Reduced tumor necrosis factor signaling in primary human fibroblasts containing a tumor necrosis factor receptor superfamily 1A mutant

Decoding Cell Death: From a Veritable Library of Babel to Vade Mecum?

Programmed cell death (PCD) is a requisite feature of development and homeostasis but can also be indicative of infections, injuries, and pathologies. In concordance with these heterogeneous contexts, an array of disparate effector responses occur downstream of cell death and its clearance-spanning tissue morphogenesis, homeostatic turnover, host defense, active dampening of inflammation, and tissue repair. This raises a fundamental question of how a single contextually appropriate response ensues after an event of PCD. To explore how complex inputs may together tailor the specificity of the resulting effector response, here we consider (a) the varying contexts during which different cell death modalities are observed, (b) the nature of the information that can be passed on by cell corpses, and (c) the ways by which efferocyte populations synthesize signals from dying cells with those from the surrounding microenvironment.

CRISPR-mediated transcriptional activation with synthetic guide RNA

The CRISPR-Cas9 system has been adapted for transcriptional activation (CRISPRa) and several second-generation CRISPRa systems (including VPR, SunTag, and SAM) have been developed to recruit different transcriptional activators to a deactivated Cas9, which is guided to a transcriptional start site via base complementarity with a target guide RNA. Multiple studies have shown the benefit of CRISPRa using plasmid or lentiviral expressed guide RNA, but the use of synthetic guide RNA has not been reported. Here we demonstrate the effective use of synthetic guide RNA for gene activation via CRISPRa. CRISPRa crRNA may be used with a canonical tracrRNA using the VPR or SunTag activation systems or with an extended tracrRNA containing an aptamer sequence for the SAM system. Transcriptional activation with synthetic crRNA:tracrRNA is comparable to activation achieved with expression vectors and combining several crRNA sequences targeting the same gene can enhance transcriptional activation. The use of synthetic crRNA is also ideal for simultaneous activation of multiple genes or use with dCas9-VPR mRNA when viral transduction is not feasible. Here, we perform a proof-of-principle arrayed screen using a CRISPRa crRNA library consisting of 153 cytokine receptor targets to identify regulators of IL-6 cytokine secretion. Together, these results demonstrate the suitability of synthetic CRISPRa guide RNA for high throughput, arrayed screening applications which allow for more complex phenotypic readouts to complement viability and drug resistance assays typically used in a pooled screening format.

Rationalized inhibition of mixed lineage kinase 3 and CD70 enhances life span and antitumor efficacy of CD8+ T cells

BACKGROUND

The mitogen-activated protein kinases (MAPKs) are important for T cell survival and their effector function. Mixed lineage kinase 3 (MLK3) (MAP3K11) is an upstream regulator of MAP kinases and emerging as a potential candidate for targeted cancer therapy; yet, its role in T cell survival and effector function is not known.

METHODS

T cell phenotypes, apoptosis and intracellular cytokine expressions were analyzed by flow cytometry. The apoptosis-associated gene expressions in CD8+CD38+ T cells were measured using RT2 PCR array. In vivo effect of combined blockade of MLK3 and CD70 was analyzed in 4T1 tumor model in immunocompetent mice. The serum level of tumor necrosis factor-α (TNFα) was quantified by enzyme-linked immunosorbent assay.

RESULTS

We report that genetic loss or pharmacological inhibition of MLK3 induces CD70-TNFα-TNFRSF1a axis-mediated apoptosis in CD8+ T cells. The genetic loss of MLK3 decreases CD8+ T cell population, whereas CD4+ T cells are partially increased under basal condition. Moreover, the loss of MLK3 induces CD70-mediated apoptosis in CD8+ T cells but not in CD4+ T cells. Among the activated CD8+ T cell phenotypes, CD8+CD38+ T cell population shows more than five fold increase in apoptosis due to loss of MLK3, and the expression of TNFRSF1a is significantly higher in CD8+CD38+ T cells. In addition, we observed that CD70 is an upstream regulator of TNFα-TNFRSF1a axis and necessary for induction of apoptosis in CD8+ T cells. Importantly, blockade of CD70 attenuates apoptosis and enhances effector function of CD8+ T cells from MLK3-/- mice. In immune-competent breast cancer mouse model, pharmacological inhibition of MLK3 along with CD70 increased tumor infiltration of cytotoxic CD8+ T cells, leading to reduction in tumor burden largely via mitochondrial apoptosis.

CONCLUSION

Together, these results demonstrate that MLK3 plays an important role in CD8+ T cell survival and effector function and MLK3-CD70 axis could serve as a potential target in cancer.

