Chronic granulomatous disease

Design and Synthesis of 2-(4-Bromophenyl)Quinoline-4-Carbohydrazide Derivatives via Molecular Hybridization as Novel Microbial DNA-Gyrase Inhibitors

Microbial DNA gyrase is regarded as an outstanding microbial target. Hence, 15 new quinoline derivatives (5-14) were designed and synthesized. The antimicrobial activity of the afforded compounds was pursued via in vitro approaches. The investigated compounds displayed eligible MIC values, particularly against G-positive Staphylococcus aureus species. Consequently, an S. aureus DNA gyrase supercoiling assay was performed, using ciprofloxacin as a reference control. Obviously, compounds 6b and 10 unveiled IC₅₀ values of 33.64 and 8.45 μM, respectively. Alongside, ciprofloxacin exhibited an IC₅₀ value of 3.80 μM. Furthermore, a significant docking binding score was encountered by compound 6b (-7.73 kcal/mol), surpassing ciprofloxacin (-7.29 kcal/mol). Additionally, both compounds 6b and 10 revealed high GIT absorption without passing the blood brain barrier. Finally, the conducted structure-activity relationship study assured the usefulness of the hydrazine moiety as a molecular hybrid for activity either in cyclic or opened form.

The Multiple Faces of Nitric Oxide in Chronic Granulomatous Disease: A Comprehensive Update

Nitric oxide (NO), a signaling molecule, regulates multiple biological functions, including a variety of physiological and pathological processes. In this regard, NO participates in cutaneous inflammations, modulation of mitochondrial functions, vascular diseases, COVID-19, neurologic diseases, and obesity. It also mediates changes in the skeletal muscle function. Chronic granulomatous disease (CGD) is a primary immunodeficiency disorder characterized by the malfunction of phagocytes caused by mutations in some of the genes encoding subunits of the superoxide-generating phagocyte NADPH (NOX). The literature consulted shows that there is a relationship between the production of NO and the NADPH oxidase system, which regulates the persistence of NO in the medium. Nevertheless, the underlying mechanisms of the effects of NO on CGD remain unknown. In this paper, we briefly review the regulatory role of NO in CGD and its potential underlying mechanisms.

Long-Term Observational Study of Chronic Granulomatous Disease About 41 Patients From Tunisia and Comparison to Other Long-Term Follow-Up Studies

Chronic granulomatous disease (CGD) is an inherited autosomal recessive or X-Linked primitive immunodeficiency (PID), due to a defective nicotinamide adenine dinucleotide phosphate (NADPH) oxidase complex impairing anti-infectious and anti-inflammatory role of peripheral blood mononuclear cells. It is characterized by severe bacterial and fungal infections and by excessive inflammation leading to granulomatous complications. This work was made over a period of 34 years on 41 Tunisian patients suffering from CGD. Cumulative follow-up of patients was 2768.5 months, median 31 months. Survival was studied by survival curves according to Kaplan-Meier method. Lymphatic nodes, pulmonary and cutaneous infections predominate as revealing manifestations and as infectious events during patients' monitoring. At study end 12 patients died mainly of invasive pulmonary aspergillosis and septicemia. Median age of death was 30 months. CGD remains compatible with a decent quality of life. Early diagnosis, anti-infectious prophylaxis, and initiation of adequate management, as soon as complication is perceived, promote pretty good evolution.

The Protective Role of 1,8-Dihydroxynaphthalene-Melanin on Conidia of the Opportunistic Human Pathogen Aspergillus fumigatus Revisited: No Role in Protection against Hydrogen Peroxide and Superoxides

Previously, 1,8-dihydroxynaphthalene (DHN)-melanin was described to protect Aspergillus fumigatus against hydrogen peroxide (H₂O₂), thereby protecting this opportunistic human pathogen from reactive oxygen species generated by the immune system. This was based on the finding that the ATCC 46645 mutant with mutations in the pksP gene of the DHN-melanin synthesis pathway showed increased sensitivity to reactive oxygen species compared to the wild type. Here, it is shown that deletion of the pksP gene in A. fumigatus strain CEA10 did not affect sensitivity for H₂O₂ and superoxide in a plate stress assay. In addition, direct exposure of the dormant white conidia of the pksP deletion strains to H₂O₂ did not result in increased sensitivity. Moreover, complementation of the ATCC 46645 pksP mutant strain with the wild-type pksP gene did result in pigmented conidia but did not rescue the H₂O₂-sensitive phenotype observed in the plate stress assay. Genome sequencing of the ATCC 46645 pksP mutant strain and its complemented strain revealed a mutation in the cat1 gene, likely due to the UV mutagenesis procedure used previously, which could explain the increased sensitivity toward H₂O₂. In summary, DHN-melanin is not involved in protection against H₂O₂ or superoxide and, thus, has no role in survival of conidia when attacked by these reactive oxygen species. IMPORTANCE Opportunistic pathogens like Aspergillus fumigatus have strategies to protect themselves against reactive oxygen species like hydrogen peroxides and superoxides that are produced by immune cells. DHN-melanin is the green pigment on conidia of Aspergillus fumigatus and more than 2 decades ago was reported to protect conidia against hydrogen peroxide. Here, we correct this misinterpretation by showing that DHN-melanin actually is not involved in protection of conidia against hydrogen peroxide. We show that UV mutagenesis that was previously used to select a pksP mutant generated many more genome-wide mutations. We discovered that a mutation in the mycelial catalase gene cat1 could explain the observed phenotype of increased hydrogen peroxide sensitivity. Our work shows that UV mutagenesis is not the preferred methodology to be used for generating mutants. It requires genome sequencing with single-nucleotide polymorphism analysis as well as additional validations to discard unwanted and confirm correct phenotypes.

Utility of Immunohistochemistry and Immunofluorescence in Determining the Pathogenic Variants of Chronic Granulomatous Disease

BACKGROUND

Chronic granulomatous disease (CGD) is a primary immunodeficiency disorder of phagocytes due to defects in any of the five subunits of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase complex. An initial diagnosis of CGD is made by flow cytometry-based dihydrorhodamine assay or nitro blue tetrazolium test, which is further confirmed by molecular assays. Expression of five subunits of NADPH oxidase components by either flow cytometric or western blot analysis provides clues toward the potential gene targets which are subsequently confirmed by various genetic assays. Immunohistochemistry (IHC) and immunofluorescence (IF) have never been earlier used to determine the expression of different subunits of NADPH oxidase system. We evaluated the utility of IHC and IF in determining the underlying pathogenic variants of CGD.

