Molecular basis of autosomal recessive chronic granulomatous disease in iran

Hematologically important mutations: The autosomal forms of chronic granulomatous disease (third update)

Chronic granulomatous disease (CGD) is an immunodeficiency disorder affecting about 1 in 250,000 individuals. CGD patients suffer from severe, recurrent bacterial and fungal infections. The disease is caused by mutations in the genes encoding the components of the leukocyte NADPH oxidase. This enzyme produces superoxide, which is subsequently metabolized to hydrogen peroxide and other reactive oxygen species (ROS). These products are essential for intracellular killing of pathogens by phagocytic leukocytes (neutrophils, eosinophils, monocytes and macrophages). The leukocyte NADPH oxidase is composed of five subunits, four of which are encoded by autosomal genes. These are CYBA, encoding p22^phox, NCF1, encoding p47^phox, NCF2, encoding p67^phox and NCF4, encoding p40^phox. This article lists all mutations identified in these genes in CGD patients. In addition, cytochrome b₅₅₈ chaperone-1 (CYBC1), recently recognized as an essential chaperone protein for the expression of the X-linked NADPH oxidase component gp91^phox (also called Nox2), is encoded by the autosomal gene CYBC1. Mutations in this gene also lead to CGD. Finally, RAC2, a small GTPase of the Rho family, is needed for activation of the NADPH oxidase, and mutations in the RAC2 gene therefore also induce CGD-like symptoms. Mutations in these last two genes are also listed in this article.

Diagnosis of radiosensitive severe combined immunodeficiency disease (RS-SCID) by Comet Assay, management of bone marrow transplantation

BACKGROUND AND OBJECTIVE

Severe combined immunodeficiency disease (SCID) is a rare inherited severe immunodeficiency, in which functions of T cells and B cells are impaired. SCID is inherited either in X-linked recessive, or autosomal recessive forms, and is either radiosensitive or radioresistant. Artemis (DCLRE1C gene), DNA ligase IV, DNA-PKC, and Cernunnos/XLF proteins are regarded as NHEJ (Non-Homologous End-Joining) proteins that are involved in the repair process of double-strand DNA breaks and their mutations would lead to cellular radiosensitivity. Diagnostic radiosensitivity assays are important for the management of clinical BMT (Bone Marrow Transplantation) conditions, such as what conditioning agents and doses should be used.

MATERIALS AND METHODS

In this study, five SCID patients and healthy controls were examined. Skin fibroblasts were cultured. After X-irradiation, cells either underwent clonogenic assay or incubated to allow DNA repair and examined by the alkaline comet assay. Finally, DCLRE1C, RAG-1, and RAG-2 genes sequenced.

RESULTS

By clonogenic assay, three patients were detected as radiosensitive with possible mutations in NHEJ genes such as DCLRE1C gene. The percentage of DNA in the tail measured by comet assay, in all three patients, was significantly different from the two other patients and the control group (p-value < 0.05). By using Sanger sequencing, a mutation in DCLRE1C gene was detected in one of the radiosensitive patients and two mutations in RAG-1, and RAG-2 genes were detected in the two radioresistant patients.

CONCLUSION

Our findings suggest that comet assay is a fast technique for the diagnosis of the radiosensitive form of SCID and is very suitable for the timely diagnosis of RS-SCID before BMT.

A novel variant in the neutrophil cytosolic factor 2 (NCF2) gene results in severe disseminated BCG infectious disease: A clinical report and literature review

Background

Chronic granulomatous disease (CGD) is a rare primary immunodeficiency disorder (PID) affecting NADPH oxidase activity. The rarest form of the disease is considered to be caused by NCF2 gene bi‐allelic variant. Here, we report the clinical and molecular characterization of a patient presenting with early‐onset severe disease due to bi‐allelic NCF2 variant.

Methods

Gene mutational analysis was performed by whole‐exome and Sanger sequencing.

Results

The patient presented with a history of fever and rash since the age of 1 month, followed by destructive osteomyelitis and necrotizing lymphadenopathy. The patient received the Bacillus Calmette‐Guérin (BCG) vaccine at birth; she was subsequently diagnosed with disseminated BCG infection. Whole‐exome sequencing identified a private (unreported) homozygous variant in NCF2 (c.290C > A) that results in a nonconservative change, p.Ala97Asp, in the p67^phox protein. The variant is located in the third helix of the TRP domain, which is crucial for the binding of GTPase RAC2 to the NADPH oxidase complex.

