The clinical continuum of cryopyrinopathies: novel CIAS1 mutations in North American patients and a new cryopyrin model

Neurological phenotypes in patients with NLRP3-, MEFV-, and TNFRSF1A low-penetrance variants

Background

Neurological manifestations and the co-occurrence of multiple sclerosis (MS) have been reported in patients with autoinflammatory diseases (AID) and variants of the NLRP3-, MEFV-, or TNFRSF1A gene. However, type and frequency of neurological involvement are widely undetermined.

Methods

We assessed clinical characteristics of 151 (108 with MS) patients carrying NLRP3-, MEFV- and TNFRSF1A low-penetrance variants  from the Institute of Clinical Neuroimmunology. We evaluated demographic, genetic, and clinical features with a focus on central nervous system (CNS) involvement including magnetic resonance imaging (MRI) results and cerebrospinal fluid (CSF) data. The disease course of AID patients with MS was compared to a matched MS control group without mutations.

Results

The genetic distribution comprised 36 patients (23%) with NLRP3- and 66 patients (43%) with TNFRSF1A low-penetrance variants as well as 53 (34%) patients carrying pathogenic mutations or low-penetrance variants in the MEFV gene. MS patients displayed most frequently the R92Q TNFRSF1A variant (n = 51; 46%) followed by the Q703K NLRP3 variant (n = 15; 14%) and the E148Q substitution (n = 9; 8%) in the MEFV gene. The disease course of MS was not influenced by the genetic variants and did not differ from MS patients (n = 51) without mutations. AID patients without MS most frequently harbored MEFV mutations (n = 19, 43%) followed by NLRP3- (n = 17, 39%) and TNFRSF1A (n = 8, 18%) low-penetrance variants. Sixteen (36%) of them suffered from severe CNS involvement predominantly recurrent aseptic meningoencephalitis and optic neuritis accompanied by abnormal MRI and CSF results. Severe CNS inflammation was associated with the Q703K allele. Headache was a highly prevalent neurological symptom (up to 74%), irrespective of the underlying genetic variation. The NLRP3 cohort without MS more frequently exhibited affections of the cranial nerves (CN) (p = 0.0228) and motor symptoms (p = 0.0455). Elevated acute-phase reactants were detected in all patients, and fever episodes were present in up to 50%. Arthralgias were the most frequently identified constitutional symptom among all subgroups.

Conclusions

Our data highlight the high prevalence of neurological manifestations, including concomitant MS, among NLRP3-, MEFV-, and TNFRSF1A low-penetrance variants. In particular, patients carrying the Q703K NLRP3 variant are at risk for severe CNS inflammation and CN affection.

Primary Atopic Disorders

Primary atopic disorders describes a series of monogenic diseases that have allergy- or atopic effector–related symptoms as a substantial feature. The underlying pathogenic genetic lesions help illustrate fundamental pathways in atopy, opening up diagnostic and therapeutic options for further study in those patients, but ultimately for common allergic diseases as well. Key pathways affected in these disorders include T cell receptor and B cell receptor signaling, cytokine signaling, skin barrier function, and mast cell function, as well as pathways that have not yet been elucidated. While comorbidities such as classically syndromic presentation or immune deficiency are often present, in some cases allergy alone is the presenting symptom, suggesting that commonly encountered allergic diseases exist on a spectrum of monogenic and complex genetic etiologies that are impacted by environmental risk factors.

Autoinflammatory Disorders with Perinatal Onset

Autoinflammatory disorders are rare genetic defects that result in inflammation in the absence of an infectious or autoimmune disease. Although very rare, these disorders can occur in the perinatal period, and recognizing their presentation is important because there are often long-term complications and effective targeted therapies for these disorders. Most of these disorders present with rash, fevers, and laboratory evidence of inflammation. Importantly, these disorders can now be separated into their pathophysiologic mechanisms of action, which can also guide therapies. The article reviews the different mechanisms of autoinflammatory disorders and highlights those disorders that can present in the newborn period.

Differential expression of the inflammasome complex genes in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a complex autoimmune disorder involving heterogeneous clinical manifestations and numerous susceptibility genes. Several findings evidence the critical role of inflammasomes in the predisposition to autoimmune diseases and in SLE. We investigated whether inflammasome polymorphins could affect susceptibility to develop and/or severity SLE. Moreover, differences in inflammasome activation in peripheral blood were also evaluated in SLE patients and controls. The distribution of 13 SNPs in eight inflammasome genes was evaluated. To assess inflammasome priming in peripheral blood monocytes of SLE and controls, differential expression of selected inflammasome genes and IL-1ß production was analyzed in resting condition as well as after LPS and ATP stimulation. Results showed that the gain-of-function variant rs10754558 (NLRP3) was significantly more frequent in SLE patients with nephritis, reinforcing the concept of a key role of NLRP3 inflammasome not only in SLE but also especially in kidney disease. SLE monocytes in resting condition showed a higher level of IL-1ß expression and produced higher levels of IL-1ß when stimulated with LPS+ATP comparing to controls. The stimulation induced a significant expression of NLRP1, AIM2, CASP1, and IL1B genes, suggesting that the NLRP1 inflammasome is responsible for the IL-1ß production observed in monocytes. These data emphasized once more the important contribution of inflammasome in SLE-associated inflammation.

Understanding the Relevance of DNA Methylation Changes in Immune Differentiation and Disease

Immune cells are one of the most complex and diverse systems in the human organism. Such diversity implies an intricate network of different cell types and interactions that are dependently interconnected. The processes by which different cell types differentiate from progenitors, mature, and finally exert their function requires an orchestrated succession of molecular processes that determine cell phenotype and function. The acquisition of these phenotypes is highly dependent on the establishment of unique epigenetic profiles that confer identity and function on the various types of effector cells. These epigenetic mechanisms integrate microenvironmental cues into the genome to establish specific transcriptional programs. Epigenetic modifications bridge environment and genome regulation and play a role in human diseases by their ability to modulate physiological programs through external stimuli. DNA methylation is one of the most ubiquitous, stable, and widely studied epigenetic modifications. Recent technological advances have facilitated the generation of a vast amount of genome-wide DNA methylation data, providing profound insights into the roles of DNA methylation in health and disease. This review considers the relevance of DNA methylation to immune system cellular development and function, as well as the participation of DNA methylation defects in immune-mediated pathologies, illustrated by selected paradigmatic diseases.

