X-linked carriers of chronic granulomatous disease: Illness, lyonization, and stability

OTULIN-related conditions: Report of a new case and review of the literature using GenIA

OTULIN encodes an eponymous linear deubiquitinase (DUB) essential for controlling inflammation as a negative regulator of the canonical NF-κB signaling pathway via the regulation of M1-Ub dynamics. Biallelic loss-of-function (LOF) mutations in OTULIN cause an autosomal recessive condition named Otulin-Related Autoinflammatory Syndrome (ORAS), also known as Otulipenia or AutoInflammation, Panniculitis, and Dermatosis Syndrome (AIPDS). Monoallelic OTULIN LOF, also known as OTULIN Haploinsufficiency (OHI) or Immunodeficiency 107 (IMD107), has been linked to an incompletely penetrant, dominantly inherited susceptibility to invasive Staphylococcal infections. At the same time, a recent novel ORAS-like inflammatory syndrome was described in association with a heterozygous missense mutation that appears to exert dominant negative (DN) effects. In this manuscript, we report the identification of a novel homozygous missense mutation, c.595 T > A; p.(Trp199Arg), in a Moroccan infant with an ORAS phenotype and provide experimental evidence for its pathogenicity. We go on to systematically review the literature for OTULIN-associated conditions by using the GenIA database (www.geniadb.net) to collect, extract and harmonize all clinical, laboratory and functional data for published patients and variants. Our comprehensive synthesis of genotypic, phenotypic, and mechanistic data enables a more in-depth view of the diverse mechanisms and pathways by which the OTULIN pathogenic variants may lead to human immune disease. This review may help variant classification activities and inform future variant evaluation, as well as the development of diagnostic and management guidelines. It also identifies current knowledge gaps and raises additional questions warranting future investigation.

A nox2/cybb zebrafish mutant with defective myeloid cell reactive oxygen species production displays normal initial neutrophil recruitment to sterile tail injuries

Reactive oxygen species are important effectors and modifiers of the acute inflammatory response, recruiting phagocytes including neutrophils to sites of tissue injury. In turn, phagocytes such as neutrophils are both consumers and producers of reactive oxygen species. Phagocytes including neutrophils generate reactive oxygen species in an oxidative burst through the activity of a multimeric phagocytic nicotinamide adenine dinucleotide phosphate oxidase complex. Mutations in the NOX2/CYBB (previously gp91phox) nicotinamide adenine dinucleotide phosphate oxidase subunit are the commonest cause of chronic granulomatous disease, a disease characterized by infection susceptibility and an inflammatory phenotype. To model chronic granulomatous disease, we made a nox2/cybb zebrafish (Danio rerio) mutant and demonstrated it to have severely impaired myeloid cell reactive oxygen species production. Reduced early survival of nox2 mutant embryos indicated an essential requirement for nox2 during early development. In nox2/cybb zebrafish mutants, the dynamics of initial neutrophil recruitment to both mild and severe surgical tailfin wounds was normal, suggesting that excessive neutrophil recruitment at the initiation of inflammation is not the primary cause of the "sterile" inflammatory phenotype of chronic granulomatous disease patients. This nox2 zebrafish mutant adds to existing in vivo models for studying reactive oxygen species function in myeloid cells including neutrophils in development and disease.

Wiskott-Aldrich syndrome protein expression in female WAS carriers: A flow cytometry study from North India

INTRODUCTION

Wiskott-Aldrich syndrome (WAS) is a rare X-linked inborn error of immunity characterized by microthrombocytopenia, infections, eczema, and increased predisposition to develop autoimmunity and malignancy. Flow cytometric assay for determining WAS protein (WASp) is a rapid and cost-effective tool for detecting patients. However, very few studies described WASp expression in female carriers. Most WAS carriers are clinically asymptomatic. Active screening of female family members helps identify female carriers, distinguish de novo mutations, and to select appropriate donor prior to curative stem cell transplantation. This study was undertaken to evaluate the diagnostic capability of flow cytometry-based WASp expression in peripheral blood cells to identify carriers and compare WASp expression in different blood cell lineages.

PATIENTS AND METHODS

Female patients, heterozygous for WAS gene, were enrolled in this study conducted at Pediatric Allergy Immunology Unit, Advanced Pediatric Centre, Post Graduate Institute of Medical Education and Research, Chandigarh, India. Flow cytometric assessment of WASp expression in lymphocytes, monocytes, and neutrophils was carried out and compared with healthy control and affected patients. The results were expressed in delta (Δ) median fluorescence intensity (MFI) as well as stain index (SI), which is the ratio of ΔMFI of patient and ΔMFI of control.

RESULTS

Thirteen mothers and two sisters of genetically confirmed WAS patients were enrolled in the study. All enrolled females were clinically asymptomatic and did not have microthrombocytopenia. Low WASp expression (SI < 1) was seen in lymphocytes and monocytes in 10 (66.6%) carriers. Females with variants in proximal exons (exons 1 and 2) were found to have lesser expression than those with distal (exons 3-12) variants.

CONCLUSION

Flow cytometry is a rapid, easily available, cost-effective tool for WASp estimation. Lymphocytes followed by monocytes are the best cell lineages for WASp estimation in carrier females. However, genetic testing remains the gold standard, as carrier females with variants in distal exons may have normal WASp expression.

NADPH oxidase exerts a B cell-intrinsic contribution to lupus risk by modulating endosomal TLR signals

Genome-wide association studies in systemic lupus erythematosus (SLE) have linked loss-of-function mutations in phagocytic NADPH oxidase complex (NOX2) genes, including NCF1 and NCF2, to disease pathogenesis. The prevailing model holds that reduced NOX2 activity promotes SLE via defective efferocytosis, the immunologically silent clearance of apoptotic cells. Here, we describe a parallel B cell-intrinsic mechanism contributing to breaks in tolerance. In keeping with an important role for B cell Toll-like receptor (TLR) pathways in lupus pathogenesis, NOX2-deficient B cells exhibit enhanced signaling downstream of endosomal TLRs, increased humoral responses to nucleic acid-containing antigens, and the propensity toward humoral autoimmunity. Mechanistically, TLR-dependent NOX2 activation promotes LC3-mediated maturation of TLR-containing endosomes, resulting in signal termination. CRISPR-mediated disruption of NCF1 confirmed a direct role for NOX2 in regulating endosomal TLR signaling in primary human B cells. Together, these data highlight a new B cell-specific mechanism contributing to autoimmune risk in NCF1 and NCF2 variant carriers.

In adult X-CGD patients, regulatory T cells are expanded while activated T cells display a NOX2-independent ROS increase

The X-linked chronic granulomatous disease (X-CGD), a rare genetic disease characterised by recurrent infections, is caused by mutations of NOX2. Significant proportions of X-CGD patients display signs of immune dysregulation. Regulatory T cells (Tregs) are CD4+T lymphocytes that expand in active inflammation and prevent autoimmune disorders. Here we asked whether X-CGD is associated to Treg dysfunctions in adult patients. To this aim, the frequency of Tregs was analysed through intracellular flow cytometry in a cohort of adult X-CGD patients, carriers and controls. We found that Tregs were significantly expanded and activated in blood of adult X-CGD patients, and this was associated with activation of conventional CD4+T cells (Tconvs). T cell activation was characterised by accumulation of intracellular ROS, not derived from NOX2 but likely produced by cellular metabolism. The higher TNF production by Tconvs in X-CGD patients might contribute to the expansion of Tregs through the TNFR2 receptor. In summary, our data indicate that Tregs expand in adult X-CGD in response to immune activation, and that the increase of NOX2-independent ROS content is a feature of activated T cells.

