Heterozygous STAT1 gain-of-function mutations underlie an unexpectedly broad clinical phenotype

Human immunity to fungal infections

Fungi increasingly threaten health globally. Mycoses range from life-threatening, often iatrogenic conditions, to enigmatic syndromes occurring without apparent immunosuppression. Despite some recent advances in antifungal drug development, complementary therapeutic strategies are essential for addressing these opportunistic pathogens. One promising avenue is leveraging host immunity to combat fungal infections; this necessitates deeper understanding of the molecular immunology of human fungal susceptibility to differentiate beneficial versus harmful immunopathological responses. Investigating human models of fungal diseases in natural settings, particularly through genetic immunodeficiencies and ethnographic-specific genetic vulnerabilities, reveals crucial immune pathways essential for fighting various yeasts and molds. This review highlights the diversity in intrinsic fungal susceptibility across individuals and populations, through genetic- and autoantibody-mediated processes, complementing previous principles learned from animal studies and iatrogenic contexts. Improved understanding of human immunity to fungal diseases will facilitate the development of host-directed immunotherapies and targeted public health interventions, paving the way for precision medicine in fungal disease management.

JAK-STAT pathway, type I/II cytokines, and new potential therapeutic strategy for autoimmune bullous diseases: update on pemphigus vulgaris and bullous pemphigoid

Autoimmune Bullous Diseases (AIBDs), characterized by the formation of blisters due to autoantibodies targeting structural proteins, pose significant therapeutic challenges. Current treatments, often involving glucocorticoids or traditional immunosuppressants, are limited by their non-specificity and side effects. Cytokines play a pivotal role in AIBDs pathogenesis by driving inflammation and immune responses. The JAK-STAT pathway is central to the biological effects of various type I and II cytokines, making it an attractive therapeutic target. Preliminary reports suggest that JAK inhibitors may be a promising approach in PV and BP, but further clinical validation is required. In AIBDs, particularly bullous pemphigoid (BP) and pemphigus vulgaris (PV), JAK inhibitors have shown promise in modulating pathogenic cytokine signaling. However, the safety and selectivity of JAK inhibitors remain critical considerations, with the potential for adverse effects and the need for tailored treatment strategies. This review explores the role of cytokines and the JAK-STAT pathway in BP and PV, evaluating the therapeutic potential and challenges associated with JAK inhibitors in managing these complex disorders.

Invasive fungal disease in a large cohort of hospitalized children with inborn errors of immunity in China

BACKGROUND

Invasive fungal disease (IFD) is a common complication observed in inborn errors of immunodeficiency (IEI) patients, and little is known about the overall prevalence of IFD in IEI patients. We aimed to summarize the fungal spectrum and outcomes of IFDs in a Chinese cohort of hospitalized patients with IEI.

METHODS

In this retrospective study, 607 IEI patients hospitalized from January 2018 to June 2022 were included. Demographic, clinical, and fungal infection data and IEI patient characteristics were collected and analyzed according to the IEI classification.

RESULTS

One hundred and two IEI patients were diagnosed with proven or probable IFD. The overall prevalence of IFD was 17% (102/607). There were 29 different genotypes, among which CYBB (25%), CD40LG (9%), and RAG1 (7%) mutations were the most common. Most IFD infections (87/102) were caused by one fungus. Invasive Aspergillus, Pneumocystis jirovecii pneumonia, and Penicillium infections were more commonly observed in patients with congenital defects in phagocytes, immunodeficiencies affecting cellular and humoral immunity, and defects in innate immunity, respectively. Most IFDs observed in IEI patients were single-site infections, most of which were lung infections (74%). Seventeen patients were diagnosed with disseminated IFDs, nine of which were caused by Penicillium. All patients received antifungal treatments. Eight patients (8%) died within 3 months of IFD diagnosis.

CONCLUSIONS

IFD occurrence suggests the presence of immunity impairment. The IFD fungal profile may indicate different types of IEI. Early recognition of immunodeficiency and optimal timing of antifungal therapy can reduce fatality in IEI patients.

Mpox in a Patient With a Signal Transducer and Activator of Transcription 1 Gain-of-Function Mutation

We report a case of mpox in a patient with a signal transducer and activator of transcription 1 gain-of-function mutation. Despite initial improvement with intravenous immune globulin and tecovirimat, severe symptoms developed and the patient died. This underscores the need for immune system optimization and effective virucidal treatments for mpox.

The monogenic landscape of human infectious diseases

The spectrum of known monogenic inborn errors of immunity is growing, with certain disorders underlying a specific and narrow range of infectious diseases. These disorders reveal the core mechanisms by which these infections occur in various settings, including inherited and acquired immunodeficiencies, thereby delineating the essential mechanisms of protective immunity to the corresponding pathogens. These findings also have medical implications, facilitating diagnosis and improving the management of individuals at risk of disease.

JAK-STAT signaling pathway, immunodeficiency, inflammation, immune dysregulation, and inborn errors of immunity

The Janus kinase-signal transducer and activator of transcription (JAK-STAT) signaling cascade is an evolutionarily conserved signal transduction pathway that regulates many vital cellular processes, including immune function and hematopoiesis. Human genetic variants that disrupt JAK-STAT signaling are being found to cause a rapidly increasing number of diseases, including both germline-encoded inborn errors of immunity (IEI) and acquired somatic variants, causing a so-called phenocopy of the IEI. Multiple genetic mechanisms are responsible for this growing group of JAK-STAT diseases including loss-of-function, gain-of-function, and dominant negative effects. In this review, we discuss the clinical presentation and pathogenesis of all currently described JAK-STAT defects, as well as provide an overview of the guiding principles to consider in diagnosing and treating these conditions.

STAT1 and herpesviruses: Making lemonade from lemons

Signal transducer and activator of transcription 1 (STAT1) is engaged downstream of interferon and other cytokine receptors and has traditionally been defined as an antiviral effector of the host. Consistent with the antiviral role, genetic deficiency of STAT1 leads to increased replication of diverse viruses and severe disease that can lead to host's mortality, including in rare human cases of STAT1 insufficiency. Surprisingly, excessive STAT1 activation recently identified in patients with heterozygous gain-of-function STAT1 mutations and subsequently modeled in laboratory mice, also leads to poor control of select virus infections, including herpesviruses. Thus, the function of STAT1 in viral infections might be more nuanced and extend beyond the canonical antiviral role of this host factor. This review will compare the findings in the animal models and human cases to discuss the role of STAT1 in herpesvirus infection of the intact host, including the emerging cell type-specific proviral roles of STAT1.

