NEMO mutations in 2 unrelated boys with severe infections and conical teeth

The Awesome Power of Human Genetics of Infectious Disease

Since the identification of sickle cell trait as a heritable form of resistance to malaria, candidate gene studies, linkage analysis paired with sequencing, and genome-wide association (GWA) studies have revealed many examples of genetic resistance and susceptibility to infectious diseases. GWA studies enabled the identification of many common variants associated with small shifts in susceptibility to infectious diseases. This is exemplified by multiple loci associated with leprosy, malaria, HIV, tuberculosis, and coronavirus disease 2019 (COVID-19), which illuminate genetic architecture and implicate pathways underlying pathophysiology. Despite these successes, most of the heritability of infectious diseases remains to be explained. As the field advances, current limitations may be overcome by applying methodological innovations such as cellular GWA studies and phenome-wide association (PheWA) studies as well as by improving methodological rigor with more precise case definitions, deeper phenotyping, increased cohort diversity, and functional validation of candidate loci in the laboratory or human challenge studies.

Periodontal status of children with primary immunodeficiencies: a systematic review

OBJECTIVE

The aim of this systematic review was to appraise the existing literature on periodontal disease in children affected by different types of neutrophil-associated primary immunodeficiencies (PIDs).

METHODS

A PRESS-validated search strategy was developed to search through databases MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, LILACS, Google Scholar and Open Grey. All included studies were assessed for methodological quality and risk of bias.

RESULTS

One hundred eighteen articles reporting on 160 PID patients were included for qualitative analysis. The majority (70%) were individual case reports. Clinical and radiographic manifestations of the periodontal disease included poor oral hygiene, generalised alveolar bone loss, severe gingival inflammation, increased pocket depths, tooth mobility and gingival recession. For most studies, the primary intervention was periodontal treatment in the form of scaling and root planing or dental extractions. Stabilisation of the periodontal condition varied between different PIDs. In severe congenital neutropenia (SCN), 61% of cases reported stabilisation of the periodontal condition, while for all other PIDs, 'stability' was reported in less than 43% of cases.

CONCLUSION

The published literature suggests that patients with PIDs can present with severe periodontitis and that conventional treatment approaches have limited benefits.

Rescue of recurrent deep intronic mutation underlying cell type-dependent quantitative NEMO deficiency

X-linked dominant incontinentia pigmenti (IP) and X-linked recessive anhidrotic ectodermal dysplasia with immunodeficiency (EDA-ID) are caused by loss-of-function and hypomorphic IKBKG (also known as NEMO) mutations, respectively. We describe a European mother with mild IP and a Japanese mother without IP, whose 3 boys with EDA-ID died from ID. We identify the same private variant in an intron of IKBKG, IVS4+866 C>T, which was inherited from and occurred de novo in the European mother and Japanese mother, respectively. This mutation creates a new splicing donor site, giving rise to a 44-nucleotide pseudoexon (PE) generating a frameshift. Its leakiness accounts for NF-κB activation being impaired but not abolished in the boys' cells. However, aberrant splicing rates differ between cell types, with WT NEMO mRNA and protein levels ranging from barely detectable in leukocytes to residual amounts in induced pluripotent stem cell-derived (iPSC-derived) macrophages, and higher levels in fibroblasts and iPSC-derived neuronal precursor cells. Finally, SRSF6 binds to the PE, facilitating its inclusion. Moreover, SRSF6 knockdown or CLK inhibition restores WT NEMO expression and function in mutant cells. A recurrent deep intronic splicing mutation in IKBKG underlies a purely quantitative NEMO defect in males that is most severe in leukocytes and can be rescued by the inhibition of SRSF6 or CLK.

Clinical presentation, immunologic features, and hematopoietic stem cell transplant outcomes for IKBKB immune deficiency

IKBKB immune deficiency is a rare but life-threatening primary immunodeficiency disorder, involving activation defects in adaptive and innate immunity. We present sixteen cases of a homozygous IKBKB mutation (c.1292dupG) in infants characterized by early-onset bacterial, viral, fungal and Mycobacterial infections. In most cases, T- and B-cells were quantitatively normal, but phenotypically naïve, with severe hypogammaglobulinemia. T-cell receptor excision circles were normal, meaning newborn screening by TREC analysis would miss IKBKB cases. Although IKBKB immune deficiency does not meet traditional laboratory based definitions for SCID, this combined immune deficiency appears to be at least as profound. Urgent HSCT, performed in eight patients, remains the only known curative therapy, although only three patients are survivors. Ongoing infections after transplant remain a concern, and may be due to combinations of poor social determinants of health, secondary graft failure, and failure of HSCT to replace non-hematopoietic cells important in immune function and dependent upon IKK/NF-κB pathways.

The Changing Landscape in the Genetic Etiology of Human Tooth Agenesis

Despite much progress in understanding the genetics of syndromic tooth agenesis (TA), the causes of the most common, isolated TA remain elusive. Recent studies have identified novel genes and variants contributing to the etiology of TA, and revealed new pathways in which tooth development genes belong. Further, the use of new research approaches including next-generation sequencing has provided increased evidence supporting an oligogenic inheritance model for TA, and may explain the phenotypic variability of the condition. In this review, we present current knowledge about the genetic mechanisms underlying syndromic and isolated TA in humans, and highlight the value of incorporating next-generation sequencing approaches to identify causative and/or modifier genes that contribute to the etiology of TA.

Functional Evaluation of an IKBKG Variant Suspected to Cause Immunodeficiency Without Ectodermal Dysplasia

Hypomorphic IKBKG mutations in males are typically associated with anhidrotic ectodermal dysplasia with immunodeficiency (EDA-ID). Some mutations cause immunodeficiency without EDA (NEMO-ID). The immunological profile associated with these NEMO-ID variants is not fully documented. We present a 2-year-old patient with suspected immunodeficiency in which a hemizygous p.Glu57Lys IKBKG variant was identified. At the age of 1 year, he had an episode of otitis media that evolved into a bilateral mastoiditis (Pseudomonas spp). Hypogammaglobulinemia, specific (polysaccharide) antibody deficiency, and low switched memory B cell subsets were noticed. The mother was heterozygous for the variant but had no signs of incontinentia pigmenti. Patient peripheral blood mononuclear cells produced low amounts of IL-6 after stimulation with IL-1β, Pam₃CSK_4, and FSL-1. In patient fibroblasts, IκB-α was degraded normally upon stimulation with IL-1β or TNF-α. Transduction of wild-type and variant NEMO in NEMO^-/- deficient SV40 fibroblasts revealed a slight but significant reduction of IL-6 production upon stimulation with IL-1β and TNF-α. In conclusion, we demonstrated that p.Glu57Lys leads to specific immunological defects in vitro. No other pathogenic PID variants were identified through whole exome sequencing. As rare polymorphisms have been described in IKBKG and polygenic inheritance remains an option in the presented case, this study emphasizes the need for thorough functional and genetic evaluation when encountering and interpreting suspected disease-causing NEMO-ID variants.