OTULIN-related conditions: Report of a new case and review of the literature using GenIA

OTULIN encodes an eponymous linear deubiquitinase (DUB), which through the regulation of M1-Ub dynamics, is essential for controlling inflammation as a negative regulator of the canonical NF-κB signaling pathway. Biallelic loss-of-function (LOF) mutations in OTULIN cause an autosomal recessive condition named Otulin-Related Autoinflammatory Syndrome (ORAS), also known as Otulipenia or AutoInflammation, Panniculitis, and Dermatosis Syndrome (AIPDS). Monoallelic OTULIN LOF, also known as OTULIN Haploinsufficiency (OHI) or Immunodeficiency 107 (IMD107), has been linked to an incompletely penetrant, dominantly inherited susceptibility to invasive Staphylococcal infections. At the same time, a recent novel ORAS-like inflammatory syndrome was described in association with a heterozygous missense mutation that appears to exert dominant negative effects. In this manuscript, we report the identification of a novel homozygous missense mutation, c.595T>A; p.(Trp199Arg), in a Moroccan infant with an ORAS phenotype. We go on to systematically review the literature for OTULIN-related human disease phenotypes by using the GenIA database to collect, extract and harmonize all clinical, laboratory and functional data for published patients and variants. Our comprehensive synthesis of genotypic, phenotypic, and mechanistic data enables a more in-depth view of the diverse mechanisms and pathways by which the OTULIN pathogenic variants may lead to human immune disease. This review may help variant classification activities and the drafting of diagnostic and management guidelines; but it also identifies outstanding knowledge gaps and raises additional questions for future investigation.

X-linked chronic granulomatous disease secondary to skewed X-chromosome inactivation in female patients

BACKGROUND

Chronic granulomatous disease (CGD) is a heterogeneous primary immunodeficiency. X-linked (XL) CGD caused by gene defects of CYBB is the most prevalent type of CGD.

OBJECTIVE

We aim to understand the clinical and molecule features of XL-CGD secondary to skewed X-chromosome inactivation (XCI) in female.

METHODS

We retrospectively reviewed the medical records of a female patient diagnosed with XL-CGD. Flow cytometry was used to detect the respiratory burst function. After restriction enzyme digestion of DNA, XCI was calculated by detecting fluorescent PCR products with capillary electrophoresis. The previously published female XL-CGD cases secondary to skewed XCI was summarized.

RESULTS

Clinical data were available for 15 female subjects. The median age of diagnosis was 16 years. Consistent with XL-CGD in males, infection was the most frequent manifestation in the female patients. Catalase-positive pathogens including Serratia marcescens and Staphylococcus aureus infections were the most common pathogens. Autoimmune/autoinflammation manifestations were observed in five patients. Dihydrorhodamine (DHR) assay showed that median %DHR+ values were 6.5% and the values varying with age were observed in 2 patients. All patients had a skewing XCI and there was no consistency between the daughter and carrier mother. Anti-infective treatment was effective in majority and there was no mortality reported in XL-CGD female patients to date.

CONCLUSION

XL-CGD should not be neglected in female patients manifested as CGD phenotype and it is necessary to make periodic clinical evaluation of CGD female carriers as the neutrophil oxidative function may decline with aging and increase the risk for infection.

Inflammatory Complications in Chronic Granulomatous Disease

Chronic granulomatous disease (CGD) is a rare inborn error of immunity that typically manifests with infectious complications. As the name suggest though, inflammatory complications are also common, often affecting the gastrointestinal, respiratory, urinary tracts and other tissues. These can be seen in all various types of CGD, from X-linked and autosomal recessive to X-linked carriers. The pathogenetic mechanisms underlying these complications are not well understood, but are likely multi-factorial and reflect the body's attempt to control infections. The different levels of neutrophil residual oxidase activity are thought to contribute to the large phenotypic variations. Immunosuppressive agents have traditionally been used to treat these complications, but their use is hindered by the fact that CGD patients are predisposed to infection. Novel therapeutic agents, like anti-TNFa monoclonal antibodies, anakinra, ustekinumab, and vedolizumab offer promise for the future, while hematopoietic stem cell transplantation should also be considered in these patients.

[Pulmonary complications of Chronic Granulomatous Disease]

Chronic Granulomatosis Disease (CGD) is an inherited immune deficiency due to a mutation in the genes coding for the subunits of the NADPH oxidase enzyme that affects the oxidative capacity of phagocytic cells. It is characterized by increased susceptibility to bacterial and fungal infections, particularly Aspergillus, as well as complications associated with hyperinflammation and granulomatous tissue infiltration. There exist two types of frequently encountered pulmonary manifestations: (1) due to their being initially pauci-symptomatic, possibly life-threatening infectious complications are often discovered at a late stage. Though their incidence has decreased through systematic anti-bacterial and anti-fungal prophylaxis, they remain a major cause of morbidity and mortality; (2) inflammatory complications consist in persistent granulomatous mass or interstitial pneumoniae, eventually requiring immunosuppressive treatment. Pulmonary complications recurring since infancy generate parenchymal and bronchial sequelae that impact functional prognosis. Hematopoietic stem cell allograft is a curative treatment; it is arguably life-sustaining and may limit the morbidity of the disease. As a result of improved pediatric management, life expectancy has increased dramatically. That said, new challenges have appeared with regard to adults: difficulties of compliance, increased inflammatory manifestations, acquired resistance to anti-infectious therapies. These different developments underscore the importance of the transition period and the need for multidisciplinary management.

Allogeneic HSCT for Symptomatic Female X-linked Chronic Granulomatous Disease Carriers

X-linked chronic granulomatous disease (XL-CGD) is an inherited disorder of superoxide production, causing failure to generate the oxidative burst in phagocytes. It is characterized by invasive bacterial and fungal infections, inflammation, and chronic autoimmune disease. While XL-CGD carriers were previously assumed to be healthy, a range of clinical manifestations with significant morbidity have recently been described in a subgroup of carriers with impaired neutrophil oxidative burst due to skewed lyonization. Allogeneic hematopoietic stem cell transplantation (HSCT) is the standard curative treatment for CGD but has rarely been reported in individual symptomatic carriers to date. We undertook a retrospective international survey of outcome of HSCT for symptomatic XL-CGD carriers. Seven symptomatic female XL-CGD carriers aged 1-56 years underwent HSCT in four centers, indicated for severe and recurrent infection, colitis, and autoimmunity. Two patients died from transplant-related complications, following donor engraftment and restoration of oxidative burst. All surviving patients demonstrated resolution of their neutrophil oxidative burst defect with concordant reduction in infection and inflammatory symptoms and freedom from further immunosuppressive therapy. In conclusion, allogeneic HSCT may cure the phagocyte defect in symptomatic XL-CGD carriers and improve their recurrent and disabling infective and inflammatory symptoms but risks transplant-related complications.

Haematopoietic Stem Cell Transplantation for Chronic Granulomatous Disease

Chronic granulomatous disease (CGD) is an inborn error of immunity due to defects in the transport or function of subunits of nicotinamide adenine dinucleotide phosphate oxidase, the enzyme that generates the phagocyte respiratory burst responsible for intracellular killing of engulfed micro-organisms. Patients present with infectious or inflammatory complications. Common bacterial pathogens include Staphylococcus aureus and Burkholderia cepacia complex. Fungal pathogens include Aspergillus species, particularly Aspergillus fumigatus. Inflammatory complications most commonly manifest as inflammatory bowel disease or lung disease. Granulomata are the distinguishing histological feature. Haematopoietic stem cell transplantation (HSCT) was first considered for CGD in the early 1970's. Since then, refinements in transplant technique, donor selection, conditioning regimens, and graft engineering have widened the option of HSCT to most patients with CGD. This review charts the progress made in HSCT for CGD.

