Recent advances in the molecular pathogenesis of hereditary recurrent fevers

Quality of life in monogenic autoinflammatory diseases. A review

BACKGROUND

Systemic autoinflammatory diseases (SAIDs) are a group of disorders related to defective regulation of the innate immune system. Recurrence of inflammation can severely affect the patients' outcomes with a direct or indirect impact on their physical and mental health and/or global quality of life (QoL). We therefore sought to identify currently available QoL studies for these diseases as well as measurement tools at our disposal.

BASIC PROCEDURES

A systematic literature review was carried out with a focus on monogenic SAIDs. We inventoried the study designs developed in the selected publications, grouped them into similar topics, and listed the different outcome measures used for QoL.

MAIN FINDINGS

We recorded 53 bibliographic references evaluating the impact of monogenic SAIDs on the patients' QoL. These publications revealed 150 different study designs and 82 outcome measures used for their assessment. The best-explored topics were the overall patients' QoL, followed by the evaluation of their psychosocial and physical functioning. We found fair coverage of familial Mediterranean fever, poor investigation of the mixed hereditary recurrent fever (HRF) group, cryopyrin-associated periodic diseases and cherubism, and almost no study of the other monogenic SAIDs.

CONCLUSIONS

This work revealed areas requiring further investigation such as homogenization of concepts, study of uncommon or more recent diseases, and development of more specific and validated outcome measures for SAIDs.

HSP70 is a negative regulator of NLRP3 inflammasome activation

The NOD-leucine rich repeat and pyrin containing protein 3 (NLRP3) inflammasome is a multi-protein complex, aimed at producing IL-1β in response to danger signals which must be tightly regulated. Here we investigated the importance of the stress sensor, Heat Shock Protein 70 (HSP70) on NLRP3 inflammasome activation. HSP70 deficiency leads to the worsening of NLRP3-dependent peritonitis in mice. HSP70 deficiency also enhances caspase-1 activation and IL-1β production in murine Bone Marrow-Derived Macrophages (BMDMs) under NLRP3 activator treatment in vitro. This observation is associated with an increased number and size of Apoptosis associated Speck-like protein containing a CARD domain (ASC)/NLRP3 specks. Conversely, the overexpression of HSP70 in BMDMs decreases caspase-1 activation and IL-1β production under NLRP3 activator treatment. HSP70 interacts with NLRP3 and this interaction is lost upon NLRP3 inflammasome activation. Heat shock inhibits NLRP3 inflammasome activation in vitro and inhibits peritonitis in mice. Therefore this study provides evidence on the inhibitory role of HSP70 on NLRP3 inflammasome and open the possibility of treating inflammatory diseases via HSP70 induction and/or by hyperthermia.

Current knowledge on procaspase-1 variants with reduced or abrogated enzymatic activity in autoinflammatory disease

Caspase-1 is a proinflammatory enzyme that is essential in many inflammatory conditions including infectious, autoimmune, and autoinflammatory disorders. The inflammation is mainly mediated by the generation of inflammasomes that activate caspase-1 and subsequently interleukin (IL)-1β and IL-18. In addition, homotypic CARD/CARD interaction of procaspase-1 with RIP2 and thereby activation of the NF-κB pathways may play some role in the inflammation. However, normally, this pathway seems to become downregulated rapidly by the cleavage and excretion of RIP2 by active (pro-)caspase-1. In patients with unexplained recurrent systemic inflammation, CASP1 variants were detected, which often destabilized the caspase-1 dimer interface. Obviously, the resulting decreased or abrogated enzymatic activity and IL-1β production did not prevent the febrile episodes. As an unexpected finding, the inactive procaspase-1 variants significantly enhanced proinflammatory signaling by increasing RIP2 mediated NF-κB activation in an in vitro cell transfection model. A likely reason is the failure of inactive procaspase-1 to cleave bound RIP2 and also to mediate its excretion out of the intracelluar space thereby keeping the RIP2-NF-κB pathway upregulated. Hence, proinflammatory effects of enzymatically inactive procaspase-1 variants may partially explain the inflammatory episodes of the patients.

NLRP3 inflammasome: from a danger signal sensor to a regulatory node of oxidative stress and inflammatory diseases

IL-1β production is critically regulated by cytosolic molecular complexes, termed inflammasomes. Different inflammasome complexes have been described to date.

While all inflammasomes recognize certain pathogens, it is the distinctive feature of NLRP3 inflammasome to be activated by many and diverse stimuli making NLRP3 the most versatile, and importantly also the most clinically implicated inflammasome. However, NLRP3 activation has remained the most enigmatic. It is not plausible that the intracellular NLRP3 receptor is able to detect all of its many and diverse triggers through direct interactions; instead, it is discussed that NLRP3 is responding to certain generic cellular stress-signals induced by the multitude of molecules that trigger its activation.

An ever increasing number of studies link the sensing of cellular stress signals to a direct pathophysiological role of NLRP3 activation in a wide range of autoinflammatory and autoimmune disorders, and thus provide a novel mechanistic rational, on how molecules trigger and support sterile inflammatory diseases. A vast interest has created to unravel how NLRP3 becomes activated, since mechanistic insight is the prerequisite for a knowledge-based development of therapeutic intervention strategies that specifically target the NLRP3 triggered IL-1β production. In this review, we have updated knowledge on NLRP3 inflammasome assembly and activation and on the pyrin domain in NLRP3 that could represent a drug target to treat sterile inflammatory diseases. We have reported mutations in NLRP3 that were found to be associated with certain diseases. In addition, we have reviewed the functional link between NLRP3 inflammasome, the regulator of cellular redox status Trx/TXNIP complex, endoplasmic reticulum stress and the pathogenesis of diseases such as type 2 diabetes. Finally, we have provided data on NLRP3 inflammasome, as a critical regulator involved in the pathogenesis of obesity and cardiovascular diseases.

