Spectrum of function of neutrophils from carriers of sex-linked chronic granulomatous disease

Geographic Variability and Pathogen-Specific Considerations in the Diagnosis and Management of Chronic Granulomatous Disease

Chronic granulomatous disease (CGD) is a rare but serious primary immunodeficiency with varying prevalence and rates of X-linked and autosomal recessive disease worldwide. Functional defects in the phagocyte nicotinamide adenine dinucleotide phosphate oxidase complex predispose patients to a relatively narrow spectrum of bacterial and fungal infections that are sometimes fastidious and often difficult to identify. When evaluating and treating patients with CGD, it is important to consider their native country of birth, climate, and living situation, which may predispose them to types of infections that are atypical to your routine practice. In addition to recurrent and often severe infections, patients with CGD and X-linked female carriers are also susceptible to developing many non-infectious complications including tissue granuloma formation and autoimmunity. The DHR-123 oxidation assay is the gold standard for making the diagnosis and it along with genetic testing can help predict the severity and prognosis in patients with CGD. Disease management focuses on prophylaxis with antibacterial, antifungal, and immunomodulatory medications, prompt identification and treatment of acute infections, and prevention of secondary granulomatous complications. While hematopoietic stem-cell transplantation is the only widely available curative treatment for patients with CGD, recent advances in gene therapy may provide a safer, more direct alternative.

Considerations in the Diagnosis of Chronic Granulomatous Disease

Chronic granulomatous disease (CGD) is a rare primary immunodeficiency that is caused by defects in the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase complex. The disease presents in most patients initially with infection, especially of the lymph nodes, lung, liver, bone, and skin. Patients with CGD are susceptible to a narrow spectrum of pathogens, and Staphylococcus aureus, Burkholderia cepacia complex, Serratia marcescens, Nocardia species, and Aspergillus species are the most common organisms implicated in North America. Granuloma formation, most frequently in the gastrointestinal and genitourinary systems, is a common complication of CGD and can be seen even before diagnosis. An increased incidence of autoimmune disease has also been described in patients with CGD and X-linked female carriers. In patients who present with signs and symptoms consistent with CGD, a flow cytometric dihydrorhodamine neutrophil respiratory burst assay is a quick and cost-effective way to evaluate NADPH oxidase function. The purpose of this review is to highlight considerations for and challenges in the diagnosis of CGD.

NOX2 As a Target for Drug Development: Indications, Possible Complications, and Progress

SIGNIFICANCE

NOX2 is important for host defense, and yet is implicated in a large number of diseases in which inflammation plays a role in pathogenesis. These include acute and chronic lung inflammatory diseases, stroke, traumatic brain injury, and neurodegenerative diseases, including Alzheimer's and Parkinson's Diseases.

RECENT ADVANCES

Recent drug development programs have targeted several NOX isoforms that are implicated in a variety of diseases. The focus has been primarily on NOX4 and NOX1 rather than on NOX2, due, in part, to concerns about possible immunosuppressive side effects. Nevertheless, NOX2 clearly contributes to the pathogenesis of many inflammatory diseases, and its inhibition is predicted to provide a novel therapeutic approach.

CRITICAL ISSUES

Possible side effects that might arise from targeting NOX2 are discussed, including the possibility that such inhibition will contribute to increased infections and/or autoimmune disorders. The state of the field with regard to existing NOX2 inhibitors and targeted development of novel inhibitors is also summarized.

FUTURE DIRECTIONS

NOX2 inhibitors show particular promise for the treatment of inflammatory diseases, both acute and chronic. Theoretical side effects include pro-inflammatory and autoimmune complications and should be considered in any therapeutic program, but in our opinion, available data do not indicate that they are sufficiently likely to eliminate NOX2 as a drug target, particularly when weighed against the seriousness of many NOX2-related indications. Model studies demonstrating efficacy with minimal side effects are needed to encourage future development of NOX2 inhibitors as therapeutic agents.