MATERIALS AND METHODS

Twelve genetically confirmed cases of CGD, comprising of biopsy specimens (n = 6), tissue blocks from autopsy cases (n = 3), and cellblocks of cell pellet prepared from peripheral blood (n = 4) were included. IHC for p67phox and p47phox subunits and IF for cytochrome b558 were performed.

RESULTS

All 4 cases with pathogenic variation of NCF2 gene showed loss of expression for p67phox subunit. Two cases with pathogenic variation of NCF1 gene showed loss of expression for p47phox subunit. Five cases, except a single case with CYBB gene pathogenic variation, showed loss of expression for cytochrome b558 on IF. Thus, loss of expression consistently matched with the underlying genetic defects assessed by sequencing.

CONCLUSIONS

Our results confirm our hypothesis that IHC and IF are two rapid, economical, pathologist-friendly techniques providing pertinent information regarding the underlying pathogenic variants and such immuno-analysis can be easily performed on the tissue.

Chromobacterium violaceum: A Review of an Unexpected Scourge

Chromobacterium violaceum is a common environmental bacterium that rarely causes disease in humans but has a high fatality rate if it does. Due to the rarity of the cases, clinicians are often unaware of the rapid progression of C. violaceum infection and its unexpected antibiotic resistance pattern, which contribute to the failure of patient management. Our review provides the clinical characteristics, possible sources of exposure, and comorbidities and determines factors associated with survival. We gathered information on 132 cases of C. violaceum causing disease in humans published between 1953 and 2020. Patients were predominantly male with a median age of 17.5, interquartile range (IQR) of 5.0-40.0 years, and a third of them were known to have immune deficiencies or comorbidities. Portals of entry were mainly through a wound in the leg and feet (28.0%), the torso (8.5%), or hands and arms (6.8%). It is not uncommon to acquire infection through unintended contact with contaminated water or dust through the mouth or inhalation. The median incubation period is 4.0 days (IQR 2.0-8.0 days) with a duration of clinical course of 17.5 days (IQR 8.0-30.8 days). The high rate of positive blood cultures (56.1%) and abscesses in internal organs (36.4%) shows the significant severity of this disease. Sepsis and Bacteremia were related to mortality with a risk ratio (RR) of 5.20 (95% CI, 0.831-32.58) and 2.14 (95% CI, 1.05-4.36), respectively. Appropriate antibiotic use prevented death at a RR 0.33 (95% CI, 0.21-0.52). Most patients who recovered and survived were treated with aminoglycosides, fluoroquinolones and carbapenems. This review shows the malignant nature of C. violaceum infection and the need for clinicians to be aware and provide prompt source management for patients. Appropriate empiric and targeted antibiotic regiment guided by susceptibility test results is of vital importance.

Kinetic Separation of Oxidative and Non-oxidative Metabolism in Single Phagosomes from Alveolar Macrophages: Impact on Bacterial Killing

The relative contribution of the two phagosomal catabolic processes, oxidative and metabolic, was assessed in the killing of Pseudomonas aeruginosa in phagosomes of alveolar macrophages (AMs) from wild-type (p47-phox^+/+) or NOX-defective (p47-phox^−/−) mice. Free radical release and degradative acidification within AM phagosomes is sequential and separable. The initial NOX activity, identifiable as a transient alkalinization, leads to fast bacterial wall permeabilization by ROS. This is followed by V-ATPase-induced acidification and enzymatic bacterial degradation contributed through phagosomal-lysosomal fusion. The alkalinization/acidification ratio was variable among phagosomes within single cells of a given genotype and not as a function of macrophage M1 or M2 classification, possibly owing to uneven distribution of phagosomal transporter proteins. Irregular, excessive NOX activity prevents phago-lysosomal fusion, and the lack of V-ATPase-induced acidification leads to bacterial stasis in the phagosome. Thus, efficient phagosomal bacterial killing is a result of tightly balanced activity between two processes.

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Phagosomal NOX and V-ATPase activation is sequential and separable in macrophages

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Superoxide (O₂^-) inhibits lysosomal fusion thereby inhibiting phagosomal acidification

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Phagosomes in single cells are heterogeneous in NOX activity and thereby acidification

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NOX activity is the dominant factor in bactericidal efficacy in macrophage phagosomes

A rare infection in the tropics that is not uncommon in cases of chronic granulomatous disease

Chromobacterium violaceum is a rare cause of infection in immunocompromised patients in the tropics with a spectrum of disease manifestations, including severe disease. Early identification of this micro-organism is essential for appropriate management. We present a case of C. violaceum septicaemia in a patient with chronic granulomatous disease.

A rare case of a prostatic abscess, bacteremia and chronic granulomatous disease associated with Klebsiella pneumoniae

Chronic granulomatous disease (CGD) is a primary immunodeficiency disease characterized by severe recurrent infections such as pneumonia, liver and skin infections. However, prostatic abscesses are rare as only two cases have been reported thus far. We present the case of a 41-year-old patient with CGD who was admitted to the hospital with fever and subsequently, Klebsiella pneumoniae was identified on blood culture. Abdominal computed tomography revealed a prostatic abscess. He improved with intravenous antibiotics and drainage of the abscess. After he was taken off the intravenous antibiotics and started on an oral agent, he was discharged from the hospital. We confirmed a reduction in the prostatic abscess size and continued the antibiotic therapy for 52 days. A prostatic abscess is an uncommon disease being diagnosed at a median age of 49 years. Sometimes it is discovered in patients with fever of unknown origin and might be considered as an infection site of CGD patients.

Fungal Musculoskeletal Infections

Fungi are rare but important causes of osteoarticular infections, and can be caused by a wide array of yeasts and molds. Symptoms are often subacute and mimic those of other more common causes of osteoarticular infection, which can lead to substantial delays in treatment. A high index of suspicion is required to establish the diagnosis. The severity of infection depends on the inherent pathogenicity of the fungi, the immune status of the host, the anatomic location of the infection, and whether the infection involves a foreign body. Treatment often involves a combination of surgical debridement and prolonged antifungal therapy.

