as a future therapeutic target.

Clinical Characteristics of Patients Carrying the Q703K Variant of the NLRP3 Gene: A 10-year Multicentric National Study

Objective.

The aim of our study was to analyze the clinical and functional effect of the p.Q703K (p. Q705K, c. 2107C>A) variant of the NLRP3 gene in a population of patients screened for suspected cryopyrin-associated periodic syndrome (CAPS).

Methods.

Since 2002, 580 patients underwent molecular analysis for NLRP3. Data on clinical presentation, response to treatment, and longterm followup were collected using a uniform questionnaire. The pattern of cytokine secretion after lipopolysaccharide stimulation from isolated monocytes was analyzed in 3 patients carrying the p.Q703K variant and 1 patient with a chronic infantile neurologic, cutaneous, articular syndrome phenotype carrying both the p.M406I and p.Q703K, and compared with 7 patients with CAPS with sure pathogenic variants and 6 healthy controls.

Results.

The p.Q703K variant was found in 57 screened patients with an overall allelic frequency of 5%. The frequency in normal controls was 5.5%. Clinical data at the moment of molecular analysis and at followup were available in 36 patients. Two patients displayed additional mutations of NLRP3. The mean followup was 2.5 years. Thirteen patients (39%) had a final diagnosis different from the original suspicion of CAPS. The remaining 21 patients displayed a mild phenotype mainly characterized by recurrent episodes of urticarial rash and arthralgia. Only 8 patients were treated with anti-interleukin (IL)-1 treatment, with a complete response in 5 patients. The pattern of secretion of IL-1β and other cytokines (IL-6 and IL-1 receptor antagonist) in patients did not display the aberrancies observed in patients with CAPS and was similar to that observed in healthy controls.

Conclusion.

The present study confirms the weak clinical and functional effect of the p.Q703K variant.

Acquired familial Mediterranean fever associated with a somatic MEFV mutation in a patient with JAK2 associated post-polycythemia myelofibrosis

Background

A study was designed to identify the source of fever in a patient with post-polycythemia myelofibrosis, associated with clonal Janus Kinase 2 (JAK2) mutation involving duplication of exon 12. The patient presented with 1–2 day long self-limited periodic episodes of high fever that became more frequent as the hematologic disease progressed.

Methods

After ruling out other causes for recurrent fever, analysis of the pyrin encoding Mediterranean fever gene (MEFV) was carried out by Sanger sequencing in peripheral blood DNA samples obtained 4 years apart, in buccal cells, laser dissected kidney tubular cells, and FACS-sorted CD3-positive or depleted mononucleated blood cells. Hematopoeitc cells results were validated by targeted deep sequencing. A Sanger sequence based screen for pathogenic variants of the autoinflammatory genes NLRP3, TNFRSF1A and MVK was also performed.

Results

A rare, c.1955G>A, p.Arg652His MEFV gene variant was identified at negligible levels in an early peripheral blood DNA sample, but affected 46 % of the MEFV alleles and was restricted to JAK2-positive, polymorphonuclear and CD3-depleted mononunuclear DNA samples obtained 4 years later, when the patient experienced fever bouts. The patient was also heterozygous for the germ line, non-pathogenic NLRP3 gene variant, p.Q705K. Upon the administration of colchicine, the gold standard treatment for familial Mediterranean fever (FMF), the fever attacks subsided.

Conclusions

This is the first report of non-transmitted, acquired FMF, associated with a JAK2 driven clonal expansion of a somatic MEFV exon 10 mutation. The non-pathogenic germ line NLRP3 p.Q705K mutation possibly played a modifier role on the disease phenotype.

From bench to bedside and back again: translational research in autoinflammation

Translational research approaches brought major changes to the understanding and treatment options of autoinflammatory diseases. Patients with common complex multifactorial diseases such as systemic-onset juvenile idiopathic arthritis (sJIA), and particularly those with rare monogenic autoinflammatory diseases such as cryopyrin-associated periodic syndromes (CAPS) or TNF receptor-associated periodic syndrome (TRAPS), benefited from a deeper understanding of the pathophysiological mechanisms and new treatment options emerging from preclinical studies. The study of IL-1 and IL-6 in this context led to novel therapies by forward translation. Conversely, effective treatment of sJIA and TRAPS with IL-1 blockade stimulated reverse translational efforts to study the pathophysiology of these cytokines in autoinflammatory diseases. These translational efforts led to the discovery of biomarkers such as S100 proteins, IL-18 or serum amyloid A, which are components of the inflammatory process, support diagnosis and allow for monitoring of disease activity, helping to predict patient outcomes. The ongoing characterization of autoinflammatory diseases in individual patients has led to classification into heterogeneous subgroups. Further characterization of relevant subgroups and the design of tailored treatment regimens, as well as the identification of new therapeutic targets and treatment options, are the major future challenges in the field of autoinflammatory diseases, particularly for paediatric rheumatologists.

CAPS--pathogenesis, presentation and treatment of an autoinflammatory disease

The cryopyrin-associated periodic syndrome (CAPS) is a severity spectrum of rare diseases. CAPS comprises the three conditions previously described as familial cold autoinflammatory syndrome (FCAS), Muckle-Wells syndrome (MWS), and neonatal-onset multisystem inflammatory disorder (NOMID), also known as chronic infantile neurologic, cutaneous, and articular (CINCA) syndrome. The clinical phenotype of CAPS is characterized by systemic inflammation. General symptoms are fatigue and fever. Local manifestations affect multiple tissues such as skin, joints, muscles, eyes, and the central nervous system. Distinct clinical features are characteristic for each subphenotype. In FCAS, these are cold-induced urticaria and fever, in MWS systemic amyloidosis and hearing loss and in NOMID/CINCA central nervous system inflammation and bone deformities. CAPS is caused by single heterozygous germline or somatic gain of function mutations in the NLRP3 gene encoding the protein cryopyrin. Cryopyrin nucleates an NLRP3 inflammasome, which regulates the activation and cleavage of caspase-1 that cleaves the pro-inflammatory cytokines, IL-1β and IL-18. IL-1β plays the key role in the induction of inflammation in CAPS. This has been confirmed by the application of IL-1 blocking agents, which lead not only to a rapid and sustained reversal of daily symptoms but also to some extent of long-term disease sequelae. To prevent CAPS-induced organ damage, early diagnosis and swift initiation of effective treatment are mandatory.