Chronic Granulomatous Disease; fundamental stages in our understanding of CGD

Efficacy and Safety of Interferon-Gamma in Chronic Granulomatous Disease: a Systematic Review and Meta-analysis

BACKGROUND

Chronic granulomatous disease (CGD) is a primary immunodeficiency with increased susceptibility to several bacteria, fungi, and mycobacteria, caused by defective or null superoxide production by the NADPH oxidase enzymatic complex. Accepted treatment consists mainly of antimicrobial prophylaxis. The role of human recombinant subcutaneous interferon-gamma (IFNγ) is less clear since the available evidence on its efficacy derives mainly from a single clinical trial that has been challenged.

OBJECTIVE

We aimed to assess the efficacy and safety of IFNγ as an added treatment for CGD when compared to antimicrobial prophylaxis alone.

METHODS

A literature search was conducted using MeSH terms "Chronic granulomatous disease" AND ("interferon gamma" OR "interferon-gamma"), as well as antibiotics, placebo, no therapy, clinical trial, and trial, on MEDLINE, EMBASE, LILACS, WHOs, CENTRAL, KOREAMED, The Cochrane Library, clinicaltrials.gov, and abstracts from meetings, from 1976 to July 2022. We included clinical trials (CT) and prospective follow-up studies and registered the number of serious infections (requiring hospitalization and IV antibiotics) and deaths, adverse events, and autoimmune complications, in patients treated for CGD with antimicrobial prophylaxis plus IFN-γ, versus antimicrobial prophylaxis alone. We assessed the quality of the studies using risk of bias and STROBE. We performed a meta-analysis by calculating both Peto's odds ratio (OR) and risk reduction (RR) through the Mantel-Haenszel method with a fixed-effect model, using Review Manager 5.4, and we reported the number needed to treat (NNT).

RESULTS

We identified 54 matches from databases and 4 from other sources. We excluded 12 duplicates, 7 titles, and 9 abstracts for relevance, after which we had 30 eligible studies. Twenty-four were then excluded after reading the full text. Six papers were included: one randomized CT and 5 follow-up studies. In total, 324 patients with Chronic granulomatous disease were followed for 319 months under treatment with antibiotic prophylaxis plus interferon-gamma or placebo (or antibiotic prophylaxis alone), reported between the years 1991 and 2016. Three of the studies included a control group, allowing for the aggregate analysis of efficacy (prevention of serious infections). The aggregate OR was 0.49, with a 95% confidence interval of 0.19 to 1.23. The risk ratio for serious infection was 0.56 (95%CI 0.35-0.90) under IFN-γ. The meta-analysis thus favors interferon-gamma for a risk reduction of serious infection.

DISCUSSION

The results from this meta-analysis support the use of IFN-γ in the treatment of patients with CGD. However, we found insufficient clinical evidence and believe more clinical trials are needed to better assess the efficacy and long-term safety of IFN-γ.

Precision medicine: The use of tailored therapy in primary immunodeficiencies

Primary immunodeficiencies (PID) are rare, complex diseases that can be characterised by a spectrum of phenotypes, from increased susceptibility to infections to autoimmunity, allergy, auto-inflammatory diseases and predisposition to malignancy. With the introduction of genetic testing in these patients and wider use of next-Generation sequencing techniques, a higher number of pathogenic genetic variants and conditions have been identified, allowing the development of new, targeted treatments in PID. The concept of precision medicine, that aims to tailor the medical interventions to each patient, allows to perform more precise diagnosis and more importantly the use of treatments directed to a specific defect, with the objective to cure or achieve long-term remission, minimising the number and type of side effects. This approach takes particular importance in PID, considering the nature of causative defects, disease severity, short- and long-term complications of disease but also of the available treatments, with impact in life-expectancy and quality of life. In this review we revisit how this approach can or is already being implemented in PID and provide a summary of the most relevant treatments applied to specific diseases.

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.

Metabolic reprogramming of myeloid-derived suppressor cells: An innovative approach confronting challenges

Immune cells such as T cells, macrophages, dendritic cells, and other immunoregulatory cells undergo metabolic reprogramming in cancer and inflammation-derived microenvironment to meet specific physiologic and functional demands. Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of immature myeloid cells that are characterized by immunosuppressive activity, which plays a key role in host immune homeostasis. In this review, we have discussed the core metabolic pathways, including glycolysis, lipid and fatty acid biosynthesis, and amino acid metabolism in the MDSCs under various pathologic situations. Metabolic reprogramming is a determinant of the phenotype and functions of MDSCs, and is therefore a novel therapeutic possibility in various diseases.

Management of osteoarticular fungal infections in the setting of immunodeficiency

Introduction: Osteoarticular fungal infections (OAFIs) complicate the clinical course of high-risk patients, including immunosuppressed individuals. Their management, however, despite being intricate, is governed by evidence arising from sub-optimal quality research, such as case series. Guidelines are scarce and when present result in recommendations based on low quality evidence. Furthermore, the differences between the management of immunocompromised and immunocompetent patients are not distinct. This is a narrative review after a literature search in PubMed, up to November 2019.Areas covered: The major fungal groups causing osteomyelitis and/or arthritis are Candida spp., Aspergillus spp., non-Aspergillus filamentous fungi, non-Candida yeasts and endemic dimorphic fungi. Their epidemiology is briefly analyzed with emphasis on immunodeficiency and other risk factors. Management of OAFIs includes appropriate antifungal drug therapy (liposomal amphotericin B, triazoles or echinocandins), local surgery and immunotherapy for primary immunodeficiencies. Cessation of immunosuppressive drugs is also mandated.Expert opinion: Management of OAFIs includes affordable and available options and approaches. However, research on therapeutic practices is urgently required to be further improved, due to the rarity of affected patients. Evolution is expected to translate into novel antifungal drugs, less invasive and precise surgical approaches and targeted enhancement of immunoregulatory pathways in defense of challenging fungal pathogens.