Inflammasome-independent regulation of IL-1-family cytokines

Induction, production, and release of proinflammatory cytokines are essential steps to establish an effective host defense. Cytokines of the interleukin-1 (IL-1) family induce inflammation and regulate T lymphocyte responses while also displaying homeostatic and metabolic activities. With the exception of the IL-1 receptor antagonist, all IL-1 family cytokines lack a signal peptide and require proteolytic processing into an active molecule. One such unique protease is caspase-1, which is activated by protein platforms called the inflammasomes. However, increasing evidence suggests that inflammasomes and caspase-1 are not the only mechanism for processing IL-1 cytokines. IL-1 cytokines are often released as precursors and require extracellular processing for activity. Here we review the inflammasome-independent enzymatic processes that are able to activate IL-1 cytokines, paying special attention to neutrophil-derived serine proteases, which subsequently induce inflammation and modulate host defense. The inflammasome-independent processing of IL-1 cytokines has important consequences for understanding inflammatory diseases, and it impacts the design of IL-1-based modulatory therapies.

Phenotypic and genotypic characteristics of cryopyrin-associated periodic syndrome: a series of 136 patients from the Eurofever Registry

OBJECTIVE

To evaluate genetic, demographic and clinical features in patients with cryopyrin-associated periodic syndrome (CAPS) from the Eurofever Registry, with a focus on genotype-phenotype correlations and predictive disease severity markers.

METHODS

A web-based registry retrospectively collected data on patients with CAPS. Experts in the disease independently validated all cases. Patients carrying NLRP3 variants and germline-mutation-negative patients were included.

RESULTS

136 patients were analysed. The median age at disease onset was 9 months, and the median duration of follow-up was 15 years. Skin rash, musculoskeletal involvement and fever were the most prevalent features. Neurological involvement (including severe complications) was noted in 40% and 12% of the patients, respectively, with ophthalmological involvement in 71%, and neurosensory hearing loss in 42%. 133 patients carried a heterozygous, germline mutation, and 3 patients were mutation-negative (despite complete NLRP3 gene screening). Thirty-one different NLRP3 mutations were recorded; 7 accounted for 78% of the patients, whereas 24 rare variants were found in 27 cases. The latter were significantly associated with early disease onset, neurological complications (including severe complications) and severe musculoskeletal involvement. The T348M variant was associated with early disease onset, chronic course and hearing loss. Neurological involvement was less strongly associated with V198M, E311 K and A439 V alleles. Early onset was predictive of severe neurological complications and hearing loss.

CONCLUSIONS

Patients carrying rare NLRP3 variants are at risk of severe CAPS; onset before the age of 6 months is associated with more severe neurological involvement and hearing loss. These findings may have an impact on treatment decisions.

Role of autoimmunity and autoinflammation in the pathogenesis of idiopathic recurrent pericarditis

Idiopathic recurrent pericarditis is the most common and troublesome complication of acute pericarditis affecting about one third of such patients. The pericardium may be involved in different systemic autoimmune diseases (i.e., systemic lupus erythematosus, rheumatoid arthritis, progressive systemic sclerosis, mixed connective tissue disease, Sjogren's Syndrome, polyarteritis, giant cell arteritis, other systemic vasculitides) either in a symptomatic form (usually during the active phase of the disease) or as asymptomatic pericardial effusion. Moreover, idiopathic recurrent pericarditis mimicks hereditary periodic fever syndromes (HPFSs). HPFSs are a group of disorders characterized by primary dysfunction of the innate immune system mostly caused by mutations of genes involved in the regulation or activation of the inflammatory response, without any apparent involvement of antigen-specific T cells or significant production of autoantibodies. These disorders usually manifest in the pediatric population, with onset ranging from the first hours to the first decade of life, however a limited number of patients experience disease onset during adulthood.

Association of NALP2 polymorphism with arsenic induced skin lesions and other health effects

Prolonged consumption of arsenic-laden water above the threshold limit of 10μg/L causes a plethora of dermatological and non-dermatological multi-organ health problems, including cancer and death. Among several mechanisms of arsenic-induced toxicity and carcinogenicity studied so far, role of arsenic in impairment of immune system is less understood. Epidemiological data, animal model as well as cell line based studies have indicated that arsenic targets immune system and is associated with characteristic immunosupression, which may further adversely affect respiratory function. However, to the best of our knowledge, there is no study with respect to arsenic susceptibility investigating the role of genetic variation having immunological function. Hence, we have recruited a total of 432 arsenic-exposed individuals, of which 219 individuals with characteristic arsenic-induced skin lesions (cases) and 213 individuals without arsenic-induced skin lesion(controls), from arsenic-exposed districts of West Bengal, India. To find any probable association between arsenicism and the exonic single nucleotide polymorphisms (SNPs) in NALP2 gene, an important component of inflammasome complex, we screened the entire coding region (exon) in all the study participants. Among 9 SNPs found in NALP2 gene, the A1052E polymorphism (at least with one minor allele), was significantly overrepresented in controls and hence implies decreased risk toward the development of skin lesions [OR=0.67, 95% CI: 0.46-0.97]. Since, development of non-dermatological health effects are also important factor to properly look into, we have attempted to correlate the genetic variation of NALP2 with the extent of cytogenetic damage as measured by chromosomal aberration assay and adverse health effects including peripheral neuropathy, eye problem and respiratory diseases in the study population. We observed individuals with the protective genotype had less chromosomal aberration (p<0.05), and were also less susceptible toward arsenic-related respiratory diseases [OR=0.47; 95%CI: 0.23-0.89]. These findings suggest that NALP2 A1052E SNP plays an important role toward development of arsenic-induced skin lesions, chromosomal damage and respiratory diseases.