Prolonged STAT1 signaling in neurons causes hyperactive behavior

The interferon (IFN)-induced STAT1 signaling pathway is a canonical immune pathway that has also been implicated in regulating neuronal activity. The pathway is enriched in brains of individuals with autism spectrum disorder (ASD) and schizophrenia (SZ). Over-activation of the STAT1 pathway causes pathological transcriptional responses, however it is unclear how these responses might translate into behavioral phenotypes. We hypothesized that prolonged STAT1 signaling in neurons would be sufficient to cause behavioral deficits associated with neurodevelopmental disorders. In this study, we developed a novel mouse model with the clinical STAT1 gain-of-function mutation, T385M, in neurons. These mice were hyperactive and displayed neural hypoactivity with less neuron counts in the caudate putamen. Driving the STAT1 gain-of-function mutation exclusively in dopaminergic neurons, which project to the caudate putamen of the dorsal striatum, mimicked some hyperactive behaviors without a reduction of neurons. Moreover, we demonstrated that this phenotype is neuron specific, as mice with prolonged STAT1 signaling in all excitatory or inhibitory neurons or in microglia were not hyperactive. Overall, these findings suggest that STAT1 signaling in neurons is a crucial player in regulating striatal neuron activity and aspects of motor behavior.

Monocyte STAT1 phosphorylation and treatment response of JAK inhibitors in chronic nonbacterial osteomyelitis

BACKGROUND

Chronic nonbacterial osteomyelitis (CNO) is a rare autoinflammatory disease of unknown cause, predominantly affecting teens and young adults. The early diagnosis and management are challenging due to the lack of reliable diagnostic markers and the occasional intractable cases despite conventional anti-inflammatory treatments. Janus kinase (JAK) inhibitors have recently shown potential utility; however, reports on their use for pediatric patients with CNO remain limited, and no established biomarkers exist to monitor disease activity. We aimed to investigate the pathophysiology of CNO and explore the rapid testing methods for accurate diagnosis and also assessing the disease activity.

METHODS

We assessed intracellular phosphorylation of signal transducer and activator of transcription 1 (pSTAT1) in peripheral blood monocytes or T cells following interferon-gamma (IFNγ) stimulation, using flow cytometry in 9 patients under 15 years old with CNO. The pSTAT1 expression levels were compared with those in patients with STAT1-gain of function (STAT1-GOF) mutations (n = 5), other autoinflammatory diseases (n = 7), and healthy controls. Clinical and immunological data were monitored in 4 patients with intractable CNO treated with adjunctive JAK inhibitors, focusing on scoring scales, imaging data, lymphocyte subsets, cytokine profiles, and pSTAT1 levels.

RESULTS

Monocyte pSTAT1 expression after IFNγ stimulation was elevated at diagnosis or during active CNO, similar to levels observed in STAT1-GOF cases. The pSTAT1 levels in CNO patients were significantly higher than those in other autoinflammatory diseases (p = 0.024) or controls (p < 0.001). Notably, pSTAT1 levels in CNO monocytes fluctuated with disease activity, decreasing in 5 patients during clinical remission following conventional therapies (p = 0.016). In four intractable cases, pSTAT1 levels remained high despite conventional treatments but significantly decreased after initiating JAK inhibitors (p = 0.036). This reduction correlated with improved patient pain visual analog scale (p = 0.008), CNO clinical disease activity score (p = 0.029), and better bone and joint imaging, though cytokine levels remained unchanged.

CONCLUSIONS

The monocyte pSTAT1 levels after IFNγ stimulation reflect the activity of CNO, indicating the diagnostic utility as well as the monitoring effect of disease control. Adjunctive JAK inhibitors successfully controlled inflammation in treatment-resistant cases. Rapid pSTAT1 testing may help reduce osteo-articular complications, although the long-term adverse effects and resistance should be further investigated.

Coinfection of Leprosy and Chronic Mucocutaneous Candidiasis in a Family with STAT1 Gain-of-Function Mutation

This report documents the first known cases of lepromatous leprosy in patients with chronic mucocutaneous candidiasis (CMC) linked to a gain-of-function mutation in the STAT1 gene. Two related patients, a mother and daughter, who both suffer from CMC and lepromatous leprosy, carry a heterozygous STAT1 mutation (c.821G>A; p.R274Q). Both individuals exhibited similarly high levels of total and phosphorylated STAT1 in CD4+ T cells and decreased interleukin 17A transcripts. This mutation underscores a complex relationship between genetic susceptibility to infections and the necessity to evaluate each case individually.

Inborn Errors of Immunity Presenting with Early-Onset Severe Atopy

Inborn errors of immunity (IEIs), also known as primary immunodeficiencies, are a group of genetic disorders affecting the development and function of the immune system. While IEIs traditionally present with recurrent infections, an increasing number of cases manifest with early-onset severe atopy, including atopic dermatitis, food allergies, asthma, and allergic rhinitis-features that are often overlooked. This can lead to delayed diagnosis and treatment, which is crucial for IEI patients due to the risk of severe infections. We conducted a literature search and reviewed all IEIs that can present with early-onset severe atopy. The hallmark features of these disorders often include early-onset, persistent, and severe atopic dermatitis, food allergies, and recurrent episodes of asthma, which may be refractory to treatments. Additionally, we discuss the importance of recognizing such severe atopy as a potential indicator of an underlying immune deficiency, particularly when accompanied by unusual infections, growth failure, or autoimmunity. This review aims to raise awareness of this association and emphasize the need for early diagnosis and genetic testing in patients with atypical or treatment-resistant allergic diseases, allowing for more timely diagnosis of underlying immunodeficiencies and appropriate treatments.

Chronic mucocutaneous candidiasis, mycobacterial infections and rosacea in a Mexican adult with STAT1 gain of function

STAT1 is a cytoplasmic transcription factor associated with cell growth regulation, differentiation, proliferation, metabolism, and apoptosis. IFN-mediated JAK/STAT signaling pathway is involved in eliminating intracellular pathogens and viruses. However, pathogenic variants in STAT1 can result in impaired or increased function. Increased activity or function in STAT1 was described in 2011 and is characterized by excessive phosphorylation of the transcription factor. Carriers can develop autoimmune and inflammatory diseases and are susceptible to fungal, viral, and bacterial infections. The early and common manifestation is chronic mucocutaneous candidiasis. Here, we report a clinical case of a patient with increased STAT1 activity or gain of function, which started in the first year of his life. He is currently 27 years old and has presented bacillus Calmette-Guérin and Mycobacterium tuberculosis infection, chronic mucocutaneous candidiasis, tinea capitis, and facial and ocular rosacea. HIV infection was ruled out. Given the clinical manifestations, an inborn error of immunity was suspected, specifically STAT1 with gain of function. The diagnosis was corroborated by the sequencing of multiple genes associated with inborn errors of immunity. The pathogenic variant c.961A>G (p.Arg321Gly) in the STAT1 gene, previously reported as a gain of function mutation, was found in the patient. Finally, this case illustrates that mutations in immune-associated genes can contribute to producing severe and recurrent infections, even in adult patients. Chronic mucocutaneous candidiasis should raise suspicion of gain of function in STAT1.