Prolonged neutrophil dysfunction after Plasmodium falciparum malaria is related to hemolysis and heme oxygenase-1 induction

It is not known why people are more susceptible to bacterial infections such as nontyphoid Salmonella during and after a malaria infection, but in mice, malarial hemolysis impairs resistance to nontyphoid Salmonella by impairing the neutrophil oxidative burst. This acquired neutrophil dysfunction is a consequence of induction of the cytoprotective, heme-degrading enzyme heme oxygenase-1 (HO-1) in neutrophil progenitors in bone marrow. In this study, we assessed whether neutrophil dysfunction occurs in humans with malaria and how this relates to hemolysis. We evaluated neutrophil function in 58 Gambian children with Plasmodium falciparum malaria [55 (95%) with uncomplicated disease] and examined associations with erythrocyte count, haptoglobin, hemopexin, plasma heme, expression of receptors for heme uptake, and HO-1 induction. Malaria caused the appearance of a dominant population of neutrophils with reduced oxidative burst activity, which gradually normalized over 8 wk of follow-up. The degree of neutrophil impairment correlated significantly with markers of hemolysis and HO-1 induction. HO-1 expression was increased in blood during acute malaria, but at a cellular level HO-1 expression was modulated by changes in surface expression of the haptoglobin receptor (CD163). These findings demonstrate that neutrophil dysfunction occurs in P. falciparum malaria and support the relevance of the mechanistic studies in mice. Furthermore, they suggest the presence of a regulatory pathway to limit HO-1 induction by hemolysis in the context of infection and indicate new targets for therapeutic intervention to abrogate the susceptibility to bacterial infection in the context of hemolysis in humans.

Disorders of Neutrophil Number and Function

This review of disorders of neutrophil number and function will discuss important research advances in the field and then provide a clinical diagnostic approach. The focus will be on two recent clinical developments in the field of phagocyte disorders. First, an important natural history study from the Severe Chronic Neutropenia International Registry has recently quantitated the incidence and risk factors for death from sepsis and for progression to myelodysplastic syndrome and acute myeloid leukemia in a large cohort of severe chronic neutropenia patients, many of whom were followed 10 or more years on treatment with granulocyte colony-stimulating factor. Second, in the past year, a multinational group has announced successful gene therapy of two adults with chronic granulomatous disease, the most common disorder of neutrophil function. However, monitoring of retroviral insertion sites revealed expansion of the multiclonal population of gene-modified cells, raising concerns about eventual leukemogenesis. The review also provides a pragmatic approach to the evaluation of a patient with a suspected disorder of neutrophil number or function.

Genetic analysis of patients with defects in early B-cell development

Approximately 85% of patients with defects in early B-cell development have X-linked agammaglobulinemia (XLA), a disorder caused by mutations in the cytoplasmic Bruton's tyrosine kinase (Btk). Although Btk is activated by cross-linking of a variety of cell-surface receptors, the most critical signal transduction pathway is the one initiated by the pre-B cell and B-cell antigen receptor complex. Mutations in Btk are highly diverse, and no single mutation accounts for more than 3% of patients. Although there is no strong genotype/phenotype correlation in XLA, the specific mutation in Btk is one of the factors that influences the severity of disease. Mutations in the components of the pre-B cell and B-cell antigen receptor complex account for an additional 5-7% of patients with defects in early B-cell development. Patients with defects in these proteins are clinically indistinguishable from those with XLA. However, they tend to be younger at the time of diagnosis, and whereas most patients with XLA have a small number of B cells in the peripheral circulation, these cells are not found in patients with defects in micro heavy chain or Igalpha. Polymorphic variants in the components of the pre-B cell and B-cell receptor complex, particularly micro heavy chain and lambda5, may contribute to the severity of XLA.

Females with a disorder phenotypically identical to X-linked agammaglobulinemia

Clinical and laboratory findings in two girls with a disorder phenotypically indistinguishable from typical X-linked agammaglobulinemia (XLA) are described. To examine the possibility that subtle defects in the X chromosome might explain the findings, detailed genetic studies were performed on one of these patients. Cytogenetic studies showed a normal 46XX karyotype. Southern blot analysis of her DNA showed that she had inherited a maternal and a paternal allele at sites flanking the locus for typical XLA at Xq22, making a microdeletion or uniparental disomy unlikely. To determine whether both of her X chromosomes could function as the active X, somatic-cell hybrids that selectively retained the active X were produced from her activated T cells. A normal random pattern of X inactivation was seen. Of 21 T-cell hybrids, 3 retained both X chromosomes, 7 had one X as the active X, and 11 had the other X as the active X. We have interpreted these studies as indicating that there is an autosomal recessive disorder that is phenotypically identical to XLA.