Life-Threatening Infections Due to Live-Attenuated Vaccines: Early Manifestations of Inborn Errors of Immunity

Live-attenuated vaccines (LAVs) can protect humans against 12 viral and three bacterial diseases. By definition, any clinical infection caused by a LAV that is sufficiently severe to require medical intervention attests to an inherited or acquired immunodeficiency that must be diagnosed or identified. Self-healing infections can also result from milder forms of immunodeficiency. We review here the inherited forms of immunodeficiency underlying severe infections of LAVs. Inborn errors of immunity (IEIs) underlying bacille Calmette-Guérin (BCG), oral poliovirus (OPV), vaccine measles virus (vMeV), and oral rotavirus vaccine (ORV) disease have been described from 1951, 1963, 1966, and 2009 onward, respectively. For each of these four LAVs, the underlying IEIs show immunological homogeneity despite genetic heterogeneity. Specifically, BCG disease is due to inborn errors of IFN-γ immunity, OPV disease to inborn errors of B cell immunity, vMeV disease to inborn errors of IFN-α/β and IFN-λ immunity, and ORV disease to adaptive immunity. Severe reactions to the other 11 LAVs have been described yet remain "idiopathic," in the absence of known underlying inherited or acquired immunodeficiencies, and are warranted to be the focus of research efforts. The study of IEIs underlying life-threatening LAV infections is clinically important for the affected patients and their families, as well as immunologically, for the study of the molecular and cellular basis of host defense against both attenuated and parental pathogens.

A transgenic zebrafish line for in vivo visualisation of neutrophil myeloperoxidase

The neutrophil enzyme myeloperoxidase (MPO) is a major enzyme made by neutrophils to generate antimicrobial and immunomodulatory compounds, notably hypochlorous acid (HOCl), amplifying their capacity for destroying pathogens and regulating inflammation. Despite its roles in innate immunity, the importance of MPO in preventing infection is unclear, as individuals with MPO deficiency are asymptomatic with the exception of an increased risk of candidiasis. Dysregulation of MPO activity is also linked with inflammatory conditions such as atherosclerosis, emphasising a need to understand the roles of the enzyme in greater detail. Consequently, new tools for investigating granular dynamics in vivo can provide useful insights into how MPO localises within neutrophils, aiding understanding of its role in preventing and exacerbating disease. The zebrafish is a powerful model for investigating the immune system in vivo, as it is genetically tractable, and optically transparent. To visualise MPO activity within zebrafish neutrophils, we created a genetic construct that expresses human MPO as a fusion protein with a C-terminal fluorescent tag, driven by the neutrophil-specific promoter lyz. After introducing the construct into the zebrafish genome by Tol2 transgenesis, we established the Tg(lyz:Hsa.MPO-mEmerald,cmlc2:EGFP)sh496 line, and confirmed transgene expression in zebrafish neutrophils. We observed localisation of MPO-mEmerald within a subcellular location resembling neutrophil granules, mirroring MPO in human neutrophils. In Spotless (mpxNL144) larvae-which express a non-functional zebrafish myeloperoxidase-the MPO-mEmerald transgene does not disrupt neutrophil migration to sites of infection or inflammation, suggesting that it is a suitable line for the study of neutrophil granule function. We present a new transgenic line that can be used to investigate neutrophil granule dynamics in vivo without disrupting neutrophil behaviour, with potential applications in studying processing and maturation of MPO during development.

Inhibition of phosphodiesterase 2 reverses gp91phox oxidase-mediated depression- and anxiety-like behavior

Phosphodiesterase 2 (PDE2) plays an important role in treatment of stress-related depression through regulation of antioxidant defense and neuroprotective mechanisms. However, the causal relationship between PDE2 and the prevalence of depression and anxiety upon exposure to oxidative stress has not been investigated. The present study examined whether the effects of PDE2 inhibition on oxidative stress were directly involved in reduced ROS by regulating NADPH subunits gp91phox oxidase. The results suggested that the PDE2 inhibitor Bay 60-7550 reversed oxidative stress-induced behavioral signature, i.e. depression and anxiety. Pretreatment with the oxidizing agent DTNB completely blocked, while the reducing agent DTT and the NADPH oxidase inhibitor apocynin potentiated the effects of Bay 60-7550 on behavioral abnormalities, demonstrating the relationship between PDE2 and oxidative stress. Consistently, an in vitro test revealed the positive correlation between ROS and PDE2 levels. Moreover, Bay 60-7550 decreased corticosterone-induced gp91phox expression, which is the source of ROS. The subsequent study suggested that Bay 60-7550 induced decrease in ROS and increase in cAMP/cGMP, pVASP, pCREB, and the neurotrophic factor BDNF levels, which were completely blocked by CRISPR/Cas9-mediated gp91phox overexpression and potentiated by gp91phox siRNA-based antioxidant strategies. The in vivo test in stressed mice further suggested that gp91phox overexpression completely blocked the antidepressant- and anxiolytic-like effects of Bay 60-7550, while gp91phox knockdown enhanced such effects. These results provide solid evidence that the antidepressant- and anxiolytic-like effects of Bay 60-7550 against stress are causally related to down-regulation of gp91phox and activation of the cAMP/cGMP-pVASP-CREB-BDNF signaling pathway.

The other myeloperoxidase: Emerging functions

Myeloperoxidase (MPO) is a member of the mammalian peroxidase family. It is mainly expressed in neutrophils, monocytes and macrophages. As a catalyzer of reactive oxidative species and radical species formation, it contributes to neutrophil bactericidal activity. Nevertheless MPO invalidation does not seem to have major health consequences in affected individuals. This suggests that MPO might have alternative functions supporting its conservation during evolution. We will review the available data supporting these non-canonical functions in terms of tissue specific expression, function and enzymatic activity. Thus, we discuss its cell type specific expression. We review in between others its roles in angiogenesis, endothelial (dys-) function, immune reaction, and inflammation. We summarize its pathological actions in clinical conditions such as cardiovascular disease and cancer.

Inflammatory bowel disease in chronic granulomatous disease: An emerging problem over a twenty years' experience

BACKGROUND

Chronic granulomatous disease (CGD) is a primary immunodeficiency of phagocytes, characterized by life-threatening infections and hyperinflammation. Due to survival improvement, inflammatory bowel disease (IBD) is becoming increasingly relevant. Here, we report our 20 year experience.

METHODS

We retrospectively analyzed clinic, endoscopic, and histologic features, as well as the management of CGD-IBD patients referred to the Bambino Gesù Children's Hospital in Rome, Italy.