Nature and nurture: understanding phenotypic variation in inborn errors of immunity

The overall disease burden of pediatric infection is high, with widely varying clinical outcomes including death. Among the most vulnerable children, those with inborn errors of immunity, reduced penetrance and variable expressivity are common but poorly understood. There are several genetic mechanisms that influence phenotypic variation in inborn errors of immunity, as well as a body of knowledge on environmental influences and specific pathogen triggers. Critically, recent advances are illuminating novel nuances for fundamental concepts on disease penetrance, as well as raising new areas of inquiry. The last few decades have seen the identification of almost 500 causes of inborn errors of immunity, as well as major advancements in our ability to characterize somatic events, the microbiome, and genotypes across large populations. The progress has not been linear, and yet, these developments have accumulated into an enhanced ability to diagnose and treat inborn errors of immunity, in some cases with precision therapy. Nonetheless, many questions remain regarding the genetic and environmental contributions to phenotypic variation both within and among families. The purpose of this review is to provide an updated summary of key concepts in genetic and environmental contributions to phenotypic variation within inborn errors of immunity, conceptualized as including dynamic, reciprocal interplay among factors unfolding across the key dimension of time. The associated findings, potential gaps, and implications for research are discussed in turn for each major influencing factor. The substantial challenge ahead will be to organize and integrate information in such a way that accommodates the heterogeneity within inborn errors of immunity to arrive at a more comprehensive and accurate understanding of how the immune system operates in health and disease. And, crucially, to translate this understanding into improved patient care for the millions at risk for serious infection and other immune-related morbidity.

Unlocking the power of NOX2: A comprehensive review on its role in immune regulation

Reactive oxygen species (ROS) are a family of highly reactive molecules with numerous, often pleiotropic functions within the cell and the organism. Due to their potential to destroy biological structures such as membranes, enzymes and organelles, ROS have long been recognized as harmful yet unavoidable by-products of cellular metabolism leading to "oxidative stress" unless counterbalanced by cellular anti-oxidative defense mechanisms. Phagocytes utilize this destructive potential of ROS released in high amounts to defend against invading pathogens. In contrast, a regulated and fine-tuned release of "signaling ROS" (sROS) provides essential intracellular second messengers to modulate central aspects of immunity, including antigen presentation, activation of antigen presenting cells (APC) as well as the APC:T cell interaction during T cell activation. This regulated release of sROS is foremost attributed to the specialized enzyme NADPH-oxidase (NOX) 2 expressed mainly in myeloid cells such as neutrophils, macrophages and dendritic cells (DC). NOX-2-derived sROS are primarily involved in immune regulation and mediate protection against autoimmunity as well as maintenance of self-tolerance. Consequently, deficiencies in NOX2 not only result in primary immune-deficiencies such as Chronic Granulomatous Disease (CGD) but also lead to auto-inflammatory diseases and autoimmunity. A comprehensive understanding of NOX2 activation and regulation will be key for successful pharmaceutical interventions of such ROS-related diseases in the future. In this review, we summarize recent progress regarding immune regulation by NOX2-derived ROS and the consequences of its deregulation on the development of immune disorders.

Inborn Errors of Immunity and Autoimmune Disease

Autoimmunity may be a manifestation of inborn errors of immunity, specifically as part of the subgroup of primary immunodeficiency known as primary immune regulatory disorders. However, although making a single gene diagnosis can have important implications for prognosis and management, picking patients to screen can be difficult, against a background of a high prevalence of autoimmune disease in the population. This review compares the genetics of common polygenic and rare monogenic autoimmunity, and explores the molecular mechanisms, phenotypes, and inheritance of autoimmunity associated with primary immune regulatory disorders, highlighting the emerging importance of gain-of-function and non-germline somatic mutations. A novel framework for identifying rare monogenic cases of common diseases in children is presented, highlighting important clinical and immunologic features that favor single gene disease and guides clinicians in selecting appropriate patients for genomic screening. In addition, there will be a review of autoimmunity in non-genetically defined primary immunodeficiency such as common variable immunodeficiency, and of instances where primary autoimmunity can result in clinical phenocopies of inborn errors of immunity.

Inborn Errors of Immunity: A Role for Functional Testing and Flow Cytometry in Aiding Clinical Diagnosis

With the exponential discovery of new inborn errors of immunity (IEI), it is becoming increasingly difficult to differentiate between a number of the more recently defined disorders. This is compounded by the fact that although IEI primarily present with immunodeficiency, the spectrum of disease is broad and often extends to features typical of autoimmunity, autoinflammation, atopic disease, and/or malignancy. Here we use case studies to discuss the laboratory and genetic tests used that ultimately led to the specific diagnoses.

R, Eley B, Bhattad S. Genetically confirmed chronic granulomatous disease in a Kenyan child: case report

Introduction

We report the first case of genetically confirmed chronic granulomatous disease (CGD) in a Kenyan child.

Clinical findings

A 7-month-old male infant, the only child of non-consanguineous parents, presented with cough, fever, fast breathing, oral thrush, and axillary lymphadenopathy ipsilateral to the Calmette-Guérin bacillus scar. He had been hospitalized 5 weeks prior for severe pneumonia. Plain chest radiography showed bilateral patchy airspace opacification; chest computed tomography revealed multiple large lung nodules and left axillary lymphadenopathy. HIV ELISA was negative; tuberculin skin test was positive; lymph node biopsy macroscopically revealed caseous granulomas seen on histology; isoniazid- and rifampicin-susceptible Mycobacterium tuberculosis complex isolate was detected on the Hain test. First-line anti-tuberculous drugs were added to his empiric treatment comprising piperacillin-tazobactam, amikacin, cotrimoxazole, and fluconazole. He was discharged after 10 days based on clinical resolution.

Diagnoses interventions and outcome

An inborn error of immunity (IEI) was considered given the recurrent fevers and atypical lung nodules. Genetic analysis revealed a hemizygous pathogenic variant on CYBB in keeping with X-linked CGD. The child's fevers recurred 2 weeks post-discharge but completely resolved on prophylactic itraconazole and cotrimoxazole. He underwent a successful haplo-identical hematopoietic stem cell transplantation at an experienced center in India with his father as the donor and is currently doing well on post-transplant follow-up.

Conclusion

Genetic testing is relatively accessible and cost-effective for the diagnosis of IEI in low-and-middle-income countries. Expert multi-disciplinary collaboration is key for successful outcomes.

Characterization of AR-CGD female patient with a novel homozygous deletion in CYBC1 gene presenting with unusual clinical phenotype

Chronic granulomatous disease (CGD) is a human IEI caused by mutations in genes encoding the NADPH oxidase subunits, the enzyme responsible for the respiratory burst. CGD patients have severe life-threatening infections, hyperinflammation and immune dysregulation. Recently, an additional autosomal recessive (AR)-CGD (type 5) caused by mutations in CYBC1/EROS gene was identified. We report a AR-CGD5 patient with a novel loss of function (LOF) homozygous deletion c.8_7del in the CYBC1 gene including the initiation ATG codon that leads to failure of CYBC1/EROS protein expression and presenting with an unusual clinical manifestation of childhood-onset sarcoidosis-like disease requiring multiple immunosuppressive therapies. We described an abnormal gp91phox protein expression/function in the patient's neutrophils and monocytes (about 50%) and a severely compromised B cell subset (gp91phox < 15%; DHR+ < 4%). Our case-report emphasized the importance of considering a diagnosis of AR-CGD5 deficiency even in absence of typical clinical and laboratory findings.