Eat Prey, Live: Dictyostelium discoideum As a Model for Cell-Autonomous Defenses

The soil-dwelling social amoeba Dictyostelium discoideum feeds on bacteria. Each meal is a potential infection because some bacteria have evolved mechanisms to resist predation. To survive such a hostile environment, D. discoideum has in turn evolved efficient antimicrobial responses that are intertwined with phagocytosis and autophagy, its nutrient acquisition pathways. The core machinery and antimicrobial functions of these pathways are conserved in the mononuclear phagocytes of mammals, which mediate the initial, innate-immune response to infection. In this review, we discuss the advantages and relevance of D. discoideum as a model phagocyte to study cell-autonomous defenses. We cover the antimicrobial functions of phagocytosis and autophagy and describe the processes that create a microbicidal phagosome: acidification and delivery of lytic enzymes, generation of reactive oxygen species, and the regulation of Zn²⁺, Cu²⁺, and Fe²⁺ availability. High concentrations of metals poison microbes while metal sequestration inhibits their metabolic activity. We also describe microbial interference with these defenses and highlight observations made first in D. discoideum. Finally, we discuss galectins, TNF receptor-associated factors, tripartite motif-containing proteins, and signal transducers and activators of transcription, microbial restriction factors initially characterized in mammalian phagocytes that have either homologs or functional analogs in D. discoideum.

Vps13F links bacterial recognition and intracellular killing in Dictyostelium

Bacterial sensing, ingestion, and killing by phagocytic cells are essential processes to protect the human body from infectious microorganisms. The cellular mechanisms involved in intracellular killing, their relative importance, and their specificity towards different bacteria are however poorly defined. In this study, we used Dictyostelium discoideum, a phagocytic cell model amenable to genetic analysis, to identify new gene products involved in intracellular killing. A random genetic screen led us to identify the role of Vps13F in intracellular killing of Klebsiella pneumoniae. Vps13F knock‐out (KO) cells exhibited a delayed intracellular killing of K. pneumoniae, although the general organization of the phagocytic and endocytic pathway appeared largely unaffected. Transcriptomic analysis revealed that vps13F KO cells may be functionally similar to previously characterized fspA KO cells, shown to be defective in folate sensing. Indeed, vps13F KO cells showed a decreased chemokinetic response to various stimulants, suggesting a direct or indirect role of Vps13F in intracellular signaling. Overstimulation with excess folate restored efficient killing in vps13F KO cells. Finally, genetic inactivation of Far1, the folate receptor, resulted in inefficient intracellular killing of K. pneumoniae. Together, these observations show that stimulation of Dictyostelium by bacterial folate is necessary for rapid intracellular killing of K. pneumoniae.

Adolescent with recurrent tuberculosis: Can it be chronic granulomatous disease?

Chronic granulomatous disease (CGD) is an inherited primary immunodeficiency disorder with recurrent bacterial and fungal infections like Staphylococcus aureus, Nocardia spp, Serratia marcescens, Burkholderia cepacia, Salmonella spp. and Aspergillus species. We present a 13-year-old male child who had 3 episodes of tuberculosis (TB) at 5 years, 8 years and 13 years of age, respectively, with no other intercurrent infections and who was diagnosed as CGD at the age of 13 years. This case highlights the possibility of phenotypic variations of CGD. The diagnosis of CGD should also be sought in all children with recurrent TB.

Primary immunodeficiencies associated with eosinophilia

Background

Eosinophilia is not an uncommon clinical finding. However, diagnosis of its cause can be a dilemma once common culprits, namely infection, allergy and reactive causes are excluded. Primary immunodeficiency disorders (PID) are among known differentials of eosinophilia. However, the list of PIDs typically reported with eosinophilia is small and the literature lacks an inclusive list of PIDs which have been reported with eosinophilia. This motivated us to review the literature for all PIDs which have been described to have elevated eosinophils as this may contribute to an earlier diagnosis of PID and further the understanding of eosinophilia.

Methods

A retrospective PubMed, and Google Scholar search using the terms “eosinophilia” and “every individual PID” as classified by Expert Committee of the International Union of Immunological Societies with the limit of the English language was performed. Results were assessed to capture case(s) which reported eosinophilia in the context of PID conditions. Absolute eosinophil counts (AEC) were retrieved from manuscripts whenever reported.

Results

In addition to the typical PID conditions described with eosinophilia, we document that MHC class II deficiency, CD3γ deficiency, STAT1 deficiency (AD form), Kostmann disease, cyclic neutropenia, TCRα deficiency, Papillon-Lefevre syndrome, CD40 deficiency, CD40L deficiency, anhidrotic ectodermal dysplasia with immune deficiency, ataxia-telangiectasia, common variable immunodeficiency disorders (CVID), Blau syndrome, CARD9 deficiency, neonatal onset multisystem inflammatory disease or chronic infantile neurologic cutaneous and articular syndrome (NOMID/CINCA), chronic granulomatous disease, MALT1 deficiency and Roifman syndrome have been noted to have elevated eosinophils. Severe eosinophilia (>5.0 × 10⁹/L) was reported in Omenn syndrome, Wiskott Aldrich syndrome, ADA deficiency, autoimmune lymphoproliferative syndrome, immunodysregulation polyendocrinopathy enteropathy X-linked, STAT3 deficiency, DOCK8 deficiency, CD40 deficiency, MHC II deficiency, Kostmann disease, Papillon-Lefevre syndrome, and CVID.

Conclusions

This literature review shows that there is an extensive list of PIDs which have been reported with eosinophilia. This list helps clinicians to consider an extended differential diagnoses when tasked with exclusion of PID as a cause for eosinophilia.

Electronic supplementary material

The online version of this article (doi:10.1186/s13223-016-0130-4) contains supplementary material, which is available to authorized users.

Eicosanoids up-regulate production of reactive oxygen species by NADPH-dependent oxidase in Spodoptera exigua phagocytic hemocytes

Eicosanoids mediate cellular immune responses in insects, including phagocytosis of invading microbes. Phagocytosis entails two major steps, the internalization of microbes and the subsequent killing of them via formation of reactive oxygen species (ROS). Here, we posed the hypothesis that eicosanoids mediate ROS production by activating NADPH-dependent oxidase (NOX) and tested the idea in the model insect, Spodoptera exigua. A NOX gene (we named SeNOX4) was identified and cloned, yielding a full open reading frame encoding 547 amino acid residues with a predicted molecular weight of 63,410Da and an isoelectric point at 9.28. A transmembrane domain and a large intracellular domain containing NADPH and FAD-binding sites were predicted. Phylogenetic analysis indicated SeNOX4 clusters with other NOX4 genes. SeNOX4 was expressed in all life stages except eggs, and exclusively in hemocytes. Bacterial challenge and, separately, arachidonic acid (AA, a precursor of eicosanoid biosynthesis) injection increased its expression. The internalization step was assessed by counting hemocytes engulfing fluorescence-labeled bacteria. The phagocytic behavior was inhibited by dsRNA suppression of SeNOX4 expression and, separately by dexamethasone (DEX, a specific inhibitor of eicosanoid biosynthesis) treatments. However, injecting AA to dsSeNOX4-treated larvae did not rescue the phagocytic activity. Hemocytic ROS production increased following bacterial challenge, which was sharply reduced in dsSeNOX4-treated, and separately, in DEX-treated larvae. AA partially reversed the suppressed ROS production in dsSeNOX4-treated larvae. Treating larvae with either the ROS-suppressing dsSeNOX4 construct or DEX rendered experimental larvae unable to inhibit bacterial proliferation in their hemocoels. We infer that eicosanoids mediate ROS production during phagocytosis by inducing expression of SeNOX4.