Polymorphisms in the NLRP3 gene and risk of primary gouty arthritis

The aim of the present study was to investigate the association between genetic variants in 17 tagSNPs of the NLRP3 gene and the susceptibility to primary gouty arthritis. A genotype-phenotype analysis of 480 primary gout and 480 control patients was performed. Samples from all the patients were collected from The Affiliated Hospital of Medical College (Qingdao, China). Seventeen tagSNPs of the NLRP3 gene were amplified using polymerase chain reaction (PCR) and MassARRAY technology was used for single nucleotide polymorphism (SNP) genotyping. The genetic frequency of rs7512998 was significantly different between the gout and control patients (P<0.05), whereas no significant differences were identified for the remaining SNPs. The 17 SNPs conformed to the Hardy-Weinberg equilibrium (HWE) in the control group (P>0.05). The haplotype association among the 17 SNPs of the NLRP3 gene indicated that no individual SNP was significantly associated with primary gouty arthritis. CTATCAGCGCCCAGTGC was the most common haplotype in the case and control groups, with a frequency of 0.224 and 0.243, respectively. However, the odds ratios (ORs) of the 8 haplotypes were not identified to be significantly associated with gouty arthritis (P>0.05 for all the 8 haplotypes). To the best of our knowledge, this is the first study to investigate the association between SNPs of the NLRP3 gene and the risk of primary gouty arthritis, although no significant association was identified. Further clinical studies and functional analysis are required to explore the potential associations between NLRP3 gene polymorphisms and the risk of primary gouty arthritis.

The association of TNFRSF1A gene and MEFV gene mutations with adult onset Still's disease

Adult onset Still's disease (ASD) is a systemic inflammatory disorder of unknown etiology. ASD is characterized by fever with unknown etiology, rash, arthritis, and involvement of several organ systems. FMF and TRAPS are two important autoinflammatory diseases which characterized with recurrent inflammatory attacks. We aimed in this study to investigate the MEFV gene and TNFRSF1A gene variations in ASD. Twenty consecutive Turkish ASD patients (14 female and 6 male; mean age 38.45 ± 14; mean disease duration 3.3 ± 2.3; mean age of the disease onset 35.1 ± 14.4) and 103 healthy controls of Turkish origin were analyzed. All ASD patients were genotyped for the 4 MEFV mutations (M694V, E148Q, V726A, M680I) and TNFRSF1A gene exon 2-3 and exon 4-5 by using sequence analysis. The healthy controls are genotyped using PCR-RFLP method for intron 4 variation. The results of MEFV gene mutations screening show an increase in the MEFV mutation rate in ASD group, but it was not significantly different (p = 0.442, OR 1.64, 95 % CI 0.409-6.589). T-C polymorphism (rs1800692) was the only variation in the intron 4 of TNFRSF1A gene that we observed at the ASD patients. The frequency of TT genotype was 15 %, TC: 45 %, and CC: 40 % in ASD patients and the frequencies were 22, 41, and 37 % in healthy controls, respectively. When we analyzed the allele difference between both groups, there was no difference (p = 0.54, OR 1.24, 0.619-2.496-2.654). The variations in MEFV may have role in ASD pathogenesis. Our findings suggest that there is no significant association between ASD and TNFRSF1A variations.

Validation of a diagnostic score for the diagnosis of autoinflammatory diseases in adults

Most autoinflammatory disorders typically come out in the pediatric population, although a limited number of patients may experience disease onset during adulthood. To date, a late disease onset has been described only in familial Mediterranean fever, caused by mutations in the MEFV gene, and in tumor necrosis factor receptor-associated periodic syndrome, caused by mutations in the TNFRSF1A gene. The relative rarity and lack of information on adult-onset autoinflammatory diseases make it likely that mutations will be found in an even smaller percentage of cases. With the aim of improving the genetic diagnosis in adults with suspected autoinflammatory disorders, we recently identified a set of variables related to the probability of detecting gene mutations in MEFV and TNFRSF1A and, in addition, we have also proposed a diagnostic score for identifying those patients at high risk of carrying mutations in these genes. In the present study we evaluated the preliminary score sensitivity and specificity on a wider number of patients in order to validate the goodness of fit of the model. Two hundred and nineteen consecutive patients with a clinical history of periodic fever attacks were screened for mutations in MEFV and TNFRSF1A genes; detailed information about family/personal history and clinical manifestations were also collected. For the validation of the score we considered data both from the 110 patients used to build the preliminary diagnostic score and from the additional 219 patients enrolled in the present study, for a total number of 329 patients. Early age at disease onset, positive family history for recurrent fever episodes, thoracic pain, abdominal pain and skin rash, which are the variables that had previously been shown to be significantly associated with a positive genetic test result (12), were used for validation. On univariate analysis the associations with a positive genetic test were: age at onset (odds ratio [OR] 0.43, p=0.003), positive family history for recurrent fever episodes (OR 5.81, p<0.001), thoracic pain (OR 3.17, p<0.001), abdominal pain (OR 3.80, p<0.001) and skin rash (OR 1.58, p=0.103). The diagnostic score was calculated using the linear combination of the estimated coefficients of the logistic multivariate model (cut-off equals to 0.24) revealing good sensitivity (0.778) and good specificity (0.718). In conclusion, our score may serve in the diagnostic evaluation of adult patients presenting with recurrent fever episodes suspected of having an autoinflammatory disorder, helping identify the few subjects among them who may be carriers of mutations in MEFV and TNFRSF1A genes.