Hints for Genetic and Clinical Differentiation of Adult-Onset Monogenic Autoinflammatory Diseases

Monogenic autoinflammatory diseases (mAIDs) are inherited errors of innate immunity characterized by systemic inflammation recurring with variable frequency and involving the skin, serosal membranes, synovial membranes, joints, the gastrointestinal tube, and/or the central nervous system, with reactive amyloidosis as a potential severe long-term consequence. Although individually uncommon, all mAIDs set up an emerging chapter of internal medicine: recent findings have modified our knowledge regarding mAID pathophysiology and clarified that protean inflammatory symptoms can be variably associated with periodic fevers, depicting multiple specific conditions which usually start in childhood, such as familial Mediterranean fever, tumor necrosis factor receptor-associated periodic syndrome, cryopyrin-associated periodic syndrome, and mevalonate kinase deficiency. There are no evidence-based studies to establish which potential genotype analysis is the most appropriate in adult patients with clinical phenotypes suggestive of mAIDs. This review discusses genetic and clinical hints for an ideal diagnostic approach to mAIDs in adult patients, as their early identification is essential to prompt effective treatment and improve quality of life, and also highlights the most recent developments in the diagnostic work-up for the most frequent hereditary periodic febrile syndromes worldwide.

NLRP3-associated autoinflammatory diseases: Phenotypic and molecular characteristics of germline versus somatic mutations

BACKGROUND

NLRP3-associated autoinflammatory diseases (NLRP3-AIDs) include conditions of various severities, due to germline or somatic mosaic NLRP3 mutations.

OBJECTIVE

To identify mosaic- versus germline-specific NLRP3 mutations' characteristics, we reinterpreted all the mutations reported in NLRP3-AIDs and performed an in-depth study of 3 novel patients.

METHODS

The pathogenicity of all reported mosaic/germline mutations was reassessed according to international recommendations and their location on the NLRP3 3-dimensional structure. Deep-targeted sequencing and NLRP3-inflammasome-activation assays were used to identify the disease-causing mutation in 3 patients.

RESULTS

We identified, in 3 patients, mosaic mutations affecting the same NLRP3 amino acid (Glu569). This residue belongs to 1 of the 2 mosaic mutational hot spots that face each other in the core of the NLRP3 ATPase domain. The review of the 90 NLRP3 mutations identified in 277 patients revealed that those hot spots account for 68.5% of patients (37 of 54) with mosaic mutations. Glu569 is affected in 22% of the patients (12 of 54) with mosaic mutations and in 0.4% of patients (1 of 223) with germline mutations. Only 8 of 90 mutations were found in mosaic and germinal states. All of the germline mutations were associated with a severe phenotype. These data suggest that mutations found only in mosaic state could be incompatible with life if present in germinal state. None of the 5 most frequent germline mutations was identified in mosaic state. Mutations found only in germinal state could, therefore, be asymptomatic in mosaic state.

CONCLUSIONS

The phenotypic spectrum of NLRP3-AIDs appears to be related to the germinal/mosaic status and localization of the underlying mutations.

Mesenchymal stem cell-derived exosomes ameliorate intervertebral disc degeneration via anti-oxidant and anti-inflammatory effects

Excessive oxidative stress and inflammation are the key early events in the development of intervertebral disc degeneration (IVDD). The NACHT, LRR, and PYD domain-containing protein 3 (NLRP3) inflammasome has been identified as the major source of oxidative stress and the inflammatory responses and thus is an attractive therapeutic target for IVDD. However, currently, there are no reports on the use of mesenchymal stem cell (MSC)-derived exosomes to reduce NLRP3 inflammasome expression for IVDD treatment. The present study aimed to investigate the therapeutic effect of exosomes for use as IVDD therapeutics. We first manufactured and evaluated the characteristics of exosomes. Then, we investigated the effects of exosomes on H₂O₂-induced nucleus pulposus (NP) cell inflammation. Third, we tested the function of exosomes with respect to H₂O₂-induced ROS production and mitochondrial dysfunction. Finally, the therapeutic effect of exosomes on IVDD was investigated using a rabbit IVDD model. Results showed that exosomes play an anti-inflammatory role in pathological NP cells by suppressing inflammatory mediators and NLRP3 inflammasome activation. Moreover, it was suggested that exosomes might supply mitochondrial proteins to NP cells, and that the damaged mitochondria could be restored with this supplement. Further, in the rabbit IVDD model, exosomes significantly prevented the progression of degenerative changes. Our results confirmed that the NLRP3 inflammasome is an effective target for IVDD treatment and that the injection of exosomes could be a promising therapeutic strategy.

Inflammasomes in the pathophysiology of autoinflammatory syndromes

Inflammasomes are a specialized group of intracellular sensors that are key components of the host innate immune system. Autoinflammatory diseases are disorders of the innate immune system that are characterized by recurrent inflammation and serious complications. Dysregulation of the inflammasome is associated with the onset and progression of several autoinflammatory and autoimmune diseases, including cryopyrin-associated periodic fever syndrome, familial Mediterranean fever, rheumatoid arthritis, and systemic lupus erythematosus. In this review, we discuss the involvement of various inflammasome components in the regulation of autoinflammatory disorders and describe the manifestations of these autoinflammatory diseases caused by inflammasome activation.