RESULTS

Of 20 patients with CGD, 9 presented with CGD-IBD at diagnosis and/or during follow-up. Symptoms occurred at a median age of 16 years (range 3.2-42), with a median delay of 6 months for endoscopic confirmation. Patients mainly complained of nonspecific diarrhea (55%), with discrepancy between symptom paucity and severe endoscopic appearance, mainly represented by extensive colonic involvement (44%). Histology revealed at least 2 characteristic features (epithelioid granulomas, pigmented macrophages, and increased eosinophils) in 78% of patients. Eight of 9 patients received oral mesalamine, and 5 required systemic steroids. One patient received azathioprine due to steroid dependence. No patient required biological therapy or surgery. Clinical remission was obtained in all patients, but the majority complained of mild relapses. Two episodes of severe infection occurred early after steroid therapy.

CONCLUSIONS

Penetrance of CGD-IBD increases with age. Clinical manifestations may be subtle, and clinicians should have a low threshold to recommend endoscopy. Treatment with NSAIDs and/or steroids achieves a good response, but relapses usually occur. Infection surveillance is mandatory during treatment, to prevent opportunistic infections. A close collaboration between pediatric immunologists and gastroenterologists is pivotal, including combined follow-up.

Epic Immune Battles of History: Neutrophils vs. Staphylococcus aureus

Neutrophils are the most abundant leukocytes in human blood and the first line of defense after bacteria have breached the epithelial barriers. After migration to a site of infection, neutrophils engage and expose invading microorganisms to antimicrobial peptides and proteins, as well as reactive oxygen species, as part of their bactericidal arsenal. Ideally, neutrophils ingest bacteria to prevent damage to surrounding cells and tissues, kill invading microorganisms with antimicrobial mechanisms, undergo programmed cell death to minimize inflammation, and are cleared away by macrophages. Staphylococcus aureus (S. aureus) is a prevalent Gram-positive bacterium that is a common commensal and causes a wide range of diseases from skin infections to endocarditis. Since its discovery, S. aureus has been a formidable neutrophil foe that has challenged the efficacy of this professional assassin. Indeed, proper clearance of S. aureus by neutrophils is essential to positive infection outcome, and S. aureus has developed mechanisms to evade neutrophil killing. Herein, we will review mechanisms used by S. aureus to modulate and evade neutrophil bactericidal mechanisms including priming, activation, chemotaxis, production of reactive oxygen species, and resolution of infection. We will also highlight how S. aureus uses sensory/regulatory systems to tailor production of virulence factors specifically to the triggering signal, e.g., neutrophils and defensins. To conclude, we will provide an overview of therapeutic approaches that may potentially enhance neutrophil antimicrobial functions.

New clinical phenotypes of fungal infections in special hosts

Incidence of invasive fungal infections increases over time with the rise in at-risk populations; in particular, patients with acquired immunodeficiencies due to immunosuppressive therapies such as anti-tumour necrosis factor-α (TNF-α) treatment, cirrhosis or burns. Some primary immunodeficiencies (PID) can also predispose selectively to invasive fungal diseases. Conversely, some atypical fungal diseases can reveal new PID. Deep dermatophytosis, Candida central nervous system infections or gastrointestinal disease, or disseminated phaeohyphomycosis-revealed CARD9 deficiency. Most patients with inherited chronic mucocutaneous candidiasis were found to carry STAT1 gain-of-function mutations. The spectrum of fungal susceptibility and clinical presentation varies according to the PID. Among acquired immunodeficiencies, immunosuppressive treatments such as TNF-α blocker therapy, which has revolutionized autoimmune disorder treatment, may be complicated by endemic mycosis, aspergillosis, pneumocystosis or cryptococcosis. Burn patients with damaged skin barrier protection are susceptible to severe Candida infections and filamentous fungal infections (such as Aspergillus spp., Mucorales). Moreover, patients with cirrhosis are at increased risk of fungal infections. Therefore, physicians should think of any potential underlying acquired or inherited immunodeficiency in a patient developing an atypical fungal infection, or of a potential fungal disease in the context of an atypical presentation in specific hosts.

Lack of p47(phox) in Akita Diabetic Mice Is Associated with Interstitial Pneumonia, Fibrosis, and Oral Inflammation

Excess reactive oxygen species production is central to the development of diabetic complications. The contribution of leukocyte reactive oxygen species produced by the NADPH oxidase to altered inflammatory responses associated with uncontrolled hyperglycemia is poorly understood. To get insight into the role of phagocytic superoxide in the onset of diabetic complications, we used a model of periodontitis in mice with chronic hyperglycemia and lack of leukocyte p47(phox) (Akita/Ncf1) bred from C57BL/6-Ins2(Akita)/J (Akita) and neutrophil cytosolic factor 1 knockout (Ncf1) mice. Akita/Nfc1 mice showed progressive cachexia starting at early age and increased mortality by six months. Their lungs developed infiltrative interstitial lesions that obliterated air spaces as early as 12 weeks when fungal colonization of lungs also was observed. Neutrophils of Akita/Ncf1 mice had normal degranulation and phagocytic efficiency when compared with wild-type mice. Although Akita/Ncf1 mice had increased prevalence of oral infections and more severe periodontitis compared with wild-type mice, bone loss was only marginally higher compared with Akita and Ncf1 null mice. Altogether these results indicate that lack of leukocyte superoxide production in mice with chronic hyperglycemia results in interstitial pneumonia and increased susceptibility to infections.

BcNoxD, a putative ER protein, is a new component of the NADPH oxidase complex in Botrytis cinerea

NADPH oxidases (Nox) are major enzymatic producer of reactive oxygen species (ROS). In fungi these multi-enzyme complexes are involved in sexual differentiation and pathogenicity. However, in contrast to mammalian systems, the composition and recruitment of the fungal Nox complexes are unresolved. Here we introduce a new Nox component, the membrane protein NoxD in the grey mold fungus Botrytis cinerea. It has high homology to the ER protein Pro41 from Sordaria macrospora, similar functions to the catalytic Nox subunit BcNoxA in differentiation and pathogenicity, and shows similarities to phagocytic p22phox. BcNoxA and BcNoxD interact with each other. Both proteins are involved in pathogenicity, fusion of conidial anastomosis tubes (CAT) and formation of sclerotia and conidia. These data support our earlier view based on localization studies, for an ER-related function of the Nox complex. We present the first evidence that some functions of the BcNoxA complex are indeed linked to the ER, while others clearly require export from the ER.