Chronic granulomatous disease: Review of a cohort of Egyptian patients

BACKGROUND

Chronic granulomatous disease (CGD) is an inherited disease that results from a defect in the phagocytic cells of the immune system. It is caused by defects in one of the major subunits of the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase complex. The clinical presentations of CGD patients are heterogeneous.

OBJECTIVES

This is the first report from Egypt discussing clinical and laboratory data of twenty-nine patients (from 26 families) with CGD from a single tertiary referral centre.

RESULTS

There were twenty male and nine female patients. The consanguinity rate was 76% (19/25). Their age of diagnosis ranged from 2 to 168 months with a mean of 52.8 months ± 49.6 SD. The most common manifestations were abscesses in 79.3% (deep organ abscesses in 37.9% of patients), followed by pneumonia in 75.8% and gastrointestinal symptoms in 27.5%. Rare but fatal complications were also reported among patients as one patient developed haemophagocytic lymphohistiocytosis (HLH) syndrome. Although X linked-CGD universally constitutes the most common pattern of inheritance; only 6 of our patients 6/25 (24%) belonged to this group with a Stimulation Index (SI) of 1-5, and confirmed by carrier pattern of their mothers. Mothers were not available for testing in four male children. Nineteen patients (76%) had autosomal recessive patterns; ten males and nine females patients based on having abnormal SI, positive history of consanguinity and their mothers showing normal SI.

CONCLUSION

Increasing the awareness of physicians about symptoms of CGD may lead to earlier diagnosis of the disease, thus enhancing proper management and better quality of life.

Very early-onset inflammatory bowel disease: gaining insight through focused discovery

The pathogenesis of pediatric inflammatory bowel disease (IBD) is only partially understood. Strong evidence implicates a strong genetic component including high monozygotic twin concordance and familial disease phenotype concordance rates. Genome-wide association studies have identified associations between >160 genetic loci and the risk for developing IBD. The roles of implicated genes are largely immune-mediated, although other functions include cellular migration, oxidative stress, and carbohydrate metabolism. Additionally, growing literature describes monogenic causes of IBD that frequently present as infantile or very early-onset IBD. The interplay between IBD risk single nucleotide polymorphisms and rare genetic variants has yet to be determined. Studying patients with very early-onset IBD may elicit genetic factors that could be applied to broader populations of IBD. This review describes what is known about the genetic causes of very early-onset IBD and genetic strategies that may unravel more of the genetic causes of IBD.

The BER necessities: the repair of DNA damage in human-adapted bacterial pathogens

During colonization and disease, bacterial pathogens must survive the onslaught of the host immune system. A key component of the innate immune response is the generation of reactive oxygen and nitrogen species by phagocytic cells, which target and disrupt pathogen molecules, particularly DNA, and the base excision repair (BER) pathway is the most important mechanism for the repair of such oxidative DNA damage. In this Review, we discuss how the human-specific pathogens Mycobacterium tuberculosis, Helicobacter pylori and Neisseria meningitidis have evolved specialized mechanisms of DNA repair, particularly their BER pathways, compared with model organisms such as Escherichia coli. This specialization in DNA repair is likely to reflect the distinct niches occupied by these important human pathogens in the host.

Detection of inheritance pattern in thirty-three Mexican males with chronic granulomatous disease through 123 dihydrorhodamine assay

BACKGROUND

There are two inheritance patterns, the X-linked recessive (XL) pattern and the autosomal recessive pattern. There is no information on the predominant inheritance pattern of male patients with chronic granulomatous disease (CGD) in Mexico.

OBJECTIVE

The aim of this study was to determine the inheritance pattern in a cohort of Mexican male patients with CGD by means of the detection of an XL status carrier among their female relatives, and to describe the frequency of discoid lupus (DL) among carriers.

METHODS

We detected the female relatives within the families of male patients with CGD, and carried out the 123 dihydrorhodamine (DHR) assay in all female participants. All carriers were questioned for current or past established DL diagnosis.

RESULTS

We detected 33 families with one or more CGD male patients; we found an XL-CGD in 79% of the relatives from at least one female relative with a bimodal pattern. For the remaining seven relatives we were not able to confirm a carrier status by means of a DHR assay. Moreover, we detected one mother with CGD secondary to skewed X-chromosome inactivation. We also found 47 carriers, and only one carrier with DL among them.

CONCLUSION

We concluded that XL-CGD is the most frequent form of CGD in a cohort of CGD male patients in Mexico. DHR assay is a fast and practical tool to determine the CGD form in the Latin-American countries. Finally, DL frequency in Mexico is lower than that reported in the literature for other regions of the world.

Atypical presentation of chronic granulomatous disease with Burkholderia cepacia

Chronic granulomatous disease (CGD) is a rare inherited disorder of neutrophil oxidative burst. In patients with CGD, phagocyte destruction of catalase-producing organisms is impaired, resulting in recurrent and potentially fatal infections. Burkholderia cepacia, a catalase-producing organism, is known to infect patients with dysfunctional immune systems. We report a case of a 3-year-old boy with this rare infection that unravelled the diagnosis of CGD.

Intracellular killing of bacteria: is Dictyostelium a model macrophage or an alien?