Lack of TYK2 signaling enhances host resistance to Candida albicans skin infection

Candida albicans is the most common human fungal pathogen, causing diseases ranging from local to life-threating systemic infections. Tyrosine kinase 2 (TYK2), a crucial mediator in several cytokine signaling pathways, has been associated with protective functions in various microbial infections. However, its specific contribution in the immune response to fungal infections has remained elusive. In this study, we show that mice lacking TYK2 or its enzymatic activity exhibit enhanced resistance to C. albicans skin infections, limiting fungal spread and accelerating wound healing. Impaired TYK2-signaling prompted the formation of a distinctive layer of necrotic neutrophils around the fungal pathogens. Transcriptomic analysis revealed TYK2's pivotal role in regulating interferon-inducible genes in neutrophils, thereby impacting their antifungal capacity during infection. Furthermore, we show that TYK2-dependent interferon-gamma (IFNγ) production contributes to fungal dissemination from the skin to the kidneys. Our study uncovers a hitherto unrecognized detrimental role of TYK2 in cutaneous C. albicans infections.

Inborn errors of immunity and invasive fungal infections: presentation and management

PURPOSE OF REVIEW

We review the clinical presentations of invasive fungal infections in a selection of inborn errors of immunity. In addition, we review the particularities of their management, including antifungal therapy, prophylaxis, and immunomodulatory treatments.

RECENT FINDINGS

Patients with chronic granulomatous disease and with signal transducer and activator of transcription 3 (STAT3) deficiency are particularly prone to aspergillosis. Mold-active antifungal prophylaxis should be prescribed to all patients with chronic granulomatous disease, and in patients with STAT3 deficiency and underlying parenchymal lung disease. Invasive fungal infections are rare in patients with STAT1 gain-of-function mutations, while the clinical phenotype of caspase-associated recruitment domain-containing protein 9 deficiency encompasses a wide range of superficial and invasive fungal infections. Most patients with inborn errors of immunity and invasive fungal infections require prolonged durations of antifungals. Hematopoietic stem cell transplantation should be considered early for patients with chronic granulomatous disease, but results have been more mixed for other inborn errors of immunity with active invasive fungal infections.

SUMMARY

Inborn errors of immunity can confer increased susceptibility to a variety of invasive fungal infections, which can present with specific clinical and radiological features. Management of fungal infections in these patients is often challenging, and relies on a combination of antimicrobial prophylaxis, antifungal treatments, and immunomodulation.

STAT1 and STAT3 gain of function: clinically heterogenous immune regulatory disorders

PURPOSE OF REVIEW

The identification of STAT1 gain-of-function (GOF) in 2011 and STAT3 GOF in 2014 has advanced our understanding of the host immunity along the JAK/STAT pathway and allowed targeted treatment approaches. We review the clinical features and pathogenesis of STAT1 and STAT3 GOF and how this has shaped new approaches to therapy.

RECENT FINDINGS

STAT1 GOF, initially described in patients with chronic mucocutaneous candidiasis (CMC) and autoimmune thyroid disease, is now recognized to cause early-onset multisystem autoimmunity and a range of infections. STAT3 GOF comprises mostly lymphoproliferation and autoimmunity but also with varying severity, including some with life threatening organ dysfunction. Treatment has evolved along with the understanding of the pathogenesis, with patients now receiving JAK inhibition to block upstream of the STAT defect with good response in autoimmunity and CMC in STAT1 GOF. Blockade of IL-6 signaling has also been used in STAT3 GOF. Hematopoietic cell transplantation had initial poor outcomes, but outcomes are now improving with focus on the control of inflammation pretransplant.

SUMMARY

Understanding the pathogenesis of STAT1 and STAT3 GOF has allowed great recent advancements in therapy, but many questions remain as to the best approach to therapy for each patient's clinical presentation as well as the durability of these therapies.

Chronic mucocutaneous candidiasis due to signal transducer and activator of transcription 1 mutation in a Saudi patient: a case report

Chronic mucocutaneous candidiasis (CMC) is a primary immunodeficiency condition caused by a genetic abnormality that increases the risk of recurrent and persistent skin, nail, and mucous membrane infections with Candida species, typically Candida albicans. Signal transducer and activator of transcription 1 (STAT1) gene mutation is a genetic trigger that causes CMC, which increases the risk of infections, multisystem disorders, and cancer susceptibility. We describe the first case of a Saudi female patient with clinical features of CMC with an underlying (STAT1) gene mutation.

STATs, promising targets for the treatment of autoimmune and inflammatory diseases

Cytokines play a crucial role in the pathophysiology of autoimmune and inflammatory diseases, with over 50 cytokines undergoing signal transduction through the Signal Transducers and Activators of Transcription (STAT) signaling pathway. Recent studies have solidly confirmed the pivotal role of STATs in autoimmune and inflammatory diseases. Therefore, this review provides a detailed summary of the immunological functions of STATs, focusing on exploring their mechanisms in various autoimmune and inflammatory diseases. Additionally, with the rapid advancement of structural biology in the field of drug discovery, many STAT inhibitors have been identified using structure-based drug design strategies. In this review, we also examine the structures of STAT proteins and compile the latest research on STAT inhibitors currently being tested in animal models and clinical trials for the treatment of immunological diseases, which emphasizes the feasibility of STATs as promising therapeutic targets and provides insights into the design of the next generation of STAT inhibitors.

Infections in Inborn Errors of STATs

The Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway is highly conserved and essential for numerous biological functions triggered by extracellular signals, including cell proliferation, metabolism, immune response, and inflammation. Defects in STATs, either loss-of-function or gain-of-function defects, lead to a broad spectrum of clinical phenotypes in humans, including a wide range of infectious complications. The susceptibility to pathogens can stem from defects in immune cells within the hematopoietic compartment, impaired barrier functions of non-hematopoietic compartment, or a combination of both, depending on the specific STAT defect as well as the pathogen exposure history. Effective management involves antimicrobial prophylaxis tailored to the patient's infection risk and improving disease control with targeted therapies and/or hematopoietic cell transplantation.

Management of a Patient with Cardiovascular Disease Should Include Assessment of Primary and Secondary Immunodeficiencies: Part 1-Primary Immunodeficiencies

BACKGROUND

Cardiovascular diseases are some of the most prevalent chronic diseases that generate not only high social but also economic costs. It is becoming increasingly crucial to take into account inborn errors of immunity (IEIs, formerly known as primary immunodeficiencies (PIDs)) and secondary immunodeficiencies (SIDs) in the diagnostic and therapeutic management of cardiac patients. The number of diseases classified as IEIs is on the rise, with a current total of 485. It is essential to pay attention not only to already confirmed conditions but also to symptoms suggestive of immunodeficiencies.

OBJECTIVES

The aim of this article is to present IEIs with cardiovascular symptoms that may cause or exacerbate cardiovascular disease, as well as diagnostic and therapeutic procedures.

RESULTS

It is becoming increasingly evident that immunodeficiencies can be responsible for certain cardiovascular conditions, their hastened progression, and difficulties in their control.

CONCLUSIONS

Early detection of deficiencies improves not only the quality and longevity of patients, but also allows for better control of cardiovascular diseases and even prevention of their occurrence.