Tumor necrosis factor receptor associated periodic fever syndrome with photographic evidence of various skin disease and unusual phenotypes: case report and literature review

OBJECTIVES

To report a case of tumor necrosis factor receptor associated periodic fever syndrome (TRAPS) with unusual clinical phenotypes and a systematic review.

METHODS

The relevant English literature of TRAPS was searched using the keywords TRAPS, autoinflammatory disease, and gene mutation. Original and review articles were reviewed and the clinical scenarios were exemplified with a case report.

RESULTS

A 58-year-old Jewish woman with Eastern European Ashkenazic background presented with photographic evidence of various skin disease, including previously unreported vesicles and alopecia, as well as other systemic manifestations. The complaints of urinary foreign bodies prompted a discovery of ureteral strictures with atypia perhaps from autoinflammation. A R92Q gene mutation of TNFRSFA1 was detected. The clinical manifestations of this disease are protean and its pathogenesis is complex, involving the interaction of wild-type and mutated gene products, innate immune system, and proinflammatory cytokines. Glucocorticoid and anticytokine therapy is generally efficacious but some cases remain refractory to the current treatment.

CONCLUSIONS

TRAPS is a systemic autoinflammatory disease with variable clinical phenotypes associated with gene mutations. Recognition of the unusual phenotypes may enhance early accurate diagnosis.

A mutation in the immunoproteasome subunit PSMB8 causes autoinflammation and lipodystrophy in humans

Proteasomes are multisubunit proteases that play a critical role in maintaining cellular function through the selective degradation of ubiquitinated proteins. When 3 additional β subunits, expression of which is induced by IFN-γ, are substituted for their constitutively expressed counterparts, the structure is converted to an immunoproteasome. However, the underlying roles of immunoproteasomes in human diseases are poorly understood. Using exome analysis, we found a homozygous missense mutation (G197V) in immunoproteasome subunit, β type 8 (PSMB8), which encodes one of the β subunits induced by IFN-γ in patients from 2 consanguineous families. Patients bearing this mutation suffered from autoinflammatory responses that included recurrent fever and nodular erythema together with lipodystrophy. This mutation increased assembly intermediates of immunoproteasomes, resulting in decreased proteasome function and ubiquitin-coupled protein accumulation in the patient's tissues. In the patient's skin and B cells, IL-6 was highly expressed, and there was reduced expression of PSMB8. Downregulation of PSMB8 inhibited the differentiation of murine and human adipocytes in vitro, and injection of siRNA against Psmb8 in mouse skin reduced adipocyte tissue volume. These findings identify PSMB8 as an essential component and regulator not only of inflammation, but also of adipocyte differentiation, and indicate that immunoproteasomes have pleiotropic functions in maintaining the homeostasis of a variety of cell types.

Development and preliminary validation of a diagnostic score for identifying patients affected with adult-onset autoinflammatory disorders

To date, the rate of detection of autoinflammatory gene mutations in patients suspected of having an autoinflammatory disorder is very low. However, most of these data refer to pediatric populations. The relative rarity and lack of information on adult-onset autoinflammatory diseases make it likely that mutations will be found in an even smaller percentage of cases. Our aim was to develop and validate a set of variables for predicting the risk that a given adult patient presenting with recurrent fever episodes carries mutations in the MEFV or TNFRSF1A genes, in order to increase the probability of obtaining positive results on genetic testing. One hundred and ten consecutive patients with a clinical history of periodic fever attacks were screened for mutations in the TNFRSF1A and the MEFV genes. The mean age at disease onset was 27.85 years. Detailed information about each patient?s family history, personal history, and clinical manifestations were retrospectively collected. A diagnostic score was constructed based on univariate and multivariate analysis in a randomly-selected dataset (training set; n=40). The score was validated on an independent set of the remaining patients (validation set; n=70). Age at onset (odds ratio 0.958, P =0.050), positive family history of recurrent fever episodes (OR 5.738, P = 0.006 ), thoracic pain (OR 7.390, P = 0.002), abdominal pain (OR 2.853, P = 0.038) and skin involvement (OR 8.241, P = 0.003) were independently correlated with a positive genetic test result. A diagnostic score was calculated using the linear combination of the estimated coefficients of the logistic model (cut off equal to 0.24) revealing high sensitivity (0.94), high specificity (0.94) and high accuracy (0.94). We have identified variables that appear to be strongly related to the probability of detecting gene mutations in MEF and TNFRSF1A in adults, thus improving the evaluation of patients with suspected autoinflammatory disorders.