Human IκBα Gain of Function: a Severe and Syndromic Immunodeficiency

Germline heterozygous gain-of-function (GOF) mutations of NFKBIA, encoding IκBα, cause an autosomal dominant (AD) form of anhidrotic ectodermal dysplasia with immunodeficiency (EDA-ID). Fourteen unrelated patients have been reported since the identification of the first case in 2003. All mutations enhanced the inhibitory activity of IκBα, by preventing its phosphorylation on serine 32 or 36 and its subsequent degradation. The mutation certainly or probably occurred de novo in 13 patients, whereas it was inherited from a parent with somatic mosaicism in one patient. Eleven mutations, belonging to two groups, were identified: (i) missense mutations affecting S32, S36, or neighboring residues (8 mutations, 11 patients) and (ii) nonsense mutations upstream from S32 associated with the reinitiation of translation downstream from S36 (3 mutations, 3 patients). Thirteen patients had developmental features of EDA, the severity and nature of which differed between cases. All patient cells tested displayed impaired NF-κB-mediated responses to the stimulation of various surface receptors involved in cell-intrinsic (fibroblasts), innate (monocytes), and adaptive (B and T cells) immunity, including TLRs, IL-1Rs, TNFRs, TCR, and BCR. All patients had profound B-cell deficiency. Specific immunological features, found in some, but not all patients, included a lack of peripheral lymph nodes, lymphocytosis, dysfunctional α/β T cells, and a lack of circulating γ/δ T cells. The patients had various pyogenic, mycobacterial, fungal, and viral severe infections. Patients with a missense mutation tended to display more severe phenotypes, probably due to higher levels of GOF proteins. In the absence of hematopoietic stem cell transplantation (HSCT), this condition cause death before the age of 1 year (one child). Two survivors have been on prophylaxis (at 9 and 22 years). Six children died after HSCT. Five survived, four of whom have been on prophylaxis (3 to 21 years post HSCT), whereas one has been well with no prophylaxis. Heterozygous GOF mutations in IκBα underlie a severe and syndromic immunodeficiency, the interindividual variability of which might partly be ascribed to the dichotomy of missense and nonsense mutations, and the hematopoietic component of which can be rescued by HSCT.

Lack of interaction between NEMO and SHARPIN impairs linear ubiquitination and NF-κB activation and leads to incontinentia pigmenti

BACKGROUND

Incontinentia pigmenti (IP; MIM308300) is a severe, male-lethal, X-linked, dominant genodermatosis resulting from loss-of-function mutations in the IKBKG gene encoding nuclear factor κB (NF-κB) essential modulator (NEMO; the regulatory subunit of the IκB kinase [IKK] complex). In 80% of cases of IP, the deletion of exons 4 to 10 leads to the absence of NEMO and total inhibition of NF-κB signaling. Here we describe a new IKBKG mutation responsible for IP resulting in an inactive truncated form of NEMO.

OBJECTIVES

We sought to identify the mechanism or mechanisms by which the truncated NEMO protein inhibits the NF-κB signaling pathway.

METHODS

We sequenced the IKBKG gene in patients with IP and performed complementation and transactivation assays in NEMO-deficient cells. We also used immunoprecipitation assays, immunoblotting, and an in situ proximity ligation assay to characterize the truncated NEMO protein interactions with IKK-α, IKK-β, TNF receptor-associated factor 6, TNF receptor-associated factor 2, receptor-interacting protein 1, Hemo-oxidized iron regulatory protein 2 ligase 1 (HOIL-1), HOIL-1-interacting protein, and SHANK-associated RH domain-interacting protein. Lastly, we assessed NEMO linear ubiquitination using immunoblotting and investigated the formation of NEMO-containing structures (using immunostaining and confocal microscopy) after cell stimulation with IL-1β.

RESULTS

We identified a novel splice mutation in IKBKG (c.518+2T>G, resulting in an in-frame deletion: p.DelQ134_R256). The mutant NEMO lacked part of the CC1 coiled-coil and HLX2 helical domain. The p.DelQ134_R256 mutation caused inhibition of NF-κB signaling, although the truncated NEMO protein interacted with proteins involved in activation of NF-κB signaling. The IL-1β-induced formation of NEMO-containing structures was impaired in fibroblasts from patients with IP carrying the truncated NEMO form (as also observed in HOIL-1^-/- cells). The truncated NEMO interaction with SHANK-associated RH domain-interacting protein was impaired in a male fetus with IP, leading to defective linear ubiquitination.

CONCLUSION

We identified a hitherto unreported disease mechanism (defective linear ubiquitination) in patients with IP.

Myeloid Deletion of Nemo Causes Osteopetrosis in Mice Owing to Upregulation of Transcriptional Repressors

The transcription factor NF-κB is central to numerous physiologic processes including bone development, and its activation is controlled by IKKγ (also called NEMO), the regulatory subunit of IKK complex. NEMO is X-linked, and mutations in this gene result in Incontinentia Pigmenti in human hemizygous females. In mice, global deficiency causes embryonic lethality. In addition, certain point mutations in the NEMO (IKBKG) human gene manifest skeletal defects implicating NEMO in the regulation of bone homeostasis. To specifically investigate such role, we conditionally deleted Nemo from osteoclast and myeloid progenitors. Morphometric, histologic, and molecular analyses demonstrate that myeloid NEMO deletion causes osteopetrosis in mice. Mechanistically, NEMO deficiency hampered activation of IKK complex in osteoclast precursors, causing arrest of osteoclastogenesis and apoptosis. Interestingly, inhibiting apoptosis by genetic ablation of TNFr1 significantly increased cell survival, but failed to rescue osteoclastogenesis or reverse osteopetrosis. Based on this observation, we analyzed the expression of different regulators of osteoclastogenesis and discovered that NEMO deletion leads to increased RBPJ expression, resulting in a decrease of Blimp1 expression. Consequently, expression of IRF8 and Bcl6 which are targets of Blimp1 and potent osteoclastogenic transcriptional repressors, is increased. Thus, NEMO governs survival and osteoclast differentiation programs through serial regulation of multiple transcription factors.

Toll-like receptor signaling in primary immune deficiencies

Toll-like receptors (TLRs) recognize common microbial or host-derived macromolecules and have important roles in early activation of the immune system. Patients with primary immune deficiencies (PIDs) affecting TLR signaling can elucidate the importance of these proteins to the human immune system. Defects in interleukin-1 receptor-associated kinase-4 and myeloid differentiation factor 88 (MyD88) lead to susceptibility to infections with bacteria, while mutations in nuclear factor-κB essential modulator (NEMO) and other downstream mediators generally induce broader susceptibility to bacteria, viruses, and fungi. In contrast, TLR3 signaling defects are specific for susceptibility to herpes simplex virus type 1 encephalitis. Other PIDs induce functional alterations of TLR signaling pathways, such as common variable immunodeficiency in which plasmacytoid dendritic cell defects enhance defective responses of B cells to shared TLR agonists. Dampening of TLR responses is seen for TLRs 2 and 4 in chronic granulomatous disease (CGD) and X-linked agammaglobulinemia (XLA). Enhanced TLR responses, meanwhile, are seen for TLRs 5 and 9 in CGD, TLRs 4, 7/8, and 9 in XLA, TLRs 2 and 4 in hyper IgE syndrome, and for most TLRs in adenosine deaminase deficiency.