Partial correction of the phagocyte defect in patients with X-linked chronic granulomatous disease by subcutaneous interferon gamma

Chronic granulomatous disease, a disorder of host defense, is characterized by an impairment in the killing of microbes that results from a defect in the production of superoxide anion by phagocytes. We examined the efficacy of interferon gamma, a physiologic activator of phagocytic-cell function, in the treatment of the disease. Two subcutaneous injections of recombinant interferon gamma (0.1 mg per square meter of body-surface area per dose) were administered on consecutive days to four patients with the X-linked form of the disease. Treatment resulted in 5- to 10-fold increases in superoxide production by granulocytes and monocytes; the improvement was sustained for more than two weeks. Granulocyte bactericidal activity rose proportionally. In the two most responsive patients, both phagocytic functions reached the normal range of activity. In association with these functional changes, we observed an increase in cellular contents of phagocyte cytochrome b (a critical component of the superoxide-producing oxidase) and immunoreactive cytochrome b heavy chain (the product of the gene that is defective in X-linked chronic granulomatous disease). Levels of cytochrome b detected by spectrophotometry rose from near zero to 10 to 50 percent of normal values. This study demonstrates partial correction of the cellular defects in chronic granulomatous disease by interferon gamma and provides a basis for clinical trials of the agent.

Prenatal diagnosis of X-linked chronic granulomatous disease using restriction fragment length polymorphism analysis

Prenatal diagnosis of X-linked chronic granulomatous disease (CGD) was performed with restriction fragment length polymorphism (RFLP) analysis using probes flanking the gene. The male fetus and an affected male displayed the same haplotype for RFLPs belonging to six linked loci extending from DXS164 to DXS7, which encompass the CGD locus, and for which the mother was heterozygous. Diagnosis of an affected fetus was confirmed after termination of the pregnancy by the study of fetal granulocytes using the nitroblue tetrazolium reduction test. In informative families prenatal diagnosis of CGD can be made earlier by RFLP analysis than by fetal blood sampling.

Recurrent severe infections in a girl with apparently variable expression of mosaicism for chronic granulomatous disease

A carrier of chronic granulomatous disease (CGD) has had recurrent severe purulent infections like those characteristic of CGD. The carrier state was demonstrated by the presence of both normal and CGD granulocytes in her blood; the percentage of normal granulocytes varied from 4% to 44% over 4 years. In addition, her granulocytes were partially defective in killing Escherichia coli and staphylococci and in the release of superoxide anion during stimulation. Extensive evaluation of her immune system and phagocyte function failed to reveal a second abnormality. The course in this child indicates that the carrier state for X-linked CGD cannot be considered a benign condition and might be more properly conceptualized as a continuum in expression of the full disease. Screening assays for CGD should possess the capacity to diagnose carriers of the X-linked form of the disease.

Chronic granulomatous disease in two sisters

Two sisters with chronic granulomatous disease (CGD) have been studied. The diagnosis was suggested by the histopathological findings from the spleen and lymph nodes of the proband and confirmed by the low values obtained in the following tests performed on polymorphonuclear leukocytes (PMN): chemiluminescence, nitroblue tetrazolium (NBT) reduction, killing of Staphylococcus aureus, and O2- production. NADPH oxidase activity was not detected in the homogenates of the patients' PMN but cytochrome b was normally present. In addition, PMN depolarization induced by phorbol-myristate acetate was absent, thus suggesting a defect of the activation mechanism of the respiratory enzyme. The normal depolarization induced by ouabain indicated that the membrane polarity regulated by the Na/K pump in the patients' cells was not affected. The low, but not completely absent, respiratory activity of the patients' PMN could suggest an X-linked mode of inheritance with incomplete Lyonization. From a clinical point of view, one sister had mild symptoms whereas the other was almost symptomless, thus confirming once more the heterogeneity of CGD syndrome.

Chronic granulomatous disease, a heterogeneous syndrome

Chronic granulomatous disease (CGD) is a clinical syndrome, the unifying characteristics of which are a severe predisposition to bacterial and fungal infections, an impaired ability of phagocytic leukocytes to kill certain microorganisms and the failure of these cells to produce microbicidal oxygen metabolites. In CGD the causal biochemical defect and the mechanism of genetic transmission vary from family to family. At least six different molecular defects have been found to underly the X-linked and at least three other the autosomal recessive form of CGD. Diagnosis of carriers is possible in most instances, and prenatal diagnosis by fetoscopic placental vessel puncture has become feasible.