The classification, genetic diagnosis and modelling of monogenic autoinflammatory disorders

Monogenic autoinflammatory disorders are an increasingly heterogeneous group of conditions characterised by innate immune dysregulation. Improved genetic sequencing in recent years has led not only to the discovery of a plethora of conditions considered to be 'autoinflammatory', but also the broadening of the clinical and immunological phenotypic spectra seen in these disorders. This review outlines the classification strategies that have been employed for monogenic autoinflammatory disorders to date, including the primary innate immune pathway or the dominant cytokine implicated in disease pathogenesis, and highlights some of the advantages of these models. Furthermore, the use of the term 'autoinflammatory' is discussed in relation to disorders that cross the innate and adaptive immune divide. The utilisation of next-generation sequencing (NGS) in this population is examined, as are potential in vivo and in vitro methods of modelling to determine pathogenicity of novel genetic findings. Finally, areas where our understanding can be improved are highlighted, such as phenotypic variability and genotype-phenotype correlations, with the aim of identifying areas of future research.

A novel TNFRSF1A gene mutation in a patient with tumor necrosis factor receptor-associated periodic syndrome

Tumor necrosis factor receptor-associated periodic syndrome (TRAPS) is a periodic fever syndrome inherited in an autosomal dominant fashion. It stems from mutations in the TNFRSF1A (accession number: NM_001065) gene expressing the receptor for tumor necrosis factor α. A patient with TRAPS may present with prolonged episodes of fever attacks, abdominal pain, severe myalgia, and painful erythema on the trunk or extremities. Here, we report an 8-year-old boy with febrile attacks occurring every 1-2months and continuing for 3-4days. The patient experienced 40°C-fever attacks without chills. Approximately 80% of fever attacks were accompanied by abdominal manifestations. Direct sequencing analysis was used to assess the genomic DNA of the patient, and a heterozygous R426L mutation in exon 10 of the TNFRSF1A gene in an autosomal dominant inheritance fashion was identified. Further genetic analyses were also carried out on his parents. Due to the fact that the mutation was not inherited from the parents, it was likely that R426L was a de novo and novel mutation in the TNFRSF1A gene, which can trigger TRAPS or TRAPS-like symptoms.

Tumor necrosis factor receptor-associated periodic syndrome as a model linking autophagy and inflammation in protein aggregation diseases

Autophagy prevents cellular damage by eliminating insoluble aggregates of mutant misfolded proteins, which accumulate under different pathological conditions. Downregulation of autophagy enhances the inflammatory response and thus represents a possible common pathogenic event underlying a number of autoinflammatory syndromes, such as tumor necrosis factor (TNF) receptor-associated periodic syndrome (TRAPS). The pathogenesis of other monogenic or complex disorders that display symptoms of excessive inflammation also involve the autophagy pathway. Studies have shown that TRAPS-associated TNFRSF1A mutations induce cytoplasmic retention of the TNFR1 receptor, defective TNF-induced apoptosis, and production of reactive oxygen species (ROS). Furthermore, autophagy impairment may account for the pathogenic effects of TNFRSF1A mutations, thus inducing inflammation in TRAPS. In this review, we summarize the molecular interactions and functional links between autophagy with regard to nuclear factor-kappa B activation, ROS production, and apoptosis. Furthermore, we propose a complex interplay of these pathways as a model to explain the relationship between mutant protein misfolding and inflammation in genetically determined and aggregation-prone diseases. Accordingly, autophagy function should be investigated in all diseases showing an inflammatory component, and for which the molecular pathogenesis is still unclear.

Regulation and dysregulation of tumor necrosis factor receptor-1

TNF is an essential regulator of the immune system. Dysregulation of TNF plays a role in the pathology of many auto-immune diseases. TNF-blocking agents have proven successful in the treatment of such diseases. Development of novel, safer or more effective drugs requires a deeper understanding of the regulation of the pro-inflammatory activities of TNF and its receptors. The ubiquitously expressed TNFR1 is responsible for most TNF effects, while TNFR2 has a limited expression pattern and performs immune-regulatory functions. Despite extensive knowledge of TNFR1 signaling, the regulation of TNFR1 expression, its modifications, localization and processing are less clear and the data are scattered. Here we review the current knowledge of TNFR1 regulation and discuss the impact this has on the host.

Involvement of the same TNFR1 residue in mendelian and multifactorial inflammatory disorders

Objectives

TNFRSF1A is involved in an autosomal dominant autoinflammatory disorder called TNFR-associated periodic syndrome (TRAPS). Most TNFRSF1A mutations are missense changes and, apart from those affecting conserved cysteines, their deleterious effect remains often questionable. This is especially true for the frequent R92Q mutation, which might not be responsible for TRAPS per se but represents a susceptibility factor to multifactorial inflammatory disorders. This study investigates TRAPS pathophysiology in a family exceptional by its size (13 members) and compares the consequences of several mutations affecting arginine 92.