EDA-ID and IP, two faces of the same coin: how the same IKBKG/NEMO mutation affecting the NF-κB pathway can cause immunodeficiency and/or inflammation

Anhidrotic Ectodermal Dysplasia with ImmunoDeficiency (EDA-ID, OMIM 300291) and Incontinentia Pigmenti (IP, OMIM 308300) are two rare diseases, caused by mutations of the IKBKG/NEMO gene. The protein NEMO/IKKγ is essential for the NF-κB activation pathway, involved in a variety of physiological and cellular processes, such as immunity, inflammation, cell proliferation, and survival. A wide spectrum of IKBKG/NEMO mutations have been identified so far, and, on the basis of their effect on NF-κB activation, they are considered hypomorphic or amorphic (loss of function) mutations. IKBKG/NEMO hypomorphic mutations, reducing but not abolishing NF-κB activation, have been identified in EDA-ID and IP patients. Instead, the amorphic mutations, abolishing NF-κB activation by complete IKBKG/NEMO gene silencing, cause only IP. Here, we present an overview of IKBKG/NEMO mutations in EDA-ID and IP patients and describe similarities and differences between the clinical/immunophenotypic and genetic aspects, highlighting any T and B lymphocyte defect, and paying particular attention to the cellular and molecular defects that underlie the pathogenesis of both diseases.

Value of allohaemagglutinins in the diagnosis of a polysaccharide antibody deficiency

Polysaccharide antibody deficiency is characterized by a poor or absent antibody response after vaccination with an unconjugated pneumococcal polysaccharide vaccine. Allohaemagglutinins (AHA) are antibodies to A or B polysaccharide antigens on the red blood cells, and are often used as an additional or alternative measure to assess the polysaccharide antibody response. However, few studies have been conducted to establish the clinical significance of AHA. To investigate the value of AHA to diagnose a polysaccharide antibody deficiency, pneumococcal polysaccharide antibody titres and AHA were studied retrospectively in 180 subjects in whom both tests had been performed. Receiver operating characteristic curves for AHA versus the pneumococcal vaccine response as a marker for the anti-polysaccharide immune response revealed an area under the curve between 0·5 and 0·573. Sensitivity and specificity of AHA to detect a polysaccharide antibody deficiency, as diagnosed by vaccination response, were low (calculated for cut-off 1/4-1/32). In subjects with only low pneumococcal antibody response, the prevalence of bronchiectasis was significantly higher than in subjects with only low AHA (45·5 and 1·3%, respectively) or normal pneumococcal antibody response and AHA (2·4%). A logistic regression model showed that low pneumococcal antibody response but not AHA was associated with bronchiectasis (odds ratio 46·2). The results of this study do not support the routine use of AHA to assess the polysaccharide antibody response in patients with suspected immunodeficiency, but more studies are warranted to clarify the subject further.

Correlating interleukin-12 stimulated interferon-γ production and the absence of ectodermal dysplasia and anhidrosis (EDA) in patients with mutations in NF-κB essential modulator (NEMO)

OBJECTIVE

Patients with hypomorphic mutations in Nuclear Factor-κB Essential Modulator (NEMO) are immunodeficient (ID) and most display ectodermal dysplasia and anhidrosis (EDA). We compared cytokine production by NEMO-ID patients with and without EDA.

METHODS

PBMCs of NEMO-ID patients, four with EDA carrying E315A, C417R, D311N and Q403X, and three without EDA carrying E315A, E311_L333del and R254G, were cultured with PHA, PHA plus IL-12p70, LPS, LPS plus IFN-γ, TNF and IL-1β. The production of various cytokines was measured in the supernatants. Fifty-nine healthy individuals served as controls.

RESULTS

PBMCs of NEMO-ID patients without EDA produce subnormal amounts of IFN-γ after stimulation with PHA, but normal amounts of IFN-γ after PHA plus IL-12p70. In contrast, IFN-γ production by patients with EDA was low in both cases. Patients with EDA also generate lower PHA-stimulated IL-10 and IL-1β than controls, whereas the production of these cytokines by patients without EDA was normal.

CONCLUSION

Responses of PBMCs in NEMO-ID patients with EDA to PHA with and without IL-12p70 appear less robust than in NEMO-ID patients without EDA. This possibly indicates a better preserved NEMO function in our patients without EDA.

Novel missense mutations in the AXIN2 gene associated with non-syndromic oligodontia

OBJECTIVE

Oligodontia, which is the congenital absence of six or more permanent teeth excluding third molars, may contribute to masticatory dysfunction, speech alteration, aesthetic problems and malocclusion. To date, mutations in EDA, AXIN2, MSX1, PAX9, WNT10A, EDAR, EDARADD, NEMO and KRT 17 are known to associate with non-syndromic oligodontia. The aim of the study was to search for AXIN2 mutations in 96 patients with non-syndromic oligodontia.

DESIGN

We performed mutation analysis of 10 exons of the AXIN2 gene in 96 patients with isolated non-syndromic oligodontia.

RESULTS

We identified two novel missense mutations (Exon 3 c.923C>T and Exon 11 c.2490G>C) in two patients. One mutation (c.923C>T) results in a Thr308Met substitution and the other mutation (c.2490G>C) results in a Met830Ile substitution.

CONCLUSIONS

This is the first report indicating that mutations in AXIN2 are responsible for oligodontia in the Chinese population. Our findings indicate that AXIN2 can be regarded as a candidate gene for mutation detection in individuals with non-syndromic oligodontia in the Chinese population.

Genetic background of nonsyndromic oligodontia: a systematic review and meta-analysis

OBJECTIVES

The goal of this work was to identify all known gene mutations that have been associated with the development of nonsyndromic oligodontia.

METHODS

A systematic literature search was performed electronically in two databases (PubMed, Medpilot) supplemented by a hand search. Articles published up to March 2012 were considered. Search terms were combined as follows: oligodontia and genes, oligodontia and mutations, tooth agenesis and genes, and tooth agenesis and mutations. A meta-analysis of the data was conducted based on the Tooth Agenesis Code (TAC).