Co-Occurring X-Linked Agammaglobulinemia and X-Linked Chronic Granulomatous Disease: Two Isolated Pathogenic Variants in One Patient

We present a unique and unusual case of a male patient diagnosed with two coexisting and typically unassociated X-linked conditions: he was initially diagnosed with X-linked agammaglobulinemia (XLA) followed by a diagnosis of X-linked chronic granulomatous disease (XCGD) and an as of yet unpublished hypomorphic gp91phox variant in the CYBB gene. The latter was tested after the finding of granulomatous gingivitis. Hematopoietic stem cell transplant (HSCT) was performed due to severe colitis and nodular regenerative hyperplasia (NRH) of the liver. Following transplant, complete donor engraftment was observed with the restoration of a normal oxidative burst and full restoration of normal levels of circulating, mature CD19+ B cells. This case is singular in that it does not involve a contiguous gene syndrome in which deleted genes are in close proximity to either BTK and CYBB, which has been previously reported. To our knowledge, this is the first reported case of XLA and XCGD co-existing in a single patient and of having both inborn errors of immunity successfully treated by HSCT.

Correcting inborn errors of immunity: From viral mediated gene addition to gene editing

Allogeneic hematopoietic stem cell transplantation is an effective treatment to cure inborn errors of immunity. Remarkable progress has been achieved thanks to the development and optimization of effective combination of advanced conditioning regimens and use of immunoablative/suppressive agents preventing rejection as well as graft versus host disease. Despite these tremendous advances, autologous hematopoietic stem/progenitor cell therapy based on ex vivo gene addition exploiting integrating γ-retro- or lenti-viral vectors, has demonstrated to be an innovative and safe therapeutic strategy providing proof of correction without the complications of the allogeneic approach. The recent advent of targeted gene editing able to precisely correct genomic variants in an intended locus of the genome, by introducing deletions, insertions, nucleotide substitutions or introducing a corrective cassette, is emerging in the clinical setting, further extending the therapeutic armamentarium and offering a cure to inherited immune defects not approachable by conventional gene addition. In this review, we will analyze the current state-of-the art of conventional gene therapy and innovative protocols of genome editing in various primary immunodeficiencies, describing preclinical models and clinical data obtained from different trials, highlighting potential advantages and limits of gene correction.

The first successful bone marrow transplantation in Vietnam for a young Vietnamese boy with chronic granulomatous disease: a case report

Background

Chronic granulomatous disease (CGD) is an inborn error of immunity (IEI) disorder that results from defects in the respiratory burst activity in phagocytes, leading to the inability to kill bacterial and fungal microorganisms. CGD patients usually have a high incidence of morbidity such as infections and autoinflammatory diseases and a high mortality rate. Allogeneic bone marrow transplantation (BMT) is the only definitive cure for patients who suffer from CGD.

Case presentation

We report the first transplant case of chronic granulomatous disease in Vietnam. A 25-month-old boy with X-linked CGD underwent bone marrow transplantation from his 5-year-old, full-matched human leukocyte antigen (HLA)-carrier sibling after myeloablative conditioning regimen with busulfan 5.1 mg/kg/day for 4 days, fludarabine 30 mg/m²/day for 5 days, and rATG (Grafalon-Fresenius) 10 mg/kg/day for 4 days. Neutrophil was engrafted on day 13 posttransplant, donor chimerism was 100% on day 30 with the dihydrorhodamine-1,2,3 (DHR 123) flow cytometric assay test that reached 38% of the normal 45 days posttransplant. Five months after transplant, the patient was free of infection with stable DHR 123 assay at 37%, and donor chimerism remained 100%. No sign of a graft-versus-host disease had been observed posttransplant.

Conclusion

We suggest that bone marrow transplantation is a safe and effectual cure for CGD patients, especially for patients with HLA-identical siblings.

Severe G6PD deficiency leads to recurrent infections and defects in ROS production: Case report and literature review

Purpose: Severe glucose-6-phosphate dehydrogenase (G6PD) deficiency can lead to reduced nicotinamide adenine dinucleotide phosphate oxidase activity in phagocytes, resulting in immunodeficiency, with a limited number of reported cases. Here, we aimed to report a child with severe G6PD deficiency in China and investigate the mechanism of his recurrent infections.

Methods: The clinical manifestations and immunological phenotypes of this patient were retrospectively collected. Gene mutation was detected by whole-exome sequencing and confirmed by Sanger sequencing. Dihydrorhodamine (DHR) analysis was performed to measure the respiratory burst of neutrophils. Messenger ribonucleic acid and protein levels were detected in the patient under lipopolysaccharide stimulation by real-time quantitative reverse transcription polymerase chain reaction and Western blot. A review of the literature was performed.

Results: A male child with G6PD deficiency presented with recurrent respiratory infections, Epstein‒Barr virus infection and tonsillitis from 8 months of age. Gene testing revealed that the proband had one hemizygous mutation in the G6PD gene (c.496 C>T, p. R166C), inherited from his mother. This mutation might affect hydrophobic binding, and the G6PD enzyme activity of the patient was 0. The stimulation indexes of the neutrophils in the patient and mother were 22 and 37, respectively. Compared with healthy controls, decreased reactive oxygen species (ROS) production was observed in the patient. Activation of nuclear factor kappa-B (NF-κB) signaling was found to be influenced, and the synthesis of tumor necrosis factor alpha (TNF-α) was downregulated in the patient-derived cells. In neutrophils of his mother, 74.71% of the X chromosome carrying the mutated gene was inactivated. By performing a systematic literature review, an additional 15 patients with severe G6PD deficiency and recurrent infections were identified. Four other G6PD gene mutations have been reported, including c.1157T>A, c.180_182del, c.514C>T, and c.953_976del.

Conclusion: Severe G6PD deficiency, not only class I but also class II, can contribute to a chronic granulomatous disease-like phenotype. Decreased reactive oxygen species synthesis led to decreased activation of the NF-κB pathway in G6PD-deficient patients. Children with severe G6PD deficiency should be aware of immunodeficiency disease, and the DHR assay is recommended to evaluate neutrophil function for early identification.

A Novel Assay in Whole Blood Demonstrates Restoration of Mitochondrial Activity in Phagocytes After Successful HSCT in Hyperinflamed X-Linked Chronic Granulomatous Disease

X-linked chronic granulomatous disease is a rare disease caused by mutations in the CYBB gene. While more extensive knowledge is available on genetics, pathogenesis, and possible therapeutic options, mitochondrial activity and its implications on patient monitoring are still not well-characterized. We have developed a novel protocol to study mitochondrial activity on whole blood of XCGD patients before and after transplantation, as well as on XCGD carriers. Here we present results of these analyses and of the restoration of mitochondrial activity in hyperinflamed X-linked Chronic Granulomatous Disease after hematopoietic stem cell transplantation. Moreover, we show a strong direct correlation between mitochondrial activity, chimerism, and DHR monitored before and after transplantation and in XCGD carriers. In conclusion, based on these findings, we suggest testing this new ready-to-use marker to better characterize patients before and after treatment and to investigate disease expression in carriers.