Methods

TNFRSF1A screening was performed by PCR-sequencing. Comparison of the 3-dimensional structure and electrostatic properties of wild-type and mutated TNFR1 proteins was performed by in silico homology modeling. TNFR1 expression was assessed by FACS analysis, western blotting and ELISA in lysates and supernatants of HEK293T cells transiently expressing wild-type and mutated TNFR1.

Results

A TNFRSF1A heterozygous missense mutation, R92W (c.361C>T), was shown to perfectly segregate with typical TRAPS manifestations within the family investigated (p<5.10⁻⁴). It was associated with very high disease penetrance (0.9). Prediction of its impact on the protein structure revealed local conformational changes and alterations of the receptor electrostatic properties. R92W also impairs the TNFR1 expression at the cell surface and the levels of soluble receptor. Similar results were obtained with R92P, another mutation previously identified in a very small familial form with incomplete penetrance and variable expressivity. In contrast, TNFR1-R92Q behaves like the wild-type receptor.

Conclusions

These data demonstrate the pathogenicity of a mutation affecting arginine 92, a residue whose involvement in inflammatory disorders is deeply debated. Combined with previous reports on arginine 92 mutations, this study discloses an unusual situation in which different amino acid substitutions at the same position in the protein are associated with a clinical spectrum bridging Mendelian to multifactorial conditions.

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.

Tumour necrosis factor receptor trafficking dysfunction opens the TRAPS door to pro-inflammatory cytokine secretion

Cytokines are secreted from macrophages and other cells of the immune system in response to pathogens. Additionally, in autoinflammatory diseases cytokine secretion occurs in the absence of pathogenic stimuli. In the case of TRAPS [TNFR (tumour necrosis factor receptor)-associated periodic syndrome], inflammatory episodes result from mutations in the TNFRSF1A gene that encodes TNFR1. This work remains controversial, however, with at least three distinct separate mechanisms of receptor dysfunction having been proposed. Central to these hypotheses are the NF-κB (nuclear factor κB) and MAPK (mitogen-activated protein kinase) families of transcriptional activators that are able to up-regulate expression of a number of genes, including pro-inflammatory cytokines. The present review examines each proposed mechanism of TNFR1 dysfunction, and addresses how these processes might ultimately impact upon cytokine secretion and disease pathophysiology.

Setting up TRAPS

Tumour necrosis factor (TNF) receptor-associated periodic syndrome (TRAPS) is a dominantly inherited autoinflammatory disease caused by heterozygous mutations in the TNFRSF1A gene encoding for the TNF receptor 1 (TNFR1). TRAPS is a multi-faceted and heterogeneous disease which commonly manifests as recurrent episodes of high fever accompanied by abdominal pain, pleurisy, migratory rash, and myalgia. Disease attacks occur spontaneously or may be elicited by minor triggers. Because of a vigorous and sustained acute-phase response it may be complicated by systemic AA amyloidosis. Therapeutically interleukin-1 blockade seems even more promising than TNF blockade. Studies on the pathogenesis of TRAPS have shown TNFα-dependent cellular signalling to be defective, an enigmatic finding considering the hyperinflammatory phenotype of the disease. Several studies indicate that most mutated receptors never reach the cell surface but are misfolded and trapped in the endoplasmic reticulum, where they may elicit an intracellular inflammatory response, and thus lead to constitutional expression of proinflammatory cytokines. The aim of this review is to describe the current understanding of the pathogenesis of TRAPS by integrating recent clinical and laboratory data.

Role of tumour necrosis factor (TNF)-α and TNFRSF1A R92Q mutation in the pathogenesis of TNF receptor-associated periodic syndrome and multiple sclerosis

It has long been known that tumour necrosis factor (TNF)/TNFRSF1A signalling is involved in the pathophysiology of multiple sclerosis (MS). Different genetic and clinical findings over the last few years have generated renewed interest in this relationship. This paper provides an update on these recent findings. Genome-wide association studies have identified the R92Q mutation in the TNFRSF1A gene as a genetic risk factor for MS (odds ratio 1·6). This allele, which is also common in the general population and in other inflammatory conditions, therefore only implies a modest risk for MS and provides yet another piece of the puzzle that defines the multiple genetic risk factors for this disease. TNFRSF1A mutations have been associated with an autoinflammatory disease known as TNF receptor-associated periodic syndrome (TRAPS). Clinical observations have identified a group of MS patients carrying the R92Q mutation who have additional TRAPS symptoms. Hypothetically, the co-existence of MS and TRAPS or a co-morbidity relationship between the two could be mediated by this mutation. The TNFRSF1A R92Q mutation behaves as a genetic risk factor for MS and other inflammatory diseases, including TRAPS. Nevertheless, this mutation does not appear to be a severity marker of the disease, neither modifying the clinical progression of MS nor its therapeutic response. An alteration in TNF/TNFRS1A signalling may increase proinflammatory signals; the final clinical phenotype may possibly be determined by other genetic or environmental modifying factors that have not yet been identified.