RESULTS

Seven genes are currently known to have a potential for causing nonsyndromic oligodontia. All these genes vary both in terms of number of identified mutations and in terms of number of documented patients: 33 mutations and 93 patients are on record for PAX9, 10 mutations and 51 patients for EDA, 12 mutations and 33 patients for MSX1, 6 mutations and 17 patients for AXIN2, and 1 mutation in 1 patient for EDARADD, NEMO, and KRT17 each. A total TAC score of 250 was found to have cutoff properties, as 100% of MSX1 and 80% of EDA patients exhibited TAC ≤ 250, whereas 96.9% of PAX9 and 90% of AXIN2 patients exhibited TAC >250. Furthermore, 94.3% of EDA patients but only 28.6% of MSX1 patients exhibited odd-numbered TAC scores in at least one quadrant, and 72.7% of PAX9 but none of the AXIN2 patients were found to show TAC scores of 112 in at least one quadrant.

CONCLUSION

In order of decreasing frequency, PAX9, EDA, MSX1, AXIN2, EDARADD, NEMO, and KRT17 are the seven genes currently known to have a potential for causing nonsyndromic oligodontia. TAC scores enabled us to identify an association between oligodontia phenotypes and genotypes in the patients covered by this meta-analysis.

Genetic lessons learned from X-linked Mendelian susceptibility to mycobacterial diseases

Mendelian susceptibility to mycobacterial disease (MSMD) is a rare syndrome conferring predisposition to clinical disease caused by weakly virulent mycobacteria, such as Mycobacterium bovis Bacille Calmette Guérin (BCG) vaccines and nontuberculous, environmental mycobacteria (EM). Since 1996, MSMD-causing mutations have been found in six autosomal genes involved in IL-12/23-dependent, IFN-γ-mediated immunity. The aim of this review is to provide the description of the two described forms of X-linked recessive (XR) MSMD. Germline mutations in two genes, NEMO and CYBB, have long been known to cause other human diseases-incontinentia pigmenti (IP) and anhidrotic ectodermal dysplasia with immunodeficiency (EDA-ID) (NEMO/IKKG), and X-linked chronic granulomatous disease (CGD) (CYBB)-but specific mutations in either of these two genes have recently been shown to cause XR-MSMD. NEMO is an essential component of several NF-κB-dependent signaling pathways. The MSMD-causing mutations in NEMO selectively affect the CD40-dependent induction of IL-12 in mononuclear cells. CYBB encodes gp91(phox) , which is an essential component of the NADPH oxidase in phagocytes. The MSMD-causing mutation in CYBB selectively affects the respiratory burst in macrophages. Mutations in NEMO and CYBB may therefore cause MSMD by selectively exerting their deleterious impact on a single signaling pathway (CD40-IL-12, NEMO) or a single cell type (macrophages, CYBB). These experiments of Nature illustrate how specific germline mutations in pleiotropic genes can dissociate signaling pathways or cell lineages, thereby resulting in surprisingly narrow clinical phenotypes.

The pathology of Mycobacterium tuberculosis infection

Mycobacterium tuberculosis is an old enemy of the human race, with evidence of infection observed as early as 5000 years ago. Although more host-restricted than Mycobacterium bovis, which can infect all warm-blooded vertebrates, M. tuberculosis can infect, and cause morbidity and mortality in, several veterinary species as well. As M. tuberculosis is one of the earliest described bacterial pathogens, the literature describing this organism is vast and overwhelming. This review strives to distill what is currently known about this bacterium and the disease it causes for the veterinary pathologist.

Infectious diseases in patients with IRAK-4, MyD88, NEMO, or IκBα deficiency

Autosomal recessive IRAK-4 and MyD88 deficiencies predispose affected patients to recurrent invasive pyogenic bacterial infection. Both defects result in the selective impairment of cellular responses to Toll-like receptors (TLRs) other than TLR3 and of cellular responses to most interleukin-1 receptors (IL-1Rs), including IL-1R, IL-18R, and IL-33R. Hypomorphic mutations in the X-linked NEMO gene and hypermorphic mutations in the autosomal IKBA gene cause X-linked recessive and autosomal dominant anhidrotic ectodermal dysplasia with immunodeficiency (EDA-ID) syndromes. Both of these defects impair NF-κB-mediated cellular responses to multiple receptors, including TLRs, IL-1Rs, and tumor necrosis factor receptors (TNF-Rs). They therefore confer a much broader predisposition to infections than that for IRAK-4 and MyD88 deficiencies. These disorders were initially thought to be rare but have now been diagnosed in over 170 patients worldwide. We review here the infectious diseases affecting patients with inborn errors of NF-κB-dependent TLR and IL-1R immunity.

Pathogenesis and pathophysiology of pneumococcal meningitis

Pneumococcal meningitis continues to be associated with high rates of mortality and long-term neurological sequelae. The most common route of infection starts by nasopharyngeal colonization by Streptococcus pneumoniae, which must avoid mucosal entrapment and evade the host immune system after local activation. During invasive disease, pneumococcal epithelial adhesion is followed by bloodstream invasion and activation of the complement and coagulation systems. The release of inflammatory mediators facilitates pneumococcal crossing of the blood-brain barrier into the brain, where the bacteria multiply freely and trigger activation of circulating antigen-presenting cells and resident microglial cells. The resulting massive inflammation leads to further neutrophil recruitment and inflammation, resulting in the well-known features of bacterial meningitis, including cerebrospinal fluid pleocytosis, cochlear damage, cerebral edema, hydrocephalus, and cerebrovascular complications. Experimental animal models continue to further our understanding of the pathophysiology of pneumococcal meningitis and provide the platform for the development of new adjuvant treatments and antimicrobial therapy. This review discusses the most recent views on the pathophysiology of pneumococcal meningitis, as well as potential targets for (adjunctive) therapy.

NEMO is a key component of NF-κB- and IRF-3-dependent TLR3-mediated immunity to herpes simplex virus

BACKGROUND

Children with germline mutations in Toll-like receptor 3 (TLR3), UNC93B1, TNF receptor-associated factor 3, and signal transducer and activator of transcription 1 are prone to herpes simplex virus-1 encephalitis, owing to impaired TLR3-triggered, UNC-93B-dependent, IFN-α/β, and/or IFN-λ-mediated signal transducer and activator of transcription 1-dependent immunity.

OBJECTIVE

We explore here the molecular basis of the pathogenesis of herpes simplex encephalitis in a child with a hypomorphic mutation in nuclear factor-κB (NF-κB) essential modulator, which encodes the regulatory subunit of the inhibitor of the Iκβ kinase complex.

METHODS

The TLR3 signaling pathway was investigated in the patient's fibroblasts by analyses of IFN-β, IFN-λ, and IL-6 mRNA and protein levels, by quantitative PCR and ELISA, respectively, upon TLR3 stimulation (TLR3 agonists or TLR3-dependent viruses). NF-κB activation was assessed by electrophoretic mobility shift assay and interferon regulatory factor 3 dimerization on native gels after stimulation with a TLR3 agonist.

RESULTS

The patient's fibroblasts displayed impaired responses to TLR3 stimulation in terms of IFN-β, IFN-λ, and IL-6 production, owing to impaired activation of both NF-κB and IRF-3. Moreover, vesicular stomatitis virus, a potent IFN-inducer in human fibroblasts, and herpes simplex virus-1, induced only low levels of IFN-β and IFN-λ in the patient's fibroblasts, resulting in enhanced viral replication and cell death, as reported for UNC-93B-deficient fibroblasts.

