Smita Y. Patel

Mutations in GATA2 are associated with the autosomal dominant and sporadic monocytopenia and mycobacterial infection (MonoMAC) syndrome

The syndrome of monocytopenia, B-cell and NK-cell lymphopenia, and mycobacterial, fungal, and viral infections is associated with myelodysplasia, cytogenetic abnormalities, pulmonary alveolar proteinosis, and myeloid leukemias. Both autosomal dominant and sporadic cases occur. We identified 12 distinct mutations in GATA2 affecting 20 patients and relatives with this syndrome, including recurrent missense mutations affecting the zinc finger-2 domain (R398W and T354M), suggesting dominant interference of gene function. Four discrete insertion/deletion mutations leading to frame shifts and premature termination implicate haploinsufficiency as a possible mechanism of action as well. These mutations were found in hematopoietic and somatic tissues, and several were identified in families, indicating germline transmission. Thus, GATA2 joins RUNX1 and CEBPA not only as a familial leukemia gene but also as a cause of a complex congenital immunodeficiency that evolves over decades and combines predisposition to infection and myeloid malignancy.

Adult-onset immunodeficiency in Thailand and Taiwan

BACKGROUND Autoantibodies against interferon-γ are associated with severe disseminated opportunistic infection, but their importance and prevalence are unknown. METHODS We enrolled 203 persons from sites in Thailand and Taiwan in five groups: 52 patients with disseminated, rapidly or slowly growing, nontuberculous mycobacterial infection (group 1); 45 patients with another opportunistic infection, with or without nontuberculous mycobacterial infection (group 2); 9 patients with disseminated tuberculosis (group 3); 49 patients with pulmonary tuberculosis (group 4); and 48 healthy controls (group 5). Clinical histories were recorded, and blood specimens were obtained. RESULTS Patients in groups 1 and 2 had CD4+ T-lymphocyte counts that were similar to those in patients in groups 4 and 5, and they were not infected with the human immunodeficiency virus (HIV). Washed cells obtained from patients in groups 1 and 2 had intact cytokine production and a response to cytokine stimulation. In contrast, plasma obtained from these patients inhibited the activity of interferon-γ in normal cells. High-titer anti-interferon-γ autoantibodies were detected in 81% of patients in group 1, 96% of patients in group 2, 11% of patients in group 3, 2% of patients in group 4, and 2% of controls (group 5). Forty other anticytokine autoantibodies were assayed. One patient with cryptococcal meningitis had autoantibodies only against granulocyte-macrophage colony-stimulating factor. No other anticytokine autoantibodies or genetic defects correlated with infections. There was no familial clustering. CONCLUSIONS Neutralizing anti-interferon-γ autoantibodies were detected in 88% of Asian adults with multiple opportunistic infections and were associated with an adult-onset immunodeficiency akin to that of advanced HIV infection. (Funded by the National Institute of Allergy and Infectious Diseases and the National Institute of Dental and Craniofacial Research; ClinicalTrials.gov number, NCT00814827.).

Confirmation and improvement of criteria for clinical phenotyping in common variable immunodeficiency disorders in replicate cohorts