Disease causing mutations in the TNF and TNFR superfamilies: Focus on molecular mechanisms driving disease

The tumor necrosis factor (TNF) and TNF receptor (TNFR) superfamilies comprise multidomain proteins with diverse roles in cell activation, proliferation and cell death. These proteins play pivotal roles in the initiation, maintenance and termination of immune responses and have vital roles outside the immune system. The discovery and analysis of diseases associated with mutations in these families has revealed crucial mechanistic details of their normal functions. This review focuses on mutations causing four different diseases, which represent distinct pathological mechanisms that can exist within these superfamilies: autoimmune lymphoproliferative syndrome (ALPS; FAS mutations), common variable immunodeficiency (CVID; TACI mutations), tumor necrosis factor receptor associated periodic syndrome (TRAPS; TNFR1 mutations) and hypohidrotic ectodermal dysplasia (HED; EDA1/EDAR mutations). In particular, we highlight how mutations have revealed information about normal receptor-ligand function and how such studies might direct new therapeutic approaches.

Long-term clinical profile of children with the low-penetrance R92Q mutation of the TNFRSF1A gene

Objective

To analyze the long-term impact of the R92Q mutation of TNFRSF1A in children with periodic fever, in comparison with children with tumor necrosis factor receptor–associated periodic syndrome (TRAPS) with TNFRSF1A structural mutations and children with periodic fever of unknown origin fulfilling the criteria for periodic fever, aphthosis, pharyngitis, and adenitis syndrome (PFAPA).

Methods

The extracellular region of TNFRSF1A was analyzed in 720 consecutive children with periodic fever, using denaturing high-performance liquid chromatography and DNA sequencing. Followup data on 11 pediatric patients with TNFRSF1A structural mutations (cysteine or T50M), 23 pediatric patients with an R92Q substitution, and 64 pediatric patients with PFAPA were collected during routine clinic visits. The 50-item Child Health Questionnaire was used to assess health-related quality of life (HRQOL).

Results

The frequency of typical TRAPS-related clinical manifestations was significantly lower and the impact of the disease on HRQOL was significantly reduced in patients with the R92Q mutation compared with TRAPS patients carrying structural mutations of TNFRSF1A. Followup data on 11 TRAPS patients with TNFRSF1A structural mutations (mean followup 7.9 years), 16 patients with theR92Q substitution (mean followup 7.3 years), and 64 patients with PFAPA (mean followup 5.2 years) were available. Patients with R92Q mutations and patients with PFAPA displayed a higher rate of self-resolution or amelioration of the fever episodes than did TRAPS patients with structural mutations.

Conclusion

Although some cases may progress to a more chronic disease course, the majority of children with an R92Q mutation of the TNFRSFA1 gene show a milder disease course than that in children with TNFRSFA1 structural mutations and have a high rate of spontaneous resolution and amelioration of the recurrent fever episodes.

A novel TNFRSF1 gene mutation in a Turkish family: a report of three cases

Tumor necrosis factor (TNF) receptor-associated periodic syndrome (TRAPS) is an autosomal dominantly inherited rare autoinflammatory disease. It is caused by mutations in exons 2-3 and 4-5 of the tumor necrosing factor receptor superfamily 1A (TNFRSF1A) gene on chromosome 12p13.2. TNFRSF1A gene encodes the 55-kDa receptor for tumor necrosis factor. Attacks are associated with abdominal pain, myalgia, erythematous skin rash, conjunctivitis, and periorbital edema. Until now, more than 80 mutations have been identified. We herein report three patients with TRAPS of Turkish origin. The patients were followed up in our outpatient clinic in Kocaeli University Division of Rheumatology. Because of their TRAPS associated clinical features, we isolated genomic DNA from whole blood and sequenced the exon 2-3 and 4-5 third exon of TNFRSF1A gene after amplification with appropriate primers. One of the patients with TRAPS was 47-year-old female, who described recurrent attacks of fever, urticarial rash, conjunctivitis, arthralgia, myalgia, abdominal pain, thoracic pain, headache, fatigue, and elevated acute phase response since her childhood. With the sequencing of the TNFRSF1A gene, we identified heterozygous C29R mutation, which has not been reported before in any TRAPS patient. The other patients are her sons with similar findings and age 29 and 26. They were heterozygous for C29R mutation in TNFRSF1A gene too. We report novel C29R mutation in three TRAPS patients of Turkish origin, in which the main clinical features are recurrent fever attacks, erythematous skin rash, conjunctivitis, myalgia, and arthralgia. Treatment with steroids resolved the symptoms and lesions.

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.