Predation of bacteria by phagocytic cells was first developed during evolution by environmental amoebae. Many of the core mechanisms used by amoebae to sense, ingest and kill bacteria have also been conserved in specialized phagocytic cells in mammalian organisms. Here we focus on recent results revealing how Dictyostelium discoideum senses and kills non-pathogenic bacteria. In this model, genetic analysis of intracellular killing of bacteria has revealed a surprisingly complex array of specialized mechanisms. These results raise new questions on these processes, and challenge current models based largely on studies in mammalian phagocytes. In addition, recent studies suggest one additional level on complexity by revealing how Dictyostelium recognizes specifically various bacterial species and strains, and adapts its metabolism to process them. It remains to be seen to what extent mechanisms uncovered in Dictyostelium are also used in mammalian phagocytic cells.

Chromobacterium violaceum necrotizing fasciitis: a case report and review of the literature

Necrotizing fasciitis is a severe, rapidly progressive infection of the subcutaneous tissue that causes significant destruction. It is rarely encountered in the pediatric population. We describe the case of a 14-year-old boy who was diagnosed with Chromobacterium violaceum necrotizing fasciitis and subsequently found to have autosomal recessive chronic granulomatous disease.

Effects of C-reactive protein on the neutrophil respiratory burst in vitro

This study determined the influence of physiologically relevant concentrations of C-reactive protein (CRP) on reactive oxygen species (ROS) production by neutrophils. Neutrophils from healthy individuals were incubated with soluble pentameric CRP prior to TLR stimulation with Fusobacterium nucleatum, or FcγR stimulation with IgG-opsonised Staphylococcus aureus or heat-aggregated IgG. ROS generation by unstimulated cells and those after stimulation were determined using luminol, isoluminol and lucigenin chemiluminescence, detecting predominantly intracellular hypochlorous acid (HOCl), extracellular hydrogen peroxide (detected as HOCl) and extracellular superoxide respectively. Baseline (unstimulated) neutrophil ROS generation and release was reduced compared with vehicle control by 10 µg/ml CRP. There was no consistent effect of CRP on FcγR-stimulated HOCl production, but the extracellular superoxide response was reduced by 10 µg/ml CRP. By contrast, CRP reduced intracellular (10 µg/ml) and extracellular (3 and 10 µg/ml) HOCl generation, but increased superoxide release (1-10 µg/ml) in response to TLR stimulation. Physiologically relevant concentrations of CRP inhibited baseline ROS generation and reduced FcγR-stimulated extracellular superoxide and TLR-stimulated HOCl release, suggesting that CRP may offer some degree of host protection from neutrophil-associated, low-level oxidative stress. However, CRP enhanced TLR-mediated superoxide release from neutrophils, potentially increasing oxidative stress but aiding host protection from infection.

Successful cord blood transplantation after repeated transfusions of unmobilized neutrophils in addition to antifungal treatment in an infant with chronic granulomatous disease complicated by invasive pulmonary aspergillosis

BACKGROUND

Chronic granulomatous disease (CGD) is a rare inherited primary immunodeficiency that affects phagocytic cells. CGD patients are susceptible to fungal infections, especially Aspergillus infections. The management of life-threatening Aspergillus infections in CGD is particularly difficult because some infections cannot be eradicated with standard antifungal treatments and, hence, result in death.

CASE REPORT

A 2-week-old girl developed invasive pulmonary aspergillosis, which rapidly progressed to respiratory failure. Liposomal amphotericin B, micafungin, and voriconazole were not effective. At the age of 2 months, she was diagnosed with p67phox-deficient CGD. In addition to antifungal treatment, the patient received 21 granulocyte transfusions (GTX), which were obtained from 300- or 400-mL whole blood samples from healthy random donors who were not treated with granulocyte-colony-stimulating factor or dexamethasone. The median neutrophil count of the GTX was 1.88 × 10(8) /kg body weight. Rituximab was administered to reduce alloimmunization to human leukocyte antigens (HLA) after the eighth GTX, resulting in their absence of anti-HLA before and after cord blood transplantation (CBT). A marked improvement in her invasive pulmonary aspergillosis was achieved, although the first CBT was rejected. Complete hematopoietic recovery was obtained after the second CBT.

CONCLUSION

Repeated GTX containing relatively low doses of neutrophils might be able to control severe Aspergillus infections in infants with CGD.

Resolution of inflammation as a novel chemopreventive strategy

Acute inflammation, a physiologic response to protect cells from microbial infection and other noxious stimuli, is automatically terminated by endogenous anti-inflammatory and pro-resolving mediators to restore homeostatic conditions. However, if timely resolution of inflammation is failed, inflammation persists and can progress to a chronic inflammation which has long been thought as a predisposing factor to carcinogenesis. Excessive and pathologic inflammation causes DNA damage, genomic instability, epigenetic dysregulation, and alteration of intracellular signaling, all of which are involved in neoplastic transformation. To prevent chronic inflammation and resulting inflammation-promoted cancer development, understanding the process that resolves inflammation is essential. Resolution of inflammation is an active coordinated process regulated by distinct anti-inflammatory and pro-resolving endogenous lipid mediators, such as resolvins and lipoxins. The role of pro-inflammatory signaling in carcinogenesis has become more and more evident and well characterized, but the potential role of pro-resolving mediators in cancer prevention remains still elusive. In searching for an efficacious way to prevent chronic inflammation-associated cancer, the pro-resolving signal transduction pathways and their regulators should be unraveled.

Insights into the PX (phox-homology) domain and SNX (sorting nexin) protein families: structures, functions and roles in disease

The mammalian genome encodes 49 proteins that possess a PX (phox-homology) domain, responsible for membrane attachment to organelles of the secretory and endocytic system via binding of phosphoinositide lipids. The PX domain proteins, most of which are classified as SNXs (sorting nexins), constitute an extremely diverse family of molecules that play varied roles in membrane trafficking, cell signalling, membrane remodelling and organelle motility. In the present review, we present an overview of the family, incorporating recent functional and structural insights, and propose an updated classification of the proteins into distinct subfamilies on the basis of these insights. Almost all PX domain proteins bind PtdIns3P and are recruited to early endosomal membranes. Although other specificities and localizations have been reported for a select few family members, the molecular basis for binding to other lipids is still not clear. The PX domain is also emerging as an important protein–protein interaction domain, binding endocytic and exocytic machinery, transmembrane proteins and many other molecules. A comprehensive survey of the molecular interactions governed by PX proteins highlights the functional diversity of the family as trafficking cargo adaptors and membrane-associated scaffolds regulating cell signalling. Finally, we examine the mounting evidence linking PX proteins to different disorders, in particular focusing on their emerging importance in both pathogen invasion and amyloid production in Alzheimer's disease.