Decoding inflammation, its causes, genomic responses, and emerging countermeasures

Inflammation is the mechanism of diseases caused by microbial, autoimmune, allergic, metabolic and physical insults that produce distinct types of inflammatory responses. This aetiologic view of inflammation informs its classification based on a cause‐dependent mechanism as well as a cause‐directed therapy and prevention. The genomic era ushered in a new understanding of inflammation by highlighting the cell's nucleus as the centre of the inflammatory response. Exogenous or endogenous inflammatory insults evoke genomic responses in immune and non‐immune cells. These genomic responses depend on transcription factors, which switch on and off a myriad of inflammatory genes through their regulatory networks. We discuss the transcriptional paradigm of inflammation based on denying transcription factors’ access to the nucleus. We present two approaches that control proinflammatory signalling to the nucleus. The first approach constitutes a novel intracellular protein therapy with bioengineered physiologic suppressors of cytokine signalling. The second approach entails control of proinflammatory transcriptional cascades by targeting nuclear transport with a cell‐penetrating peptide that inhibits the expression of 23 out of the 26 mediators of inflammation along with the nine genes required for metabolic responses. We compare these emerging anti‐inflammatory countermeasures to current therapies. The transcriptional paradigm of inflammation offers nucleocentric strategies for microbial, autoimmune, metabolic, physical and other types of inflammation afflicting millions of people worldwide.

Familial Mediterranean fever is associated with a wide spectrum of inflammatory disorders: results from a large cohort study

Familial Mediterranean fever (FMF) is characterized by recurrent short-lived/self-limiting inflammatory attacks. Besides these, a substantial number of patients with FMF present with a variety of other inflammatory diseases; however, this issue has not been systematically studied previously. Hence, we aimed to investigate the frequency of inflammatory comorbid diseases in a large FMF cohort. All patients were recruited from "FMF in Central Anatolia (FiCA) Cohort", comprising 971 (mean age 35.3 ± 12 years, 61.5% female) adult subjects. All patients fulfilled Tel Hashomer criteria. Demographic data, FMF disease characteristics, MEFV gene mutations, and comorbid inflammatory diseases were meticulously questioned, and laboratory features and genotype data were retrieved from hospital records. There were comorbid inflammatory diseases in 205 (21.1%) patients. The most common inflammatory disease was spondyloarthritis (12.9%). Other remarkable inflammatory disorders were psoriasis, immunoglobulin A vasculitis/Henoch-Schönlein purpura, Behçet's disease and inflammatory bowel diseases. Cryptogenic organizing pneumonia is a newly defined entity in our cohort which is seemed to be associated with FMF (0.3%). Number of patients with persistent inflammation was higher in those with comorbid diseases (p < 0.001). Our results suggest that FMF is commonly associated with other inflammatory diseases. Therefore, clinicians should be cautious about comorbid inflammatory diseases in FMF patients, particularly in those with persistent inflammation. Identification of pathogenic pathways linking FMF to these diseases warrants further investigations.

Magnetic resonance imaging findings in a patient with cryopyrin-associated periodic syndrome: A rare hereditary multi-system inflammatory disorder

Cryopyrin-associated periodic syndrome is a hereditary inflammatory disorder encompassing a wide spectrum of clinical phenotypes. This disorder has been associated with mutation of the NLRP3 gene coding for cryopyrin, which leads to overproduction of interleukin-1. The condition causes relapsing bouts of inflammation involving multiple organ systems, including the central nervous system, and, if untreated, can lead to long-term debilitating effects. A literature review revealed only a few brief descriptions of magnetic resonance imaging findings in cryopyrin-associated periodic syndrome patients. We describe serial magnetic resonance imaging findings in an 11-year-old female with clinically diagnosed cryopyrin-associated periodic syndrome who presented with intermittent headaches, progressive sensorineural hearing loss, fevers, and abdominal pain. The magnetic resonance imaging showed progressively worsening low T2 signal in the cochlea, cochlear enhancement, and leptomeningeal enhancement. We also describe some previously unreported findings in this syndrome, including cranial nerve and cauda equina enhancement.

Retrospective case series describing the efficacy, safety and cost-effectiveness of a vial-sharing programme for canakinumab treatment for paediatric patients with cryopyrin-associated periodic syndrome

BACKGROUND

Cryopyrin-associated periodic syndrome (CAPS) is a rare autoinflammatory disease, caused by gain of function mutation in NLRP3 resulting in excess production of interleukin-1 (IL-1). Canakinumab is a human monoclonal antibody against Interleukin-1 beta (IL-1β), licensed for the treatment of CAPS. The objective of the study was to describe the feasibility and cost-effectiveness of a canakinumab vial-sharing programme for paediatric patients with CAPS.

METHOD

Retrospective case series and clinical service description of a national specially commissioned CAPS clinic at Great Ormond Street Hospital (GOSH). Effectiveness was assessed using a CAPS disease activity score (DAS) and serum amyloid A protein (SAA). Adverse events were collected to determine safety. The number of canakinumab vials saved was considered when investigating the cost-effectiveness of vial-sharing.

RESULTS

Nineteen/20 (95%) of our paediatric patients achieved minimally active clinical disease activity with canakinumab monotherapy; and 75% achieved both minimally active clinical disease and serological remission using a pre-specified definition based on the CAPS DAS and SAA level. Canakinumab was well tolerated, with only one child developing an infection requiring hospitalisation during the study. Canakinumab vial sharing resulted in 117 vials of canakinumab saved over a 24-month period, equating to a direct drug-related cost saving of £1,385,821, and a conservative estimated 5-year cost-saving of £3,464,552.50.

CONCLUSION

We provide further evidence for the effectiveness and safety of canakinumab in children with CAPS, and highlight the cost-effectiveness of a vial-sharing programme for this high cost medicine. We suggest that this could have important implications for the delivery of other high cost medicines used in paediatric practice.

Autoinflammatory disease with focus on NOD2-associated disease in the era of genomic medicine

Systemic autoinflammatory diseases (SAIDs) represent a spectrum of genetically heterogeneous inflammatory disorders. Some SAID-associated genes are located in chromosome 16, including familial Mediterranean fever gene (MEFV) and nucleotide-binding oligomerization domain 2 [NOD2] gene that are linked to Crohn's disease, Blau syndrome, and Yao syndrome. These disorders share overlapping clinical phenotypes, and genotyping is diagnostically helpful and distinctive. Using next generation sequencing in SAIDs, digenic variants or combinations of more genetic variants in different genes can be detected, and they may be related to the MEFV and NOD2 genes. These variants may contribute to heterogeneous phenotypes in an individual, complicating the diagnosis and therapy. An awareness of the clinical significance of the digenic or combined gene variants is important in the era of genomic medicine.