Falling into TRAPS--receptor misfolding in the TNF receptor 1-associated periodic fever syndrome

TNF receptor-associated periodic syndrome (TRAPS) is a dominantly inherited disease caused by missense mutations in the TNF receptor 1 (TNFR1) gene. Patients suffer from periodic bouts of severe abdominal pain, localised inflammation, migratory rashes, and fever. More than 40 individual mutations have been identified, all of which occur in the extracellular domain of TNFR1. In the present review we discuss new findings describing aberrant trafficking and function of TNFR1 harbouring TRAPS mutations, challenging the hypothesis that TRAPS pathology is driven by defective receptor shedding, and we suggest that TNFR1 might acquire novel functions in the endoplasmic reticulum, distinct from its role as a cell surface receptor. We also describe the clinical manifestations of TRAPS, current treatment regimens, and the widening array of patient mutations.

Elevated CD16 expression by monocytes from patients with tumor necrosis factor receptor-associated periodic syndrome

OBJECTIVE

Tumor necrosis factor receptor-associated periodic syndrome (TRAPS) is an inherited autosomal-dominant autoinflammatory condition caused by mutations in the ectodomain of the 55-kd tumor necrosis factor (TNF) receptor superfamily 1A. Proinflammatory blood monocytes with the phenotype CD14+,CD16+,HLA-DR++ are a major source of TNF, and the number of such monocytes is increased during infection and inflammation. The aim of this study was to investigate whether the expression of circulating CD16+ monocytes is affected in patients with TRAPS.

METHODS

Peripheral blood obtained from patients with TRAPS and healthy control subjects was stained with monoclonal antibodies to detect CD14++,CD16- monocytes and CD14+,CD16+ monocytes, using flow cytometry. Lipopolysaccharide-induced TNF production was measured by intracellular cytokine staining. Activation-induced shedding of CD16 was investigated by treating blood samples with phorbol myristate acetate.

RESULTS

The level of CD16 expression by CD14+,CD16+ monocytes, but not their absolute number, was significantly elevated in patients with TRAPS, even though the patients were not experiencing clinically overt episodes of autoinflammation at the time of sampling. These findings are similar to those for the C-reactive protein levels and erythrocyte sedimentation rates in the same patients. The enhanced level of CD16 expression by monocytes from patients with TRAPS was not attributable to a defect in activation-induced shedding of CD16. The CD14+,CD16+ monocytes were the predominant source of TNF in both patients and healthy control subjects.

CONCLUSION

The level of CD16 expression by monocytes was elevated in patients with TRAPS, as a feature of the underlying constitutive inflammation status.

Auto-inflammatory fever syndromes

Human autoinflammatory diseases (except for PFAPA) are a heterogeneous group of genetically determined diseases characterized by seemingly unprovoked inflammation in the absence of autoimmune or infective causes (Table 2). The last decade has witnessed tremendous advances in the understanding of these disorders. These advances have allowed therapeutic interventions resulting in improvement in the short-term and long-term morbidity of all of these diseases. Future research into the molecular mechanisms underlying these inflammatory diseases should lead to a better understanding of inflammatory diseases in general and, it is hoped, to better and more targeted therapies.

Mutant tumor necrosis factor receptor associated with tumor necrosis factor receptor-associated periodic syndrome is altered antigenically and is retained within patients' leukocytes

OBJECTIVE

To investigate the effect of mutations in tumor necrosis factor receptor superfamily member 1A (TNFRSF1A) in TNFR-associated periodic syndrome (TRAPS) on the binding of anti-TNFRSF1A monoclonal antibodies (mAb), and to investigate the subcellular distribution of mutant versus wild-type (WT) TNFRSF1A in patients with TRAPS.

METHODS

HEK 293 cells transfected with WT and/or mutant TNFRSF1A were used to investigate the interaction of anti-TNFRSF1A mAb with the WT and mutant proteins. Monoclonal antibodies that differentially bound to C33Y TNFRSF1A were used to investigate the distribution of WT and mutant TNFRSF1A in TRAPS patients with the C33Y mutation.

RESULTS

We identified a mAb whose binding to TNFRSF1A was completely abolished by the C33Y or C52F TRAPS-associated mutations, whereas other mutations (T50M, C88Y, R92Q) had lesser effects on the binding of this mAb. A different mAb was found to bind efficiently to all of the mutant forms of TNFRSF1A examined as well as to the WT receptor. Exploitation of the differential binding properties of these mAb indicated that mutant (as distinct from WT) TNFRSF1A showed abnormal intracellular retention in the neutrophils of TRAPS patients with the C33Y mutation, with little if any expression of mutant TNFRSF1A on the cell surface or as soluble receptor in plasma.

CONCLUSION

TRAPS-associated mutant TNFRSF1A has an antigenically altered structure and shows abnormal retention in the leukocytes of patients with TRAPS, which is consistent with previous findings from in vitro and transgenic model systems. This is consistent with a misfolded protein response contributing to the pathophysiology of TRAPS.