To the Editor: The clinical diversity of common variable immunodeficiency disorders (CVIDs) required division of these patients into distinct clinical phenotypes to provide more homogeneous groups for immunopathologic studies as well as individual patient prognosis. By using data on clinical complications and disease progression from 334 patients with CVID from 7 European centers including Oxford (‘‘Northern European cohort’’), distinct clinical phenotypes were defined with relatively little overlap: 83% of the patients had only 1 clinical phenotype. The prognostic significance of the defined phenotypes was confirmed by significant correlation with survival. Comparison of data in 2 independent databases (DEFI and Mount Sinai) (see this article’s Online Repository at www. jacionline.org) showed that it was feasible to confirm clinical phenotyping criteria in replicate cohorts, using identical definitions for each clinical complication and laboratory finding. In addition, further associations were sought to improve the criteria for clinical phenotyping and survival. Predictors of clinical phenotypes were previously limited to IgM serum levels for the lymphoproliferative (LP) phenotype and malignancy as well as low peripheral CD8 counts for autoimmunity. Further searches for predictive laboratory measurements were undertaken on the combined cohorts. Since the dates of diagnosis for complications in patients in 2 cohorts (Oxford and the DEFI study) were known, the interval from the diagnoses of CVID and the first disease-related complication was calculated to search for the earliest date for reliable prognosis. Initially, it was important to confirm the concept of clinical phenotyping in CVIDs. The proportions of patients in the independent replicate cohorts with features of only 1 clinical phenotype were similar between cohorts when the original criteria were used (see Fig E1 in this article’s Online Repository at www.jacionline.org). By using the discovery (Northern European; n 5 334) cohort, further associations between complications were found to improve the phenotyping criteria. Considering the LP phenotype, no significant correlation was found between granuloma or lymphoid interstitial pneumonitis (LIP) and hepatomegaly, and so hepatomegaly was discarded. Lymphadenopathy remained as a criterion for LP, since although only 1 patient of 11 in the extended Oxford cohort did not also have granuloma or LIP, there were 29 patients with persistent lymphadenopathy in the Mount Sinai cohort of whom 10 had no obvious symptoms of granuloma and/or LIP.When autoimmunity was split into 2 categories, autoimmune cytopenias and organ-specific autoimmune diseases, only cytopenias showed decreased survival (P 5 .0001); organ-specific autoimmunity was not associated with cytopenias or the other clinical phenotypes. Lymphoid malignancies were excluded in the revised phenotyping criteria since CVID may not be the primary event. Thus, the revised phenotyping criteria were as follows:

Characterization of Crohn disease in X-linked inhibitor of apoptosis–deficient male patients and female symptomatic carriers

BACKGROUND Crohn disease is an inflammatory bowel disease (IBD) with a complex mode of inheritance. Although nucleotide binding and oligomerization domain containing 2 (NOD2) is the strongest risk factor, the cause of Crohn disease remains unknown in the majority of the cases. X-linked inhibitor of apoptosis (XIAP) deficiency causes X-linked lymphoproliferative syndrome type 2. IBD has been reported in some XIAP-deficient patients. OBJECTIVE We characterize the IBD affecting a large cohort of patients with mutations in XIAP and examine the possible pathophysiologic mechanisms. METHODS We performed a phenotypical and histologic analysis of the IBD affecting 17 patients with hemizygous mutations in XIAP, including 3 patients identified by screening 83 patients with pediatric-onset IBD. The X chromosome inactivation was analyzed in female carriers of heterozygous XIAP mutations, including 2 adults with IBD. The functional consequences of XIAP deficiency were analyzed. RESULTS Clinical presentation and histology of IBD in patients with XIAP deficiency overlapped with those of patients with Crohn disease. The age at onset was variable (from 3 months to 41 years), and IBD was severe and difficult to treat. In 2 patients hematopoietic stem cell transplantation fully restored intestinal homeostasis. Monocytes of patients had impaired NOD2-mediated IL-8 and monocyte chemoattractant protein 1 (MCP-1) production, as well as IL-10, in response to NOD2 and Toll-like receptor 2/4 costimulation. Nucleotide binding and oligomerization domain containing 1 (NOD1)-mediated IL-6 and IL-8 production was defective in fibroblasts from XIAP-deficient patients. The 2 heterozygous female carriers of XIAP mutations with IBD displayed abnormal expression of the XIAP mutated allele, resulting in impaired activation of the NOD2 pathway. CONCLUSION IBD in patients with XIAP deficiency is similar to Crohn disease and is associated with defective NOD2 function in monocytes. Importantly, we report that it is not restricted to male patients because we identified 2 symptomatic female heterozygous carriers of XIAP mutations.