CONCLUSION

Herpes simplex encephalitis may occur in patients carrying NF-κB essential modulator mutations, due to the impairment of NF-κB- and interferon regulatory factor 3-dependent-TLR3-mediated antiviral IFN production.

Disseminated BCG infection mimicking metastatic nasopharyngeal carcinoma in an immunodeficient child with a novel hypomorphic NEMO mutation

BACKGROUND

Nuclear factor-κB essential modulator (NEMO) deficiency is a developmental and immunological disorder. The genetic and phenotypic correlation has been described.

METHODS

We report a unique clinical presentation and the identification of a novel missense mutation in the NEMO gene in a 3-year-old boy with bacillus Calmette-Guerin (BCG) infection.

RESULTS

The patient presented with fever, cervical lymphadenopathy, and abnormal anti-Epstein-Barr virus (EBV) antibody titers, suggestive of EBV-related diseases including chronic active EBV infection, X-linked lymphoproliferative syndrome, or nasopharyngeal carcinoma. Although the biopsy specimen from a nasopharyngeal lesion was initially diagnosed as squamous cell carcinoma, this was changed to disseminated BCG infection involving the nasopharynx, multiple systemic lymph nodes, and brain. A novel mutation (designated D311E) in the NEMO gene, located in the NEMO ubiquitin-binding (NUB) domain, was identified as the underlying cause of the immunodeficiency. Impaired immune responses which are characteristic of patients with NEMO deficiency were demonstrated. The patient underwent successful unrelated bone marrow transplantation at 4.9 years of age.

CONCLUSION

This study suggests the importance of the NUB domain in host defense against mycobacteria. The unique presenting features in our patient indicate that a hypomorphic NEMO mutation can be associated with atypical pathological findings of the epithelial tissues in patients with BCG infection.

Human TLRs and IL-1Rs in host defense: natural insights from evolutionary, epidemiological, and clinical genetics

Toll-like receptors (TLRs) and interleukin-1 receptors (IL-1Rs) have TIR intracellular domains that engage two main signaling pathways, via the TIR-containing adaptors MyD88 (which is not used by TLR3) and TRIF (which is used only by TLR3 and TLR4). Extensive studies in inbred mice in various experimental settings have attributed key roles in immunity to TLR- and IL-1R-mediated responses, but what contribution do human TLRs and IL-1Rs actually make to host defense in the natural setting? Evolutionary genetic studies have shown that human intracellular TLRs have evolved under stronger purifying selection than surface-expressed TLRs, for which the frequency of missense and nonsense alleles is high in the general population. Epidemiological genetic studies have yet to provide convincing evidence of a major contribution of common variants of human TLRs, IL-1Rs, or their adaptors to host defense. Clinical genetic studies have revealed that rare mutations affecting the TLR3-TRIF pathway underlie herpes simplex virus encephalitis, whereas mutations in the TIR-MyD88 pathway underlie pyogenic bacterial diseases in childhood. A careful reconsideration of the contributions of TLRs and IL-1Rs to host defense in natura is required.

New mechanism of X-linked anhidrotic ectodermal dysplasia with immunodeficiency: impairment of ubiquitin binding despite normal folding of NEMO protein

Nuclear factor-κB essential modulator (NEMO), the regulatory subunit of the IκB kinase complex, is a critical component of the NF-κB pathway. Hypomorphic mutations in the X-linked human NEMO gene cause various forms of anhidrotic ectodermal dysplasia with immunodeficiency (EDA-ID). All known X-linked EDA-ID-causing mutations impair NEMO protein expression, folding, or both. We describe here 2 EDA-ID-causing missense mutations that affect the same residue in the CC2-LZ domain (D311N and D311G) that do not impair NEMO production or folding. Structural studies based on pull-down experiments showed a defect in noncovalent interaction with K63-linked and linear polyubiquitin chains for these mutant proteins. Functional studies on the patients' cells showed an impairment of the classic NF-κB signaling pathways after activation of 2 NEMO ubiquitin-binding-dependent receptors, the TNF and IL-1β receptors, and in the CD40-dependent NF-κB pathway. We report the first human NEMO mutations responsible for X-linked EDA-ID found to affect the polyubiquitin binding of NEMO rather than its expression and folding. These experiments demonstrate that the binding of human NEMO to polyubiquitin is essential for NF-κB activation. They also demonstrate that the normal expression and folding of NEMO do not exclude a pathogenic role for NEMO mutations in patients with EDA-ID.

Impediment of NEMO oligomerization inhibits osteoclastogenesis and osteolysis

The transcription factor NF-kappaB is essential for osteoclastogenesis and is considered an immune-modulator of rheumatoid arthritis and inflammatory osteolysis. Activation of NF-kappaB subunits is regulated by the upstream IkappaB kinase (IKK) complex which contains IKKalpha, IKKbeta, and IKKgamma; the latter also known as NF-kappaB essential modulator (NEMO). The role of IKKalpha and IKKbeta in the skeletal development and inflammatory osteolysis has been described, whereas little is known regarding the role of NEMO in this setting. Typically, signals induced by RANK ligand (RANKL) or TNF prompt oligomerization of NEMO monomers through the coiled-coil-2 (CC2) and leucine zipper (LZ) motifs. This step facilitates binding to IKKs and further relaying signal transduction. Given the central role of NF-kappaB in osteoclastogenesis, we asked whether NEMO is essential for osteoclastogenesis and whether interruption of NEMO oligomerization impedes osteoclast differentiation in vitro and in vivo. Using cell-permeable short peptides overlapping the CC2 and LZ motifs we show that these peptides specifically bind to NEMO monomers, prevent trimer formation, and render NEMO monomers susceptible for ubiquitin-mediated degradation. Further, CC2 and LZ peptides attenuate RANKL- and TNF-induced NF-kappaB signaling in bone marrow-derived osteoclast precursors (OCPs). More importantly, these peptides potently inhibit osteoclastogenesis, in vitro, and arrest RANKL-induced osteolysis, in mice. To further ascertain its role in osteoclastogenesis, we were able to block osteoclastogenesis using NEMO siRNA knockdown approach. Collectively, our data establish that obstruction of NEMO oligomerization destabilizes NEMO monomers, inhibits NF-kappaB activation, impedes osteoclastogenesis and arrests inflammatory osteolysis. Thus, NEMO presents itself as a promising target for anti-osteolytic intervention.