Role of etanercept in the treatment of tumor necrosis factor receptor-associated periodic syndrome: personal experience and review of the literature

Tumor necrosis factor-alpha receptor (TNFR1)-associated periodic syndrome (TRAPS) is the most common autosomal-dominant autoinflammatory condition and is caused by mutations in the TNFRSF1A gene. TRAPS is characterized by recurrent attacks of fever typically lasting from 1 to 3 weeks; in addition to fever, common clinical features include mainly periorbital oedema, conjunctivitis, a migratory erythematous plaque simulating erysipela with underlying myalgia, and arthritis or arthralgia; serosal membrane inflammation is also possible. The identification of TNFRSF1A mutations as the genetic cause of TRAPS coincided with the wider use of biological agents in medicine and raised the possibility that blocking TNF could potentially represent the primary therapeutic goal in TRAPS, thus disclosing new treatment choices for this complex disease. In the past few years, isolated reports and case-series have been published suggesting that inhibition of TNF-alpha might represent a promising therapeutic approach in TRAPS. We present here our experience with etanercept in the treatment of patients affected with TRAPS, and we also add a review of the literature.

Mechanisms of uric acid crystal-mediated autoinflammation

Gout is an arthritis characterized by elevated uric acid in the bloodstream. In this condition, crystals of uric acid are formed and accumulate in the synovial fluids. Crystal deposition leads to acute inflammation, which is associated with the spontaneous resolution of the disease. Recent studies have led to significant advances in the understanding of the basic biology of crystal-mediated inflammation. Uric acid has been identified as a danger signal that triggers a cytosolic sensor, the inflammasome. This signaling platform is required for the activation of interleukin-1, a cytokine that is critical to the initiation of acute inflammation in gout. Importantly, both molecular and pathological evidence support the notion that gout is a prototypical member of the growing family of autoinflammatory diseases. This review discusses the role of the inflammasome in gout and the emerging new therapeutic strategies aimed at controlling inflammation in crystal arthritis.

Inflammasome-associated nucleotide-binding domain, leucine-rich repeat proteins and inflammatory diseases

The nucleotide-binding domain, leucine-rich repeat (NLR) proteins are a recently discovered family of intracellular pathogen and danger signal sensors. NLRs have emerged as important contributors to innate immunity in animals. The physiological impact of these genes is increasingly evident, underscored by the genetic association of variant family members with an array of inflammatory diseases. The association of mutations in NLR genes with autoinflammatory diseases indicates an important function of these genes in inflammation in vivo. This review summarizes the role of the inflammasome NLR proteins in innate immunity and inflammatory diseases and explores the possible utility of some of these NLRs as pharmacological targets.

Innate versus acquired immune response in the pathogenesis of recurrent idiopathic pericarditis

The pathogenesis of recurrent pericarditis is still poorly understood and may be related either to viral infections or autoimmune and autoinflammatory disorders. The immune system plays a major role in the pathogenesis of the disease, modulating individual responses to different noxa and explaining the variable reported recurrence rate (ranging from 20% to 50% of patients) following an attack of acute or recurrent pericarditis. Increasing interest is currently being devoted to autoinflammatory disorders, a group of conditions characterized by spontaneously relapsing and remitting bouts of systemic inflammation without apparent involvement of antigen-specific T cells or significant production of auto-antibodies. Ongoing basic and clinical research is needed to provide further evidence for the understanding of this common and troublesome disease, and to develop targeted and more efficacious therapies.

Toll-like receptors (TLRs) and Nod-like receptors (NLRs) in inflammatory disorders

Toll-like receptors (TLRs) and Nod-like receptors (NLRs) are two major forms of innate immune sensors, which provide immediate responses against pathogenic invasion or tissue injury. Activation of these sensors induces the recruitment of innate immune cells such as macrophages and neutrophils, initiates tissue repair processes, and results in adaptive immune activation. Abnormalities in any of these innate sensor-mediated processes may cause excessive inflammation due to either hyper responsive innate immune signaling or sustained compensatory adaptive immune activation. Recent gene association studies appear to reveal strong associations of NLR gene mutations and development of several idiopathic inflammatory disorders. In contrast, TLR polymorphisms are less often associated with inflammatory disorders. Nevertheless, TLRs are up-regulated in the affected tissue of most inflammatory disorders, suggesting TLR signaling is involved in the pathogenesis of chronic and/or idiopathic inflammatory disorders. NLR signaling results in the formation of a molecular scaffold complex (termed an inflammasome) and orchestrates with TLRs to induce IL-1beta and IL-18, both of which are important mediators in the majority of inflammatory disorders. Therefore, understanding the roles of TLRs and NLRs in the pathogenesis of chronic and idiopathic inflammatory disorders may provide novel targets for the prevention and/or treatment of many common and uncommon diseases involving inflammation.

The inflammasomes: guardians of the body

The innate immune system relies on its capacity to rapidly detect invading pathogenic microbes as foreign and to eliminate them. The discovery of Toll-like receptors (TLRs) provided a class of membrane receptors that sense extracellular microbes and trigger antipathogen signaling cascades. More recently, intracellular microbial sensors have been identified, including NOD-like receptors (NLRs). Some of the NLRs also sense nonmicrobial danger signals and form large cytoplasmic complexes called inflammasomes that link the sensing of microbial products and metabolic stress to the proteolytic activation of the proinflammatory cytokines IL-1beta and IL-18. The NALP3 inflammasome has been associated with several autoinflammatory conditions including gout. Likewise, the NALP3 inflammasome is a crucial element in the adjuvant effect of aluminum and can direct a humoral adaptive immune response. In this review, we discuss the role of NLRs, and in particular the inflammasomes, in the recognition of microbial and danger components and the role they play in health and disease.