Human immunodeficiencies that predispose to intracellular bacterial infections

Purpose of reviewPatients treated with anti-tumour necrosis factor agents have an increased risk of active tuberculosis. Mycobacteria are bacterial pathogens capable of surviving and multiplying within macrophages; these infections are characterised by granulomatous inflammation. This review addresses the effects of inherited and acquired immunodeficiencies on the susceptibility to the development of intracellular bacterial infections. Recent findingsPrimary and secondary immunodeficiencies that result in severely impaired T cell function or macrophage activation result in an increased risk of mycobacterial and Salmonella infection. Conversely, inherited or acquired antibody or complement deficiency does not lead to increased susceptibility to these pathogens. Inherited defects in the interleukin-12/interleukin-23-dependent interferon-γ pathway due to mutations in genes encoding the p40 chain common to interleukin-12 and interleukin-23, the β1 chain shared by interleukin-12 and interleukin-23 receptors, interferon-γ receptor chains 1 or 2, or signal transducer and activator of transcription, predispose to severe infections caused by poorly pathogenic mycobacteria and Salmonella species. Acquired defects of cytokine function causing increased susceptibility to these pathogens include anti-tumor necrosis factor therapy and the generation of interferon-γ-neutralising autoantibodies. Defective nuclear factor κB activation caused by hypomorphic mutations of the nuclear factor κB essential modulator gene, which compromises the function of Toll receptors, interleukin-IL receptors, and tumor necrosis factor-α receptors, also increases susceptibility to severe mycobacterial infections. Patients with inherited defects in the phagocyte nicotine-adenine dinucleotide phosphate oxidase system are highly susceptible to Salmonella infections but only exhibit slightly increased susceptibility to mycobacteria. SummaryCollectively, these observations highlight immune mechanisms that are essential for protection against intracellular bacteria. This information provides clinicians with a framework for investigating patients with potentially life-threatening intracellular bacterial infections.

Efficiency of immunoglobulin G replacement therapy in common variable immunodeficiency: correlations with clinical phenotype and polymorphism of the neonatal Fc receptor

Treatment of common variable immunodeficiency disorders (CVID) is based on replacement therapy using intravenous (i.v.) or subcutaneous (s.c.) immunoglobulin (Ig)G. Interindividual variation of IgG dose is common. A total of 380 CVID patients on stable IgG replacement from two prospective cohorts were analysed. An ‘efficiency’ index was defined as the ratio of serum IgG trough level minus IgG residual to the average weekly dose of IgG infusion. A reduced efficiency of IgG was associated independently with the i.v. route (P < 0·001) and with the presence of at least one CVID disease‐related phenotype (lymphoproliferation, autoimmune cytopenia or enteropathy) (P < 0·001). High IgG efficiency was noted in patients homozygotes for the variable number tandem repeat (VNTR) 3/3 polymorphism of the neonatal Fc receptor gene [IgG Fc fragment receptor transporter alpha chain (FCGRT)] promoter, and this was particularly significant in patients treated with IVIG (P < 0.01). In a multivariate analysis, FCGRT VNTR 3/3 genotype (P = 0·008) and high serum albumin (P < 0·001) were associated independently with increased efficiency of i.v. Ig.

Genetically determined susceptibility to mycobacterial infection

Individuals with impaired cell mediated immunity exhibit increased susceptibility to infections caused by poorly pathogenic mycobacteria (non-tuberculous mycobacteria and BCG), as well as salmonella species. However, these infections may also occur in a disseminated, fatal form, sometimes with a familial distribution, in the absence of any recognised primary or secondary immunodeficiency. Genetic analysis of affected families has defined mutations in seven different genes participating in the interleukin 12 (IL12) dependent, high output interferon γ (IFNγ) pathway. The first category of defect is mutations in the IFNγR1 or R2 genes, resulting in defective expression or function of the IFNγ receptor. The second category of mutations abrogates the cell surface expression IL12Rβ1gene, resulting in the inability to respond to IL12. The third category of defect is the inability to produce IL12, due to deletion within the gene coding for the inducible chain of IL12 (IL12-p40). Patients with X-linked recessive mutations of the gene encoding the NFκB essential modulator may also develop mycobacterial infections, although they usually have a more complex phenotype and are susceptible to a broad spectrum of pathogens. Mutations of the gene encoding the signal transducing molecule STAT1, which impairs the ability to respond to IFNγ, and mutations of the gene encoding TYK2 (which is associated with a failure to respond to IL12), are both rare genetic defects predisposing to mycobacterial infections. This review summarises the clinical spectrum seen in this group of patients and indicates a strategy for the identification of putative genetic defects in the type-1 cytokine pathway.