[TNF receptor-associated periodic syndrome (TRAPS) in Japan: clinical characterization, pathogenesis, diagnostic criteria, and treatment]

TNF receptor-associated periodic syndrome (TRAPS) is an autosomal dominant inherited disease characterized by prolonged episodes of periodic fever and localized inflammation. The hypothetical pathogenesis of TRAPS is defective TNF receptor 1 (TNFRSF1A) shedding from cell membranes in response to a stimulus including TNFalpha. This mechanism has recently been shown to account for a minor population of TRAPS patients and other mechanisms are reported to explain the disease, such as resistance to apoptosis, TNFRSF1A internalization, or TNFRSF1A misfolding and aggregation, leading to NF-kappaB activation and apoptosis. Until now 15 TRAPS patients from 5 pedigree including 5 different mutations (C30R, C30Y, T61I, C70S, C70G) had been reported in Japan. There were many sporadic cases of TRAPS without TNFRSF1A mutation in our epidemiological study. In this issue, we described the clinical characterization, pathogenesis, diagnostic criteria, and treatment of TRAPS according to our case and literature.

The systemic autoinflammatory diseases: inborn errors of the innate immune system

The autoinflammatory syndromes are a newly recognized group of immune disorders that lack the high titers of self-reactive antibodies and T cells characteristic of classic autoimmune disease. Nevertheless, patients with these illnesses experience unprovoked inflammatory disease in the absence of underlying infection. Here we discuss recent advances in eight Mendelian autoinflammatory diseases. The causative genes and the proteins they encode play a critical role in the regulation of innate immunity. Both pyrin and cryopyrin, the proteins mutated in familial Mediterranean fever and the cryopyrinopathies, respectively, are involved in regulation of the proinflammatory cytokine, IL-1beta, and may influence the activity of the transcription factor, NFkappaB. NOD2, the Blau syndrome protein, shares certain domains with cryopyrin and appears to be a sensor of intracellular bacteria. PSTPIP1, mutated in the syndrome of pyogenic arthritis with pyoderma gangrenosum and acne, interacts both with pyrin and a protein tyrosine phosphatase to regulate innate and adaptive immune responses. Somewhat unexpectedly, mutations in the p55 TNF receptor lead not to immunodeficiency but to dramatic inflammatory disease, the mechanisms of which are still under investigation. Finally, the discovery of the genetic basis of the hyperimmunoglobulinemia D with periodic fever syndrome has provided a fascinating but incompletely understood link between cholesterol biosynthesis and autoinflammation. In this manuscript, we summarize the current state of the art with regard to the diagnosis, pathogenesis, and treatment of these inborn errors of the innate immune system.

Pathogenesis of familial periodic fever syndromes or hereditary autoinflammatory syndromes

Familial periodic fever syndromes, otherwise known as hereditary autoinflammatory syndromes, are inherited disorders characterized by recurrent episodes of fever and inflammation. The general hypothesis is that the innate immune response in these patients is wrongly tuned, being either too sensitive to very minor stimuli or turned off too late. The genetic background of the major familial periodic fever syndromes has been unraveled, and through research into the pathophysiology, a clearer picture of the innate immune system is emerging. After an introduction on fever, interleukin-1beta and inflammasomes, which are involved in the majority of these diseases, this manuscript offers a detailed review of the pathophysiology of the cryopyrin-associated periodic syndromes, familial Mediterranean fever, the syndrome of pyogenic arthritis, pyoderma gangrenosum and acne, Blau syndrome, TNF-receptor-associated periodic syndrome and hyper-IgD and periodic fever syndrome. Despite recent major advances, there are still many questions to be answered regarding the pathogenesis of these disorders.

Abnormal disulfide-linked oligomerization results in ER retention and altered signaling by TNFR1 mutants in TNFR1-associated periodic fever syndrome (TRAPS)

Tumor necrosis factor (TNF) receptor-associated periodic syndrome (TRAPS) is an autosomal dominant systemic autoinflammatory disease associated with heterozygous mutations in TNF receptor 1 (TNFR1). Here we examined the structural and functional alterations caused by 9 distinct TRAPS-associated TNFR1 mutations in transfected cells and a mouse "knock-in" model of TRAPS. We found that these TNFR1 mutants did not generate soluble versions of the receptor, either through membrane cleavage or in exosomes. Mutant receptors did not bind TNF and failed to function as dominant-negative inhibitors of TNFR1-induced apoptosis. Instead, TRAPS mutant TNFR1 formed abnormal disulfide-linked oligomers that failed to interact with wild-type TNFR1 molecules through the preligand assembly domain (PLAD) that normally governs receptor self-association. TRAPS mutant TNFR1 molecules were retained intracellularly and colocalized with endoplasmic reticulum (ER) markers. The capacity of mutant receptors to spontaneously induce both apoptosis and nuclear factor kappaB (NF-kappaB) activity was reduced. In contrast, the R92Q variant of TNFR1 behaved like the wild-type receptor in all of these assays. The inflammatory phenotype of TRAPS may be due to consequences of mutant TNFR1 protein misfolding and ER retention.

