Human STAT1 Gain-of-Function Heterozygous Mutations: Chronic Mucocutaneous Candidiasis and Type I Interferonopathy.

Heterozygous gain-of-function (GOF) mutations in STAT1 in patients with chronic mucocutaneous candidiasis (CMC) and hypothyroidism were discovered in 2011. CMC is the recurrent or persistent mucocutaneous infection by Candida fungi, and hypothyroidism results from autoimmune thyroiditis. Patients with these diseases develop other infectious diseases, including viral, bacterial, and fungal diseases, and other autoimmune manifestations, including enterocolitis, immune cytopenia, endocrinopathies, and systemic lupus erythematosus. STAT1-GOF mutations are highly penetrant with a median age at onset of 1 year and often underlie an autosomal dominant trait. As many as 105 mutations at 72 residues, including 65 recurrent mutations, have already been reported in more than 400 patients worldwide. The GOF mechanism involves impaired dephosphorylation of STAT1 in the nucleus. Patient cells show enhanced STAT1-dependent responses to type I and II interferons (IFNs) and IL-27. This impairs Th17 cell development, which accounts for CMC. The pathogenesis of autoimmunity likely involves enhanced type I IFN responses, as in other type I interferonopathies. The pathogenesis of other infections, especially those caused by intramacrophagic bacteria and fungi, which are otherwise seen in patients with diminished type II IFN immunity, has remained mysterious. The cumulative survival rates of patients with and without severe disease (invasive infection, cancer, and/or symptomatic aneurysm) at 60 years of age are 31% and 87%, respectively. Severe autoimmunity also worsens the prognosis. The treatment of patients with STAT1-GOF mutations who suffer from severe infectious and autoimmune manifestations relies on hematopoietic stem cell transplantation and/or oral JAK inhibitors.

Progressive bronchiectasis and CMC in a patient with STAT1 GOF - a rare case of primary immunodeficiency.

Bronchiestasis is a common complication developing in patients with primary immunodeficiency disorders. AD GOF STAT1 defi-ciency is characterized by CMC, repeated infections, and autoimmunity. It is the most frequently diagnosed entity in a group of PIDs with CMC. Here, we present the first Polish case of a female patient with early-onset bronchiestasis accompanied by CMC and a severe course of infections who was genetically diagnosed with AD GOF1 STAT1 mutation at the age of 15.

Recurrent, Severe Aphthous Stomatitis and Mucosal Ulcers as Primary Manifestations of a Novel STAT1 Gain-of-Function Mutation.

Chronic mucocutaneous candidiasis (CMC) characterized by persistent and recurrent Candida infection of the skin, nails, and the mucosa membranes has been proposed as the major infectious phenotype in patients with gain-of-function mutation of signal transducer and activator of transcription 1 (STAT1) 1. However, viral infections caused mostly by herpesviruses, and a broad range of autoimmune disorders may also be part of the clinical phenotype. We report here on a 31 years old female patient suffering from severe mucosal aphthous mucositis and ulcers and recurrent herpes simplex for decades. We found a previously unknown heterozygous sequence variant in STAT1 (c.1219C>G; L407V) affecting the DNA-binding domain of the protein in the patient and her 4 years old daughter. We found this mutation gain-of-function (GOF) by using immunoblot and luciferase assays. We detected low proportion of IL-17A-producing CD4+ T cell lymphocytes by using intracellular staining and flow cytometry. Candida-induced secretion of IL-17A and IL-22 by mononuclear cells from the patient was markedly decreased compared to controls. These data suggest that the novel mutant allele may result in impaired differentiation of CD4+ T cells to CD4+/IL-17+ cells. The clinical phenotype of the disease in this patient was unique as it was dominated primarily by severe aphthous stomatitis and ulcerative esophagitis and only partly by typical CMC resulting in diagnostic delay. We suggest that patients with severe recurrent aphthous stomatitis and esophagitis should be evaluated for STAT1 GOF mutation. Based on the broad clinical spectrum of the disease, we also suggest that CMC and CMC disease may not be an appropriate term to define clinically STAT1 GOF mutation.