Clinical and molecular findings of chronic granulomatous disease in Oman: family studies

Chronic granulomatous disease (CGD), a rare inherited disorder of the innate immune system, results from mutations in any one of the five genes encoding the subunits of the nicotinamide adenine dinucleotide phosphate-oxidase (NADPH) oxidase enzyme, and is characterized by recurrent life-threatening bacterial and fungal infections. Molecular analysis of 14 Omani CGD patients from 10 families, diagnosed to have CGD on clinical (recurrent infections) and biochemical grounds (positive for both the nitroblue tetrazolium (NBT) test and the dihydrorhodamine (DHR-1,2,3 assay), revealed that only one patient had X-linked CGD, with a large deletion involving both the gp91-phox gene (CYBB) and the McLeod gene (XK). The remaining 13 patients were all homozygotes from a previously described c.579G>A (p.Trp193X) mutation in the NCF1 gene on chromosome 7, responsible for autosomal recessive CGD (AR-CGD). Although X-linked CGD is the most common type of CGD disorder in most population groups, AR-CGD is the most prevalent type in Oman.

TLR3-triggered reactive oxygen species contribute to inflammatory responses by activating signal transducer and activator of transcription-1

Intracellular reactive oxygen species (ROS) are essential secondary messengers in many signaling cascades governing innate immunity and cellular functions. TLR3 signaling is crucially involved in antiviral innate and inflammatory responses; however, the roles of ROS in TLR3 signaling remain largely unknown. In this study, we show that TLR3-induced ROS generation is required for the activation of NF-κB, IFN-regulatory factor 3, and STAT1-mediated innate immune responses in macrophages. TLR3 induction led to a rapid increase in ROS generation and a physical association between components of the NADPH oxidase (NOX) enzyme complex (NOX2 and p47(phox)) and TLR3 via a Ca(2+)-c-Src tyrosine kinase-dependent pathway. TLR3-induced ROS generation, NOX2, and p47(phox) were required for the phosphorylation and nuclear translocation of STAT1 and STAT2. TLR3-induced activation of STAT1 contributed to the generation of inflammatory mediators, which was significantly attenuated in NOX2- and p47(phox)-deficient macrophages, suggesting a role for ROS-STAT1 in TLR3-mediated innate immune responses. Collectively, these results provide a novel insight into the crucial role that TLR3-ROS signaling plays in innate immune responses by activating STAT1.

Redox reactions and microbial killing in the neutrophil phagosome

SIGNIFICANCE

When neutrophils kill microorganisms, they ingest them into phagosomes and bombard them with a burst of reactive oxygen species.

RECENT ADVANCES

This review focuses on what oxidants are produced and how they kill. The neutrophil NADPH oxidase is activated and shuttles electrons from NADPH in the cytoplasm to oxygen in the phagosomal lumen. Superoxide is generated in the narrow space between the ingested organism and the phagosomal membrane and kinetic modeling indicates that it reaches a concentration of around 20 μM. Degranulation leads to a very high protein concentration with up to millimolar myeloperoxidase (MPO). MPO has many substrates, but its main phagosomal reactions should be to dismutate superoxide and, provided adequate chloride, catalyze efficient conversion of hydrogen peroxide to hypochlorous acid (HOCl). Studies with specific probes have shown that HOCl is produced in the phagosome and reacts with ingested bacteria. The amount generated should be high enough to kill. However, much of the HOCl reacts with phagosomal proteins. Generation of chloramines may contribute to killing, but the full consequences of this are not yet clear.

CRITICAL ISSUES

Isolated neutrophils kill most of the ingested microorganisms rapidly by an MPO-dependent mechanism that is almost certainly due to HOCl. However, individuals with MPO deficiency rarely have problems with infection. A possible explanation is that HOCl provides a frontline response that kills most of the microorganisms, with survivors killed by nonoxidative processes. The latter may deal adequately with low-level infection but with high exposure, more efficient HOCl-dependent killing is required.

FUTURE DIRECTIONS

Better quantification of HOCl and other oxidants in the phagosome should clarify their roles in antimicrobial action.

Myeloperoxidase: a front-line defender against phagocytosed microorganisms

Successful immune defense requires integration of multiple effector systems to match the diverse virulence properties that members of the microbial world might express as they initiate and promote infection. Human neutrophils--the first cellular responders to invading microbes--exert most of their antimicrobial activity in phagosomes, specialized membrane-bound intracellular compartments formed by ingestion of microorganisms. The toxins generated de novo by the phagocyte NADPH oxidase and delivered by fusion of neutrophil granules with nascent phagosomes create conditions that kill and degrade ingested microbes. Antimicrobial activity reflects multiple and complex synergies among the phagosomal contents, and optimal action relies on oxidants generated in the presence of MPO. The absence of life-threatening infectious complications in individuals with MPO deficiency is frequently offered as evidence that the MPO oxidant system is ancillary rather than essential for neutrophil-mediated antimicrobial activity. However, that argument fails to consider observations from humans and KO mice that demonstrate that microbial killing by MPO-deficient cells is less efficient than that of normal neutrophils. We present evidence in support of MPO as a major arm of oxidative killing by neutrophils and propose that the essential contribution of MPO to normal innate host defense is manifest only when exposure to pathogens overwhelms the capacity of other host defense mechanisms.

TIPE2 protein serves as a negative regulator of phagocytosis and oxidative burst during infection

Phagocytosis and oxidative burst are two major effector arms of innate immunity. Although it is known that both are activated by Toll-like receptors (TLRs) and Rac GTPases, how their strengths are controlled in quiescent and TLR-activated cells is not clear. We report here that TIPE2 (TNFAIP8L2) serves as a negative regulator of innate immunity by linking TLRs to Rac. TLRs control the expression levels of TIPE2, which in turn dictates the strengths of phagocytosis and oxidative burst by binding to and blocking Rac GTPases. Consequently, TIPE2 knockout cells have enhanced phagocytic and bactericidal activities and TIPE2 knockout mice are resistant to bacterial infection. Thus, TIPE2 sets the strengths of phagocytosis and oxidative burst and may be targeted to effectively control infections.