Severe cryopyrin-associated periodic syndrome first characterized by early childhood-onset sensorineural hearing loss - Case report and literature review

Infant-onset bilateral sensorineural hearing loss is a key presenting symptom of the autoinflammatory cryopyrin-associated periodic syndrome. Other symptoms include periodic fever, cold-induced urticaria-like rash, chronic aseptic meningitis, polyarticular arthralgias, and renal AA amyloidosis. Early recognition and treatment with interleukin-1 blockade are critical for preventing disabling or fatal complications. We describe a patient with severe cryopyrin-associated periodic syndrome who presented at age 18 months with macrocephaly and moderate sensorineural hearing loss, later developing systemic sequelae. The pathogenic nature of the de novo NLRP3 gene variant identified was supported by a markedly elevated serum amyloid A level and sustained clinical response to anti-IL-1 therapy.

Metabolic regulation of inflammasomes in inflammation

Inflammasome activation and subsequent inflammatory cytokine secretion are essential for innate immune defence against multiple stimuli and are regarded as a link to adaptive immune responses. Dysfunction of inflammasome activation has been discovered at the onset or progression of infectious diseases, autoimmune diseases and cancer, all of which are also associated with metabolic factors. Furthermore, many studies concerning the metabolic regulation of inflammasome activation have emerged in recent years, especially regarding the activity of the NLRP3 inflammasome under metabolic reprogramming. In this review, we discuss the molecular mechanisms of the interactions between metabolic pathways and inflammasome activation, which exerts further important effects on various diseases.

CAPS and NLRP3

Cryopyrin-associated periodic syndrome (CAPS) is a rare inherited autoinflammatory disorder characterized by systemic, cutaneous, musculoskeletal, and central nervous system inflammation. Gain-of-function mutations in NLRP3 in CAPS patients lead to activation of the cryopyrin inflammasome, resulting in the inappropriate release of inflammatory cytokines including IL-1β and CAPS-related inflammatory symptoms. Several mechanisms have been identified that are important for the normal regulation of the cryopyrin inflammasome in order to prevent uncontrolled inflammation. Investigators have taken advantage of some of these pathways to develop and apply novel targeted therapies, which have resulted in improved quality of life for patients with this orphan disease.

NOD-like receptors and inflammasomes: A review of their canonical and non-canonical signaling pathways

The NOD-like receptor (NLR) family of proteins is a group of pattern recognition receptors (PRRs) known to mediate the initial innate immune response to cellular injury and stress. The NLRP proteins represent a fourteen-member subset of the NLR family that contains an N-terminal pyrin domain. Some NLRs are known to form multi-protein complexes known as inflammasomes. Inflammasomes consist of an NLR, the adaptor protein ASC, and the effector molecule pro-caspase-1. Once activated, these inflammasomes facilitate the cleavage and activation of caspase-1, which in turn mediates the cleavage of the pro-inflammatory cytokines IL-1β and IL-18 into their active and secreted forms. Activated caspase-1 also drives the cleavage of gasdermin D, which triggers an inflammatory form of cell death known as pyroptosis. Several NLRs are also known to possess non-canonical, inflammasome-independent functions, regulating a variety of signaling pathways. In this review, a thorough overview of both inflammasome-dependent and -independent NLR signaling will be presented, with highlights from the field as well as promising future directions and postulates based on the known science.

Challenges to Practicing Pediatric Rheumatology

Pediatric rheumatology is an exciting and rewarding career area. However, challenges when attracting trainees to this field include practice often occurring in smaller groups compared with general pediatrics, available positions requiring relocation, and fluctuation in funding resulting in uncertainty regarding training positions. Having critical mass in pediatric divisions is important to ensure adequate mentoring and people power to produce scholarly work, reduce on-call frequency and mitigate faculty absences that result in unplanned addition of clinical work. Compensation has historically lagged behind that of general pediatrics. Increased research opportunities through organized networks, patient and parent engagement, and the increasing recognition of pediatric rheumatologists as contributing to scholarship has heightened the profile of pediatric rheumatology nationally and internationally.

Hereditary Autoinflammatory Disorders: Recognition and Treatment

The autoinflammatory diseases encompass approximately 30 monogenic disorders in which inborn errors in the innate immune system lead to episodic systemic inflammation. Largely mediated by dysregulation of myeloid cells, interleukin (IL)-1β, type I interferon, and NF-κB, these disorders have rapidly expanded over the past several years, and increasing numbers of patients identified. Crossover disorders, bridging autoinflammation and immunodeficiency, have recently been described. This article focuses on the clinical presentation of IL-1 and interferon-driven autoinflammatory disorders, and discusses novel diseases with features of immunodeficiency. Approaches to the clinical diagnosis, genetic testing, and treatment of these disorders are addressed.

Chronic urticaria in infants as the first manifestation of autoinflammatory disease

We report two unrelated infants in whom chronic urticaria was the first clinical manifestation of cryopyrin-associated periodic syndrome, which should be suspected in infants with early-onset chronic urticaria, especially if there is a neutrophil-rich infiltrate in the skin biopsy. Early diagnosis of cryopyrin-associated periodic syndrome may lead to early and successful treatment with anti-interleukin-1 medications.

Disease modeling of immunological disorders using induced pluripotent stem cells

Disease-associated induced pluripotent stem cells (iPSCs) established from patients are now widely used for disease modeling. They can provide an unlimited source of hematopoietic cells that carry the patients' genetic background, making them advantageous for modeling immunological disorders. To obtain functional immune cells from human iPSCs, we have developed a differentiation system that generates immortalized myeloid cells including neutrophils and monocytic cells. By using this strategy, we have established in vitro models of many immunological disorders. In this review, we focus on autoinflammatory disorders. These models have proven useful for genetic diagnosis and elucidation of the disease mechanism.