Identifying cellular genes crucial for the reactivation of Kaposi's sarcoma-associated herpesvirus latency

Kaposi's sarcoma-associated herpesvirus (KSHV) is the latest addition to the long list of human herpesviruses. Reactivation of latent herpesvirus infections is still a mystery. It was demonstrated recently that the phorbol ester TPA was efficient in inducing a reactivation of KSHV infection in the S phase of the cell cycle. In the present study, flow cytometry-sorted, TPA-induced, KSHV-infected haematopoietic cells (BCBL-1) were used to analyse the expression profiles of cancer-related cellular genes in the S phase of the cell cycle compared with the G0/1 phase by using microarrays. Overall, the S phase of the cell cycle seems to provide KSHV with an apt environment for a productive lytic cycle of infection. The apt conditions include cellular signalling that promotes survivability, DNA replication and lipid metabolism, while blocking cell-cycle progression to M phase. Some of the important genes that were overexpressed during the S phase of the cell cycle compared with the G0/1 phase of TPA-induced BCBL-1 cells are v-myb myeloblastosis (MYBL2), protein kinase-membrane associated tyrosine/threonine 1 (PKMYT1), ribonucleotide reductase M1 polypeptide (RRM1) and peroxisome proliferator-activated receptors delta (PPARD). Inhibition of PKMYT1 expression by the use of specific short interfering RNAs significantly lowered the TPA-induced KSHV lytic cycle of infection. The significance of these and other genes in the reactivation of KSHV is discussed in the following report. Taken together, a flow cytometry-microarray-based method to study the cellular conditions critical for the reactivation of KSHV infection is reported here for the first time.

Intra-abdominal abscess in a patient with tumour necrosis factor receptor-associated periodic syndrome

Tumour necrosis factor (TNF) receptor-associated periodic syndrome (TRAPS) is an autoinflammatory disorder characterized by periodic attacks of fever and inflammation, due to mutations in the gene coding for the TNF type I receptor (TNFRSF1A). A 16-year-old patient with the diagnosis of TRAPS was admitted to hospital because of fever and abdominal pain. Initially, the symptoms were interpreted as manifestations of another TRAPS attack, but the patient's condition worsened, despite treatment with corticosteroids and antibiotics. A repeated computer tomography revealed an intra-abdominal abscess, which necessitated urgent surgical intervention. This case stresses the importance of differential diagnostic vigilance when dealing with patients with rare genetic diseases.

Modeling of tumor necrosis factor receptor superfamily 1A mutants associated with tumor necrosis factor receptor–associated periodic syndrome indicates misfolding consistent with abnormal function

OBJECTIVE

To investigate the effect of mutations in the tumor necrosis factor receptor superfamily 1A (TNFRSF1A) gene on the conformation and behavior of the TNFRSF1A protein. Mutations in TNFRSF1A cause the autosomal-dominant, autoinflammatory TNFR-associated periodic syndrome (TRAPS).

METHODS

The expression of recombinant TNFRSF1A was compared in SK-HEp-1 endothelial cells and HEK 293 epithelial cells stably transfected with full-length R347A or Deltasig constructs of wild-type or TRAPS-associated mutant TNFRSF1A. TNF binding was assessed in HEK 293 cell lines expressing R347A wild-type or mutant TNFRSF1A. Homology modeling of the 3-dimensional structure of the ectodomains of wild-type and mutant TNFRSF1A was performed.

RESULTS

TRAPS-associated mutant and wild-type TNFRSF1A behaved differently and had different localization properties within the cell, as a direct result of mutations in the ectodomains of TNFRSF1A. From a structural perspective, mutants with a predicted structure similar to that of the wild-type protein (e.g., R92Q) behaved similarly to wild-type TNFRSF1A, whereas forms of TNFRSF1A with mutations predicted to drastically destabilize the protein structure (e.g., cysteine mutations) showed defects in cell surface expression and TNF binding.

CONCLUSION

The results obtained from the in vitro experiments, in combination with the modeled structures, indicate that the phenotype and clinical differences between different TRAPS-associated mutants of TNFRSF1A result from different conformations of the TNFRSF1A ectodomains.

Neutrophils from patients withTNFRSF1A mutations display resistance to tumor necrosis factor–induced apoptosis: Pathogenetic and clinical implications

OBJECTIVE

To explore tumor necrosis factor (TNF)-induced apoptosis in neutrophils from patients with TNF receptor-associated periodic syndrome (TRAPS) and to correlate the results with the different kinds of TNFRSF1A mutations.