Interferon signature in patients with STAT1 gain-of-function mutation is epigenetically determined.

STAT1 gain-of-function (GOF) variants lead to defective Th17 cell development and chronic mucocutaneous candidiasis (CMC), but frequently also to autoimmunity. Stimulation of cells with STAT1 inducing cytokines like interferons (IFN) result in hyperphosphorylation and delayed dephosphorylation of GOF STAT1. However, the mechanism how the delayed dephosphorylation exactly causes the increased expression of STAT1-dependent genes, and how the intracellular signal transduction from cytokine receptors is affected, remains unknown. In this study we show that the circulating levels of IFN-α were not persistently elevated in STAT1 GOF patients. Nevertheless, the expression of interferon signature genes was evident even in the patient with low or undetectable serum IFN-α levels. Chromatin immunoprecipitation (ChIP) experiments revealed that the active chromatin mark trimethylation of lysine 4 of histone 3 (H3K4me3), was significantly enriched in areas associated with interferon-stimulated genes in STAT1 GOF cells in comparison to cells from healthy donors. This suggests that the chromatin binding of GOF STAT1 variant promotes epigenetic changes compatible with higher gene expression and elevated reactivity to type I interferons, and possibly predisposes for interferon-related autoimmunity. The results also suggest that epigenetic rewiring may be responsible for treatment failure of Janus kinase 1/2 (JAK1/2) inhibitors in certain patients.

Utility of Ruxolitinib in a Child with Chronic Mucocutaneous Candidiasis Caused by a Novel STAT1 Gain-of-Function Mutation.

PURPOSE: Signal transducer and activator of transcription 1 gain-of-function (STAT1 GOF) mutations are the most common cause of chronic mucocutaneous candidiasis (CMC). We aim to report the effect of oral ruxolitinib, the Janus kinase (JAK) family tyrosine kinase inhibitor, on clinical and immune status of a 12-year-old boy with severe CMC due to a novel STAT1 GOF mutation. METHODS: Clinical features and laboratory data were analyzed, particularly lymphocyte subsets, ex vivo IFNγ- and IFNα-induced STAT1, 3, 5 phosphorylation dynamics during the course of JAK1/2 inhibition therapy, and Th17-related, STAT1- and STAT3-inducible gene expression before and during the treatment. Sanger sequencing was used to detect the STAT1 mutation. Literature review of ruxolitinib in treatment of CMC is appended. RESULTS: A novel STAT1 GOF mutation (c.617T > C; p.L206P), detected in a child with recalcitrant CMC, was shown to be reversible in vitro with ruxolitinib. Major clinical improvement was achieved after 8 weeks of ruxolitinib treatment, while sustained suppression of IFNγ- and IFNα-induced phosphorylation of STAT1, STAT3, and STAT5, as well as increased STAT3-inducible and Th17-related gene expression, was demonstrated ex vivo. Clinical relapse and spike of all monitored phosphorylated STAT activity was registered shortly after unplanned withdrawal, decreasing again after ruxolitinib reintroduction. No increase of peripheral CD4+ IL17+ T cells was detected after 4 months of therapy. No adverse effects were noted. CONCLUSION: JAK1/2 inhibition with ruxolitinib represents a viable option for treatment of refractory CMC, if HSCT is not considered. However, long-term administration is necessary, as the effect is not sustained after treatment discontinuation.

IRF and STAT Transcription Factors - From Basic Biology to Roles in Infection, Protective Immunity, and Primary Immunodeficiencies.