Genes as Medicine: The Development of Gene Therapies for Inborn Errors of Immunity

The field of gene therapy has experienced tremendous growth in the last decade ranging from improvements in the design of viral vectors for gene addition of therapeutic gene cassettes to the discovery of site-specific nucleases targeting transgenes to desired locations in the genome. Such advancements have not only enabled the development of disease models but also created opportunities for the development of tailored therapeutic approaches. There are 3 main methods of gene modification that can be used for the prevention or treatment of disease. This includes viral vector-mediated gene therapy to supply or bypass a missing/defective gene, gene editing enabled by programmable nucleases to create sequence-specific alterations in the genome, and gene silencing to reduce the expression of a gene or genes. These gene-modification platforms can be delivered either in vivo, for which the therapy is injected directed into a patient's body, or ex vivo, in which cells are harvested from a patient and modified in a laboratory setting, and then returned to the patient.

Defects of the Innate Immune System and Related Immune Deficiencies

The innate immune system is the host's first line of defense against pathogens. Toll-like receptors (TLRs) are pattern recognition receptors that mediate recognition of pathogen-associated molecular patterns. TLRs also activate signaling transduction pathways involved in host defense, inflammation, development, and the production of inflammatory cytokines. Innate immunodeficiencies associated with defective TLR signaling include mutations in NEMO, IKBA, MyD88, and IRAK4. Other innate immune defects have been associated with susceptibility to herpes simplex encephalitis, viral infections, and mycobacterial disease, as well as chronic mucocutaneous candidiasis and epidermodysplasia verruciformis. Phagocytes and natural killer cells are essential members of the innate immune system and defects in number and/or function of these cells can lead to recurrent infections. Complement is another important part of the innate immune system. Complement deficiencies can lead to increased susceptibility to infections, autoimmunity, or impaired immune complex clearance. The innate immune system must work to quickly recognize and eliminate pathogens as well as coordinate an immune response and engage the adaptive immune system. Defects of the innate immune system can lead to failure to quickly identify pathogens and activate the immune response, resulting in susceptibility to severe or recurrent infections.

HSCT using carrier donors for CD40L deficiency results in excellent immune function and higher CD40L expression in cTfh

Data are limited regarding the immune status of CD40 ligand (CD40L)-deficient carriers and hematopoietic stem cell transplantation (HSCT) outcomes using them as donors for CD40L-deficient patients. Therefore, we studied the immune profiles of 7 carriers, 4 of whom were HSCT donors for family members with CD40L deficiency, and we characterized their HSCT outcomes. Immunoglobulin profiles, CD4, CD8, circulating T-follicular helper (cTfh) cells, and regulatory T cells (Tregs) in carriers were comparable to those in healthy controls. CD40L expression in carriers ranged from 37% to 78%. cTfh cells from carriers expressed higher CD40L compared with total CD4 cells or the memory CD4 compartment, suggesting a potential advantage to CD40L-expressing cTfh cells. Tregs had minimal CD40L expression in carriers and healthy controls. So we postulated that HSCT using donors who were CD40L carriers may result in excellent immune reconstitution without immune dysregulation. Four CD40L-deficient patients underwent HSCT from carriers who had CD40L expression from 37% to 63%. All patients engrafted, achieved excellent immune reconstitution with lack of opportunistic infections, graft-versus-host disease, and immune dysregulation; stable CD40L expression mimicked that of donors 1 to 5 years after HSCT. Immunoglobulin independence was achieved in 3 of the 4 patients. We demonstrated higher CD40L expression in the cTfh compartment of carriers and excellent immune reconstitution using donors who were CD40L carriers in CD40L-deficient patients.

Novel mutations in unrelated Vietnamese patients with chronic granulomatous disease

BACKGROUND

Chronic granulomatous disease (CGD) is a rare primary immunodeficiency disorder (PID) due to genetic defects in the NADPH oxidase of phagocytes. Affected patients become susceptible to infections such as pneumonia, diarrhea, and skin ulcer types. The patients require life-long treatment with prophylactic antibiotics, antifungals, or hematopoietic stem cell transplantation (HSCT) therapy. Early, accurate diagnosis will contribute to the life-prolonging of patients with CGD. This study's aim is to identify the mutation related to the disease. Case presentation Six patients from different Vietnamese families were collected for genetic analysis at Allergy, Immunology, and Rheumatology Department, Vietnam National Hospital Pediatrics. They were diagnosed with CGD by flow cytometry test with the conversion of dihydrorhodamine (DHR) 123 to rhodamine 123.

METHODS

We performed whole exome sequencing (WES) as a tool for detecting novel mutations. The mutations were confirmed by the Sanger sequencing method in patients and their families. The influence of the mutations was predicted with the in silico analysis tools: PROVEAN, SIFT, PolyPhen 2, Mutation Taster, and MaxEntScan.

RESULTS

In this study, five mutations were found in six unrelated patients with CGD from different Vietnamese families. Three novel pathogenic mutations were detected including one mutation (c.45+2T>G) in the CYBB gene and two mutations (c.187_188insA and c.289G>C) in the NCF2 gene.

CONCLUSIONS

Our results of CGD-related mutations contribute to the general understanding of the etiology of the disease and emphasize that WES sequencing can be used as a tool to help to diagnose carriers as well as assist in genetic counseling and prenatal screening.

Chronic Granulomatous Disease: an Updated Experience, with Emphasis on Newly Recognized Features

Purpose

Chronic granulomatous disease (CGD) is an uncommon, inborn error of immunity. We updated our large, single-center US experience with CGD and describe some newly recognized features.

Methods

We retrospectively reviewed 26 patients seen from November 2013 to December 2019. Serious infections required intravenous antibiotics or hospitalization.

Results

There were 21 males and 5 females. The most frequent infectious agents at presentation were aspergillus (4), serratia (4), burkholderia (2), Staphylococcus aureus (2), and klebsiella (2). The most common serious infections at presentation were pneumonia (6), lymphadenitis (6), and skin abscess (3). Our serious infection rate was 0.2 per patient-year from December 2013 through November 2019, down from 0.62 per patient-year from the previous study period (March 1985–November 2013). In the last 6 years, four patients were evaluated for human stem cell transplantation, two were successfully transplanted, and we had no deaths. Several patients had unusual infections or autoimmune manifestations of disease, such as pneumocystis pneumonia, basidiomycete/phellinus fungal pneumonia, and retinitis pigmentosa. We included one carrier female with unfavorable Lyonization in our cohort.

Conclusion

We update of a large US single-center experience with CGD and describe some recently identified features of the illness.

Autoimmunity in Primary Immunodeficiencies (PID)

Primary immunodeficiency (PID) may impact any component of the immune system. The number of PID and immune dysregulation disorders is growing steadily with advancing genetic detection methods. These expansive recognition methods have changed the way we characterize PID. While PID were once characterized by their susceptibility to infection, the increase in genetic analysis has elucidated the intertwined relationship between PID and non-infectious manifestations including autoimmunity. The defects permitting opportunistic infections to take hold may also lead the way to the development of autoimmune disease. In some cases, it is the non-infectious complications that may be the presenting sign of PID autoimmune diseases, such as autoimmune cytopenia, enteropathy, endocrinopathies, and arthritis among others, have been reported in PID. While autoimmunity may occur with any PID, this review will look at certain immunodeficiencies most often associated with autoimmunity, as well as their diagnosis and management strategies.