Monocyte-regulated interleukin 12 production drives clearance of Staphylococcus aureus

Staphylococcus aureus is a versatile bacterium responsible for conditions ranging from mild skin and soft-tissue infections to serious disorders such as pneumonia and sepsis. Monocytes play a role in protection against pathogens by migrating to inflamed tissues and differentiating into macrophages but their specific role in the context of S. aureus pulmonary infection has not been fully elucidated. Using a CCR2-DTR transgenic mouse model we demonstrate that over the course of infection monocyte depletion resulted in worse airway clearance of S. aureus. The bronchoalveolar lavage fluid (BALF) of CCR2-DTR mice after S. aureus infection displayed significant decreases in interleukin-12 (IL-12), IFN-γ, IP-10, MIG and RANTES, all IFN-γ regulated, compared to wild-type (WT) infected controls. NK cells were identified as the main producers of IFN-γ, but both NK cells and IFN-γ were dispensable for clearance. We demonstrated through cytokine production and RNA-seq analysis that IL-12 and IL-12 regulated genes are strongly induced in monocytes upon S. aureus infection. Administration of IL-12 during infection restored the bacterial burdens in the BALF and lungs of monocyte-depleted CCR2-DTR mice to the levels of WT mice, independent of IFN-γ. In the absence of monocytes, alveolar macrophages are the primary phagocytic cells, and IL-12 influences their capacity to produce reactive oxygen species and clear S. aureus. These results show that production of IL-12 contributes to the control of S. aureus via its influence on alveolar macrophage function.

PTPN2 deficiency: Amping up JAK/STAT

Identification of monogenic causes of immune dysregulation provides insight into human immune response and signaling pathways associated with autoimmunity. Here, Jeanpierre et al. (https://doi.org/10.1084/jem.20232337) identify new germline variants in the gene encoding PTPN2 associated with loss of regulatory function, enhanced JAK/STAT signaling, and early-onset autoimmunity.

Nucleotide metabolism, leukodystrophies, and CNS pathology

The balance between a protective and a destructive immune response can be precarious, as exemplified by inborn errors in nucleotide metabolism. This class of inherited disorders, which mimics infection, can result in systemic injury and severe neurologic outcomes. The most common of these disorders is Aicardi Goutières syndrome (AGS). AGS results in a phenotype similar to "TORCH" infections (Toxoplasma gondii, Other [Zika virus (ZIKV), human immunodeficiency virus (HIV)], Rubella virus, human Cytomegalovirus [HCMV], and Herpesviruses), but with sustained inflammation and ongoing potential for complications. AGS was first described in the early 1980s as familial clusters of "TORCH" infections, with severe neurology impairment, microcephaly, and basal ganglia calcifications (Aicardi & Goutières, Ann Neurol, 1984;15:49-54) and was associated with chronic cerebrospinal fluid (CSF) lymphocytosis and elevated type I interferon levels (Goutières et al., Ann Neurol, 1998;44:900-907). Since its first description, the clinical spectrum of AGS has dramatically expanded from the initial cohorts of children with severe impairment to including individuals with average intelligence and mild spastic paraparesis. This broad spectrum of potential clinical manifestations can result in a delayed diagnosis, which families cite as a major stressor. Additionally, a timely diagnosis is increasingly critical with emerging therapies targeting the interferon signaling pathway. Despite the many gains in understanding about AGS, there are still many gaps in our understanding of the cell-type drivers of pathology and characterization of modifying variables that influence clinical outcomes and achievement of timely diagnosis.

A Japanese retrospective study of non-tuberculous mycobacterial infection in children, adolescents, and young adult patients with hematologic-oncologic diseases

Non-tuberculous mycobacterial infection (NTM) is rare in healthy children, with lymphadenitis being the most common presentation. Immunocompromised populations are known to be at high risk, but the clinical picture of NTM infection in pediatric hematology/oncology patients is unclear. In this nationwide retrospective analysis of patients under the age of 40 treated in Japanese pediatric hematology/oncology departments who developed NTM infection between January 2010 and December 2020, 36 patients were identified: 21 patients with hematopoietic stem cell transplantation (HSCT) and 15 non-transplant patients. Post-transplant patients were infected with NTM at 24 sites, including the lungs (N=12), skin and soft tissues (N=6), bloodstream (N=4), and others (N=2). Nine of 12 patients with pulmonary NTM infection had a history of pulmonary graft-versus-host disease (GvHD), and rapid-growing mycobacteria (RGM) were isolated from 5 of them. In non-transplant patients, the primary diseases were acute lymphoblastic leukemia (ALL; N=5), inborn errors of immunity (IEI; N=6), and others (N=4). All cases of ALL had bloodstream infections with RGM, whereas all cases of IEI were infected with slow-growing mycobacteria (SGM). In summary, 3 typical clinical scenarios for pediatric hematology/oncology patients have been established: RGM-induced pulmonary disease in patients with pulmonary GvHD, RGM bloodstream infection in patients with ALL, and SGM infection in patients with IEI. Our findings suggest that NTM must be regarded as a pathogen for infections in these high-risk patients, especially those with pulmonary GvHD, who may require active screening for NTM.

A unified metric of human immune health

Immunological health has been challenging to characterize but could be defined as the absence of immune pathology. While shared features of some immune diseases and the concept of immunologic resilience based on age-independent adaptation to antigenic stimulation have been developed, general metrics of immune health and its utility for assessing clinically healthy individuals remain ill defined. Here we integrated transcriptomics, serum protein, peripheral immune cell frequency and clinical data from 228 patients with 22 monogenic conditions impacting key immunological pathways together with 42 age- and sex-matched healthy controls. Despite the high penetrance of monogenic lesions, differences between individuals in diverse immune parameters tended to dominate over those attributable to disease conditions or medication use. Unsupervised or supervised machine learning independently identified a score that distinguished healthy participants from patients with monogenic diseases, thus suggesting a quantitative immune health metric (IHM). In ten independent datasets, the IHM discriminated healthy from polygenic autoimmune and inflammatory disease states, marked aging in clinically healthy individuals, tracked disease activities and treatment responses in both immunological and nonimmunological diseases, and predicted age-dependent antibody responses to immunizations with different vaccines. This discriminatory power goes beyond that of the classical inflammatory biomarkers C-reactive protein and interleukin-6. Thus, deviations from health in diverse conditions, including aging, have shared systemic immune consequences, and we provide a web platform for calculating the IHM for other datasets, which could empower precision medicine.

Immunophenotyping and Therapeutic Insights from Chronic Mucocutaneous Candidiasis Cases with STAT1 Gain-of-Function Mutations

PURPOSE

Heterozygous STAT1 Gain-of-Function (GOF) mutations are the most common cause of chronic mucocutaneous candidiasis (CMC) among Inborn Errors of Immunity. Clinically, these mutations manifest as a broad spectrum of immune dysregulation, including autoimmune diseases, vascular disorders, and malignancies. The pathogenic mechanisms of immune dysregulation and its impact on immune cells are not yet fully understood. In treatment, JAK inhibitors have shown therapeutic effectiveness in some patients.