The role of neutrophils during intestinal inflammation

Polymorphonuclear leukocytes or neutrophils play a critical role in the maintenance of intestinal homeostasis. They have elegant defense mechanisms to eliminate microbes that have translocated across a single layer of mucosal epithelial cells that form a critical barrier between the gut lumen and the underlying tissue. During the inflammatory response, neutrophils also contribute to the recruitment of other immune cells and facilitate mucosal healing by releasing mediators necessary for the resolution of inflammation. Although the above responses are clearly beneficial, excessive recruitment and accumulation of activated neutrophils in the intestine under pathological conditions such as inflammatory bowel disease is associated with mucosal injury and debilitating disease symptoms. Thus, depending on the circumstances, neutrophils can be viewed as either good or bad. In this article, we summarize the beneficial and deleterious roles of neutrophils in the intestine during health and disease and provide an overview of what is known about neutrophil function in the gut.

Degranulation deconstructed

Pediatricians first described the clinical features of chronic granulomatous disease (CGD) in 1959. Almost a decade later, in a collaborative effort that crossed disciplines, we participated in the discoveries that defined the cellular deficiencies of CGD, specifically finding that improper degranulation of leukocytes did not explain their failure to fight pathogens, rather that the fundamental defect was due to problems in the unique NADPH oxidase system of phagocytizing leukocytes. In the years that followed, the subunit components and structure of NADPH oxidase and their translocation during leukocyte phagocytosis to form the active enzyme were well described, leading to the identification of the component genes, the mapping of their chromosomal locations, and their subsequent cloning. This remarkable progress has led to effective therapies, including bone marrow transplants and gene therapy, that would have been unimaginable when we began.

Autosomal recessive chronic granulomatous disease presenting with cutaneous dermatoses and ocular infection

Dermatoses such as eczematous dermatitis and cutaneous infection are recognized presentations of primary immunodeficiency (PID). However, atopic dermatitis affects approximately 10% of infants, and cutaneous infections are not uncommon in children, therefore the challenge for the dermatologist is to distinguish the few patients that have PID from the many that do not. We report on a 6-year-old girl who was ultimately diagnosed with autosomal recessive chronic granulomatous disease (AR-CGD) after presenting to various hospitals with dermatitis, scalp plaques recalcitrant to treatment, and recurrent infections over a 3-year period, and describe some aspects of her diagnosis and management. This report highlights the importance of considering rare disorders such as AR-CGD in the differential diagnosis of recurrent or recalcitrant dermatological infections in children.

Flavonoids inhibit the respiratory burst of neutrophils in mammals

Neutrophils represent the front-line defence cells in protecting organisms against infection and play an irreplaceable role in the proper performance of the immune system. As early as within the first minutes of stimulation, neutrophilic NADPH oxidase is activated, and cells release large quantities of highly toxic reactive oxygen species (ROS). These oxidants can be highly toxic not only for infectious agents but also for neighboring host tissues. Since flavonoids exhibit antioxidant and anti-inflammatory effects, they are subjects of interest for pharmacological modulation of ROS production. The present paper summarizes contemporary knowledge on the effects of various flavonoids on the respiratory burst of mammalian neutrophils. It can be summarized that the inhibitory effects of flavonoids on the respiratory burst of phagocytes are mediated via inhibition of enzymes involved in cell signaling as well as via modulation of redox status. However, the effects of flavonoids are even more complex, and several sites of action, depending upon the flavonoid structure and way of application, are included.

Primary immune deficiency disorders in the South Pacific: the clinical utility of a customized genetic testing program in New Zealand

Primary immune deficiency disorders (PIDs) are a group of diseases associated with a genetic susceptibility to recurrent infections, malignancy, autoimmunity, and allergy. The molecular basis of many of these disorders has been identified in the last two decades. Most are inherited as single gene defects. As discussed in this paper, identifying the underlying genetic defect plays a critical role in many areas-including patient management, diagnosis, identifying atypical presentations, family studies, providing prognostic information, prenatal diagnosis, and defining new diseases. New Zealand is a geographically isolated, developed country in the South Pacific. We have introduced a dedicated customized genetic testing service for PID patients in New Zealand. This accredited diagnostic program offers rapid turnaround times for genetic tests and minimizes the risk of laboratory errors. Here we review the clinical indications for genetic testing for PIDs based on cases referred to the molecular immunology diagnostic service at Auckland City Hospital.

Identification and functional characterization of two novel mutations in the α-helical loop (residues 484-503) of CYBB/gp91(phox) resulting in the rare X91(+) variant of chronic granulomatous disease

Chronic granulomatous disease (CGD) is mainly caused by mutations in X-linked CYBB that encodes gp91. We have identified two novel mutations in CYBB resulting in the rare X91(+)-CGD variant, c.1500T>G (p.Asp500Glu) in two male siblings and c.1463C>A (p.Ala488Asp) in an unrelated male. Zymosan and/or PMA (Phorbol 12-myristate 13-acetate)-induced recruitment of p47(phox) and p67(phox) to the membrane fraction was normal for both mutants. Cell-free assays using recombinant wild-type and the mutant proteins revealed that these mutants were not activated by NADPH (nicotinamide adenine dinucleotide phosphate). Interestingly, the Ala488Asp mutant was activated by NADPH in the presence of glutathione. These data suggest that the mutations prevented NADPH from binding to gp91(phox) and the requirement of a negative charge at residue 500 in gp91(phox) for NADPH oxidase assembly, in contrast to a previously described Asp500Gly change. These mutations and the effect of glutathione provide a unique insight into disease pathogenesis and potential therapy in variant X91(+)-CGD.