Heightened turnover and failed maturation of monocyte-derived macrophages in murine chronic granulomatous disease

Loss of NADPH oxidase activity leads to altered phagocyte responses and exaggerated inflammation in chronic granulomatous disease (CGD). We sought to assess the effects of Nox2 absence on monocyte-derived macrophages (MoMacs) in gp91phox-/y mice during zymosan-induced peritonitis. MoMacs from CGD and wild-type (WT) peritonea were characterized over time after zymosan injection. Although numbers lavaged from both genotypes were virtually identical, there were marked differences in maturation: newly recruited WT MoMacs rapidly enlarged and matured, losing Ly6C and gaining MHCII, CD206, and CD36, whereas CGD MoMacs remained small and were mostly Ly6C+MHCII-. RNA-sequencing analyses showed few intrinsic differences between genotypes in newly recruited MoMacs but significant differences with time. WT MoMacs displayed changes in metabolism, adhesion, and reparative functions, whereas CGD MoMacs remained inflammatory. PKH dye labeling revealed that although WT MoMacs were mostly recruited within the first 24 hours and remained in the peritoneum while maturing and enlarging, CGD monocytes streamed into the peritoneum for days, with many migrating to the diaphragm where they were found in fibrin(ogen) clots surrounding clusters of neutrophils in nascent pyogranulomata. Importantly, these observations seemed to be driven by milieu: adoptive transfer of CGD MoMacs into inflamed peritonea of WT mice resulted in immunophenotypic maturation and normal behavior, whereas altered maturation/behavior of WT MoMacs resulted from transfer into inflamed peritonea of CGD mice. In addition, Nox2-deficient MoMacs behaved similarly to their Nox2-sufficient counterparts within the largely WT milieu of mixed bone marrow chimeras. These data show persistent recruitment with fundamental failure of MoMac maturation in CGD.

Pneumocystis jirovecii pneumonia in a X-linked chronic granulomatous disease female carrier

The X-chromosome linked (XL) female carriers of chronic granulomatous disease (CGD) are considered to have no risk for infection. Herein we present a female CGD XL-carrier who developed Pneumocystis jirovecii pneumonia and Serratia marcescens infection associated with age-related skewing of X-chromosome inactivation.

Late Onset of Chronic Granulomatous Disease Revealed by Paecilomyces lilacinus Cutaneous Infection

Chronic granulomatous disease (CGD) is an inherited immunodeficiency due to defective leukocyte NADPH responsible for recurrent infections and aberrant inflammation. Mutations in the CYBB gene are responsible for the X-linked CGD and account for approximately 70% of the cases. CGD is diagnosed during childhood in males. Female carriers may have biased X-inactivation and may present with clinical manifestations depending on the level of residual NADPH oxidase activity. We report the case of a previously asymptomatic female carrier who was diagnosed at age 67 with a skin infection with the rare fungus Paecilomyces lilacinus as the first manifestation of CGD. Dihydrorhodamine 123 (DHR) activity was below 10%. Next-generation sequencing (NGS) revealed mutations in DNMT3A, ASXL1, and STAG2 suggesting that clonal hematopoiesis could be responsible for a progressive loss of NADPH oxidase activity and the late onset of X-linked CGD in this patient. Long-term follow-up of asymptomatic carrier women seems to be essential after 50 years old.

How I Treat: Allogeneic HSCT for adults with Inborn Errors of Immunity

Inborn Errors of Immunity (IEI) are rare inherited disorders arising from monogenic germline mutations in genes that regulate the immune system. The majority of IEI are Primary Immunodeficiencies characterised by severe infection often associated with autoimmunity, autoinflammation and/or malignancy. Allogeneic hematopoietic stem cell transplant (HSCT) has been the corrective treatment of choice for many IEI presenting with severe disease in early childhood and experience has made this a successful and comparatively safe treatment in affected children. Early HSCT outcomes in adults were poor, resulting in extremely limited use worldwide. This is changing due to a combination of improved IEI diagnosis to inform patient selection, better understanding of the natural history of specific IEI and improvements in transplant practice. Recently published HSCT outcomes for adults with IEI have been comparable with pediatric data, making HSCT an important option for correction of clinically severe IEI in adulthood. Here we discuss our practice for patient selection, timing of HSCT, donor selection and conditioning, peri- and post HSCT management and our approach to long term follow up. We stress the importance of multidisciplinary involvement in the complex decision-making process that we believe is required for successful outcomes in this rapidly emerging area.

Correction of X-CGD patient HSPCs by targeted CYBB cDNA insertion using CRISPR/Cas9 with 53BP1 inhibition for enhanced homology-directed repair

X-linked chronic granulomatous disease is an immunodeficiency characterized by defective production of microbicidal reactive oxygen species (ROS) by phagocytes. Causative mutations occur throughout the 13 exons and splice sites of the CYBB gene, resulting in loss of gp91phox protein. Here we report gene correction by homology-directed repair in patient hematopoietic stem/progenitor cells (HSPCs) using CRISPR/Cas9 for targeted insertion of CYBB exon 1-13 or 2-13 cDNAs from adeno-associated virus donors at endogenous CYBB exon 1 or exon 2 sites. Targeted insertion of exon 1-13 cDNA did not restore physiologic gp91phox levels, consistent with a requirement for intron 1 in CYBB expression. However, insertion of exon 2-13 cDNA fully restored gp91phox and ROS production upon phagocyte differentiation. Addition of a woodchuck hepatitis virus post-transcriptional regulatory element did not further enhance gp91phox expression in exon 2-13 corrected cells, indicating that retention of intron 1 was sufficient for optimal CYBB expression. Targeted correction was increased ~1.5-fold using i53 mRNA to transiently inhibit nonhomologous end joining. Following engraftment in NSG mice, corrected HSPCs generated phagocytes with restored gp91phox and ROS production. Our findings demonstrate the utility of tailoring donor design and targeting strategies to retain regulatory elements needed for optimal expression of the target gene.

Immunological Aspects of X-Linked Chronic Granulomatous Disease Female Carriers

X-linked Granulomatous Disease (XL-CGD) carriers were previously thought to be clinically healthy because random X-chromosome inactivation (XCI) allows approximately half of their phagocytes/monocytes to express functional gp91phox protein. This supports the NADPH oxidase activity necessary for the killing of engulfed pathogens. Some XL-CGD carriers suffer from inflammatory and autoimmune manifestations as well as infections, although the skewed-XCI of a mutated allele is reported to be exclusively determinant for infection susceptibility. Indeed, immune dysregulation could be determined by dysfunctional non-phagocytic leukocytes rather than the percentage of functioning neutrophils. Here we investigated in a cohort of 12 X-CGD female carriers at a particular time of their life the gp91phox protein expression/function and how this affects immune cell function. We showed that 50% of carriers have an age-independent skewed-XCI and 65% of them have a misrepresented expression of the wild-type gene. The majority of carriers manifested immune dysregulation and GI manifestations regardless of age and XCI. Immunological investigations revealed an increase in CD19+ B cells, CD56bright-NK cell percentage, a slightly altered CD107a upregulation on CD4+ T cells, and reduced INFγ-production by CD4+ and CD8+ cells. Notably, we demonstrated that the residual level of ROS robustly correlates with INFγ-expressing T cells, suggesting a role in promoting immune dysregulation in carriers.