METHODS

We analyzed clinical presentations, cellular phenotypes, and functional impacts in five Taiwanese patients with STAT1 GOF.

RESULTS

We identified two novel GOF mutations in 5 patients from 2 Taiwanese families, presenting with symptoms of CMC, late-onset rosacea, and autoimmunity. The enhanced phosphorylation and delayed dephosphorylation were displayed by the patients' cells. There are alterations in both innate and adaptive immune cells, including expansion of CD38+HLADR +CD8+ T cells, a skewed activated Tfh cells toward Th1, reduction of memory, marginal zone and anergic B cells, all main functional dendritic cell lineages, and a reduction in classical monocyte. Baricitinib showed therapeutic effectiveness without side effects.

CONCLUSION

Our study provides the first comprehensive clinical and molecular characteristics in STAT1 GOF patient in Taiwan and highlights the dysregulated T and B cells subsets which may hinge the autoimmunity in STAT1 GOF patients. It also demonstrated the therapeutic safety and efficacy of baricitinib in pediatric patient. Further research is needed to delineate how the aberrant STAT1 signaling lead to the changes in cellular populations as well as to better link to the clinical manifestations of the disease.

An improved SNAP-ADAR tool enables efficient RNA base editing to interfere with post-translational protein modification

RNA base editing relies on the introduction of adenosine-to-inosine changes into target RNAs in a highly programmable manner in order to repair disease-causing mutations. Here, we propose that RNA base editing could be broadly applied to perturb protein function by removal of regulatory phosphorylation and acetylation sites. We demonstrate the feasibility on more than 70 sites in various signaling proteins and identify key determinants for high editing efficiency and potent down-stream effects. For the JAK/STAT pathway, we demonstrate both, negative and positive regulation. To achieve high editing efficiency over a broad codon scope, we applied an improved version of the SNAP-ADAR tool. The transient nature of RNA base editing enables the comparably fast (hours to days), dose-dependent (thus partial) and reversible manipulation of regulatory sites, which is a key advantage over DNA (base) editing approaches. In summary, PTM interference might become a valuable field of application of RNA base editing.

Illuminating the pathogenic role of SARS-CoV-2: Insights into competing endogenous RNAs (ceRNAs) regulatory networks

The appearance of SARS-CoV-2 in 2019 triggered a significant economic and health crisis worldwide, with heterogeneous molecular mechanisms that contribute to its development are not yet fully understood. Although substantial progress has been made in elucidating the mechanisms behind SARS-CoV-2 infection and therapy, it continues to rank among the top three global causes of mortality due to infectious illnesses. Non-coding RNAs (ncRNAs), being integral components across nearly all biological processes, demonstrate effective importance in viral pathogenesis. Regarding viral infections, ncRNAs have demonstrated their ability to modulate host reactions, viral replication, and host-pathogen interactions. However, the complex interactions of different types of ncRNAs in the progression of COVID-19 remains understudied. In recent years, a novel mechanism of post-transcriptional gene regulation known as "competing endogenous RNA (ceRNA)" has been proposed. Long non-coding RNAs (lncRNAs), circular RNAs (circRNAs), and viral ncRNAs function as ceRNAs, influencing the expression of associated genes by sequestering shared microRNAs. Recent research on SARS-CoV-2 has revealed that disruptions in specific ceRNA regulatory networks (ceRNETs) contribute to the abnormal expression of key infection-related genes and the establishment of distinctive infection characteristics. These findings present new opportunities to delve deeper into the underlying mechanisms of SARS-CoV-2 pathogenesis, offering potential biomarkers and therapeutic targets. This progress paves the way for a more comprehensive understanding of ceRNETs, shedding light on the intricate mechanisms involved. Further exploration of these mechanisms holds promise for enhancing our ability to prevent viral infections and develop effective antiviral treatments.

Transcriptomics explores potential mechanisms for the development of Primary Sjogren's syndrome to diffuse large B-cell lymphoma in B cells

PURPOSE

Primary Sjogren's syndrome (pSS) is a prevalent autoimmune disease. The immune dysregulation it causes often leads to the development of diffuse large B-cell lymphoma (DLBCL) in clinical practice. However, how it contributes to these two disorders at the molecular level is not yet known. This study explored the potential molecular mechanisms associated with the differences between DLBCL and pSS.

PATIENTS AND METHODS

Gene expression matrices from discovery cohort 1, discovery cohort 2, and the validation cohort were downloaded from the GEO and TCGA databases. Weighted gene coexpression network analysis (WGCNA) was performed to identify the coexpression modules of DLBCL and pSS in discovery cohort 1 and obtain shared genes. GO and KEGG enrichment analyses and PPI network analysis were performed on the shared genes. Immune-related genes (IRGs) were intersected with shared genes to obtain common genes. Afterward, common genes were identified via machine learning methods. The immune infiltration analysis, miRNA-TF-hub gene regulatory chart, gene interactions of the hub genes, and gene‒drug target analysis were performed. Finally, STAT1 was identified as a possible essential gene by the above analysis, and immune infiltration and GSEA pathway analyses were performed in the high- and low-expression groups in discovery cohort 2. The diagnostic efficacy of the hub genes was assessed in the validation cohort, and clinical samples were collected for validation.

RESULTS

By WGCNA, one modular gene in each group was considered highly associated with the disease, and we obtained 28 shared genes. Enrichment analysis revealed shared genes involved in the viral response and regulation. We obtained four hub genes (ISG20, STAT1, TLR7, and RSAD2) via the algorithm. Hub genes and similar genes are primarily involved in regulating type I IFNs. The construction of a miRNA-TF-hub gene regulatory chart revealed that hsa-mir-155-5p, hsa-mir-146b-5p, hsa-mir-21-3p, and hsa-mir-126-3p play essential roles in both diseases. Hub genes were differentially expressed in B-cell memory according to immune infiltration analysis. Hub genes had a strong diagnostic effect on both diseases. STAT1 plays an essential role in immune cells in both diseases.

CONCLUSION

We identified hub susceptibility genes for DLBCL and pSS and identified hub genes and potential therapeutic targets that may act as biomarkers.