De novo ATP1A3 and compound heterozygous NLRP3 mutations in a child with autism spectrum disorder, episodic fatigue and somnolence, and muckle-wells syndrome

Complex phenotypes may represent novel syndromes that are the composite interaction of several genetic and environmental factors. We describe an 9-year old male with high functioning autism spectrum disorder and Muckle-Wells syndrome who at age 5  years of age manifested perseverations that interfered with his functioning at home and at school. After age 6, he developed intermittent episodes of fatigue and somnolence lasting from hours to weeks that evolved over the course of months to more chronic hypersomnia. Whole exome sequencing showed three mutations in genes potentially involved in his clinical phenotype. The patient has a predicted pathogenic de novo heterozygous p.Ala681Thr mutation in the ATP1A3 gene (chr19:42480621C>T, GRCh37/hg19). Mutations in this gene are known to cause Alternating Hemiplegia of Childhood, Rapid Onset Dystonia Parkinsonism, and CAPOS syndrome, sometimes accompanied by autistic features. The patient also has compound heterozygosity for p.Arg490Lys/p.Val200Met mutations in the NLRP3 gene (chr1:247588214G>A and chr1:247587343G>A, respectively). NLRP3 mutations are associated in an autosomal dominant manner with clinically overlapping auto-inflammatory conditions including Muckle-Wells syndrome. The p.Arg490Lys is a known pathogenic mutation inherited from the patient's father. The p.Val200Met mutation, inherited from his mother, is a variant of unknown significance (VUS). Whether the de novoATP1A3mutation is responsible for or plays a role in the patient's episodes of fatigue and somnolence remains to be determined. The unprecedented combination of two NLRP3 mutations may be responsible for other aspects of his complex phenotype.

MPTP-driven NLRP3 inflammasome activation in microglia plays a central role in dopaminergic neurodegeneration

Parkinson's disease (PD) is a progressive neurodegenerative disease characterized by the loss of dopaminergic neurons in the substantia nigra (SN) and the reduction of dopamine levels in the striatum. Although details of the molecular mechanisms underlying dopaminergic neuronal death in PD remain unclear, neuroinflammation is also considered a potent mediator in the pathogenesis and progression of PD. In the present study, we present evidences that microglial NLRP3 inflammasome activation is critical for dopaminergic neuronal loss and the subsequent motor deficits in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD. Specifically, NLRP3 deficiency significantly reduces motor dysfunctions and dopaminergic neurodegeneration of MPTP-treated mice. Furthermore, NLRP3 deficiency abolishes MPTP-induced microglial recruitment, interleukin-1β production and caspase-1 activation in the SN of mouse brain. In primary microglia and mixed glial cell cultures, MPTP/ATP treatment promotes the robust assembly and activation of the NLRP3 inflammasome via producing mitochondrial reactive oxygen species. Consistently, 1-methyl-4-phenyl-pyridinium (MPP⁺) induces NLRP3 inflammasome activation in the presence of ATP or nigericin treatment in mouse bone-marrow-derived macrophages. These findings reveal a novel priming role of neurotoxin MPTP or MPP⁺ for NLRP3 activation. Subsequently, NLRP3 inflammasome-active microglia induces profound neuronal death in a microglia-neuron co-culture model. Furthermore, Cx3Cr1^CreER-based microglia-specific expression of an active NLRP3 mutant greatly exacerbates motor deficits and dopaminergic neuronal loss of MPTP-treated mice. Taken together, our results indicate that microglial NLRP3 inflammasome activation plays a pivotal role in the MPTP-induced neurodegeneration in PD.

Resolution of femoral metaphyseal dysplasia in CINCA syndrome after long-term treatment with interleukin-1 blockade

Chronic infantile neurological cutaneous articular (CINCA) syndrome is a rare autoinflammatory disorder driven by uncontrolled hypersecretion of interleukin (IL)-1, which can be clinically depicted by striking cutaneous, neurologic, and skeletal features. Little is known about the exact pathogenesis of CINCA bone disease, which mainly involves the knees. We report a 20-year-old CINCA patient, who was consecutively treated firstly with anakinra, started at 7 years, then with full dose canakinumab, started at 17 years, focusing on the typical bone abnormalities of the syndrome: the comparison of radiographs of knees performed at 7 and 20 years has shown the disappearance of a typical metaphyseal dysplasia occurring in the femurs of this CINCA patient, regularly treated with IL-1 blockade for a period of 13 years. A review of the medical literature reveals poor information on the skeletal response of CINCA syndrome to IL-1-inhibiting therapies. This contribution confirms the protean striking effects of IL-1 blockade in this peculiar autoinflammatory disorder, showing for the first time the reversal of the characteristic CINCA metaphyseal dysplasia over long-term treatment.

Primary atopic disorders

Important insights from monogenic disorders into the immunopathogenesis of allergic diseases and reactions are discussed.

Monogenic disorders have provided fundamental insights into human immunity and the pathogenesis of allergic diseases. The pathways identified as critical in the development of atopy range from focal defects in immune cells and epithelial barrier function to global changes in metabolism. A major goal of studying heritable single-gene disorders that lead to severe clinical allergic diseases is to identify fundamental pathways leading to hypersensitivity that can be targeted to provide novel therapeutic strategies for patients with allergic diseases, syndromic and nonsyndromic alike. Here, we review known single-gene disorders leading to severe allergic phenotypes in humans, discuss how the revealed pathways fit within our current understanding of the atopic diathesis, and propose how some pathways might be targeted for therapeutic benefit.

Genetics of Inflammasomes

Mutations in inflammasome genes are responsible for rare monogenic and polygenic autoinflammatory diseases. On the other side, genetic polymorphisms in the same molecules contribute to the development of common multifactorial diseases (i.e., autoimmune diseases, cardiovascular pathologies, cancer). In this chapter we depicted the current knowledge about inflammasome genetics.