Role of p47phox in antigen-presenting cell-mediated regulation of humoral immunity in mice

Microbial-induced inflammation is important for eliciting humoral immunity. Genetic defects of NADPH oxidase 2-based proteins interrupt phagocyte superoxide generation and are the basis for the human immunodeficiency chronic granulomatous disease (CGD). Hyperinflammation is also a significant clinical manifestation of CGD. Herein, we evaluated humoral immunity in the phagocyte oxidase p47(phox)-deficient model of CGD and found that UV-inactivated Streptococcus pneumoniae and Listeria monocytogenes (Lm) elicited higher specific antibody (Ab) titers in p47(phox-/-) mice than wild-type (WT) mice. Both organisms elicited robust and distinct antigen-presenting cell maturation phenotypes, including IL-12 hypersecretion, and higher major histocompatibility complex II and costimulatory protein expression in Lm-stimulated p47(phox-/-) dendritic cells (DCs) relative to WT DCs. Furthermore, p47(phox-/-) DCs pulsed with Lm and adoptively transferred into naïve WT mice elicited Ab titers, whereas Lm-pulsed WT DCs did not elicit these titers. The observed robust p47(phox-/-) mouse humoral response was recapitulated with live Lm and sustained in vivo in p47(phox-/-) mice. Notably, anti-serum samples from p47(phox-/-) mice that survived secondary Lm infection were protective in WT and p47(phox-/-) mice that were rechallenged with secondary lethal Lm infection. These findings demonstrate a novel benefit of NADPH oxidase 2 deficiency (ie, dependent inflammation in antigen-presenting cell-mediated humoral immunity) and that anti-Lm Ab can be protective in an immunodeficient CGD host.

Early enhanced local neutrophil recruitment in peritonitis-induced sepsis improves bacterial clearance and survival

Neutrophils are critical for the rapid eradication of bacterial pathogens, but they also contribute to the development of multiple organ failure in sepsis. We hypothesized that increasing early recruitment of neutrophils to the focus of infection will increase bacterial clearance and improve survival. Sepsis was induced in mice, using cecal ligation and puncture (CLP); blood samples were collected at 6 and 24 h; and survival was followed for 28 d. In separate experiments, peritoneal bacteria and inflammatory cells were measured. Septic mice predicted to die based on IL-6 levels (Die-P) had higher concentrations of CXCL1 and CXCL2 in the peritoneum and plasma compared with those predicted to live (Live-P). At 6 h, Live-P and Die-P had equivalent numbers of peritoneal neutrophils and bacteria. In Die-P mice the number of peritoneal bacteria increased between 6 and 24 h post-CLP, whereas in Live-P it decreased. The i.p. injection of CXCL1 and CXCL2 in naive mice resulted in local neutrophil recruitment. When given immediately after CLP, CXC chemokines increased peritoneal neutrophil recruitment at 6 h after CLP. This early increase in neutrophils induced by exogenous chemokines resulted in significantly fewer peritoneal bacteria by 24 h [CFU (log) = 6.04 versus 4.99 for vehicle versus chemokine treatment; p < 0.05]. Chemokine treatment significantly improved survival at both 5 d (40 versus 72%) and 28 d (27 versus 52%; p < 0.02 vehicle versus chemokines). These data demonstrate that early, local treatment with CXC chemokines enhances neutrophil recruitment and clearance of bacteria as well as improves survival in the CLP model of sepsis.

The clinical utility of molecular diagnostic testing for primary immune deficiency disorders: a case based review

Primary immune deficiency disorders (PIDs) are a group of diseases associated with a genetic predisposition to recurrent infections, malignancy, autoimmunity and allergy. The molecular basis of many of these disorders has been identified in the last two decades. Most are inherited as single gene defects. Identifying the underlying genetic defect plays a critical role in patient management including diagnosis, family studies, prognostic information, prenatal diagnosis and is useful in defining new diseases. In this review we outline the clinical utility of molecular testing for these disorders using clinical cases referred to Auckland Hospital. It is written from the perspective of a laboratory offering a wide range of tests for a small developed country.

A case of severe visceral leishmaniasis resulting from travel to Greece

Visceral leishmaniasis is rare in the developed world, particularly in immunocompetent hosts. It must be considered, however, in patients who are unwell, febrile and unresponsive to conventional antibiotics with a history of travel to areas where leishmaniasis is endemic. A case of more severe clinical manifestations than have been previously reported in Australia is presented here. The recent introduction of PCR technology for the detection of Leishmania in Australia has improved the diagnosis and management of leishmaniasis. Treatment with liposomal amphotericin B proved to be very effective in this severe case of visceral leishmaniasis.

Mechanism regulating reactive oxygen species in tumor-induced myeloid-derived suppressor cells

Myeloid-derived suppressor cells (MDSC) are a major component of the immune suppressive network described in cancer and many other pathological conditions. Recent studies have demonstrated that one of the major mechanisms of MDSC-induced immune suppression is mediated by reactive oxygen species (ROS). However, the mechanism of this phenomenon remained unknown. In this study, we observed a substantial up-regulation of ROS by MDSC in all of seven different tumor models and in patients with head and neck cancer. The increased ROS production by MDSC is mediated by up-regulated activity of NADPH oxidase (NOX2). MDSC from tumor-bearing mice had significantly higher expression of NOX2 subunits, primarily p47(phox) and gp91(phox), compared with immature myeloid cells from tumor-free mice. Expression of NOX2 subunits in MDSC was controlled by the STAT3 transcription factor. In the absence of NOX2 activity, MDSC lost the ability to suppress T cell responses and quickly differentiated into mature macrophages and dendritic cells. These findings expand our fundamental understanding of the biology of MDSC and may also open new opportunities for therapeutic regulation of these cells in cancer.

Fatal hemophagocytic lymphohistiocytosis in X-linked chronic granulomatous disease associated with a perforin gene variant

A patient with previously unrecognized X-linked chronic granulomatous disease (X-CGD) died of multi-organ failure, secondary to ongoing infection and hemophagocytic lymphohistiocytosis (HLH). Post mortem histological investigations were compatible with X-CGD, and a CYBB gene mutation was confirmed. No homozygous mutations in the genes encoding perforin (PRF1), MUNC 13-4 or syntaxin-11 (STX11) were found; however, there was a heterozygous alteration c.1471G>A in the PRF1 gene causing a p.Asp491Asn substitution. Although this substitution has not been reported to cause primary or secondary HLH, we speculate that it may have made the patient more susceptible for HLH under the circumstances of ongoing infection associated with X-CGD.