The Inflammasomes: Guardians of the Body

The innate immune system relies on its capacity to rapidly detect invading pathogenic microbes as foreign and to eliminate them. The discovery of Toll-like receptors (TLRs) provided a class of membrane receptors that sense extracellular microbes and trigger antipathogen signaling cascades. More recently, intracellular microbial sensors have been identified, including NOD-like receptors (NLRs). Some of the NLRs also sense nonmicrobial danger signals and form large cytoplasmic complexes called inflammasomes that link the sensing of microbial products and metabolic stress to the proteolytic activation of the proinflammatory cytokines IL-1β and IL-18. The NALP3 inflammasome has been associated with several autoinflammatory conditions including gout. Likewise, the NALP3 inflammasome is a crucial element in the adjuvant effect of aluminum and can direct a humoral adaptive immune response. In this review, we discuss the role of NLRs, and in particular the inflammasomes, in the recognition of microbial and danger components and the role they play in health and disease.

The Inflammasomes: Guardians of the Body

The innate immune system relies on its capacity to rapidly detect invading pathogenic microbes as foreign and to eliminate them. The discovery of Toll-like receptors (TLRs) provided a class of membrane receptors that sense extracellular microbes and trigger antipathogen signaling cascades. More recently, intracellular microbial sensors have been identified, including NOD-like receptors (NLRs). Some of the NLRs also sense nonmicrobial danger signals and form large cytoplasmic complexes called inflammasomes that link the sensing of microbial products and metabolic stress to the proteolytic activation of the proinflammatory cytokines IL-1β and IL-18. The NALP3 inflammasome has been associated with several autoinflammatory conditions including gout. Likewise, the NALP3 inflammasome is a crucial element in the adjuvant effect of aluminum and can direct a humoral adaptive immune response. In this review, we discuss the role of NLRs, and in particular the inflammasomes, in the recognition of microbial and danger components and the role they play in health and disease.

The Inflammasomes: Guardians of the Body

The innate immune system relies on its capacity to rapidly detect invading pathogenic microbes as foreign and to eliminate them. The discovery of Toll-like receptors (TLRs) provided a class of membrane receptors that sense extracellular microbes and trigger antipathogen signaling cascades. More recently, intracellular microbial sensors have been identified, including NOD-like receptors (NLRs). Some of the NLRs also sense nonmicrobial danger signals and form large cytoplasmic complexes called inflammasomes that link the sensing of microbial products and metabolic stress to the proteolytic activation of the proinflammatory cytokines IL-1β and IL-18. The NALP3 inflammasome has been associated with several autoinflammatory conditions including gout. Likewise, the NALP3 inflammasome is a crucial element in the adjuvant effect of aluminum and can direct a humoral adaptive immune response. In this review, we discuss the role of NLRs, and in particular the inflammasomes, in the recognition of microbial and danger components and the role they play in health and disease.

The Inflammasomes: Guardians of the Body

The innate immune system relies on its capacity to rapidly detect invading pathogenic microbes as foreign and to eliminate them. The discovery of Toll-like receptors (TLRs) provided a class of membrane receptors that sense extracellular microbes and trigger antipathogen signaling cascades. More recently, intracellular microbial sensors have been identified, including NOD-like receptors (NLRs). Some of the NLRs also sense nonmicrobial danger signals and form large cytoplasmic complexes called inflammasomes that link the sensing of microbial products and metabolic stress to the proteolytic activation of the proinflammatory cytokines IL-1β and IL-18. The NALP3 inflammasome has been associated with several autoinflammatory conditions including gout. Likewise, the NALP3 inflammasome is a crucial element in the adjuvant effect of aluminum and can direct a humoral adaptive immune response. In this review, we discuss the role of NLRs, and in particular the inflammasomes, in the recognition of microbial and danger components and the role they play in health and disease.

Novel markers of inflammation identified in tumor necrosis factor receptor-associated periodic syndrome (TRAPS) by transcriptomic analysis of effects of TRAPS-associated tumor necrosis factor receptor type I mutations in an endothelial cell line

OBJECTIVE

To analyze the effects of tumor necrosis factor receptor-associated periodic syndrome (TRAPS)-associated mutant tumor necrosis factor receptor type I (TNFRI) expression in a cell type directly relevant to the inflammation in TRAPS, and to identify novel markers associated with mutant TNFRI expression.

METHODS

Transcriptome analysis on 30,000 human genes was performed on SK-Hep-1 human endothelial cells transfected with either wild-type (WT) or TRAPS-associated mutant TNFRI. Quantitative reverse transcriptase-polymerase chain reaction and protein expression levels measured by enzyme-linked immunosorbent assay verified transcriptional changes for selected genes both in supernatants from cells expressing mutant TNFRI and in patient plasma.

RESULTS

Cells expressing mutant TNFRI showed up-regulation of multiple proinflammatory genes relative to WT transfectants, including genes for pentraxin 3, granulocyte-macrophage colony-stimulating factor, granulocyte colony-stimulating factor, CCL2, and CCL5, which were also expressed as proteins. In addition, the expression of most of these markers was increased in the plasma and peripheral blood mononuclear cells from TRAPS patients relative to those from healthy controls. The cysteine mutations (C33Y and C52F), which are associated with a more severe clinical phenotype, induced more genes than the low-penetrance mutation R92Q, which is associated with a milder phenotype. The expression of most genes was induced by a death domain (DD)-dependent mechanism, since they were not induced by expression of TNFRI mutants with an inactivated DD.