The induction and action of type I interferon (IFN) is of fundamental importance in human immune defenses toward microbial pathogens, particularly viruses. Basic discoveries within the molecular and cellular signaling pathways regulating type I IFN induction and downstream actions have shown the essential role of the IFN regulatory factor (IRF) and the signal transducer and activator of transcription (STAT) families, respectively. However, the exact biological and immunological functions of these factors have been most clearly revealed through the study of inborn errors of immunity and the resultant infectious phenotypes in humans. The spectrum of human inborn errors of immunity caused by mutations in IRFs and STATs has proven very diverse. These diseases encompass herpes simplex encephalitis (HSE) and severe influenza in IRF3- and IRF7/IRF9 deficiency, respectively. They also include Mendelian susceptibility to mycobacterial infection (MSMD) in STAT1 deficiency, through disseminated measles infection associated with STAT2 deficiency, and finally staphylococcal abscesses and chronic mucocutaneous candidiasis (CMC) classically described with Hyper-IgE syndrome (HIES) in the case of STAT3 deficiency. More recently, increasing focus has been on aspects of autoimmunity and autoinflammation playing an important part in many primary immunodeficiency diseases (PID)s, as exemplified by STAT1 gain-of-function causing CMC and autoimmune thyroiditis, as well as a recently described autoinflammatory syndrome with hypogammaglobulinemia and lymphoproliferation as a result of STAT3 gain-of-function. Here I review the infectious, inflammatory, and autoimmune disorders arising from mutations in IRF and STAT transcription factors in humans, highlightning the underlying molecular mechanisms and immunopathogenesis as well as the clinical/therapeutic perspectives of these new insights.

Molecular mechanism and structural basis of gain-of-function of STAT1 caused by pathogenic R274Q mutation.

Gain-of-function (GOF) mutations in the STAT1 gene are critical for the onset of chronic mucocutaneous candidiasis (CMC) disease. However, the molecular basis for the gain of STAT1 function remains largely unclear. Here, we investigated the structural features of STAT1 GOF residues to better understand the impact of these pathogenic mutations. We constructed STAT1 alanine mutants of the α3 helix residues of the coiled-coil domain, which are frequently found in CMC pathogenic mutations, and measured their transcriptional activities. Most of the identified GOF residues were located inside the coiled-coil domain stem structure or at the protein surface of the anti-parallel dimer interface. Unlike those, Arg-274 was adjacent to the DNA-binding domain. In addition, Arg-274 was found to functionally interact with Gln-441 in the DNA-binding domain. Because Gln-441 is located at the anti-parallel dimer contact site, Gln-441 reorientation by Arg-274 mutation probably impedes formation of the dimer. Further, the statistical analysis of RNA-seq data with STAT1-deficient epithelial cells and primary T cells from a CMC patient revealed that the R274Q mutation affected gene expression levels of 66 and 76 non-overlapping RefSeq genes, respectively. Because their transcription levels were only slightly modulated by wild-type STAT1, we concluded that the R274Q mutation increased transcriptional activity but did not change dramatically the repertoire of STAT1 targets. Hence, we provide a novel mechanism of STAT1 GOF triggered by a CMC pathogenic mutation.

Gain-of-function STAT1 mutations are associated with intracranial aneurysms.

Chronic mucocutaneous candidiasis, characterized by persistent or recurrent fungal infections, represents the clinical hallmark in gain-of-function (GOF) signal transducer and activator of transcription 1 (STAT1) mutation carriers. Several cases of intracranial aneurysms have been reported in patients with GOF STAT1 mutation but the paucity of reported cases likely suggested this association still as serendipity. In order to endorse this association, we link the development of intracranial aneurysms with STAT1 GOF mutation by presenting the two different cases of a patient and her mother, and demonstrate upregulated phosphorylated STAT4 and IL-12 receptor ß1 upon stimulation in patient's blood cells. We also detected increased transforming growth factor (TGF)-ß type 2 receptor expression, particularly in CD14+ cells, and a slightly higher phosphorylation rate of SMAD3. In addition, the mother of the patient developed disseminated bacille Calmette-Guérin disease after vaccination, speculating that GOF STAT1 mutations may confer a predisposition to weakly virulent mycobacteria.

Th2 and Th9 responses in patients with chronic mucocutaneous candidiasis and hyper-IgE syndrome.