Retrospective identification of the first cord blood-transplanted severe aplastic anemia in a STAT1-associated chronic mucocutaneous candidiasis family: case report, review of literature and pathophysiologic background

Severe aplastic anemia (SAA) is a life-threatening bone marrow failure syndrome whose development can be triggered by environmental, autoimmune, and/or genetic factors. The latter comprises germ line pathogenic variants in genes that bring about habitually predisposing syndromes as well as immune deficiencies that do so only occasionally. One of these disorders is the autosomal dominant form of chronic mucocutaneous candidiasis (CMC), which is defined by germ line STAT1 gain-of-function (GOF) pathogenic variants. The resultant overexpression and constitutive activation of STAT1 dysregulate the Janus kinase/signal transducer and activator of transcription 1 (STAT) signaling pathway, which normally organizes the development and proper interaction of different components of the immunologic and hematopoietic system. Although SAA is an extremely rare complication in this disorder, it gained a more widespread interest when it became clear that the underlying causative pathomechanism may, in a similar fashion, also be instrumental in at least some of the idiopathic SAA cases. Based on these premises, we present herein what is the historically most likely first cord blood-transplanted SAA case in a CMC family with a documented STAT1 GOF pathogenic variant. In addition, we recapitulate the characteristics of the six CMC SAA cases that have been reported so far and discuss the significance of STAT1 GOF pathogenic variants and other STAT1 signaling derangements in the context of these specific types of bone marrow failure syndromes. Because a constitutively activated STAT1 signaling, be it driven by STAT1 GOF germ line pathogenic variants or any other pathogenic variant-independent events, is apparently important for initiating and maintaining the SAA disease process, we propose to acknowledge that SAA is one of the definite disease manifestations in STAT1-mutated CMC cases. For the same reason, we deem it necessary to also incorporate molecular and functional analyses of STAT1 into the diagnostic work-up of SAA cases.

Human life within a narrow range: The lethal ups and downs of type I interferons

The past 20 years have seen the definition of human monogenic disorders and their autoimmune phenocopies underlying either defective or enhanced type I interferon (IFN) activity. These disorders delineate the impact of type I IFNs in natural conditions and demonstrate that only a narrow window of type I IFN activity is beneficial. Insufficient type I IFN predisposes humans to life-threatening viral diseases (albeit unexpectedly few) with a central role in immunity to respiratory and cerebral viral infection. Excessive type I IFN, perhaps counterintuitively, appears to underlie a greater number of autoinflammatory and/or autoimmune conditions known as type I interferonopathies, whose study has revealed multiple molecular programs involved in the induction of type I IFN signaling. These observations suggest that the manipulation of type I IFN activity to within a physiological range may be clinically relevant for the prevention and treatment of viral and inflammatory diseases.

Lethal phenotypes in Mendelian disorders

PURPOSE

Existing resources that characterize the essentiality status of genes are based on either proliferation assessment in human cell lines, viability evaluation in mouse knockouts, or constraint metrics derived from human population sequencing studies. Several repositories document phenotypic annotations for rare disorders; however, there is a lack of comprehensive reporting on lethal phenotypes.

METHODS

We queried Online Mendelian Inheritance in Man for terms related to lethality and classified all Mendelian genes according to the earliest age of death recorded for the associated disorders, from prenatal death to no reports of premature death. We characterized the genes across these lethality categories, examined the evidence on viability from mouse models and explored how this information could be used for novel gene discovery.

RESULTS

We developed the Lethal Phenotypes Portal to showcase this curated catalog of human essential genes. Differences in the mode of inheritance, physiological systems affected, and disease class were found for genes in different lethality categories, as well as discrepancies between the lethal phenotypes observed in mouse and human.

CONCLUSION

We anticipate that this resource will aid clinicians in the diagnosis of early lethal conditions and assist researchers in investigating the properties that make these genes essential for human development.

Mucocutaneous Candidiasis: Insights Into the Diagnosis and Treatment

Recent progress in the methods of genetic diagnosis of inborn errors of immunity has contributed to a better understanding of the pathogenesis of chronic mucocutaneous candidiasis (CMC) and potential therapeutic options. This review describes the latest advances in the understanding of the pathophysiology, diagnostic strategies, and management of chronic mucocutaneous candidiasis.

Inborn Errors of Immunity in Adults with Autoimmune Liver Diseases

BACKGROUND/AIMS

 Inborn errors of immunity (IEI) may associate with autoimmune diseases, including autoimmune liver diseases (AILD). However, both the IEI frequency and secondary effects of immunosuppressives are unknown in patients with AILD due to the lack of data. We aimed to evaluate the ratio of IEI in AILD.

MATERIALS AND METHODS

 A total of 82 patients with AILD (39 autoimmune hepatitis, 32 primary biliary cholangitis, 7 variant syndromes (VS), and 4 primary sclerosing cholangitis patients) were included in this single-center, cross-sectional, and descriptive study. The patients were evaluated and classified according to diagnostic criteria for IEI.

RESULTS

 Out of 82 patients with AILD, female/male ratio was 3.6. Median age of diagnosis of AILD was 45 years. We diagnosed 15 (18%) patients with immunodeficiency (ID). Inborn errors of immunity ratio was highest in VS patient group (29%). Out of 15 patients with ID, 4 (4.8%) patients had common variable immunodeficiency, 4 (4.8%) had partial immunoglobulin A deficiency, 4 (4.8%) had selective immunoglobulin M deficiency, and 3 (3.6%) had combined immunodeficiency.

CONCLUSION

 We detect ID in about one-fifth of the patients with AILD. The present study showed a significant risk of IEI that is blurred by the shadow of immune suppressive treatments. We suggest that the AILD patients with ID will benefit from the individualized and targeted therapeutic options used in IEI. Further research with larger patient groups and long-term follow-up are desperately needed to elucidate the diagnostic, therapeutic, and prognostic impacts of IEI-related individualized therapy on AILD patients.

Qualitative Immunoglobulin Deficiency Causes Bacterial Infections in Patients with STAT1 Gain-of-Function Mutations

PURPOSES

STAT1 is a transduction and transcriptional regulator that functions within the classical JAK/STAT pathway. In addition to chronic mucocutaneous candidiasis, bacterial infections are a common occurrence in patients with STAT1 gain-of-function (GOF) mutations. These patients often exhibit skewing of B cell subsets; however, the impact of STAT1-GOF mutations on B cell-mediated humoral immunity remains largely unexplored. It is also unclear whether these patients with IgG within normal range require regular intravenous immunoglobulin (IVIG) therapy.

METHODS

Eleven patients (harboring nine different STAT1-GOF mutations) were enrolled. Reporter assays and immunoblot analyses were performed to confirm STAT1 mutations. Flow cytometry, deep sequencing, ELISA, and ELISpot were conducted to assess the impact of STAT1-GOF on humoral immunity.

RESULTS

All patients exhibited increased levels of phospho-STAT1 and total STAT1 protein, with two patients carrying novel mutations. In vitro assays showed that these two novel mutations were GOF mutations. Three patients with normal total IgG levels received regular IVIG infusions, resulting in effective control of bacterial infections. Four cases showed impaired affinity and specificity of pertussis toxin-specific antibodies, accompanied by reduced generation of class-switched memory B cells. Patients also had a disrupted immunoglobulin heavy chain (IGH) repertoire, coupled with a marked reduction in the somatic hypermutation frequency of switched Ig transcripts.

CONCLUSION

STAT1-GOF mutations disrupt B cell compartments and skew IGH characteristics, resulting in impaired affinity and antigen-specificity of antibodies and recurrent bacterial infections. Regular IVIG therapy can control these infections in patients, even those with normal total IgG levels.