CONCLUSION

TRAPS-associated TNFRI mutants induce the expression of multiple genes encoding inflammatory molecules, cellular receptors, transcription factors, and regulators of apoptosis in endothelial cells that require the cytoplasmic signaling properties of the receptor. Different mutants have specific expression profiles, indicating mutation-specific effects. The expression of some of these markers was also elevated in samples from TRAPS patients.

Dysregulation of innate immunity: hereditary periodic fever syndromes

The hereditary periodic fever syndromes encompass a rare group of diseases that have lifelong recurrent episodes of inflammatory symptoms and an acute phase response in common. Clinical presentation can mimic that of lymphoproliferative disorders and patients often go undiagnosed for many years. These syndromes follow an autosomal inheritance pattern, and the major syndromes are linked to specific genes, most of which are involved in regulation of the innate immune response through pathways of apoptosis, nuclear factor kappaBeta activation and cytokine production. In others, the link between the protein involved and inflammation is less clear. The recurrent inflammation can lead to complications, such as renal impairment due to amyloidosis and vasculitis, visual impairment, hearing loss, and joint destruction, depending on the specific syndrome. In recent years, treatment options for these diseases have improved significantly. Early establishment of an accurate diagnosis and start of appropriate therapy improves prognosis in these patients.

Neutrophil dysfunction in a family with a SAPHO syndrome-like phenotype

SAPHO syndrome (synovitis, acne, pustulosis, hyperostosis, osteitis) is an inflammatory disorder of the bone, skin, and joints. We describe a family with multiple affected members who segregate a SAPHO syndrome-like phenotype, and we report the results of neutrophil studies and candidate gene analysis. We obtained written informed consent and a family history and reviewed medical records. We collected DNA and sequenced candidate genes, and we performed functional studies on neutrophils isolated from the proband and her mother. The pedigree segregated chronic osteomyelitis and cutaneous inflammation in a pattern that suggested an autosomal-dominant disorder. No coding sequence mutations were detected in PSTPIP1, PSTPIP2, LPIN2, SH3BP2, or NCF4. Analysis of neutrophil function in the proband, including nitroblue tetrazolium tests, myeloperoxidase assays, neutrophil chemotaxis, and neutrophil chemotaxis assays, revealed no identifiable abnormalities. However, an abnormality in the luminol, but not the isoluminol, respiratory burst assays following stimulation with phorbol myristate acetate (PMA) was detected in neutrophils isolated from the affected proband. Internal oxidant production was also reduced in the proband and her mother when neutrophils were treated with fMLP with or without platelet-activating factor, PMA alone, or tumor necrosis factor alpha alone. This family segregates a disorder characterized by chronic inflammation of the skin and bone. Functional differences in neutrophils exist between affected individuals and controls. The biologic significance of this defect remains unknown. Identification of the gene defect will help identify an immunologic pathway that, when dysregulated, causes inflammation of the skin and bone.

TNF receptor-associated periodic syndrome (TRAPS): description of a novel TNFRSF1A mutation and response to etanercept

TRAPS is the most common of the autosomal dominant periodic fever syndromes. It is caused by mutations in the TNFRSF1A gene, which encodes for the type 1 TNF-receptor (TNFR1). We describe here a Brazilian patient with TRAPS associated to a novel TNFRSF1A de novo mutation and the response to anti-TNF therapy. The patient is a 9-year-old girl with recurrent fevers since the age of 3 years, usually lasting 3 to 7 days, and recurring every other week. These episodes are associated with mild abdominal pain, nausea, vomiting and generalized myalgia. Recurrent conjunctivitis and erysipela-like skin lesions in the lower limbs also occur. Laboratory studies show persistent normocytic normochromic anemia, thrombocytosis, elevated erythrocyte sedimentation rate and C-reactive protein. IgD levels are normal. Mutational screening of TNFRSF1A revealed the association of a novel C30F mutation with the common R92Q low-penetrance mutation. The R92Q mutation is seen in 5% of the general population and is associated with an atypical inflammatory phenotype. The patient had a very good response to etanercept, with cessation of fever and normalization of inflammatory markers. Our report expands the spectrum of TNFRSF1A mutations associated with TRAPS, adding further evidence for possible additive effects of a low-penetration R92Q and cysteine residue mutations, and confirms etanercept as an efficacious treatment alternative.

Intermittent chronic neutropenia in a patient with familial Mediterranean fever

A 12-year-old daughter of consanguineous Moroccan parents was diagnosed with cyclic neutropenia, based on a combination of recurrent gingivostomatitis, a fluctuating neutrophil count, and several episodes of severe neutropenia. No ELA2 gene mutations were found. At age 19 years she presented with edema of the limbs, proteinuria and renal failure. Renal amyloidosis AA was diagnosed by biopsy. Gene mutations associated with family Mediterranean fever (FMF) were sought, and a homozygous mutation (M694V) was found in the MFEV gene. This is the novel finding of FMF that masqueraded as cyclic neutropenia.