BACKGROUND: STAT1 mutations cause chronic mucocutaneous candidiasis (CMC), while STAT3 mutations cause hyper-IgE syndrome (HIES). CMC and HIES patients have T helper (Th) 17 defects suffering from mucosal Candida infections, but only patients with HIES show an allergic phenotype with eczema, eosinophilia and high IgE levels. OBJECTIVE: We investigated whether differential Th2 and Th9 responses may explain the clinical differences. METHODS: Peripheral blood mononuclear cells of patients with CMC (n = 4), patients with HIES (n = 4), patients with atopic dermatitis (n = 4) and healthy volunteers (n = 13) were stimulated with Candida and Staphylococcus aureus, with and without IL-4. The cytokines IL-5, IL-13, IL-9, IL-17 and TGFß and regulatory T cells were measured in cell culture supernatants by ELISA or flow cytometry, respectively. RESULTS: Peripheral blood mononuclear cells of patients with CMC showed a significantly impaired production of the Th2 cytokines IL-5 and IL-13, especially in the presence of IL-4. Moreover, IL-9 production was significantly lower in patients with CMC compared to healthy controls. In contrast, patients with HIES and patients with AD showed normal IL-5 and IL-13 production, while IL-9 production was significantly lower in patients with HIES compared to healthy controls. Although TGFß was involved in the IL-4-induced IL-9 production, TGFß levels and the frequency of regulatory T cells did not differ between patients with HIES and controls. Flow cytometry analysis demonstrated an IL-9+ IL-17+ CD4+ subset in healthy controls after stimulation with Candida which was less present in patients with HIES. CONCLUSION: Patients with CMC have a general Th defect including Th2 and Th9, while patients with HIES have normal Th2 cytokines. These differences are in line with their clinical presentation. Surprisingly, the allergic cytokine IL-9 was deficient in both HIES and CMC, suggesting a Th-17-derived origin.

Síndrome poliglandular autoinmune tipo 1 y mutación C322fsX372 / Type i polyglandular autoimmune syndrome associated with C322fsx372 mutation

Los síndromes poliglandulares autoinmunes son raras endocrinopatías en las que coexisten alteraciones de las glándulas endocrinas, basadas en mecanismos autoinmunes con otras enfermedades no endocrinas. En el tipo 1, las manifestaciones características son la candidiasis mucocutánea crónica, el hipoparatiroidismo y la insuficiencia suprarrenal. Presentamos a una paciente que presenta la secuencia clínica típica, junto con otras alteraciones, realizando estudio genético del gen autoimmune regulator (AIRE), detectándose una mutación en homocigosis, C322fsX372. La herencia es autonómica recesiva, asociada a mutaciones en el gen AIRE, el cual codifica una protei′na que interviene en procesos de autoinmunidad e inmunodeficiencia. Para el diagnóstico, se requieren al menos 2 de las 3 manifestaciones clínicas principales, aunque en el estudio de familiares de pacientes afectados solo se requiere una de ellas. Estos síndromes deben ser diagnosticados en etapas tempranas, dada su alta morbimortalidad. Es necesario tratar cada una de las alteraciones, con el objetivo de preservar la calidad de vida

Polyglandular autoimmune syndromes are rare diseases based on autoimmune mechanisms in which endocrine and non-endocrine disorders coexist. In type 1 the characteristic manifestations are chronic mucocutaneous candidiasis, hypoparathyroidism and adrenal insufficiency. A case is presented of a patient with typical clinical sequence, along with other changes, and in whom a mutation in homozygosis, C322fsX372, was detected after performing a molecular analysis of autoimmunity regulator gene (AIRE). Polyglandular autoimmune syndromes are rare diseases based on autoimmune mechanisms in which endocrine and non-endocrine disorders coexist. In type 1 the characteristic manifestations are chronic mucocutaneous candidiasis, hypoparathyroidism and adrenal insufficiency. A case is presented of a patient with typical clinical sequence, along with other changes, and in whom a mutation in homozygosis, C322fsX372, was detected after performing a molecular analysis of autoimmunity regulator gene (AIRE)

Chronic mucocutaneous candidiasis caused by a gain-of-function mutation in the STAT1 DNA-binding domain.