Combined neutrophil and T-cell deficiency: initial report of a kindred with features of the hyper-IgE syndrome and chronic granulomatous disease

A six year old female presented with a recent history of pyoderma gangrenosum involving her legs and arms associated with an episode of Mycoplasma-like pneumonia. This was followed by Aspergillus osteomyelitis involving her left ulna and right femur. Both the skin lesions and the osteomyelitis responded to prolonged treatment with antifungal and antibiotic agents. Investigation of this patient revealed (1) an elevated serum IgE (4,800 units/ml), (2) defect in neutrophil chemotaxis that appeared to be due to immune complexes, (3) an abnormal nitroblue tetrazolium (NBT) result (0 percent stimulated and unstimulated), and (4) depressed mitogen responses to concanavalin A, phytohemagglutinin, and pokeweed mitogen, negative results of intradermal skin tests, and negative dinitrochlorobenzene (DNCB) sensitization. The patient's clinically unaffected sibling had similar findings except for a positive DNCB response. In both children, intracellular bacterial killing of catalase-positive and negative organisms was normal. Kindred studies revealed widespread T-cell abnormalities consistent with autosomal dominant inheritance. Tissue typing studies showed that affected siblings shared the A1, B8, DR3 haplotype. This kindred is unique in that both the proband and the sibling have abnormalities of both the hyper-IgE syndrome and chronic granulomatous disease.

Discoid lupus erythematosus-like lesions and stomatitis in female carriers of X-linked chronic granulomatous disease

The skin and oral mucosa were studied in an unselected series of carriers of x-linked chronic granulomatous disease, a hereditary condition in which phagocytic cells display a pronounced functional defect. Three carriers had discoid lupus erythematosus (DLE)-like skin lesions which histopathologically were consistent with DLE of the hypertrophic and profundus type. Four patients had experienced photosensitivity in childhood. Seven patients had recurrent aphthous-like stomatitis which should be distinguished from the recurrent aphthous stomatitis seen in otherwise healthy individuals. The remarkably high incidence of DLE-like symptoms in heterozygous carriers might be related to the presence of mixed populations of defective and normal phagocytes. The variable expression of skin symptoms may be related to uneven distribution of abnormal and normal phagocytes. Female patients with these clinical symptoms, especially the combination of DLE-like skin lesions and aphthous-like stomatitis, should be suspected of being carriers of chronic granulomatous disease and studies of phagocyte function in vitro should be performed, since the diagnosis of the carrier state is of utmost importance for genetic counselling before pregnancy.

X-linked inheritance in females with chronic granulomatous disease

Chronic granulomatous disease in males is familial and its transmission is is usually clearly x-linked. The mode of inheritance in females with the syndrome is unknown and the carrier state difficult to identify. Defective polymorphonuclear leukocyte bactericidal activity in this disease is associated with an absence of the respiratory burst generated in stimulated phagocytes and may be detected by the chemiluminescence assay. Polymorphonuclear leukocytes from three of four females with chronic granulomatous disease had extremely low chemiluminescence production, their asymptomatic mothers had intermediate values, and their fathers were normal. Polymorphonuclear neutrophils of two affected males in these kinships generated no chemiluminescence, whereas two of seven female relatives had intermediate values, and all nonaffected males had normal values. In the three families in which leukocytes were studied by nitroblue tetrazolium reduction, two populations of neutrophils were demonstrated for the female patients and/or their mothers. The wide phenotypic variability for clinical disease, evidence of two leukocyte populations in the patients or their mothers, and low but detectable leukocyte chemiluminescence in the affected females is consistent with the Lyon hypothesis of x-chromosome inactivation in these families. The findings suggest an x-linked inheritance in these females with chronic granulomatous disease.

Luminol-amplified chemiluminescence: a sensitive method for detecting the carrier state in chronic granulomatous disease

Patients with chronic granulomatous disease have a marked defect in neutrophil oxidative metabolism and microbicidal activity. Asymptomatic mothers of males with the disease can usually be identified as heterozygous carriers by intermediate leukocyte function. Most mothers of females with the disease, however, have normal leukocyte function, and the pattern of genetic transmission in these families has been difficult to establish. Of 14 mothers of males and females with chronic granulomatous disease, 10 had been found previously to have intermediate values for neutrophil bactericidal activity, oxygen consumption, hexose monophosphate shunt activity, and Nitro Blue Tetrazolium reduction, and 4 had normal in viro leukocyte function. In the present study, 4 of these 14 mothers had normal neutrophil bactericidal activity, 3 had normal zymosan-stimulated chemiluminescence, but none had normal luminol-amplified zymosan-stimulated chemiluminescence. The presence of luminol (5-amino-2,3-dehydro-1,4-phthalazinedione) in the phagocytic mixtures markedly increased the sensitivity of the assay, permitting detection of subtle defects in leukocyte oxidative metabolism in three previously unidentifiable carriers of the disease. Thus, luminol-amplified chemiluminescence appears to be one of the most sensitive methods available for detection of chronic granulomatous disease heterozygotes; the simplicity and reproducibility of the microtechnique permit evaluation of leukocyte function in infants and newborns.