Resolution of neutrophilic inflammation by H2O2 in antigen-induced arthritis

OBJECTIVE

Neutrophil accumulation contributes to the pathogenesis of rheumatoid arthritis. This study was undertaken to examine the ability of H2O2 to influence neutrophilic inflammation in a model of antigen-induced arthritis (AIA) in mice.

METHODS

AIA was induced by administration of antigen into the knee joints of previously immunized mice. Neutrophil accumulation was measured by counting neutrophils in the synovial cavity and assaying myeloperoxidase activity in the tissue surrounding the mouse knee joint. Apoptosis was determined by morphologic and molecular techniques. The role of H2O2 was studied using mice that do not produce reactive oxygen species (gp91phox-/- mice) and drugs that enhance the generation or enhance the degradation of H2O2.

RESULTS

Antigen challenge of immunized mice induced neutrophil accumulation that peaked at 12-24 hours after challenge. H2O2 production peaked at 24 hours, after which time, the inflammation resolved. Neutrophil recruitment was similar in wild-type and gp91phox-/- mice, but there was delayed resolution in gp91phox-/- mice or after administration of catalase. In contrast, administration of H2O2 or superoxide dismutase (SOD) resolved neutrophilic inflammation. The resolution of inflammation induced by SOD or H2O2 was accompanied by an increase in the number of apoptotic neutrophils. Apoptosis was associated with an increase in Bax and caspase 3 cleavage and was secondary to phosphatidylinositol 3-kinase (PI3K)/Akt activation.

CONCLUSION

Our findings indicate that levels of H2O2 increase during neutrophil influx and are necessary for the natural resolution of neutrophilic inflammation. Mechanistically, enhanced levels of H2O2 (endogenous or exogenous) inhibit p-Akt/NF-κB and induce apoptosis of migrated neutrophils. Modulation of H2O2 production may represent a novel strategy for controlling neutrophilic inflammation in the joints.

Inheritance pattern and clinical aspects of 93 Iranian patients with chronic granulomatous disease

BACKGROUND

Chronic granulomatous disease (CGD) is a rare immunodeficiency due to a genetic defect in one of the NADPH-oxidase components. We studied CGD inheritance forms (autosomal recessive (AR) or X-linked (XL)) and AR-CGD subtypes in Iran.

METHODS

Clinical and functional investigations were conducted in 93 Iranian CGD patients from 75 families.

RESULTS

Most of the patients were AR-CGD (87.1%). This was related to consanguineous marriages (p = 0.001). The age of onset of symptoms and diagnosis were lower in XL-CGD compared with AR-CGD (p < 0.0001 for both). Among AR-CGD patients, p47phox defect was the predominant subtype (55.5%). The most common clinical features in patients were lymphadenopathy (65.6%) and pulmonary involvement (57%). XL-CGD patients were affected more frequently with severe infectious manifestations.

CONCLUSIONS

Although XL-CGD is the most common type of the disease worldwide, only 12 patients (12.9%) were XL-CGD in our study. The relatively high frequency of AR-CGD is probable due to widely common consanguineous marriages in Iran.

Combating oxidative stress in vascular disease: NADPH oxidases as therapeutic targets

NADPH oxidases are a family of enzymes that generate reactive oxygen species (ROS). The NOX1 (NADPH oxidase 1) and NOX2 oxidases are the major sources of ROS in the artery wall in conditions such as hypertension, hypercholesterolaemia, diabetes and ageing, and so they are important contributors to the oxidative stress, endothelial dysfunction and vascular inflammation that underlies arterial remodelling and atherogenesis. In this Review, we advance the concept that compared to the use of conventional antioxidants, inhibiting NOX1 and NOX2 oxidases is a superior approach for combating oxidative stress. We briefly describe some common and emerging putative NADPH oxidase inhibitors. In addition, we highlight the crucial role of the NADPH oxidase regulatory subunit, p47phox, in the activity of vascular NOX1 and NOX2 oxidases, and suggest how a better understanding of its specific molecular interactions may enable the development of novel isoform-selective drugs to prevent or treat cardiovascular diseases.

Genetic correction of X-linked chronic granulomatous disease with novel foamy virus vectors

OBJECTIVE

The X-linked form of chronic granulomatous disease (X-CGD) results from mutations in the CYBB gene encoding gp91(phox), the larger subunit of the oxidase flavocytochrome b(558). Affected individuals suffer from recurrent life-threatening infections due to impaired superoxide production by reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase in phagocytes. Novel foamy virus vectors expressing the human codon-optimized gp91(phox) were evaluated for the genetic correction of the disease in the X-CGD cell line and in X-CGD mouse model.

MATERIALS AND METHODS

The vectors were evaluated in vitro, in the human X-CGD PLB-985 cell line and in the X-CGD bone marrow Lin(-) cells. Transplantation of transduced Lin(-) cells was performed in X-CGD mice after busulfan conditioning. Real-time polymerase chain reaction was used for chimerism and vector copy number determination. Restoration of reduced NADPH oxidase production was assessed by nitrobluetetrazolium and dihydrorhodamine assays.

RESULTS

High and stable gp91(phox) expression, as well as reconstitution of reduced NADPH activity, was achieved in the human X-CGD PLB-985 cell line and in primary murine X-CGD hematopoietic stem cells ex vivo. Transplantation of transduced bone marrow hematopoietic stem cells in the murine model of X-CGD, even with low multiplicities of infection (MOI), reconstituted the levels of oxidase-producing neutrophils and provided enzymatic activity that reached 70% of normal.

CONCLUSIONS

Foamy virus vectors expressing the human gp91(phox) transgene constitute potential candidates for the gene therapy of CGD because they combine lack of pathogenicity with efficacy even at low MOI.

Chronic granulomatous disease

Chronic granulomatous disease (CGD) is a rare congenital immunodeficiency characterized by recurrent bacterial and fungal infections as well as granuloma formation. The manifestations of this disease can involve single or multiple organ systems. The lungs are the most commonly affected organ; however, lymphatic, hepatic, skeletal, gastrointestinal, genitourinary, head and neck, and central nervous system involvement have also been described. Most patients present with symptoms in their first few years of life. Due to the nonspecific manner in which patients present, the pediatric radiologist may be among the first to recognize the pattern of infection, inflammation, and granuloma formation leading to a diagnosis of CGD. The purpose of this paper is to review the imaging findings of CGD that can manifest throughout the body.