Chronic mucocutaneous candidiasis (CMC) is a heterogeneous group of primary immunodeficiency diseases characterized by chronic and recurrent Candida infections of the skin, nails, and oropharynx. Gain-of-function mutations in STAT1 were very recently shown to be responsible for autosomal-dominant or sporadic cases of CMC. The reported mutations have been exclusively localized in the coiled-coil domain, resulting in impaired dephosphorylation of STAT1. However, recent crystallographic analysis and direct mutagenesis experiments indicate that mutations affecting the DNA-binding domain of STAT1 could also lead to persistent phosphorylation of STAT1. To our knowledge, this study shows for the first time that a DNA-binding domain mutation of c.1153C>T in exon 14 (p.T385M) is the genetic cause of sporadic CMC in two unrelated Japanese patients. The underlying mechanisms involve a gain of STAT1 function due to impaired dephosphorylation as observed in the coiled-coil domain mutations.

Patients with chronic mucocutaneous candidiasis exhibit reduced production of Th17-associated cytokines IL-17 and IL-22.

Chronic mucocutaneous candidiasis (CMC) constitutes a selective inability to clear infection with the yeast Candida, resulting in persistent debilitating inflammation of skin, nails, and mucous membranes. The underlying defect is unknown. Only recently, IL-17-producing T cells have been reported to be involved in clearing Candida infections. In order to characterize T cellular immune response to Candida, we analyzed T-cell cytokine secretion to Candida antigen and mitogenic stimuli in CMC patients, immunocompetent patients suffering from acute Candida infection, and healthy volunteers. Peripheral blood mononuclear cells (PBMCs) from CMC patients produced significantly lower amounts of IL-17 and IL-22 mRNA and protein when stimulated with Candida albicans or mitogen in vitro compared with that in matched healthy individuals. Additionally, PBMCs from immunocompetent Candida-infected patients secreted more IL-17 and IL-22 than those of both CMC patients and healthy, non-infected controls. Flow cytometry revealed a decreased number of CCR6+ IL-17-producing T cells in CMC patients, whereas the amount of CCR6+/CCR4+ cells was not altered. Levels of differentiating cytokines for human Th17 cells, IL-1beta and IL-6, tended to be higher in CMC patients. The inability to clear C. albicans in CMC patients could be due to a defect in the immune response of IL-17-producing T cells.

Serum levels of malondialdehyde and 4-hydroxy-2,3-nonenal in patients affected by familial chronic nail candidiasis.

Familial chronic nail candidiasis (FCNC.MIM 607644) is a rare disorder characterized by early onset infections caused by different species of Candida and restricted to the nails; this disorder is genetically associated with low serum concentration of intercellular adhesion molecule 1 (ICAM-1). Herein we report the evidence of high circulating levels of malondialdehyde (MDA) and 4-hydroxy-2,3-nonenal (HNE) in seven patients of a five-generation Italian family affected by FCNC.MIM 607644. The present data evidence, in these patients, an increase in circulating MDA and HNE levels. Only some merely speculative hypotheses may be suggested to explain the mechanisms subserving the oxidative stress condition observed in these genetically ICAM-1 deficient patients; however, one has to point out that a chronic oxidative stress condition could contribute to the development of concurrent pathological alterations in which an overproduction of free radicals may play a central role.

Immunodeficiency with recurrent panlymphocytopenia, impaired maturation of B lymphocytes, impaired interaction of T and B lymphocytes, and impaired integrity of epithelial tissue: a variant of idiopathic CD4+ T lymphocytopenia?

Idiopathic CD4+ T lymphocytopenia (ICL) has been defined as a cause of immunodeficiency with a variable clinical course and an unknown etiology. Here we describe a now 18-year-old boy with ICL, chronic mucocutaneous candidiasis (CMC), recurrent abscesses, and relapsing aphthous and ulcerous lesions. In addition to ICL the patient frequently showed a panlymphocytopenia. An increased percentage of gamma+delta+ T lymphocytes and IgD+ IgM+ B lymphocytes, and a decreased percentage of CD21+ B lymphocytes, were observed. In vitro assays showed normal T-cell responses to candidin and T-cell mitogens, but impaired B-cell responses to pokeweed mitogen (PWM). B-cell maturation after stimulation with Staphylococcus aureus Cowan I (SAC) and interleukin 2 (IL-2) was nearly normal. The clinical course of the patient improved substantially on administration of constant low-dose therapy with fluconazole.