A Toolkit and Framework for Optimal Laboratory Evaluation of Individuals with Suspected Primary Immunodeficiency

Knowledge related to the biology of inborn errors of immunity and associated laboratory testing methods continues to expand at a tremendous rate. Despite this, many patients with inborn errors of immunity suffer for prolonged periods of time before identification of their underlying condition, thereby delaying appropriate care. Understanding that test selection and optimal evaluation for patients with recurrent infections or unusual patterns of inflammation can be unclear, we present a document that distills relevant clinical features of immunologic disease due to inborn errors of immunity and related appropriate and available test options. This document is intended to serve the practicing clinical immunologist and, in turn, patients by describing best available test options for initial and expanded immunologic evaluations across the disease spectrum. Our goal is to demystify the process of evaluating patients with suspected immune dysfunction and to enable more rapid and accurate diagnosis of such individuals.

The New "Wholly Trinity" in the Diagnosis and Management of Inborn Errors of Immunity

The field of immunology has a rich and diverse history, and the study of inborn errors of immunity (IEIs) represents both the "cake" and the "icing on top of the cake," as it has enabled significant advances in our understanding of the human immune system. This explosion of knowledge has been facilitated by a unique partnership, a triumvirate formed by the physician who gathers detailed immunological and clinical phenotypic information from, and shares results with, the patient; the laboratory scientist/immunologist who performs diagnostic testing, as well as advanced functional correlative studies; and the genomics scientist/genetic counselor, who conducts and interprets varied genetic analyses, all of which are essential for dissecting constitutional genetic disorders. Although the basic principles of clinical care have not changed in recent years, the practice of clinical immunology has changed to reflect the prodigious advances in diagnostics, genomics, and therapeutics. An "omic/tics"-centric approach to IEI reflects the tremendous strides made in the field in the new millennium with recognition of new disorders, characterization of the molecular underpinnings, and development and implementation of personalized treatment strategies. This review brings renewed attention to bear on the indispensable "trinity" of phenotypic, genomic, and immunological analyses in the diagnosis, management, and treatment of IEIs.

Enhanced homology-directed repair for highly efficient gene editing in hematopoietic stem/progenitor cells

Lentivector gene therapy for X-linked chronic granulomatous disease (X-CGD) has proven to be a viable approach, but random vector integration and subnormal protein production from exogenous promoters in transduced cells remain concerning for long-term safety and efficacy. A previous genome editing-based approach using Streptococcus pyogenes Cas9 mRNA and an oligodeoxynucleotide donor to repair genetic mutations showed the capability to restore physiological protein expression but lacked sufficient efficiency in quiescent CD34+ hematopoietic cells for clinical translation. Here, we report that transient inhibition of p53-binding protein 1 (53BP1) significantly increased (2.3-fold) long-term homology-directed repair to achieve highly efficient (80% gp91phox+ cells compared with healthy donor control subjects) long-term correction of X-CGD CD34+ cells.

Clinical Features of Female Taiwanese Carriers with X-linked Chronic Granulomatous Disease from 2004 to 2019

PURPOSE

Female carriers with X-linked chronic granulomatous disease (XL-CGD) who have < 10% reactive oxygen species (ROS) production due to profound X-chromosome inactivation (XCI or lyonization) are more susceptible to infections. We assessed ROS production in Taiwanese female carriers with XL-CGD to investigate whether the level of ROS correlated to their clinical features of infection, autoimmunity, and autoinflammation.

METHODS

Clinical course, ROS production, flavocytochrome b558 (Cyto b558) expression, and genetic analysis in carriers were investigated after identifying their index cases between 2004 and 2019.

RESULTS

A total of 19 mothers (median 27 years; range 25-60 years) and three of four girls (range 4-6 years) relative to 22 male index XL-CGD cases from 19 unrelated families were enrolled. Approximately half (8/19, 42%) of the mothers had novel one-allele mutations. Twenty-two of the 23 females were carriers. One carrier with de novo [Arg290X]CYBB who suffered from refractory salmonella sepsis and chorioretinitis as an XL-CGD phenotype had extreme XCI, absent Cyto b558 expression, and only 8% ROS production. The remaining carriers had bimodal patterns of Cyto b558 expressions (median 40.2%, 26.8-52.4%) and ROS production (38.3%, range 28.2-54.2%) sufficient to prevent significant infections, although neck lymphadenitis recurred in one mother and sister who had ROS expressions of 28.2% and 38.0%, respectively. However, none of the carriers had manifestations of autoimmunity or autoinflammation (e.g., photosensitivity, aphthous stomatitis, or joint disorders), of which each was seen in approximately one-third of XL-CGD carriers from the Western world.

CONCLUSION

One carrier had undetectable Cyto b558 expression and an extremely low ROS production, and consequently presented with an XL-CGD phenotype. One mother and her daughter experienced recurrent neck lymphadenitis despite having sufficient ROS production. Significant autoimmunity/autoinflammation did not develop in any of the carriers. Studies with a longer follow-up period are needed to validate our findings.

Preclinical Optimization and Safety Studies of a New Lentiviral Gene Therapy for p47phox-Deficient Chronic Granulomatous Disease

Chronic granulomatous disease (CGD) is an inherited blood disorder of phagocytic cells that renders patients susceptible to infections and inflammation. A recent clinical trial of lentiviral gene therapy for the most frequent form of CGD, X-linked, has demonstrated stable correction over time, with no adverse events related to the gene therapy procedure. We have recently developed a parallel lentiviral vector for p47^phox-deficient CGD (p47^phoxCGD), the second most common form of this disease. Using this vector, we have observed biochemical correction of CGD in a mouse model of the disease. In preparation for clinical trial approval, we have performed standardized preclinical studies following Good Laboratory Practice (GLP) principles, to assess the safety of the gene therapy procedure. We report no evidence of adverse events, including mutagenesis and tumorigenesis, in human hematopoietic stem cells transduced with the lentiviral vector. Biodistribution studies of transduced human CD34⁺ cells indicate that the homing properties or engraftment ability of the stem cells is not negatively affected. CD34⁺ cells derived from a p47^phoxCGD patient were subjected to an optimized transduction protocol and transplanted into immunocompromised mice. After the procedure, patient-derived neutrophils resumed their function, suggesting that gene correction was successful. These studies pave the way to a first-in-man clinical trial of lentiviral gene therapy for the treatment of p47^phoxCGD.

Genetic Mosaicism as a Cause of Inborn Errors of Immunity

Inborn errors of immunity (IEIs) are a heterogeneous group of disorders due to genetic defects in the immune response that have a broad clinical spectrum. Diagnosis of the precise genetic cause of IEI has led to improved care and treatment of patients; however, genetic diagnosis using standard approaches is only successful in ~40% of patients and is particularly challenging in “sporadic” cases without a family history. Standard genetic testing for IEI evaluates for germline changes in genes encoding proteins important for the immune response. It is now clear that IEI can also arise from de novo mutations leading to genetic variants present in germ cells and/or somatic cells. In particular, somatic mosaicism, i.e., post-zygotic genetic changes in DNA sequence, is emerging as a significant contributor to IEI. Testing for somatic mosaicism can be challenging, and both older sequencing techniques such as Sanger sequencing and newer next-generation sequencing may not be sensitive enough to detect variants depending on the platform and analysis tools used. Investigation of multiple tissue samples and specifically targeting sequence technologies to detect low frequency variants is important for detection of variants. This review examines the role and functional consequences of genetic mosaicism in IEI. We emphasize the need to refine the current exome and genome analysis pipeline to efficiently identify mosaic variants and recommend considering somatic mosaicism in disease discovery and in the first-tier of genetic analysis.