Gene mutations and clinical phenotypes in 15 Chinese children with cryopyrin-associated periodic syndrome (CAPS)

The aim of our study is to explore the features of clinical manifestations and genetic mutations in Chinese CAPS patients. Fifteen confirmed patients with CAPS were enrolled. The onset time ranges from 2 days after birth to 6 years and 1 month. Recurrent urticaria rash (93.3%) with fever (100%) were two dominant characteristics of these patients that were presented as either acute or chronic process. Systemic involvements were found in all patients except for one with only rash and fever. The top three symptoms were fever (100%), rash (93.3%) and myalgia (76%). Other clinical manifestations include arthritis (11 cases), lung involvement (seven cases), optical dysfunction (seven cases), nerve deafness (six cases), nervous system involvement (five cases), hepatomegaly, splenomegaly and lymphadenectasis (five cases). Also, four patients had heart involvement and one patient suffered kidney involvement. The laboratory inflammation index such as leukocyte counts, platelet counts, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), serum amyloid A (SAA) and fibrinogen (FIB) increased significantly at initial stage, but decreased after therapy. As for gene mutation detection, Twelve out of 15 patients were confirmed with mutation in NLRP3, including 11 mutant site: c1789A<G, c.1703T<A, c.913G<A, c.1710G<C, c.1057G<T, c.2335C<T, c.932TvC, c.296G<C, c.663C<T, t.1702T<A, 299G<A. Mutation sites c.1703T<A, c.2335C<T, c.296G<C, c.663C<T, and 299G<A were newly identified. The association between gene mutation and clinical manifestation shows that D305N was highly associated with severe organs involvements, and therefore, the time of therapy and regimen were critical for the prognosis of disease. As the largest cohort study of Chinese CAPS patients, we confirmed that all patients presented typical clinical manifestations, identified five new mutation sites on NLRP3 and analyzed the correlation between the genotypes and phenotypes. We also raise concerns for one case with serious conditions that only had two nonsense mutations (c.663C<T and t.1702T<A) detected.

New mosaic tiles in childhood hereditary autoinflammatory disorders

The protean clinical phenotypes of hereditary autoinflammatory disorders (HAID) are caused by abnormal activation of innate immunity and consist of seemingly unprovoked inflammatory flares localized to multiple organs, such as the skin, joints, serosal membranes, gut, and central nervous system. Different mutations in genes implied in activation of the interleukin-1 (IL-1)-structured inflammasome, cytoskeletal signaling and apoptosis contribute to the pathogenesis of different HAID, which mostly start in childhood with self-limited flares unrelated to infectious agents, autoantibody production or autoreactive cells. Though IL-1 remains pivotal in many inflammasome-mediated diseases, other cytokinopathies involving IL-18, nuclear factorκ-B, interferons, and tumor necrosis factor have provided new horizons in the definition of HAID of children: the list of HAID has expanded as a consequence of a better understanding of their pathogenetic molecular mechanisms and also application of new genetic technologies. However, diagnosis of most HAID is clinical and focused on several evidence-based criteria sets: their discrimination remains challenging for unexperienced pediatricians as there are no universally accepted algorithms, and a still relevant number of patients may linger without any clarifying genetic analysis, whose interpretation combined with processing of treatment options should be discussed on a multidisciplinary basis.

An NLRP3 Mutation Causes Arthropathy and Osteoporosis in Humanized Mice

The NLRP3 inflammasome plays a critical role in host defense by facilitating caspase I activation and maturation of IL-1β and IL-18, whereas dysregulation of inflammasome activity results in autoinflammatory disease. Factors regulating human NLRP3 activity that contribute to the phenotypic heterogeneity of NLRP3-related diseases have largely been inferred from the study of Nlrp3 mutant mice. By generating a mouse line in which the NLRP3 locus is humanized by syntenic replacement, we show the functioning of the human NLRP3 proteins in vivo, demonstrating the ability of the human inflammasome to orchestrate immune reactions in response to innate stimuli. Humanized mice expressing disease-associated mutations develop normally but display acute sensitivity to endotoxin and develop progressive and debilitating arthritis characterized by granulocytic infiltrates, elevated cytokines, erosion of bones, and osteoporosis. This NLRP3-dependent arthritis model provides a platform for testing therapeutic reagents targeting the human inflammasome.

TNF regulates transcription of NLRP3 inflammasome components and inflammatory molecules in cryopyrinopathies

The NLRP3 inflammasome is a protein complex responsible for caspase-1-dependent maturation of the proinflammatory cytokines IL-1β and IL-18. Gain-of-function missense mutations in NLRP3 cause the disease spectrum known as the cryopyrin-associated periodic syndromes (CAPS). In this study, we generated Nlrp3-knockin mice on various KO backgrounds including Il1b/Il18-, caspase-1-, caspase-11- (Casp1/11-), and Tnf-deficient strains. The Nlrp3L351P Il1b-/- Il18-/- mutant mice survived and grew normally until adulthood and, at 6 months of age, exhibited marked splenomegaly and leukophilia. Injection of these mice with low-dose LPS resulted in elevated serum TNF levels compared with Nlrp3L351P Casp1/11-/- mice and Il1b-/- Il18-/- littermates. Treatment of Nlrp3A350V mice with the TNF inhibitor etanercept resulted in all pups surviving to adulthood, with normal body and spleen/body weight ratios. Nlrp3A350V Tnf-/- mice showed a similar phenotypic rescue, with marked reductions in serum IL-1β and IL-18, reduced myeloid inflammatory infiltrate in the skin and spleen, and substantial decreases in splenic mRNA expression of both inflammasome components (Nlrp3, Pycard, pro-Casp1) and pro-cytokines (Il1b, Il18). Likewise, we observed a reduction in the expression of both pro-Casp1 and pro-Il1b in cultured Nlrp3A350V Tnf-/- BM-derived DCs. Our data show that TNF is an important transcriptional regulator of NLRP3 inflammasome components in murine inflammasomopathies. Moreover, these results may have therapeutic implications for CAPS patients with partial responses to IL-1-targeted therapies.