Conclusion

We identified a novel NCF2 variant located in the region interacting with RAC2 that is linked to a severe and early CGD phenotype in the setting of disseminated BCG infection. Our findings support postponing BCG vaccination until 6–12 months of age and after PID assessment.

Variable Presentation of the CYBB Mutation in One Family, Approach to Management, and a Review of the Literature

Chronic granulomatous disease (CGD) is a primary immunodeficiency disorder marked by abnormal phagocytic function. CGD affects primarily neutrophils and manifests as an early predisposition to severe life-threatening infections. Additionally, patients with CGD are predisposed to unique autoimmune manifestations. While generally spared from infectious complications, heterozygous carriers of the abnormal genes implicated in CGD pathogenesis can still present with autoimmune disorders. A mutation in the CYBB gene is the only X-linked variant of this disease. This article describes a family with the CYBB mutation, its heterogenous presentation, and reviews the literature discussing disease management.

Genetic and molecular findings of 38 Iranian patients with chronic granulomatous disease caused by p47-phox defect

One of the components of NADPH oxidase is p47-phox, encoded by NCF1 gene. This study aims to find new genetic changes and clinical features in 38 Iranian patients with autosomal recessive chronic granulomatous disease (AR-CGD) caused by NCF1 gene defect. Patients who had abnormal NBT and DHR-1,2,3 assay with loss of p47-phox in Western blotting were included in this study. After recording demographic and clinical data, PCR amplification was performed followed by direct sequencing for all exons and exon-intron boundaries. The most common form of CGD in Iran was AR-CGD due to consanguinity marriages. Among patients with AR-CGD, NCF1 deficiency was found to be more common than other forms. Cutaneous involvements (53%), pulmonary infections (50%) and lymphadenopathy (29%) were more prevalent than other clinical manifestations of CGD. Mutation analysis of NCF1 gene identified five different mutations. Homozygous delta GT deletion (c.75_76delGT) was the most frequent mutation and was detected in more than 63% of families. Six families had a nonsense mutation in exon 7 (c.579G > A). Two novel mutations were found in exon 4 in two families, including a missense mutation (c.328C > T) and a nine-nucleotide deletion (c.331_339delTGTCCCCAC). Genetic detection of these mutations may result in early diagnosis and prevention of possible complications of the disease. This could be useful for timely decision-making for haematopoietic stem cell transplantation and for carrier detection as well as prenatal diagnosis of next children in the affected families. Our findings might help to predict outcomes, raise awareness and help effective treatment in these patients.

Characterization of two novel mutations in IL-12R signaling in MSMD patients

Mendelian Susceptibility to Mycobacterial Disease (MSMD) is a rare syndrome with infections-among other complications-after Bacillus Calmette-Guerin (BCG) vaccination in children. We focused on the IL-12/IFN-γ pathway to identify new mutations in our patients. This study included 20 patients by vulnerability to mycobacteria and clinical manifestations of severe, recurrent infections. Blood samples were activated with BCG, BCG + IL-12 and BCG + IFN-γ. Cytokine levels were analyzed by ELISA. Measurements of IL-12Rβ1 and IL-12Rβ2 on the surface of peripheral blood mononuclear cells were performed by flow cytometry. To detect genetic defects, next-generation sequencing was performed by Thermo Fisher immunodeficiency panel. Flow cytometry analysis of 20 patients indicated reduction in IL-12R (β1/β2) expression in seven patients who showed incomplete production of IFN-γ by ELISA. In the patient with reduced IL-12 production, IFN-γR and IL-12R (β1/β2) expression levels were normal. Mutation analysis showed three previously reported mutations, two novel mutations in IL-12 R (β1/β2), and one previously reported mutation in IL-12.