From Flies to Men: ROS and the NADPH Oxidase in Phagocytes

The cellular formation of reactive oxygen species (ROS) represents an evolutionary ancient antimicrobial defense system against microorganisms. The NADPH oxidases (NOX), which are predominantly localized to endosomes, and the electron transport chain in mitochondria are the major sources of ROS. Like any powerful immunological process, ROS formation has costs, in particular collateral tissue damage of the host. Moreover, microorganisms have developed defense mechanisms against ROS, an example for an arms race between species. Thus, although NOX orthologs have been identified in organisms as diverse as plants, fruit flies, rodents, and humans, ROS functions have developed and diversified to affect a multitude of cellular properties, i.e., far beyond direct antimicrobial activity. Here, we focus on the development of NOX in phagocytic cells, where the so-called respiratory burst in phagolysosomes contributes to the elimination of ingested microorganisms. Yet, NOX participates in cellular signaling in a cell-intrinsic and -extrinsic manner, e.g., via the release of ROS into the extracellular space. Accordingly, in humans, the inherited deficiency of NOX components is characterized by infections with bacteria and fungi and a seemingly independently dysregulated inflammatory response. Since ROS have both antimicrobial and immunomodulatory properties, their tight regulation in space and time is required for an efficient and well-balanced immune response, which allows for the reestablishment of tissue homeostasis. In addition, distinct NOX homologs expressed by non-phagocytic cells and mitochondrial ROS are interlinked with phagocytic NOX functions and thus affect the overall redox state of the tissue and the cellular activity in a complex fashion. Overall, the systematic and comparative analysis of cellular ROS functions in organisms of lower complexity provides clues for understanding the contribution of ROS and ROS deficiency to human health and disease.

Immunity and Genetics at the Revolving Doors of Diagnostics in Primary Immunodeficiencies

Primary immunodeficiencies (PIDs) are a large and growing group of disorders commonly associated with recurrent infections. However, nowadays, we know that PIDs often carry with them consequences related to organ or hematologic autoimmunity, autoinflammation, and lymphoproliferation in addition to simple susceptibility to pathogens. Alongside this conceptual development, there has been technical advancement, given by the new but already established diagnostic possibilities offered by new genetic testing (e.g., next-generation sequencing). Nevertheless, there is also the need to understand the large number of gene variants detected with these powerful methods. That means advancing beyond genetic results and resorting to the clinical phenotype and to immunological or alternative molecular tests that allow us to prove the causative role of a genetic variant of uncertain significance and/or better define the underlying pathophysiological mechanism. Furthermore, because of the rapid availability of results, laboratory immunoassays are still critical to diagnosing many PIDs, even in screening settings. Fundamental is the integration between different specialties and the development of multidisciplinary and flexible diagnostic workflows. This paper aims to tell these evolving aspects of immunodeficiencies, which are summarized in five key messages, through introducing and exemplifying five clinical cases, focusing on diseases that could benefit targeted therapy.

Disease Presentation, Treatment Options, and Outcomes for Myeloid Immunodeficiencies

PURPOSE OF REVIEW

Up-to-date review on various types of immunodeficiencies with a significant myeloid component including some more recently described congenital disorders.

RECENT FINDINGS

While a number of disorders have been described in the past, genetic sequencing has led to the identification of the specific disorders and clarified their pathophysiology. Advances in genetic therapies including genetic editing should provide future treatments beyond hematopoietic stem cell transplant for patients with these rare disorders. Neutrophils (or granulocytes) are a major contributor to infection surveillance and clearance, and defective neutrophils characteristically lead to pyogenic infections. Deficiency in numbers, either iatrogenic or congenital; functional defects; and/or inability to target to the sites of infection can all lead to serious morbidity and mortality; however, myeloid-based immunodeficiencies are not all the same. Having absent neutrophils, that is, neutropenia, has implications different to those of having dysfunctional neutrophils as will become evident as the various disorders are reviewed.

Gene Therapies for Primary Immune Deficiencies

Gene therapy is an innovative treatment for Primary Immune Deficiencies (PIDs) that uses autologous hematopoietic stem cell transplantation to deliver stem cells with added or edited versions of the missing or malfunctioning gene that causes the PID. Initial studies of gene therapy for PIDs in the 1990-2000's used integrating murine gamma-retroviral vectors. While these studies showed clinical efficacy in many cases, especially with the administration of marrow cytoreductive conditioning before cell re-infusion, these vectors caused genotoxicity and development of leukoproliferative disorders in several patients. More recent studies used lentiviral vectors in which the enhancer elements of the long terminal repeats self-inactivate during reverse transcription ("SIN" vectors). These SIN vectors have excellent safety profiles and have not been reported to cause any clinically significant genotoxicity. Gene therapy has successfully treated several PIDs including Adenosine Deaminase Severe Combined Immunodeficiency (SCID), X-linked SCID, Artemis SCID, Wiskott-Aldrich Syndrome, X-linked Chronic Granulomatous Disease and Leukocyte Adhesion Deficiency-I. In all, gene therapy for PIDs has progressed over the recent decades to be equal or better than allogeneic HSCT in terms of efficacy and safety. Further improvements in methods should lead to more consistent and reliable efficacy from gene therapy for a growing list of PIDs.

Oxidants in Physiological Processes

A number of diseases and conditions have been associated with prolonged or persistent exposure to non-physiological levels of reactive oxygen species (ROS). Similarly, ROS underproduction due to loss-of-function mutations in superoxide or hydrogen peroxide (H₂O₂)-generating enzymes is a risk factor or causative for certain diseases. However, ROS are required for basic cell functions; in particular the diffusible second messenger H₂O₂ that serves as signaling molecule in redox processes. This activity sets H₂O₂ apart from highly reactive oxygen radicals and influences the approach to drug discovery, clinical utility, and therapeutic intervention. Here we review the chemical and biological fundamentals of ROS with emphasis on H₂O₂ as a signaling conduit and initiator of redox relays and propose an integrated view of physiological versus non-physiological reactive species. Therapeutic interventions that target persistently altered ROS levels should include both selective inhibition of a specific source of primary ROS and careful consideration of a targeted pro-oxidant approach, an avenue that is still underdeveloped. Both strategies require attention to redox dynamics in complex cellular systems, integration of the overall spatiotemporal cellular environment, and target validation to yield effective and safe therapeutics. The only professional primary ROS producers are NADPH oxidases (NOX1-5, DUOX1-2). Many other enzymes, e.g., xanthine oxidase (XO), monoamine oxidases (MAO), lysyl oxidases (LO), lipoxygenase (LOX), and cyclooxygenase (COX), produce superoxide and H₂O₂ secondary to their primary metabolic function. Superoxide is too reactive to disseminate, but H₂O₂ is diffusible, only limited by adjacent PRDXs or GPXs, and can be apically secreted and imported into cells through aquaporin (AQP) channels. H₂O₂ redox signaling includes oxidation of the active site thiol in protein tyrosine phosphatases, which will inhibit their activity and thereby increase tyrosine phosphorylation on target proteins. Essential functions include the oxidative burst by NOX2 as antimicrobial innate immune response; gastrointestinal NOX1 and DUOX2 generating low H₂O₂ concentrations sufficient to trigger antivirulence mechanisms; and thyroidal DUOX2 essential for providing H₂O₂ reduced by TPO to oxidize iodide to an iodinating form which is then attached to tyrosyls in TG. Loss-of-function (LoF) variants in TPO or DUOX2 cause congenital hypothyroidism and LoF variants in the NOX2 complex chronic granulomatous disease.