Late-Onset Cryopyrin-Associated Periodic Syndromes Caused by Somatic NLRP3 Mosaicism-UK Single Center Experience

Cryopyrin-associated periodic syndrome (CAPS) is caused by gain-of-function NLRP3 mutations. Recently, somatic NLRP3 mosaicism has been reported in some CAPS patients who were previously classified as “mutation-negative.” We describe here the clinical and laboratory findings in eight British adult patients who presented with symptoms typical of CAPS other than an onset in mid-late adulthood. All patients underwent comprehensive clinical and laboratory investigations, including analysis of the NLRP3 gene using Sanger and amplicon-based deep sequencing (ADS) along with measurements of extracellular apoptosis-associated speck-like protein with CARD domain (ASC) aggregates. The clinical phenotype in all subjects was consistent with mid-spectrum CAPS, except a median age at disease onset of 50 years. Sanger sequencing of NLRP3 was non-diagnostic but ADS detected a somatic NLRP3 mutation in each case. In one patient, DNA isolated from blood demonstrated an increase in the mutant allele from 5 to 45% over 12 years. ASC aggregates in patients’ serum measured during active disease were significantly higher than healthy controls. This series represents 8% of CAPS patients diagnosed in a single center, suggesting that acquired NLRP3 mutations may not be an uncommon cause of the syndrome and should be sought in all patients with late-onset symptoms otherwise compatible with CAPS. Steadily worsening CAPS symptoms in one patient were associated with clonal expansion of the mutant allele predominantly affecting myeloid cells. Two patients developed AA amyloidosis, which previously has only been reported in CAPS in association with life-long germline NLRP3 mutations.

Clinical and Molecular Phenotypes of Low-Penetrance Variants of NLRP3: Diagnostic and Therapeutic Challenges

OBJECTIVE

Cryopyrin-associated periodic syndromes (CAPS) result from gain-of-function mutations in the NLRP3 gene, which causes excessive release of interleukin-1β (IL-1β) and systemic inflammation. While pathogenetic NLRP3 variant phenotypes are well-characterized, low-penetrance NLRP3 variants represent a significant clinical challenge. The aims of this study were to determine the clinical phenotype, the in vitro biologic phenotype, and the effect of anti-IL-1 treatment in patients with low-penetrance NLRP3 variants.

METHODS

A multicenter study of consecutive symptomatic patients with low-penetrance NLRP3 variants recruited from 7 centers between May 2012 and May 2013 was performed. The observed findings were transferred into a study database, from which they were extracted for analysis. Controls were patients with a known pathogenetic NLRP3 variant. Clinical presentation and CAPS markers of inflammation were captured. Functional assays of inflammasome activation, including caspase 1 activity, NF-κB release, cell death, and IL-1β release, were performed. Treatment effects of IL-1 were determined. Comparisons between low-penetrance and pathogenetic NLRP3 variants were performed.

RESULTS

The study included 45 patients, 21 of which were female (47%); 26 of the patients (58%) were children. NLRP3 low-penetrance variants identified in the patients were Q703K (n = 19), R488K (n = 6), and V198M (n = 20). In the controls, 28 had pathogenetic NLRP3 variants. Patients with low-penetrance NLRP3 variants had significantly more fever (76%) and gastrointestinal symptoms (73%); eye disease, hearing loss, and renal involvement were less common. Functional inflammasome testing identified an intermediate phenotype in low-penetrance NLRP3 variants as compared to wild-type and pathogenetic NLRP3 variants. All treated patients responded to IL-1 inhibition, with complete response documented in 50% of patients.

CONCLUSION

Patients with low-penetrance NLRP3 variants display a distinct clinical phenotype and an intermediate biologic phenotype, including IL-1β and non-IL-1β-mediated inflammatory pathway activation.

Real-World Experience and Impact of Canakinumab in Cryopyrin-Associated Periodic Syndrome: Results From a French Observational Study

OBJECTIVE

The ENVOL study was designed to assess the psychosocial impact of disease and therapy in a French cohort of cryopyrin-associated periodic syndromes (CAPS) patients (and caregivers) treated with canakinumab.

METHODS

The ENVOL study was a multicenter, observational study of CAPS patients given ≥1 canakinumab dose. Data were collected before treatment, at 6 and 12 months afterward, and at the last visit. Patients and caregivers completed questionnaires assessing changes from the 12 months of pretreatment to 12 months prior to interview. Data were analyzed retrospectively.

RESULTS

The study included 10 physicians and 68 patients (53 adults, 15 children). Sixty-five patients (95.6%) were still receiving canakinumab at the last visit (median 5 years after starting therapy). The mean ± SD score for patient-reported general health increased from 7 ± 2.9 before canakinumab to 2.7 ± 2.7 after treatment (P < 0.001). Physical and emotional symptoms resolved or improved in a substantial proportion of patients, including bodily pain (38 of 46 patients), fever (32 of 39), skin disease (35 of 41), fatigue (31 of 47), self-confidence (29 of 46), and energy (34 of 47). Social activity, relationships, sexuality, and energy measures improved in >40% of respondents. Caregivers spent a median of 3 versus 0.5 hours/week on care in the 12 months of pretreatment versus 12 months prior to interview (P < 0.001). Following treatment, patients required fewer consultations with general practitioners (mean ± SD per patient per year: 5.2 ± 7.4 versus 8.5 ± 7.2 pretreatment), internists/rheumatologists/dermatologists (2.0 ± 2.1 versus 3.7 ± 3.9), and pediatricians (1.8 ± 1.5 versus 4.4 ± 4.2).

CONCLUSION

Long-term treatment with canakinumab achieves a highly relevant improvement in the physical, emotional, and social lives of patients with CAPS, accompanied by a marked reduction in support required from caregivers and in health care consultations.