Relationship between calcium release and NADPH oxidase inhibition in human neutrophils

The aim of this study was to investigate the possible relationship between NADPH oxidase activity and changes in cytosolic Ca(2+) in response to different agonists. Treatment of neutrophils with leukotriene B4 (LTB(4)) demonstrated characteristic changes to cytoslic Ca(2+) yielding an EC(50) of 4nM. The pA(2) values for the specific LTB(4) receptor (BLT) antagonists, U-75302 and LY-255283 were 6.32 and 6.38, respectively. Similarly, neutrophils treated with N-formyl-l-methionyl-l-leucyl-l-phenylalanine (FMLP) and platelet activating factor (PAF) exhibited changes in cytoslic Ca(2+) in a dose dependant manner with pD(2) values of 9.0 and 9.9, respectively. The phorbol ester PMA prevented elevations in cytosolic Ca(2+) in response to LTB(4), FMLP and PAF with IC(50) values of 5.88, 1.44 and 5.71nM, respectively. In addition, potent NADPH oxidase inhibitors apocynin and diphenyleneiodonium (DPI) inhibited FMLP mediated cytosolic Ca(2+) release. These results demonstrate that inhibition of the NADPH oxidase suppresses cytosolic Ca(2+) release in FMLP activated human neutrophils.

X-linked primary immunodeficiencies as a bridge to better understanding X-chromosome related autoimmunity

Recent studies indicate that genes located on the X-chromosome play a major and unique role in autoimmunity. The fact that most X-linked primary immune deficiencies carry significant autoimmune manifestations greatly supports this notion. Autoimmunity and immune deficiency have been considered two opposite extremes resulting from immune dysregulation and failure of immune development and/or function, respectively. Growing evidence has been accumulating to indicate that autoimmune phenomena occur in patients suffering from primary immune deficiency (PID), and the molecular and cellular mechanisms that interconnect these conditions are being unraveled. The study of rare single-gene disorders associated with significant autoimmunity may shed light on the pathophysiology of more complex multifactorial and polygenic autoimmune disorders. In this regard, primary immunodeficiencies represent unique "experiments of Nature" that illustrate the critical role played by single-gene products in the development, function and homeostasis of the immune system. In this review we will focus on the clinical features and on the cellular and molecular pathophysiology of the known X-linked PID in which autoimmune manifestations are more common, in the attempt to understand what single-gene defects can teach us on the role that key immune pathways and cellular processes may play to prevent autoimmunity.

Granulibacter bethesdensis isolated in a child patient with chronic granulomatous disease

Chronic granulomatous disease was diagnosed in a 10-year-old boy who, after some weeks' decline, developed acute respiratory distress leading to multiple organ failure and death. All microbiological analyses were negative, except two blood cultures from which the novel bacterium Granulibacter bethesdensis was isolated.

Special article: chronic granulomatous disease in the United Kingdom and Ireland: a comprehensive national patient-based registry

There are no epidemiological studies from the British Isles of chronic granulomatous disease, characterized by recurrent, life-threatening bacterial and fungal infections and inflammatory sequelae. Patients were enrolled in a national registry and medical records were analysed. Of 94 subjects, 69 had X-linked disease, 16 had autosomal recessive disease and nine were unknown. Prevalence was 7.5/million for 1990-99 and 8.5/million for 1980-89. Suppurative adenitis, abscesses and pneumonia presented commonly. Twenty-three of 30 patients who underwent high resolution computerized tomography had chronic respiratory disease. Inflammatory sequelae included bowel stricture and urogenital tract granulomata. Growth failure was common; 75% of those measured were below the population mean. All patients received prophylactic antibiotics and 93% anti-fungal prophylaxis. Interferon gamma was used to treat infection, but rarely as prophylaxis. Despite prophylaxis, estimated survival was 88% at 10 years but 55% at age 30 years. Morbidity remains significant, severe infectious complications common. Curative treatments including stem cell transplantation should be considered for patients with frequent or serious complications.

Multiple Simultaneous Complications of Acute Otitis Media in a Child Diagnosed with Chronic Granulomatous Disease: A Case Report

While the prevalence of acute otitis media complications in pediatric patients has decreased over the past 30 years because of effective antibiotic therapy, the incidence has begun to rise again recently, possibly because of increased antibiotic resistance. Patients who simultaneously manifest multiple complications may require a more thorough evaluation, including an immunologic work-up. The presented case should encourage physicians to investigate the possibility of an underlying immunodeficiency when treating patients with multiple simultaneous complications of acute otitis media.

Clinical features, long-term follow-up and outcome of a large cohort of patients with Chronic Granulomatous Disease: an Italian multicenter study

A retrospective clinical and immunological survey was conducted in 60 patients with Chronic Granulomatous Disease. A prospective controlled non-randomized study of the efficacy of long-term IFNgamma treatment was carried out. The mean age at the time of diagnosis was 4.4 years; mean duration of follow-up was 10.4 years. Lung and skin infections were the most frequent manifestations both prior to diagnosis and during follow-up. Aspergillus species was the first cause of infection and of death in our cohort. The mortality rate was 13%. Long term prophylaxis with IFNgamma did not significantly change the rate of total infection per patient-year compared to controls (p=0.07). Our data provide clear evidence that protocols of continuing intensive surveillance and monitoring of compliance with anti-infective regimens may significantly improve the quality of life and long-term survival in patients with CGD. No evidence justifying long-term prophylaxis with IFNgamma was obtained.

Cutaneous and other lupus-like symptoms in carriers of X-linked chronic granulomatous disease: incidence and autoimmune serology

The objective of this study was to determine the utility of anti-nuclear antibody (ANA) testing in the investigation of cutaneous and other lupus symptoms in female carriers of X-linked chronic granulomatous disease (CGD). We undertook a prospective study of 19 carrier mothers attending our institution, with direct questioning of carriers concerning symptoms and testing for anti-nuclear and anti-phospholipid antibodies. A total of 58% reported significant photosensitive skin rashes, 42% reported mouth ulcers and 37% complained of joint pains that could not be attributed to other known causes. Anti-nuclear antibody (ANA) testing was negative in 73% of all carriers. The five positive ANAs were of low titre (maximum 1 : 320 on Hep 2 cells in two women) and only one weak positive double-stranded DNA antibody and no extractable nuclear antibodies were found. Several of the mothers, despite negative serology, benefited from referral to a specialist, and in some cases to specific treatment. A history of skin rashes, joint pain, fatigue and mouth ulcers should be sought actively in the female relatives of X-CGD patients but negative lupus serology should not preclude referral to appropriate dermatology or rheumatology services. as symptoms may respond well to appropriate treatment.