METHODS

Two hundred sixty-five patients with clinically suspected inherited autoinflammatory syndrome were screened for mutations of the TNFRSF1A gene. Neutrophils were isolated from heparinized blood by dextran sedimentation and incubated with and without cycloheximide (CHX) and TNFalpha. Cell apoptosis was assessed by human annexin V binding, and caspase 8 activation was assessed by flow cytometry.

RESULTS

Twenty-one patients were found to carry a variant of the TNFRSF1A gene: 13 patients had an R92Q substitution, and 8 patients presented other missense substitutions, 1 splicing mutation, and 1 in-frame interstitial deletion. Neutrophil stimulation with TNF and CHX was associated with induction of apoptosis in 12 normal controls and in 10 subjects with the R92Q mutation. Conversely, neutrophils from 8 TRAPS patients with mutations of cysteine or threonine residues or interstitial deletion did not show any induction of apoptosis after stimulation. The incidence of the R92Q mutation among patients with recurrent autoinflammatory syndromes was similar to that observed in the normal population.

CONCLUSION

Resistance to TNF-mediated apoptosis is a feature in TRAPS patients who have mutations of cysteine residues or interstitial deletion, and may play a pathogenic role. The R92Q mutation does not appear to be significantly associated with TRAPS.

Familial autoinflammatory diseases: genetics, pathogenesis and treatment

PURPOSE OF REVIEW

The systemic autoinflammatory diseases are characterized by seemingly unprovoked inflammation, without major involvement of the adaptive immune system. This review focuses mainly on a subset of these illnesses, the hereditary recurrent fevers, which include familial Mediterranean fever, the tumor necrosis factor receptor-associated periodic syndrome, the hyperimmunoglobulinemia D with periodic fever syndrome, and cryopyrin-associated periodic syndromes. This review elucidates how recent advances have impacted diagnosis, pathogenesis, and treatment.

RECENT FINDINGS

More than 170 mutations have been identified in the four genes underlying the six hereditary recurrent fevers. Genetic testing has broadened the clinical and geographic boundaries of these illnesses, given rise to the concept of the cryopyrin-associated periodic syndromes as a disease spectrum, and permitted diagnosis of compound heterozygotes for mutations in two different hereditary recurrent fever genes. Genetics has also advanced our understanding of amyloidosis, a complication of the hereditary recurrent fevers, and suggested a possible role for common hereditary recurrent fever variants in other inflammatory conditions. Recent advances in molecular pathophysiology include the elucidation of the N-terminal PYRIN domain in protein-protein interactions, the description of the NALP3 (cryopyrin) inflammasome as a macromolecular complex for interleukin-1beta activation, and the identification of signaling defects other than defective receptor shedding in patients with tumor necrosis factor receptor-associated periodic syndrome. These molecular insights form the conceptual basis for targeted biologic therapies.

SUMMARY

Advances in molecular genetics extend our ability to recognize and treat patients with systemic autoinflammatory diseases and inform our understanding of the regulation of innate immunity in humans.

Mutation of the extracellular domain of tumour necrosis factor receptor 1 causes reduced NF-κB activation due to decreased surface expression

Tumour necrosis factor receptor-associated periodic syndrome (TRAPS) results from point mutations in the extracellular domain of TNF receptor 1 (TNFRSF1A), but the effects of the mutations are controversial. This study shows that reduced NF-kappaB signalling is a feature of four TRAPS mutations. Reduced signalling correlates with reduced surface expression, measured by flow cytometry and microscopy. This suggests that correct formation of the extracellular domain of TNFRSF1A is important for localisation and receptor function. Importantly, our data provides a mechanism for the reduced TNFRSF1 signalling observed in a patient cell line.

Hereditary periodic fever syndromes

The hereditary periodic fevers are a group of Mendelian disorders characterized by seemingly unprovoked fever and localized inflammation. Recent data indicate that these illnesses represent inborn errors in the regulation of innate immunity. Pyrin, the protein mutated in familial Mediterranean fever, defines an N-terminal domain found in a large family of proteins involved in inflammation and apoptosis. Through this domain pyrin may play a role in the regulation of interleukin (IL)-1beta, nuclear factor (NF)-kappaB, and leukocyte apoptosis. Cryopyrin/NALP3, another protein in this family, is mutated in three other hereditary febrile syndromes and participates in the inflammasome, a newly recognized macromolecular complex crucial to IL-1beta activation. Somewhat unexpectedly, mutations in the 55 kDa receptor for tumor necrosis factor also give rise to a dominantly inherited periodic fever syndrome, rather than immunodeficiency, a finding that has stimulated important investigations into both pathogenesis and treatment. Finally, the discovery of the genetic basis of the hyperimmunoglobulinemia D with periodic fever syndrome suggests an as yet incompletely understood connection between the mevalonate pathway and the regulation of cytokine production. These insights extend our understanding of the regulation of innate immunity in man, while providing the conceptual basis for the rational design of targeted therapies, both for the hereditary periodic fevers themselves and other inflammatory disorders as well.