STAT1 Mutations in Chronic Mucocutaneous Candidiasis Diagnosed in an Adult

A 30-year-old man presented with oral candidiasis and a history of lung abscess. He experienced recurring oral and skin candidiasis in childhood but spent long periods without any infections. Therefore, immunodeficiency was suspected. T and B lymphocyte and natural killer cell counts as well as immunoglobulin levels were normal. Human immunodeficiency virus test results were negative. Therefore, we suspected chronic mucocutaneous candidiasis (CMC). The signal transducer and activator of transcription (STAT) mutation, the leading cause of CMC, was detected by exome sequencing. Most cases of STAT1 mutations are diagnosed in childhood, but a few are diagnosed in adulthood because Candida infections may not be severe.

Chronic Mucocutaneous Candidiasis Due to STAT1 Gene Variant

This case report describes a man in his 40s who presented with a 5-month history of recurrent pruritic papular erythema with mild scaling on the face, left forearm, and groin.

Inborn errors of immunity with susceptibility to S. aureus infections

Staphylococcus aureus (S. aureus) is a significant human pathogen, in particular in patients with an underlying medical condition. It is equipped with a large variety of virulence factors enabling both colonization and invasive disease. The spectrum of manifestation is broad, ranging from superficial skin infections to life-threatening conditions like pneumonia and sepsis. As a major cause of healthcare-associated infections, there is a great need in understanding staphylococcal immunity and defense mechanisms. Patients with inborn errors of immunity (IEI) frequently present with pathological infection susceptibility, however, not all of them are prone to S. aureus infection. Thus, enhanced frequency or severity of S. aureus infections can serve as a clinical indicator of a specific underlying immunological impairment. In addition, the analysis of immunological functions in patients with susceptibility to S. aureus provides a unique opportunity of understanding the complex interplay between staphylococcal virulence and host immune predisposition. While the importance of quantitatively and qualitatively normal neutrophils is widely known, less awareness exists about the role of specific cytokines such as functional interleukin (IL)-6 signaling. This review categorizes well-known IEI in light of their susceptibility to S. aureus and discusses the relevant associated pathomechanisms. Understanding host-pathogen-interactions in S. aureus infections in susceptible individuals can pave the way for more effective management and preventive treatment options. Moreover, these insights might help to identify patients who should be screened for an underlying IEI. Ultimately, enhanced understanding of pathogenesis and immune responses in S. aureus infections may also be of relevance for the general population.

Granulomatous rosacea: a clue to the diagnosis of STAT1 gain of function in a child with immunodeficiency

Recurrent granulomatous rosacea in a paediatric patient prompted an investigation that unveiled a rare gain-of-function mutation in the STAT1 gene. This case highlights the clinical diversity associated with STAT1 mutations and underscores the importance of considering genetic factors in unexplained immunodeficiency and skin conditions, offering valuable insights for diagnosis and treatment.

Ruxolitinib Improves Immune-Dysregulation Features but not Epigenetic Abnormality in a Patient with STAT1 GOF

PURPOSE

Patients with STAT1 gain-of-function (GOF) mutations often exhibit autoimmune features. The JAK1/2 inhibitor ruxolitinib can be administered to alleviate autoimmune symptoms; however, it is unclear how immune cells are molecularly changed by ruxolitinib treatment. Then, we aimed to investigate the trnscriptional and epigenetic status of immune cells before and after ruxolitinib treatment in a patient with STAT1 GOF.

METHODS

A patient with a heterozygous STAT1 GOF variant (p.Ala267Val), exhibiting autoimmune features, was treated with ruxolitinib, and peripheral blood mononuclear cells (PBMCs) were longitudinally collected. PBMCs were transcriptionally analyzed by single-cell cellular indexing of the transcriptomes and epitopes by sequencing (CITE-seq), and epigenetically analyzed by assay of transposase-accessible chromatin sequencing (ATAC-seq).

RESULTS

CITE-seq analysis revealed that before treatment, the patient's PBMCs exhibited aberrantly activated inflammatory features, especially IFN-related features. In particular, monocytes showed high expression levels of a subset of IFN-stimulated genes (ISGs). Ruxolitinib treatment substantially downregulated aberrantly overexpressed ISGs, and improved autoimmune features. However, epigenetic analysis demonstrated that genetic regions of ISGs-e.g., STAT1, IRF1, MX1, and OAS1-were highly accessible even after ruxolitinib treatment. When ruxolitinib was temporarily discontinued, the patient's autoimmune features were aggravated, which is in line with sustained epigenetic abnormality.

CONCLUSIONS

In a patient with STAT1 GOF, ruxolitinib treatment improved autoimmune features and downregulated aberrantly overexpressed ISGs, but did not correct epigenetic abnormality of ISGs.

Patients with STAT1 Gain-of-function Mutations Display Increased Apoptosis which is Reversed by the JAK Inhibitor Ruxolitinib

INTRODUCTION

The signal transducer and activator of transcription (STAT1) gain-of-function (GOF) syndrome accounts for most cases of chronic mucocutaneous candidiasis but is characterized by a broader clinical phenotype that may include bacterial, viral, or invasive fungal infections, autoimmunity, autoinflammatory manifestations, vascular complications, or malignancies. The severity of lymphopenia may vary and influence the infectious morbidity.

METHODS

In our cohort of seven STAT1-GOF patients, we investigated the mechanisms that may determine T lymphopenia, we characterized the interferon gene signature (IGS) and analyzed the effect of ruxolitinib in reverting the immune dysregulation.

RESULTS

STAT1-GOF patients exhibited increased T lymphocyte apoptosis that was significantly augmented in both resting conditions and following stimulation with mitogens and IFNα, as evaluated by flow cytometry by Annexin V/ Propidium iodide assay. The JAK inhibitor ruxolitinib significantly reduced the IFNα-induced hyperphosphorylation of STAT1 and reverted the stimulation-induced T-cell apoptosis, in vitro. In two adult STAT1-GOF patients, the JAKinib treatment ameliorated chronic mucocutaneous candidiasis and lymphopenia. Most STAT1-GOF patients, particularly those who had autoimmunity, presented increased IGS that significantly decreased in the two patients during ruxolitinib treatment.

CONCLUSION

In STAT1-GOF patients, T lymphocyte apoptosis is increased, and T lymphopenia may determine higher risk of severe infections. The JAKinib target therapy should be evaluated to treat severe chronic candidiasis and lymphopenia, and to downregulate the IFNs in patients with autoinflammatory or autoimmune manifestations.

Recapitulating primary immunodeficiencies with expanded potential stem cells: Proof of concept with STAT1 gain of function

BACKGROUND

Inborn errors of immunity (IEI) often lack specific disease models and personalized management. Signal transducer and activator of transcription (STAT)-1 gain of function (GoF) is such example of an IEI with diverse clinical phenotype with unclear pathomechanisms and unpredictable response to therapy. Limitations in obtaining fresh samples for functional testing and research further highlights the need for patient-specific ex vivo platforms.