Common Infections and Target Organs Associated with Chronic Granulomatous Disease in Iran

Recurrent severe bacterial and fungal infections are characteristic features of the rare genetic immunodeficiency disorder chronic granulomatous disease (CGD). The disease usually manifests within the first years of life with an incidence of 1 in approximately 200,000 live births. The incidence is higher in Iran and Morocco where it reaches 1.5 per 100,000 live births. Mutations have been described in the 5 subunits of NADPH oxidase, mostly in gp91phox and p47phox, with fewer mutations reported in p67phox, p22phox, and p40phox. These mutations cause loss of superoxide production in phagocytic cells. CYBB, the gene encoding the large gp91phox subunit of the transmembrane component cytochrome b558 of the NADPH oxidase complex, is localized on the X-chromosome. Genetic defects in CYBB are responsible for the disease in the majority of male CGD patients. CGD is associated with the development of granulomatous reactions in the skin, lungs, bones, and lymph nodes, and chronic infections may be seen in the liver, gastrointestinal tract, brain, and eyes. There is usually a history of repeated infections, including inflammation of the lymph glands, skin infections, and pneumonia. There may also be a persistent runny nose, inflammation of the skin, and inflammation of the mucous membranes of the mouth. Gastrointestinal problems can also occur, including diarrhea, abdominal pain, and perianal abscesses. Infection of the bones, brain abscesses, obstruction of the genitourinary tract and/or gastrointestinal tract due to the formation of granulomatous tissue, and delayed growth are also symptomatic of CGD. The prevention of infectious complications in patients with CGD involves targeted prophylaxis against opportunistic microorganisms such as Staphylococcus aureus, Klebsiella spp., Salmonella spp. and Aspergillus spp. In this review, we provide an update on organ involvement and the association with specific isolated microorganisms in CGD patients.

Approach to Molecular Diagnosis of Chronic Granulomatous Disease (CGD): an Experience from a Large Cohort of 90 Indian Patients

BACKGROUND

Chronic granulomatous disease (CGD) is characterized by mutation in any one of the five genes coding NADPH oxidase components that leads to functional abnormality preventing the killing of phagocytosed microbes by affecting the progression of a respiratory burst. CGD patients have an increased susceptibility to infections by opportunistic and pathogenic organisms. Though initial diagnosis of CGD using a nitroblue tetrazolium (NBT) test or dihydrorhodamine (DHR) test is relatively easy, molecular diagnosis is challenging due to involvement of multiple genes, presence of pseudogenes, large deletions, and GC-rich regions, among other factors. The strategies for molecular diagnosis vary depending on the affected gene and the mutation pattern prevalent in the target population. There is a paucity of molecular data related to CGD for Indian population.

METHOD

This report includes data for a large cohort of CGD patients (n = 90) from India, describing the diagnostic approach, mutation spectrum, and novel mutations identified. We have used mosaicism in mothers and the expression pattern of different NADPH components by flow cytometry as a screening tool to identify the underlying affected gene. The techniques like Sanger sequencing, next-generation sequencing (NGS), and Genescan analysis were used for further molecular analysis.

RESULT

Of the total molecularly characterized patients (n = 90), 56% of the patients had a mutation in the NCF1 gene, 30% had mutation in the CYBB gene, and 7% each had mutation in the CYBA and NCF2 genes. Among the patients with NCF1 gene mutation, 82% of the patients had 2-bp deletion (DelGT) mutations in the NCF1 gene. In our cohort, 41 different mutations including 9 novel mutations in the CYBB gene and 2 novel mutations each in the NCF2, CYBA, and NCF1 genes were identified.

CONCLUSION

Substantial number of the patients lack NCF1 gene on both the alleles. This is often missed by advanced molecular techniques like Sanger sequencing and NGS due to the presence of pseudogenes and requires a simple Genescan method for confirmation. Thus, the diagnostic approach may depend on the prevalence of affected genes in respective population. This study identifies potential gene targets with the help of flow cytometric analysis of NADPH oxidase components to design an algorithm for diagnosis of CGD in India. In Indian population, the Genescan method should be preferred as the primary molecular test to rule out NCF1 gene mutations prior to Sanger sequencing and NGS.

Fourth Update on the Iranian National Registry of Primary Immunodeficiencies: Integration of Molecular Diagnosis

BACKGROUND

The number of inherited diseases and the spectrum of clinical manifestations of primary immunodeficiency disorders (PIDs) are ever-expanding. Molecular diagnosis using genomic approaches should be performed for all PID patients since it provides a resource to improve the management and to estimate the prognosis of patients with these rare immune disorders.