Chronic inflammation: a failure of resolution?

Inflammation has evolved as a protective response to insult or injury, it's a primordial response that eliminates or neutralises foreign organisms or material, the resolution of inflammation encompasses the endogenous anti-inflammatory mechanisms that protect us against excessive tissue injury and promote the restoration of tissue structure and function. In fact, our well being and survival depends upon its efficiency and carefully-balanced control. In general, the innate inflammatory response initiates within minutes and, if all is well, resolves within hours. In contrast, chronic inflammation persists for weeks, months or even years. Here, we are going to discuss the key endogenous checkpoints necessary for mounting an effective yet limited inflammatory response and the crucial biochemical pathways necessary to prevent its persistence.

The NOX family of ROS-generating NADPH oxidases: physiology and pathophysiology

For a long time, superoxide generation by an NADPH oxidase was considered as an oddity only found in professional phagocytes. Over the last years, six homologs of the cytochrome subunit of the phagocyte NADPH oxidase were found: NOX1, NOX3, NOX4, NOX5, DUOX1, and DUOX2. Together with the phagocyte NADPH oxidase itself (NOX2/gp91(phox)), the homologs are now referred to as the NOX family of NADPH oxidases. These enzymes share the capacity to transport electrons across the plasma membrane and to generate superoxide and other downstream reactive oxygen species (ROS). Activation mechanisms and tissue distribution of the different members of the family are markedly different. The physiological functions of NOX family enzymes include host defense, posttranlational processing of proteins, cellular signaling, regulation of gene expression, and cell differentiation. NOX enzymes also contribute to a wide range of pathological processes. NOX deficiency may lead to immunosuppresion, lack of otoconogenesis, or hypothyroidism. Increased NOX activity also contributes to a large number or pathologies, in particular cardiovascular diseases and neurodegeneration. This review summarizes the current state of knowledge of the functions of NOX enzymes in physiology and pathology.

Glycosyl-phosphatidyl-inositol-defective granulocytes from paroxysmal nocturnal haemoglobinuria patients show increased bacterial ingestion but reduced respiratory burst induction

Paroxysmal nocturnal hemoglobinuria (PNH) is characterized by the emergence of a GPI-defective clonal hematopoiesis. Its clinical features are hemolytic anemia, cytopenia, and thrombosis. Circulating monocytes and granulocytes are largely GPI-defective in PNH patients. This study aims to investigate the granulocyte functional properties in PNH. We analyzed bacterial-dependent intracellular ingestion and the consequent activation of oxidative burst in GPI-defective granulocytes from four neutropenic PNH patients. Our data show a significant increase in the ability of GPI-defective granulocytes to ingest opsonized bacteria. In addition, an impaired respiratory burst effectiveness in response to two independent bacterial stimuli, the N-formyl-MetLeuPhe (fMLP) synthetic bacterial peptide and E. coli, was revealed. The occurrence of neutropenia and the severe impairment of oxidative burst, occurring in chronic granulomatosis disease, were unable to significantly affect phagocytosis. Thus, additional mechanisms, able to differentially affect ingestion ability and respiratory burst effectiveness, have to be hypothesized. The reduced burst effectiveness of GPI-defective granulocytes was maintained after treatment with phorbol 12-myristate 13-acetate, a pharmacological stimulus able to extensively recruit and to trigger intracellular protein kinase C (PKC). Moreover, blocking of PKC has been observed to severely affect granulocyte respiratory burst with a mild effect on the phagocytosis. These data suggest a role for a modulation of intracellular PKC in the pathogenesis of the impaired granulocyte oxidative burst.

Translocation of proteins homologous to human neutrophil p47phox and p67phox to the cell membrane in activated hemocytes of Galleria mellonella

Activation of the superoxide forming respiratory burst oxidase of human neutrophils, crucial in host defence, requires the cytosolic proteins p47phox and p67phox which translocate to the plasma membrane upon cell stimulation and activate flavocytochrome b558, the redox centre of this enzyme system. We have previously demonstrated the presence of proteins (67 and 47kDa) in hemocytes of the insect Galleria mellonella homologous to proteins of the superoxide-forming NADPH oxidase complex of neutrophils. The work presented here illustrates for the first time translocation of homologous hemocyte proteins, 67 and 47kDa from the cytosol to the plasma membrane upon phorbol 12-myristate 13 acetate (PMA) activation. In hemocytes, gliotoxin (GT), the fungal secondary metabolite significantly suppressed PMA-induced superoxide generation in a concentration dependent manner and reduced translocation to basel nonstimulated levels. Primarily these results correlate translocation of hemocyte 47 and 67kDa proteins with PMA induced oxidase activity. Collectively results presented here, demonstrate further cellular and functional similarities between phagocytes of insects and mammals and further justify the use of insects in place of mammals for modelling the innate immune response to microbial pathogens.

Leu505 of Nox2 is crucial for optimal p67phox-dependent activation of the flavocytochrome b558 during phagocytic NADPH oxidase assembly

The role of Leu505 of Nox2 on the NADPH oxidase activation process was investigated. An X-CGD PLB-985 cell line expressing the Leu505Arg Nox2 mutant was obtained, exactly mimicking the phenotype of a previously published X91+-CGD case. In a reconstituted cell-free system (CFS), NADPH oxidase and iodonitrotetrazolium (INT) reductase activities were partially maintained concomitantly with a partial cytosolic factors translocation to the plasma membrane. This suggests that assembly and electron transfer from NADPH occurred partially in the Leu505Arg Nox2 mutant. Moreover, in a simplified CFS using purified mutant cytochrome b558 and recombinant p67phox, p47phox, and Rac1proteins, we found that the Km for NADPH and for NADH was about three times higher than those of purified WT cytochrome b558, indicating that the Leu505Arg mutation induces a slight decrease of the affinity for NADPH and NADH. In addition, oxidase activity can be extended by increasing the amount of p67phox in the simplified CFS assay. However, the maximal reconstituted oxidase activity using WT purified cytochrome b558 could not be reached using mutant cytochrome b558. In a three-dimensional model of the C-terminal tail of Nox2, Leu505 appears to have a strategic position just at the entry of the NADPH binding site and at the end of the alpha-helical loop (residues 484-504), a potential cytosolic factor binding region. The Leu505Arg mutation seems to affect the oxidase complex activation process through alteration of cytosolic factors binding and more particularly the p67phox interaction with cytochrome b558, thus affecting NADPH access to its binding site.