Genetic deficiencies of innate immune signalling in human infectious disease

The type-1 cytokine (interleukin 12, interleukin 23, interferon gamma, interleukin 17) signalling pathway is triggered during infection by activation of phagocyte-expressed pattern-recognition receptors that recognise specific pathogen-associated molecular patterns. Triggering of this pathway results, among other things, in activation of microbicidal mechanisms in phagocytic cells. Individuals with a deficiency in one of the proteins in the pathway are unusually susceptible to otherwise poorly pathogenic, mostly environmental, mycobacteria and salmonellae. Individuals with deficiencies in other innate immune signalling proteins show unusual susceptibility to pathogens other than mycobacteria or salmonellae. We discuss recent insights into key molecules involved in type-1 cytokine signalling pathways and provide an update on the molecular genetic defects underlying mendelian susceptibility to mycobacterial disease. We also discuss deficiencies in the innate immune signalling proteins that lead to susceptibility to other pathogens. Knowledge of innate immune signalling has allowed the identification of defects in such patients. However, some patients have enhanced susceptibility to pathogens even though no mutations have been found in the candidate genes identified thus far. Whereas a few patients might have autoantibodies against type-1 cytokines, others might harbour mutations in new genes and pathways that still need to be identified.

ORAI1 and STIM1 deficiency in human and mice: roles of store-operated Ca2+ entry in the immune system and beyond

Store-operated Ca2+ entry (SOCE) is a mechanism used by many cells types including lymphocytes and other immune cells to increase intracellular Ca2+ concentrations to initiate signal transduction. Activation of immunoreceptors such as the T-cell receptor, B-cell receptor, or Fc receptors results in the release of Ca2+ ions from endoplasmic reticulum (ER) Ca2+ stores and subsequent activation of plasma membrane Ca2+ channels such as the well-characterized Ca2+ release-activated Ca2+ (CRAC) channel. Two genes have been identified that are essential for SOCE: ORAI1 as the pore-forming subunit of the CRAC channel in the plasma membrane and stromal interaction molecule-1 (STIM1) sensing the ER Ca2+ concentration and activating ORAI1-CRAC channels. Intense efforts in the past several years have focused on understanding the molecular mechanism of SOCE and the role it plays for cell functions in vitro and in vivo. A number of transgenic mouse models have been generated to investigate the role of ORAI1 and STIM1 in immunity. In addition, mutations in ORAI1 and STIM1 identified in immunodeficient patients provide valuable insight into the role of both genes and SOCE. This review focuses on the role of ORAI1 and STIM1 in vivo, discussing the phenotypes of ORAI1- and STIM1-deficient human patients and mice.

DARPin-assisted crystallography of the CC2-LZ domain of NEMO reveals a coupling between dimerization and ubiquitin binding

NEMO is an integral part of the IkappaB kinase complex and serves as a molecular switch by which the NF-kappaB signaling pathway can be regulated. Oligomerization and polyubiquitin (poly-Ub) binding, mediated through the regulatory CC2-LZ domain, were shown to be key features governing NEMO function, but the relationship between these two activities remains unclear. In this study, we solved the structure of this domain in complex with a designed ankyrin repeat protein, which helps its crystallization. We generated several NEMO mutants in this domain, including those associated with human diseases incontinentia pigmenti and immunodeficiency with or without anhidrotic ectodermal dysplasia. Analytical ultracentrifugation and thermal denaturation experiments were used to evaluate the dimerization properties of these mutants. A fluorescence-based assay was developed, as well, to quantify the interaction to monoubiquitin and poly-Ub chains. Moreover, the effect of these mutations was investigated for the full-length protein. We show that a proper folding of the ubiquitin-binding domain, termed NOA/UBAN/NUB, into a stable coiled-coil dimer is required but not sufficient for efficient interaction with poly-Ub. In addition, we show that binding to poly-Ub and, to a lesser extent, to monoubiquitin increases the stability of the NOA coiled-coil dimer. Collectively, these data provide structural insights into how several pathological mutations within and outside of the CC2-LZ's NOA ubiquitin binding site affect IkappaB kinase activation in the NF-kappaB signaling pathway.

Pathogen recognition and inflammatory signaling in innate immune defenses

The innate immune system constitutes the first line of defense against invading microbial pathogens and relies on a large family of pattern recognition receptors (PRRs), which detect distinct evolutionarily conserved structures on pathogens, termed pathogen-associated molecular patterns (PAMPs). Among the PRRs, the Toll-like receptors have been studied most extensively. Upon PAMP engagement, PRRs trigger intracellular signaling cascades ultimately culminating in the expression of a variety of proinflammatory molecules, which together orchestrate the early host response to infection, and also is a prerequisite for the subsequent activation and shaping of adaptive immunity. In order to avoid immunopathology, this system is tightly regulated by a number of endogenous molecules that limit the magnitude and duration of the inflammatory response. Moreover, pathogenic microbes have developed sophisticated molecular strategies to subvert host defenses by interfering with molecules involved in inflammatory signaling. This review presents current knowledge on pathogen recognition through different families of PRRs and the increasingly complex signaling pathways responsible for activation of an inflammatory and antimicrobial response. Moreover, medical implications are discussed, including the role of PRRs in primary immunodeficiencies and in the pathogenesis of infectious and autoimmune diseases, as well as the possibilities for translation into clinical and therapeutic applications.

Oral manifestations of primary immune deficiencies in children

An important task for both dentists and pediatricians dealing with patients manifesting different oral lesions is to be able to differentiate changes signaling systemic disease from those appearing without any concomitant serious health problem. In this article, symptomatology of selected primary immune deficiency diseases are discussed with particular emphasis on oral manifestations reported in this group of disorders. Facial, dental, and oral findings compose a constellation of symptoms observed in immunodeficiency diseases. Predisposition to bacterial invasion, cytokine dysregulation, tissue inflammatory process, and necrosis lead to early-onset oral lesions and periodontitis. Developmental abnormalities, periodontal disease, and oral lesions may accompany immunodeficiency and require particular awareness directed toward diagnosis of an underlying disease of the immune system.

Inflammation, cancer, and bone loss

Skeletal distortions impose grave health disparities with potentially devastating consequences, including bone pain, immobility, and morbidity. Bone erosion is chiefly caused by hyperactive osteoclasts summoned to bone in response to circulating factors produced by tumor and inflammatory cells. Intense research in the past two decades has identified crucial elements and intricate circulatory systems that maintain and exacerbate inflammatory osteolysis. This progress led to better understanding of the mechanisms underlying this response and to developing advanced therapeutic interventions. Nevertheless, the multifactorial causes of inflammatory osteolysis continue to impose a great challenge for these therapies. This article provides an overview of some of the prominent facets contributing to this process.