Monogenic Periodic Fever Syndromes: Treatment Options for the Pediatric Patient

Autoinflammatory diseases are disorders of the innate immune system characterized by uncontrolled inflammation. The most commonly encountered autoinflammatory diseases are the hereditary periodic fever syndromes, which present with fever and other features of the skin, serosal membranes, and musculoskeletal system. The main inherited (monogenic) periodic fever syndromes are familial Mediterranean fever (FMF), cryopyrin-associated periodic syndrome (CAPS), tumor necrosis factor receptor-associated periodic syndrome (TRAPS), and hyperimmunoglobulin D syndrome (HIDS)/mevalonate kinase deficiency (MKD). Recent advances in our understanding of the molecular and pathophysiological basis of autoinflammatory diseases have provided new treatment strategies. Patients with periodic fever syndromes have clearly benefited from anti-interleukin (IL)-1 treatment. Colchicine is still the mainstay of FMF therapy, but IL-1 blockade is also effective if colchicine fails. Early diagnosis and effective treatment can prevent irreversible organ damage. The scope of pathogenic mutations and more targeted therapy for better management of these rare diseases remains to be defined.

Identification of a High-Frequency Somatic NLRC4 Mutation as a Cause of Autoinflammation by Pluripotent Cell-Based Phenotype Dissection

OBJECTIVE

To elucidate the genetic background of a patient with neonatal-onset multisystem inflammatory disease (NOMID) with no NLRP3 mutation.

METHODS

A Japanese male child diagnosed as having NOMID was studied. The patient did not have any NLRP3 mutation, even as low-frequency mosaicism. We performed whole-exome sequencing on the patient and his parents. Induced pluripotent stem cells (iPSCs) were established from the patient's fibroblasts. The iPSCs were then differentiated into monocyte lineage to evaluate the cytokine profile.

RESULTS

We established multiple iPSC clones from a patient with NOMID and incidentally found that the phenotypes of monocytes from iPSC clones were heterogeneous and could be grouped into disease and normal phenotypes. Because each iPSC clone was derived from a single somatic cell, we hypothesized that the patient had somatic mosaicism of an interleukin-1β-related gene. Whole-exome sequencing of both representative iPSC clones and the patient's blood revealed a novel heterozygous NLRC4 mutation, p.T177A (c.529A>G), as a specific mutation in diseased iPSC clones. Knockout of the NLRC4 gene using the clustered regularly interspaced short palindromic repeat/Cas9 system in a mutant iPSC clone abrogated the pathogenic phenotype.

CONCLUSION

Our findings indicate that the patient has somatic mosaicism of a novel NLRC4 mutation. To our knowledge, this is the first case showing that somatic mutation of NLRC4 causes autoinflammatory symptoms compatible with NOMID. The present study demonstrates the significance of prospective genetic screening combined with iPSC-based phenotype dissection for individualized diagnoses.

Protein kinase D at the Golgi controls NLRP3 inflammasome activation

Zhang et al. show that Golgi-mediated protein kinase D (PKD) signaling is required and sufficient for NLRP3 inflammasome activation. PKD at the Golgi phosphorylates NLRP3 to release it from mitochondria-associated endoplasmic reticulum membranes, allowing for assembly of the mature inflammasome in the cytosol.

The inflammasomes are multiprotein complexes sensing tissue damage and infectious agents to initiate innate immune responses. Different inflammasomes containing distinct sensor molecules exist. The NLRP3 inflammasome is unique as it detects a variety of danger signals. It has been reported that NLRP3 is recruited to mitochondria-associated endoplasmic reticulum membranes (MAMs) and is activated by MAM-derived effectors. Here, we show that in response to inflammasome activators, MAMs localize adjacent to Golgi membranes. Diacylglycerol (DAG) at the Golgi rapidly increases, recruiting protein kinase D (PKD), a key effector of DAG. Upon PKD inactivation, self-oligomerized NLRP3 is retained at MAMs adjacent to Golgi, blocking assembly of the active inflammasome. Importantly, phosphorylation of NLRP3 by PKD at the Golgi is sufficient to release NLRP3 from MAMs, resulting in assembly of the active inflammasome. Moreover, PKD inhibition prevents inflammasome autoactivation in peripheral blood mononuclear cells from patients carrying NLRP3 mutations. Hence, Golgi-mediated PKD signaling is required and sufficient for NLRP3 inflammasome activation.

Inflammasomes and dermatology

Inflammasomes are intracellular multiprotein complexes that comprise part of the innate immune response. Since their definition, inflammasome disorders have been linked to an increasing number of diseases. Autoinflammatory diseases refer to disorders in which local factors lead to the activation of innate immune cells, causing tissue damage when in the absence of autoantigens and autoantibodies. Skin symptoms include the main features of monogenic inflammasomopathies, such as Cryopyrin-Associated Periodic Syndromes (CAPS), Familial Mediterranean Fever (FMF), Schnitzler Syndrome, Hyper-IgD Syndrome (HIDS), PAPA Syndrome, and Deficiency of IL-1 Receptor Antagonist (DIRA). Concepts from other pathologies have also been reviewed in recent years, such as psoriasis, after the recognition of a combined contribution of innate and adaptive immunity in its pathogenesis. Inflammasomes are also involved in the response to various infections, malignancies, such as melanoma, autoimmune diseases, including vitiligo and lupus erythematosus, atopic and contact dermatitis, acne, hidradenitis suppurativa, among others. Inhibition of the inflammasome pathway may be a target for future therapies, as already occurs in the handling of CAPS, through the introduction of IL-1 inhibitors. This study presents a literature review focusing on the participation of inflammasomes in skin diseases.

Antigen-specific CD8+ T cell feedback activates NLRP3 inflammasome in antigen-presenting cells through perforin

The connection between innate and adaptive immunity is best exemplified by antigen presentation. Although antigen-presenting cells (APCs) are required for antigen receptor-mediated T-cell activation, how T-cells feedback to APCs to sustain an antigen-specific immune response is not completely clear. Here we show that CD8⁺ T-cell (also called cytotoxic T lymphocytes, CTL) feedback activates the NLRP3 inflammasome in APCs in an antigen-dependent manner to promote IL-1β maturation. Perforin from antigen-specific CTLs is required for NLRP3 inflammasome activation in APCs. Furthermore, such activation of NLRP3 inflammasome contributes to the induction of antigen-specific antitumour immunity and pathogenesis of graft-versus-host diseases. Our study reveals a positive feedback loop between antigen-specific CTLs and APC to amplify adaptive immunity.