METHOD

The current update of Iranian PID registry (IPIDR) contains the clinical phenotype of newly registered patients during last 5 years (2013-2018) and the result of molecular diagnosis in patients enrolled for targeted and next-generation sequencing.

RESULTS

Considering the newly diagnosed patients (n = 1395), the total number of registered PID patients reached 3056 (1852 male and 1204 female) from 31 medical centers. The predominantly antibody deficiency was the most common subcategory of PID (29.5%). The putative causative genetic defect was identified in 1014 patients (33.1%) and an autosomal recessive pattern was found in 79.3% of these patients. Among the genetically different categories of PID patients, the diagnostic rate was highest in defects in immune dysregulation and lowest in predominantly antibody deficiencies and mutations in the MEFV gene were the most frequent genetic disorder in our cohort.

CONCLUSIONS

During a 20-year registration of Iranian PID patients, significant changes have been observed by increasing the awareness of the medical community, national PID network establishment, improving therapeutic facilities, and recently by inclusion of the molecular diagnosis. The current collective study of PID phenotypes and genotypes provides a major source for ethnic surveillance, newborn screening, and genetic consultation for prenatal and preimplantation genetic diagnosis.

Characterization of 4 New Mutations in the CYBB Gene in 10 Iranian Families With X-linked Chronic Granulomatous Disease

Chronic granulomatous disease (CGD) is an inherited disease of the innate immune system that results from defects in 1 of the 5 subunits of nicotinamide adenine dinucleotide phosphate oxidase complex and leads to life-threatening infections with granuloma formation. During 3 years of study, we recognized 10 male patients with X-linked CGD from a tertiary referral center for immune deficiencies in Iran. The CGD patients were diagnosed according to clinical features and biochemical tests, including nitroblue tetrazolium and dihydrorhodamine-1, 2, 3 tests, performed on patients and their mothers. In all patients, Western blot analysis showed a gp91 phenotype. Mutation screening by single strand conformation polymorphism and multiplex ligation-dependent probe amplification analysis of the CYBB gene encoding gp91, followed by sequencing, showed 9 different mutations, 4 of them novel as far as we know.

Correlation between flow cytometry and molecular findings in autosomal recessive chronic granulomatous disease: A cohort study from Oman

BACKGROUND

Chronic granulomatous disease (CGD) is an X-linked (XL) or autosomal recessive (AR) primary immunodeficiency disease. Respiratory burst assessment by flow cytometry is a rapid test of granulocyte stimulation, and results predict the underlying genotype. This study aims to describe the immune-phenotypic profile of patients with CGD diagnosed in our center and correlate that with underlying genetic mutations.

METHODS

Immuno-phenotypic and genetic data on all patients with CGD diagnosed at Sultan Qaboos University Hospital (SQUH) were reviewed.

RESULTS

A total of 32 patients were diagnosed with CGD using molecular studies. Genetically confirmed individuals included 1 patient with XL-CGD (a large deletion involving the CYBB and XK genes resulting in a McLeod phenotype), 27 patients with AR-CGD with a c.579G>A (p.Trp193X) mutation at the NCF1 gene, and 4 patients with AR-CGD with a c.784G>A (p.Gly262Ser) mutation at the NCF1 gene. Flow cytometry and molecular results were available for comparison in 26 patients with AR-CGD. The patients with AR-CGD had a range of flow cytometry-generated fluorescent patterns as follows: reduced neutrophil stimulation with a sharp peak (12/26), reduced neutrophil stimulation with a broad peak (11/26), and a complete lack of neutrophil stimulation (3/26). No consistent flow cytometry-generated fluorescent pattern was observed in either of the 2 AR mutations identified in our patients.

CONCLUSION

Flow cytometry is a robust test of CGD diagnosis. However, results should be interpreted with caution when predicting the underlying probable genotype, and results need to be complemented with definitive molecular studies.