The genetic heterogeneity of mendelian susceptibility to mycobacterial diseases

Primary immunodeficiencies (PIDs) were long thought to be exclusively recessive traits -- autosomal recessive (AR) in most cases, with a few X-linked recessive (XR) diseases. In recent years, autosomal dominant (AD), mitochondrial, polygenic, and even somatic PIDs have been described. However, AR remains the most frequent inheritance pattern among recently described PIDs. Some PIDs have been shown to be genetically heterogeneous. Mendelian susceptibility to mycobacterial diseases (MSMD) displays a high level of genetic heterogeneity. There are 6 MSMD-causing genes, including 1 X-linked gene (nuclear factor-kappaB-essential modulator [NEMO]) and 5 autosomal genes (IFN-gamma receptor 1 [IFNGR1], IFN-gamma receptor 2 [IFNGR2], signal transducer and activator of transcription 1 [STAT1], IL-12 p40 subunit [IL12P40], and IL-12 receptor beta-subunit [IL12RB1]). The X-linked trait is XR; STAT1 deficiency is AD; the IFNGR2, IL12P40 subunit, and IL12RB1 deficiencies are AR; and IFNGR1 deficiency may be AD or AR. Two of the AR traits (IFNGR1, IFNGR2) may be subdivided into complete and partial deficiencies, and 3 AR complete deficiencies (IFNGR1, IFNGR2, IL12RB1) may be subdivided into disorders with and without cell surface expression. Finally, there are 2 types of AD STAT1 deficiency, depending on whether the mutation impairs phosphorylation or DNA binding. Thirteen genetic disorders conferring MSMD have been described, involving 1 XR, 3 AD (2 genes), and 9 AR traits (4 genes). However, no genetic etiology has yet been identified for about half of all patients with MSMD. We expect to identify new XR and AD causes of MSMD, but new AR etiologies of MSMD are also likely to be discovered. The investigation of children from areas in which consanguineous marriages are common will probably facilitate the description of many more AR traits.

Alterations of the IKBKG locus and diseases: an update and a report of 13 novel mutations

Mutations in the inhibitor of kappa light polypeptide gene enhancer in B-cells, kinase gamma (IKBKG), also called nuclear factor-kappaB (NF-kB) essential modulator (NEMO), gene are the most common single cause of incontinentia pigmenti (IP) in females and anhydrotic ectodermal dysplasia with immunodeficiency (EDA-ID) in males. The IKBKG gene, located in the Xq28 chromosomal region, encodes for the regulatory subunit of the inhibitor of kappaB (IkB) kinase (IKK) complex required for the activation of the NF-kB pathway. Therefore, the remarkably heterogeneous and often severe clinical presentation reported in IP is due to the pleiotropic role of this signaling transcription pathway. A recurrent exon 4_10 genomic rearrangement in the IKBKG gene accounts for 60 to 80% of IP-causing mutations. Besides the IKBKG rearrangement found in IP females (which is lethal in males), a total of 69 different small mutations (missense, frameshift, nonsense, and splice-site mutations) have been reported, including 13 novel ones in this work. The updated distribution of all the IP- and EDA-ID-causing mutations along the IKBKG gene highlights a secondary hotspot mutation in exon 10, which contains only 11% of the protein. Furthermore, familial inheritance analysis revealed an unexpectedly high incidence of sporadic cases (>65%). The sum of the observations can aid both in determining the molecular basis of IP and EDA-ID allelic diseases, and in genetic counseling in affected families.

From infectious diseases to primary immunodeficiencies

The field of primary immunodeficiencies has expanded, thanks to the exploration of novel clinical phenotypes and their connection with morbid genotypes, and the subsequent exploration of new patients who have known primary immunodeficiency-defining clinical phenotypes and their connection with novel morbid genotypes. This two-way process is becoming increasingly active, particularly for patients who have infectious diseases in whom the underlying immunologic and genetic causes remain mostly unexplained. The authors review how the exploration of children who have clinical infectious diseases caused by mycobacteria, pneumococcus, and herpes simplex virus recently led to the description of three new groups of primary immunodeficiencies. These three examples justify the continuation of the genetic exploration of novel infectious phenotypes and novel patients who have infections. This challenging process will eventually reap its rewards, to the benefit of patients and their families.

The genetic basis of inherited anomalies of the teeth. Part 2: syndromes with significant dental involvement

Teeth are specialized structural components of the craniofacial skeleton. Developmental defects occur either alone or in combination with other birth defects. In this paper, we review the dental anomalies in several multiple congenital anomaly (MCA) syndromes, in which the dental component is pivotal in the recognition of the phenotype and/or the molecular basis of the disorder is known. We will consider successively syndromic forms of amelogenesis imperfecta or enamel defects, dentinogenesis imperfecta (i.e. osteogenesis imperfecta) and other dentine anomalies. Focusing on dental aspects, we will review a selection of MCA syndromes associated with teeth number and/or shape anomalies. A better knowledge of the dental phenotype may contribute to an earlier diagnosis of some MCA syndromes involving teeth anomalies. They may serve as a diagnostic indicator or help confirm a syndrome diagnosis.

Novel primary immunodeficiencies revealed by the investigation of paediatric infectious diseases

Human primary immunodeficiencies impairing myeloid and/or lymphoid cellular responses to activating receptors other than antigen receptors have recently been described in children with various infectious diseases. Germline mutations in NEMO and IKBA impair NF-kappaB-mediated signalling, at least in response to the stimulation of TLRs, IL-1Rs and TNFRs, and confer a broad predisposition to infections. Mutations in IRAK4 selectively impair TLRs other than TLR3 and most IL-1R responses, and confer a predisposition to pyogenic bacterial diseases, including invasive pneumococcal disease in particular. Mutations in TLR3 and UNC93B1 impair TLR3 responses and confer a predisposition to herpes simplex encephalitis. Mutations in STAT1 impair IFN-gamma and/or IFN-alpha/beta responses and predispose subjects to mycobacterial and viral diseases, respectively. Mutations in IFNGR1 and IFNGR2 impair IFN-gamma responses and confer a predisposition to mycobacterial diseases. Mutations in IL12B and IL12RB1 impair IL-12 and IL-23 responses and predispose subjects to infections caused by mycobacteria and Salmonella. Finally, mutations in TYK2 and STAT3 mostly impair IL-6R responses, conferring a predisposition to staphylococcal disease in particular. The infectious phenotypes associated with these novel leukocyte activation deficiencies are therefore collectively diverse, tightly dependent on the morbid gene and affected pathway, and individually narrow, often restricted to one or a few infectious diseases.

Solution structure of NEMO zinc finger and impact of an anhidrotic ectodermal dysplasia with immunodeficiency-related point mutation

The regulatory NEMO (NF-kappaB essential modulator) protein has a crucial role in the canonical NF-kappaB signaling pathway notably involved in immune and inflammatory responses, apoptosis and oncogenesis. The regulatory domain is located in the C-terminal half of NEMO and contains a classical CCHC-type zinc finger (ZF). We have investigated the structural and functional effects of a cysteine to phenylalanine point mutation (C417F) in the ZF motif, identified in patients with anhidrotic ectodermal dysplasia with immunodeficiency. The solution structures of the wild type and mutant ZF were determined by NMR. Remarkably, the mutant adopts a global betabetaalpha fold similar to that of the wild type and retains thermodynamic stability, i.e., the ability to bind zinc with a native-like affinity, although the last zinc-chelating residue is missing. However, the mutation induces enhanced dynamics in the motif and leads to an important loss of stability. A detailed analysis of the wild type solution structure and experimental evidences led to the identification of two possible protein-binding surfaces that are largely destabilized in the mutant. This is sufficient to alter NEMO function, since functional complementation assays using NEMO-deficient pre-B and T lymphocytes show that full-length C417F pathogenic NEMO leads to a partial to strong defect in LPS, IL-1beta and TNF-alpha-induced NF-kappaB activation, respectively, as compared to wild type NEMO. Altogether, these results shed light onto the role of NEMO ZF as a protein-binding motif and show that a precise structural integrity of the ZF should be preserved to lead to a functional protein-recognition motif triggering full NF-kappaB activation.