Cell mediated immunity to fungi: a reassessment

Protective immunity against fungal pathogens is achieved by the integration of two distinct arms of the immune system, the innate and adaptive responses. Innate and adaptive immune responses are intimately linked and controlled by sets of molecules and receptors that act to generate the most effective form of immunity for protection against fungal pathogens. The decision of how to respond will still be primarily determined by interactions between pathogens and cells of the innate immune system, but the actions of T cells will feed back into this dynamic equilibrium to regulate the balance between tolerogenic and inflammatory responses. In the last two decades, the immunopathogenesis of fungal infections and fungal diseases was explained primarily in terms of Th1/Th2 balance. Although Th1 responses driven by the IL-12/IFN-gamma axis are central to protection against fungi, other cytokines and T cell-dependent pathways have come of age. The newly described Th17 developmental pathway may play an inflammatory role previously attributed to uncontrolled Th1 responses and serves to accommodate the seemingly paradoxical association of chronic inflammatory responses with fungal persistence in the face of an ongoing inflammation. Regulatory T cells in their capacity to inhibit aspects of innate and adaptive antifungal immunity have become an integral component of immune resistance to fungi, and provide the host with immune defense mechanisms adequate for protection, without necessarily eliminating fungal pathogens which would impair immune memory--or causing an unacceptable level of tissue damage. The enzyme indoleamine 2,3-dioxygenase and tryptophan metabolites contribute to immune homeostasis by inducing Tregs and taming overzealous or heightened inflammatory responses.

p47phox-deficient immune microenvironment signals dysregulate naive T-cell apoptosis

The phagocyte NADPH oxidase is a multicomponent enzyme complex mediating microbial killing. We find that NADPH oxidase p47(phox)-deficient (p47(phox-/-)) chronic granulomatous disease (CGD) mice develop lymph node hyperplasia even without obvious infection, where increased number of T and B lymphocytes is associated with increased percent of naïve cells and a lower T : B cell ratio than wild type. Paradoxically, despite lymphoid hyperplasia in vivo, when lymphocytes are placed in culture, p47(phox-/-) CD8(+) lymphocytes progress more rapidly to apoptosis than wild type. This is associated in cultured p47(phox-/-) CD8(+) lymphocytes with the induction of proapoptotic Bim and Puma expression, increased mitochondrial outer membrane permeabilization and depressed Bcl-2 expression. Addition of IL-7 to the culture partially corrects Bcl-2 levels in cultured p47(phox-/-) CD8(+) lymphocytes and improves the survival. Adding glucose oxidase to the culture to generate hydrogen peroxide along with IL-7 further improves p47(phox-/-) CD8(+) lymphocyte survival, but only to 30% of wild type. We conclude that p47(phox-/-) CD8(+) lymphocytes have an intrinsic survival defect likely in part related to the oxidase deficiency, but in vivo in lymph nodes of CGD mice, there are microenvironmental factors yet to be delineated that suppress the progression of apoptosis and allow the accumulation of lymphocytes leading to lymphoid hyperplasia.

p47phox deficiency induces macrophage dysfunction resulting in progressive crystalline macrophage pneumonia

Nicotinamide dinucleotide phosphate oxidase-deficient (p47(phox-/-)) mice are a model of human chronic granulomatous disease; these mice are prone to develop systemic infections and inflammatory diseases. The use of antibiotic (Bactrim) prophylaxis in a specific pathogen-free environment, however, impedes infection in the majority of p47(phox-/-) mice. We examined infection-free p47(phox-/-) mice between 1 and 14 months of age and found that they developed proliferative macrophage lesions containing Ym1/Ym2 protein and crystals in lung, bone marrow, lymph nodes, and spleen. Here, we show that the lung lesions progressed from single macrophages with intracellular Ym1/Ym2 protein crystals to severe diffuse crystalline macrophage pneumonia without histological evidence of either granulation tissue or pulmonary fibrosis. Ym1/Ym2 is a chitinase-like secretory protein that is transiently induced in alternatively activated macrophages during T-helper (Th)2-biased pathogenesis and during chemical and traumatic inflammation. Bronchoalveolar lavage from p47(phox-/-) mice contained significantly higher levels of Th-1 (interferon-gamma), Th-2 (interleukin-4), and Th-17 (interleukin-17)-associated cytokines than wild-type mice, as well as copious amounts of interleukin-12, indicating that Ym1-secreting p47(phox-/-) macrophages are also integrated into classically activated macrophage responses. These results suggest that p47(phox-/-) macrophages are extremely pliable, due in part to an intrinsic dysfunction of macrophage activation pathways that allows for distinct classical or alternative activation phenotypes.

Impaired apoptotic cell clearance in CGD due to altered macrophage programming is reversed by phosphatidylserine-dependent production of IL-4

Chronic granulomatous disease (CGD) is characterized by overexuberant inflammation and autoimmunity that are attributed to deficient anti-inflammatory signaling. Although regulation of these processes is complex, phosphatidylserine (PS)-dependent recognition and removal of apoptotic cells (efferocytosis) by phagocytes are potently anti-inflammatory. Since macrophage phenotype also plays a beneficial role in resolution of inflammation, we hypothesized that impaired efferocytosis in CGD due to macrophage skewing contributes to enhanced inflammation. Here we demonstrate that efferocytosis by macrophages from CGD (gp91(phox)(-/-)) mice was suppressed ex vivo and in vivo. Alternative activation with interleukin 4 (IL-4) normalized CGD macrophage efferocytosis, whereas classical activation by lipopolysaccharide (LPS) plus interferon gamma (IFNgamma) had no effect. Importantly, neutralization of IL-4 in wild-type macrophages reduced macrophage efferocytosis, demonstrating a central role for IL-4. This effect was shown to involve 12/15 lipoxygenase and activation of peroxisome-proliferator activated receptor gamma (PPARgamma). Finally, injection of PS (whose exposure is lacking on CGD apoptotic neutrophils) in vivo restored IL-4-dependent macrophage reprogramming and efferocytosis via a similar mechanism. Taken together, these findings support the hypothesis that impaired PS exposure on dying cells results in defective macrophage programming, with consequent efferocytic impairment and has important implications in understanding the underlying cause of enhanced inflammation in CGD.