Application of whole genome and RNA sequencing to investigate the genomic landscape of common variable immunodeficiency disorders

Common Variable Immunodeficiency Disorders (CVIDs) are the most prevalent cause of primary antibody failure. CVIDs are highly variable and a genetic causes have been identified in <5% of patients. Here, we performed whole genome sequencing (WGS) of 34 CVID patients (94% sporadic) and combined them with transcriptomic profiling (RNA-sequencing of B cells) from three patients and three healthy controls. We identified variants in CVID disease genes TNFRSF13B, TNFRSF13C, LRBA and NLRP12 and enrichment of variants in known and novel disease pathways. The pathways identified include B-cell receptor signalling, non-homologous end-joining, regulation of apoptosis, T cell regulation and ICOS signalling. Our data confirm the polygenic nature of CVID and suggest individual-specific aetiologies in many cases. Together our data show that WGS in combination with RNA-sequencing allows for a better understanding of CVIDs and the identification of novel disease associated pathways.

Lymphoid Proliferations of Indeterminate Malignant Potential arising in Adults with Common Variable Immunodeficiency Disorders: Unusual Case Studies and Immunohistological Review in the Light of Possible Causative Events

Patients with common variable immunodeficiency disorders (CVIDs) who developed B cell lymphoproliferation of indeterminate malignant potential are described in order to raise a discussion of the relationship between infection and lymphoproliferation in infection prone patients. Those with CVID are at risk of developing either polyclonal or monoclonal lymphoproliferation in part due to the dysregulation of their adaptive immune systems. The aetiologies of the lymphoproliferations are unknown but intriguing; the relevance of infection being particularly problematic. The patients described here demonstrate variability in preceding infection, age at presentation, response to antibiotics and other types of therapy as well as outcome. The question of treatment is also controversial; issues include whether antibiotics or chemotherapy are the first line of therapy in all patients and whether transformation to aggressive B cell malignancy is inevitable or depends on other factors and if so, the length of time for such progression.

Impaired antibacterial autophagy links granulomatous intestinal inflammation in Niemann–Pick disease type C1 and XIAP deficiency with NOD2 variants in Crohn's disease

Objective Patients with Niemann–Pick disease type C1 (NPC1), a lysosomal lipid storage disorder that causes neurodegeneration and liver damage, can present with IBD, but neither the significance nor the functional mechanism of this association is clear. We studied bacterial handling and antibacterial autophagy in patients with NPC1. Design We characterised intestinal inflammation in 14 patients with NPC1 who developed IBD. We investigated bacterial handling and cytokine production of NPC1 monocytes or macrophages in vitro and compared NPC1-associated functional defects to those caused by IBD-associated nucleotide-binding oligomerization domain-containing protein 2 (NOD2) variants or mutations in X-linked inhibitor of apoptosis (XIAP). Results Patients with the lysosomal lipid storage disorder NPC1 have increased susceptibility to early-onset fistulising colitis with granuloma formation, reminiscent of Crohns disease (CD). Mutations in NPC1 cause impaired autophagy due to defective autophagosome function that abolishes NOD2-mediated bacterial handling in vitro similar to variants in NOD2 or XIAP deficiency. In contrast to genetic NOD2 and XIAP variants, NPC1 mutations do not impair NOD2-receptor-interacting kinase 2 (RIPK2)-XIAP-dependent cytokine production. Pharmacological activation of autophagy can rescue bacterial clearance in macrophages in vitro by increasing the autophagic flux and bypassing defects in NPC1. Conclusions NPC1 confers increased risk of early-onset severe CD. Our data support the concept that genetic defects at different checkpoints of selective autophagy cause a shared outcome of CD-like immunopathology linking monogenic and polygenic forms of IBD. Muramyl dipeptide-driven cytokine responses and antibacterial autophagy induction are parallel and independent signalling cascades downstream of the NOD2-RIPK2-XIAP complex.