Zahnanomalien in der Neuropädiatrie

Zahnanomalien in der Neuropädatrie sind einfach zu diagnostizieren und helfen bei der Diagnose verschiedener Erkrankungen. Sie finden sich bei gut bekannten Krankheitsbildern wie der Incontinentia pigmenti, aber auch bei seltenen wie dem Kohlschütter-Tönz-Syndrom oder dem kürzlich beschriebenen Krankheitsbild der Ataxie, verzögerten Dentition und Hypomyelinisierung. Anomalien von Zahnform, Zahnschmelz und damit Zahnfarbe, Zahnanzahl und Eruption sind möglich. Die Kenntnis dieser Auffälligkeiten ist wichtig für den Genetiker und den Kinderneurologen.

The NEMO adaptor bridges the nuclear factor-kappaB and interferon regulatory factor signaling pathways

Intracellular detection of RNA virus infection is mediated by the RNA helicase RIG-I, which is recruited to mitochondria by the adaptor protein MAVS and triggers activation of the transcription factors NF-kappaB, IRF3 and IRF7. Here we demonstrate that virus-induced activation of IRF3 and IRF7 depended on the NF-kappaB modulator NEMO, which acted 'upstream' of the kinases TBK1 and IKKepsilon. IRF3 phosphorylation, formation of IRF3 dimers and DNA binding, as well as IRF3-dependent gene expression, were abrogated in NEMO-deficient cells. IRF3 phosphorylation and interferon production were restored by ectopic expression of NEMO. Thus, NEMO, like MAVS, acts as an adaptor protein that allows RIG-I to activate both the NF-kappaB and IRF signaling pathways.

Host genetics of mycobacterial diseases in mice and men: forward genetic studies of BCG-osis and tuberculosis

In humans, genetic factors have long been suspected to contribute to the onset and outcome of tuberculosis. Such effects are difficult to identify owing to their complex inheritance, and to the confounding impact of environmental factors, notably pathogen-associated virulence determinants. Recently, forward genetic approaches in mouse models and in human populations have been used to elucidate a molecular basis for predisposition to mycobacterial diseases. The genetic dissection of host predisposition to infection with Mycobacterium bovis BCG and M. tuberculosis will help to define the key molecules involved in host antituberculous immunity and should provide new insights into this important infectious disease.

Inborn errors of IL-12/23- and IFN-γ-mediated immunity: molecular, cellular, and clinical features

Mendelian susceptibility to mycobacterial diseases confers predisposition to clinical disease caused by weakly virulent mycobacterial species in otherwise healthy individuals. Since 1996, disease-causing mutations have been found in five autosomal genes (IFNGR1, IFNGR2, STAT1, IL12B, IL12BR1) and one X-linked gene (NEMO). These genes display a high degree of allelic heterogeneity, defining at least 13 disorders. Although genetically different, these conditions are immunologically related, as all result in impaired IL-12/23-IFN-gamma-mediated immunity. These disorders were initially thought to be rare, but have now been diagnosed in over 220 patients from over 43 countries worldwide. We review here the molecular, cellular, and clinical features of patients with inborn errors of the IL-12/23-IFN-gamma circuit.

[Genetic predisposition and children infectious disease]

The classic primary immunodeficiencies confer predisposition to multiple infectious diseases. However since ten years severe pediatric infections which were idiopathic have now molecular explanation. Indeed, defects in several genes confer a predisposition to infection with specific pathogenes in otherwise healthy individuals. These children present a new kind of hereditary immunodeficiency with severe and/or recurrent infections caused by only one microorganisms family, in opposition of others patients with "classic" primary immunodeficiency.

IRAK4 and NEMO mutations in otherwise healthy children with recurrent invasive pneumococcal disease

BACKGROUND

About 2% of childhood episodes of invasive pneumococcal disease (IPD) are recurrent, and most remain unexplained.

OBJECTIVE

To report two cases of otherwise healthy, unrelated children with recurrent IPD as the only clinical infectious manifestation of an inherited disorder in nuclear factor-kappaB(NF-kappaB)-dependent immunity.

RESULTS

One child carried two germline mutations in IRAK4, and had impaired cellular responses to interleukin (IL)1 receptor and toll-like receptor (TLR) stimulation. The other child carried a hemizygous mutation in NEMO, associated with a broader impairment of NF-kappaB activation, with an impaired cellular response to IL-1R, TLR and tumour necrosis factor receptor stimulation. The two patients shared a narrow clinical phenotype, associated with two related but different genotypes.

CONCLUSIONS

Otherwise healthy children with recurrent IPD should be explored for underlying primary immunodeficiencies affecting the IRAK4-dependent and NEMO-dependent signalling pathways.

X-linked susceptibility to mycobacteria is caused by mutations in NEMO impairing CD40-dependent IL-12 production

Germline mutations in five autosomal genes involved in interleukin (IL)-12–dependent, interferon (IFN)-γ–mediated immunity cause Mendelian susceptibility to mycobacterial diseases (MSMD). The molecular basis of X-linked recessive (XR)–MSMD remains unknown. We report here mutations in the leucine zipper (LZ) domain of the NF-κB essential modulator (NEMO) gene in three unrelated kindreds with XR-MSMD. The mutant proteins were produced in normal amounts in blood and fibroblastic cells. However, the patients' monocytes presented an intrinsic defect in T cell–dependent IL-12 production, resulting in defective IFN-γ secretion by T cells. IL-12 production was also impaired as the result of a specific defect in NEMO- and NF-κB/c-Rel–mediated CD40 signaling after the stimulation of monocytes and dendritic cells by CD40L-expressing T cells and fibroblasts, respectively. However, the CD40-dependent up-regulation of costimulatory molecules of dendritic cells and the proliferation and immunoglobulin class switch of B cells were normal. Moreover, the patients' blood and fibroblastic cells responded to other NF-κB activators, such as tumor necrosis factor-α, IL-1β, and lipopolysaccharide. These two mutations in the NEMO LZ domain provide the first genetic etiology of XR-MSMD. They also demonstrate the importance of the T cell– and CD40L-triggered, CD40-, and NEMO/NF-κB/c-Rel–mediated induction of IL-12 by monocyte-derived cells for protective immunity to mycobacteria in humans.