Pharmacological evidence for the stimulation of NADPH oxidase by P2X(7) receptors in mouse submandibular glands

ATP in the 100 μM-1 mM concentration range provoked a calcium-independent increase of the oxidation of dichlorodihydrofluorescein (DCFH) to dichlorofluorescein (DCF) by mouse submandibular cells. 3′-O-(4-benzoyl)benzoyl adenosine 5′-triphosphate (BzATP), a P2X₇ agonist, but not a muscarinic or an adrenergic agonist, reproduced the effect of ATP. The inhibition of phospholipase C by U73122 or the potentiation of P2X₄ receptor activation with ivermectin did not modify the response to ATP. ATP did not increase the oxidation of DCFH in cells isolated from submandibular glands of P2X₇ knockout mice or in cells pretreated with a P2X₇ antagonist. The inhibition of protein kinase C or of mitogen-activated protein kinase (MAP kinase) or of reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase blocked the oxidation of DCFH without affecting the increase of the intracellular concentration of calcium or the uptake of ethidium bromide in response to extracellular ATP. From these results it is concluded that the activation of the P2X₇ receptors from submandibular glands triggers an intracellular signalling cascade involving protein kinase C and MAP kinase leading to the stimulation of NADPH oxidase and the subsequent generation of reactive oxygen species.

Neutrophil-mediated oxidative burst and host defense are controlled by a Vav-PLCgamma2 signaling axis in mice

Oxidative burst, a critical antimicrobial mechanism of neutrophils, involves the rapid generation and release of reactive oxygen intermediates (ROIs) by the NADPH oxidase complex. Genetic mutations in an NADPH oxidase subunit, gp91 (also referred to as NOX2), are associated with chronic granulomatous disease (CGD), which is characterized by recurrent and life-threatening microbial infections. To combat such infections, ROIs are produced by neutrophils after stimulation by integrin-dependent adhesion to the ECM in conjunction with stimulation from inflammatory mediators, or microbial components containing pathogen-associated molecular patterns. In this report, we provide genetic evidence that both the Vav family of Rho GTPase guanine nucleotide exchange factors (GEFs) and phospholipase C-gamma2 (PLC-gamma2) are critical mediators of adhesion-dependent ROI production by neutrophils in mice. We also demonstrated that Vav was critically required for neutrophil-dependent host defense against systemic infection by Staphylococcus aureus and Pseudomonas aeruginosa, 2 common pathogens associated with fatal cases of hospital-acquired pneumonia. We identified a molecular pathway in which Vav GEFs linked integrin-mediated signaling with PLC-gamma2 activation, release of intracellular Ca2+ cations, and generation of diacylglycerol to control assembly of the NADPH oxidase complex and ROI production by neutrophils. Taken together, our data indicate that integrin-dependent signals generated during neutrophil adhesion contribute to the activation of NADPH oxidase by a variety of distinct effector pathways, all of which require Vav.

Defective tryptophan catabolism underlies inflammation in mouse chronic granulomatous disease

Half a century ago, chronic granulomatous disease (CGD) was first described as a disease fatally affecting the ability of children to survive infections. Various milestone discoveries have since been made, from an insufficient ability of patients' leucocytes to kill microbes to the underlying genetic abnormalities. In this inherited disorder, phagocytes lack NADPH oxidase activity and do not generate reactive oxygen species, most notably superoxide anion, causing recurrent bacterial and fungal infections. Patients with CGD also suffer from chronic inflammatory conditions, most prominently granuloma formation in hollow viscera. The precise mechanisms of the increased microbial pathogenicity have been unclear, and more so the reasons for the exaggerated inflammatory response. Here we show that a superoxide-dependent step in tryptophan metabolism along the kynurenine pathway is blocked in CGD mice with lethal pulmonary aspergillosis, leading to unrestrained Vgamma1(+) gammadelta T-cell reactivity, dominant production of interleukin (IL)-17, defective regulatory T-cell activity and acute inflammatory lung injury. Although beneficial effects are induced by IL-17 neutralization or gammadelta T-cell contraction, complete cure and reversal of the hyperinflammatory phenotype are achieved by replacement therapy with a natural kynurenine distal to the blockade in the pathway. Effective therapy, which includes co-administration of recombinant interferon-gamma (IFN-gamma), restores production of downstream immunoactive metabolites and enables the emergence of regulatory Vgamma4(+) gammadelta and Foxp3(+) alphabeta T cells. Therefore, paradoxically, the lack of reactive oxygen species contributes to the hyperinflammatory phenotype associated with NADPH oxidase deficiencies, through a dysfunctional kynurenine pathway of tryptophan catabolism. Yet, this condition can be reverted by reactivating the pathway downstream of the superoxide-dependent step.

Dysregulation of innate immune receptors on neutrophils in chronic granulomatous disease

BACKGROUND

Chronic granulomatous disease (CGD) is the most common inherited disorder of neutrophil function, is caused by mutations in the reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, and results in recurrent bacterial infections.

OBJECTIVE

We sought to investigate the expression and function of innate immune receptors on neutrophils in patients with CGD.

METHODS

We quantified mRNA and protein expression of Toll-like receptors (TLRs), complement receptors, and chemokine receptors on neutrophils from 15 patients with CGD compared with that seen in healthy control subjects (n = 15) and control patients with bacterial pneumonia (n = 15). Phagocytosis, chemotaxis, and TLR function of isolated neutrophils were analyzed. The effect of NADPH oxidase inhibition on receptor expression and function was analyzed in control neutrophils.

RESULTS

Neutrophils from patients with CGD had lower expression levels of TLR5, TLR9, CD11b, CD18, CD35, and CXCR1 compared with those from healthy control subjects, whereas similar or increased receptor expressions were found in patients without CGD but with bacterial pneumonia. Reduced TLR5 expression resulted in impaired neutrophil activation by bacterial flagella, reduced CD11b/CD18 expression was associated with impaired phagocytosis of Staphylococcus aureus, and reduced CXCR1 expression was associated with decreased chemotaxis. TLR5 and CD18 expression levels correlated with disease severity in patients with CGD. TLR5 and TLR9 expression were greater in patients with residual NADPH oxidase activity. Inhibition of the NADPH oxidase in control neutrophils in vitro decreased TLR5 and TLR9 expression and impaired TLR5 function.

CONCLUSION

These results provide the first evidence that innate immune receptors are dysregulated in patients with CGD.