Phenotype-genotype analysis of cryopyrin-associated periodic syndromes (CAPS): description of a rare non-exon 3 and a novel CIAS1 missense mutation

We describe in this paper the phenotype-genotype analysis of a Brazilian cohort of patients with cryopyrin-associated periodic syndromes (CAPS). Patient 1 presented with an urticarial rash and recurrent fever exacerbated by cold weather, arthritis, and anterior uveitis, thus, receiving a clinical diagnosis of familial cold autoinflammatory syndrome. CIAS1 sequencing identified the T436I mutation, previously associated to a clinical phenotype of chronic infantile neurological cutaneous and articular/neonatal onset multisystem inflammatory disease. Patient 2 developed a papular exanthema with daily fever shortly after birth, frontal bossing, patellae enlargement, and cognitive and motor impairments. Sequencing identified the exceedingly rare G755R CIAS1 mutation in exon 4. Patient 3 developed skin rash and articular symptoms 6 h after birth, followed by aseptic meningitis. He was found to have the novel C148Y missense mutation in CIAS1. This report expands the spectrum of CIAS1 mutations associated to clinical disease, suggests that the same mutation can be associated with different clinical syndromes, and supports the evidence that CAPS patients should always be screened for mutations outside exon 3.

The inflammasome, autoinflammatory diseases, and gout

IL-1beta is a cytokine with major roles in inflammation and innate immune responses. IL-1beta is produced as an inactive proform that must be cleaved within the cell to generate biologically active IL-1beta. The enzyme caspase-1 catalyzes the reaction. Recent work showed that caspase-1 must be activated by a complex known as the inflammasome. The inflammasome comprises NALP, which is an intracellular receptor involved in innate immunity, and an ASC adapter that ensures caspase-1 recruitment to the receptor. The most extensively described inflammasome to date is formed by the NALP3 receptor within monocytes. Mutations involving the NALP3 gene cause hereditary periodic fever syndromes in humans. Increased inflammasome activity responsible for uncontrolled IL-1beta production occurs in these syndromes. Inhibition of the IL-1beta pathway by IL-1 receptor antagonist (anakinra) is a highly effective treatment for inherited periodic fever syndromes. A major role for inflammasome activity in the development of gout attacks was established recently. Urate monosodium crystals are specifically detected via the NALP3 inflammasome, which results in marked IL-1beta overproduction and initiation of an inflammatory response. This finding opens up new possibilities for the management of gouty attacks.

Detection of immune danger signals by NALP3

The innate immune system in animals has been forged to detect microbes, coordinate symbiotic responses, and mount immune defenses against pathogens. Recently, innate immunity was shown to detect signals released by damaged cells or tissues such as uric acid or ATP. These danger signals were proposed to be important in promoting and regulating inflammation upon trauma or pathogen insults. The physiological relevance of these signals in the immune response and their mechanisms of action are still unclear. Recent findings suggest that some danger signals activate the NALP3 inflammasome, an innate immune complex that controls inflammatory caspases and IL-1 activation.

The child with recurrent respiratory infections: normal or not?

Respiratory infections (RI) are one of the major complaints in children and adolescents, and represent a demanding challenge for the pediatrician. It has been estimated that at least 6% of Italian children younger than 6 yr of age present recurrent respiratory infections (RRI). Children with RRI are not affected by severe alterations of the immune system. RRI represent essentially the consequence of an increased exposure to infectious agents during the first years of life, when immune functions are still largely immature. Several social and environmental factors, such as day-care attendance, family size, air pollution, parental smoking, and home dampness, represent important risk factors for airway diseases and may contribute in various degrees to determine the incidence of RRI. The main problem for the pediatrician is to discriminate normal children with high RI frequency related to an augmented exposure to environmental risk factors from children affected by other underlying pathological conditions (immunological or not), predisposing to infectious diseases. When RRI diagnosis has been formulated, removal of environmental risk factors (i.e. precocious day-care attendance, smoking in the household) must first be suggested.

Autoinflammatory bone disorders

PURPOSE OF REVIEW

This review provides an update on clinical, genetic, and immunologic aspects of the autoinflammatory bone disorders.

RECENT FINDINGS

Chronic noninfectious inflammation of the bone is a clinical feature of both chronic recurrent multifocal osteomyelitis and (to a lesser degree) cherubism. The genes responsible for Majeed syndrome (LPIN2), murine chronic multifocal osteomyelitis (pstpip2), and cherubism (SH3BP2 and possibly PTPN11) have been identified. Murine models of both chronic recurrent multifocal osteomyelitis and cherubism have demonstrated that the bone inflammation is mediated by hematopoietically derived cells and can occur in the absence of a functioning adaptive immune system. As the immunologic defects become better defined, the cells of the myeloid lineage are emerging as the primary players.

SUMMARY

Chronic multifocal osteomyelitis and cherubism are hereditary chronic inflammatory disorders in which bone is the primary inflammatory target. Recent genetic and immunologic discoveries demonstrate involvement of the innate immune system, which places these entities in the category of autoinflammatory disorders.

NALP inflammasomes: a central role in innate immunity

Inflammasomes are cytoplasmic multiprotein complexes that mediate the maturation of the proinflammatory cytokines interleukin-1beta (IL-1beta), IL-18, and possibly IL-33 by controlling the activation of the inflammatory caspases-1 and -5. Assembly of inflammasomes depends on NOD-like receptor (NLR) family members such as NALPs, NAIP, and IPAF. Various microbial and endogenous stimuli activate different types of inflammasomes. This article focuses on the Pyrin domain containing NLRs, known as NALP proteins. Recent findings provide exciting insights into how these proteins might be activated and also provide evidence of the critical role of the NALP inflammasomes in innate immunity and inflammatory diseases.