An Overview of Inflammatory Bowel Disease: General Consideration and Genetic Screening Approach in Diagnosis of Early Onset Subsets

Inflammatory bowel disease (IBD) is the consequence of an aberrant hemostasis of the immune cells at the gut mucosal border. Based on clinical manifestation, laboratory tests, radiological studies, endoscopic and histological features, this disease is divided into three main types including Crohn's disease (CD), Ulcerative colitis (UC), and IBDunclassified (IBD-U). IBD is frequently presented in adults, but about 20% of IBD cases are diagnosed during childhood called pediatric IBD (PIBD). Some patients in the latter group emerge the first symptoms during infancy or under 5 years of age named infantile and very early onset IBD (VEO-IBD), respectively. These subtypes make a small fraction of PIBD, but they have exclusive phenotypic and genetic characteristics such that they are accompanied by severe disease course and resistance to conventional therapy. In this context, understanding the underlying molecular pathology opens a promising field for individualized and effective treatment. Here, we describe current hypotheses on IBD pathophysiology then explain the new idea about genetic screening technology as a good potential approach to identify the causal variants early in the disease manifestation, which is especially important for the fast and accurate treatment of VEO-IBD.

Allelic heterogeneity in NCF2 associated with systemic lupus erythematosus (SLE) susceptibility across four ethnic populations

Recent reports have associated NCF2, encoding a core component of the multi-protein NADPH oxidase (NADPHO), with systemic lupus erythematosus (SLE) susceptibility in individuals of European ancestry. To identify ethnicity-specific and -robust variants within NCF2, we assessed 145 SNPs in and around the NCF2 gene in 5325 cases and 21 866 controls of European-American (EA), African-American (AA), Hispanic (HS) and Korean (KR) ancestry. Subsequent imputation, conditional, haplotype and bioinformatic analyses identified seven potentially functional SLE-predisposing variants. Association with non-synonymous rs17849502, previously reported in EA, was detected in EA, HS and AA (P(EA) = 1.01 × 10(-54), PHS = 3.68 × 10(-10), P(AA) = 0.03); synonymous rs17849501 was similarly significant. These SNPs were monomorphic in KR. Novel associations were detected with coding variants at rs35937854 in AA (PAA = 1.49 × 10(-9)), and rs13306575 in HS and KR (P(HS) = 7.04 × 10(-7), P(KR) = 3.30 × 10(-3)). In KR, a 3-SNP haplotype was significantly associated (P = 4.20 × 10(-7)), implying that SLE predisposing variants were tagged. Significant SNP-SNP interaction (P = 0.02) was detected between rs13306575 and rs17849502 in HS, and a dramatically increased risk (OR = 6.55) with a risk allele at each locus. Molecular modeling predicts that these non-synonymous mutations could disrupt NADPHO complex assembly. The risk allele of rs17849501, located in a conserved transcriptional regulatory region, increased reporter gene activity, suggesting in vivo enhancer function. Our results not only establish allelic heterogeneity within NCF2 associated with SLE, but also emphasize the utility of multi-ethnic cohorts to identify predisposing variants explaining additional phenotypic variance ('missing heritability') of complex diseases like SLE.

Review: Stem cells and gene therapy

Both stem cell and gene therapy research are currently the focus of intense research in institutions and companies around the world. Both approaches hold great promise by offering radical new and successful ways of treating debilitating and incurable diseases effectively. Gene therapy is an approach to treat, cure, or ultimately prevent disease by changing the pattern of gene expression. It is mostly experimental, but a number of clinical human trials have already been conducted. Gene therapy can be targeted to somatic or germ cells; the most common vectors are viruses. Scientists manipulate the viral genome and thus introduce therapeutic genes to the target organ. Viruses, in this context, can cause adverse events such as toxicity, immune and inflammatory responses, as well as gene control and targeting issues. Alternative modalities being considered are complexes of DNA with lipids and proteins. Stem cells are primitive cells that have the capacity to self renew as well as to differentiate into 1 or more mature cell types. Pluripotent embryonic stem cells derived from the inner cell mass can develop into more than 200 different cells and differentiate into cells of the 3 germ cell layers. Because of their capacity of unlimited expansion and pluripotency, they are useful in regenerative medicine. Tissue or adult stem cells produce cells specific to the tissue in which they are found. They are relatively unspecialized and predetermined to give rise to specific cell types when they differentiate. The current review provides a summary of our current knowledge of stem cells and gene therapy as well as their clinical implications and related therapeutic options.