OBJECTIVE

Using STAT1-GoF as an example IEI, we investigated the potential of patient-derived expanded potential stem cells (EPSC) as an ex vivo platform for disease modeling and personalized treatment.

METHODS

We generated EPSC derived from individual STAT1-GoF patients. STAT1 mutations were confirmed with Sanger sequencing. Functional testing including STAT1 phosphorylation/dephosphorylation and gene expression with or without Janus activating kinase inhibitors were performed. Functional tests were repeated on EPSC lines with GoF mutations repaired by CRISPR/Cas9 (clustered regularly interspaced short palindromic repeats/CRISPR-associated protein 9) editing.

RESULTS

EPSC were successfully reprogrammed from STAT1-GoF patients and expressed the same pluripotent makers as controls, with distinct morphologic differences. Patient-derived EPSC recapitulated the functional abnormalities of index STAT1-GoF patients with STAT1 hyperphosphorylation and increased expression of STAT1 and its downstream genes (IRF1, APOL6, and OAS1) after IFN-γ stimulation. Addition of ruxolitinib and baricitinib inhibited STAT1 hyperactivation in STAT1-GoF EPSC in a dose-dependent manner, which was not observed with tofacitinib. Corrected STAT1 phosphorylation and downstream gene expression were observed among repaired STAT1-GoF EPSC cell lines.

CONCLUSION

This proof-of-concept study demonstrates the potential of our patient-derived EPSC platform to model STAT1-GoF. We propose this platform when researching, recapitulating, and repairing other IEI in the future.

Clinical updates in inborn errors of immunity: a focus on the noninfectious clinical manifestations

PURPOSE OF REVIEW

In the last 5 years, several new inborn errors of immunity (IEI) have been described, especially in the areas of immune dysregulation and autoinflammation. As a result, the clinical presentation of IEIs has broadened. We review the heterogeneous presentation of IEIs and detail several of the recently described IEIs with a focus on the noninfectious manifestations commonly seen.

RECENT FINDINGS

IEIs may present with early onset and/or multiple autoimmune manifestations, increased risk for malignancy, lymphoproliferation, severe atopy, autoinflammation and/or hyperinflammation. Because of this, patients can present to a wide array of providers ranging from primary care to various pediatric subspecialists. The International Union of Immunological Societies (IUIS) expert committee has created a phenotypic classification of IEIs in order to help clinicians narrow their evaluation based on the laboratory and clinical findings.

SUMMARY

Both primary care pediatricians and pediatric subspecialists need to be aware of the common clinical features associated with IEI and recognize when to refer to allergy-immunology for further evaluation. Early diagnosis can lead to earlier treatment initiation and improve clinical outcomes for our patients.

Role of IL-27 in Epstein-Barr virus infection revealed by IL-27RA deficiency

Epstein-Barr virus (EBV) infection can engender severe B cell lymphoproliferative diseases1,2. The primary infection is often asymptomatic or causes infectious mononucleosis (IM), a self-limiting lymphoproliferative disorder3. Selective vulnerability to EBV has been reported in association with inherited mutations impairing T cell immunity to EBV4. Here we report biallelic loss-of-function variants in IL27RA that underlie an acute and severe primary EBV infection with a nevertheless favourable outcome requiring a minimal treatment. One mutant allele (rs201107107) was enriched in the Finnish population (minor allele frequency = 0.0068) and carried a high risk of severe infectious mononucleosis when homozygous. IL27RA encodes the IL-27 receptor alpha subunit5,6. In the absence of IL-27RA, phosphorylation of STAT1 and STAT3 by IL-27 is abolished in T cells. In in vitro studies, IL-27 exerts a synergistic effect on T-cell-receptor-dependent T cell proliferation7 that is deficient in cells from the patients, leading to impaired expansion of potent anti-EBV effector cytotoxic CD8+ T cells. IL-27 is produced by EBV-infected B lymphocytes and an IL-27RA-IL-27 autocrine loop is required for the maintenance of EBV-transformed B cells. This potentially explains the eventual favourable outcome of the EBV-induced viral disease in patients with IL-27RA deficiency. Furthermore, we identified neutralizing anti-IL-27 autoantibodies in most individuals who developed sporadic infectious mononucleosis and chronic EBV infection. These results demonstrate the critical role of IL-27RA-IL-27 in immunity to EBV, but also the hijacking of this defence by EBV to promote the expansion of infected transformed B cells.

Human STAT1 gain of function with chronic mucocutaneous candidiasis: A comprehensive review for strengthening the connection between bedside observations and laboratory research

Germline human heterozygous STAT1 gain-of-function (GOF) variants were first discovered a common cause of chronic mucocutaneous candidiasis (CMC) in 2011. Since then, numerous STAT1 GOF variants have been identified. A variety of clinical phenotypes, including fungal, viral, and bacterial infections, endocrine disorders, autoimmunity, malignancy, and aneurysms, have recently been revealed for STAT1 GOF variants, which has led to the expansion of the clinical spectrum associated with STAT1 GOF. Among this broad range of complications, it has been determined that invasive infections, aneurysms, and malignancies are poor prognostic factors for STAT1 GOF. The effectiveness of JAK inhibitors as a therapeutic option has been established, although further investigation of their long-term utility and side effects is needed. In contrast to the advancements in treatment options, the precise molecular mechanism underlying STAT1 GOF remains undetermined. Two primary hypotheses for this mechanism involve impaired STAT1 dephosphorylation and increased STAT1 protein levels, both of which are still controversial. A precise understanding of the molecular mechanism is essential for not only advancing diagnostics but also developing therapeutic interventions. Here, we provide a comprehensive review of STAT1 GOF with the aim of establishing a stronger connection between bedside observations and laboratory research.

JAK/STAT defects and immune dysregulation, and guiding therapeutic choices

Inborn errors of immunity (IEIs) encompass a diverse spectrum of genetic disorders that disrupt the intricate mechanisms of the immune system, leading to a variety of clinical manifestations. Traditionally associated with an increased susceptibility to recurrent infections, IEIs have unveiled a broader clinical landscape, encompassing immune dysregulation disorders characterized by autoimmunity, severe allergy, lymphoproliferation, and even malignancy. This review delves into the intricate interplay between IEIs and the JAK-STAT signaling pathway, a critical regulator of immune homeostasis. Mutations within this pathway can lead to a wide array of clinical presentations, even within the same gene. This heterogeneity poses a significant challenge, necessitating individually tailored therapeutic approaches to effectively manage the diverse manifestations of these disorders. Additionally, JAK-STAT pathway defects can lead to simultaneous susceptibility to both infection and immune dysregulation. JAK inhibitors, with their ability to suppress JAK-STAT signaling, have emerged as powerful tools in controlling immune dysregulation. However, questions remain regarding the optimal selection and dosing regimens for each specific condition. Hematopoietic stem cell transplantation (HSCT) holds promise as a curative therapy for many JAK-STAT pathway disorders, but this procedure carries significant risks. The use of JAK inhibitors as a bridge to HSCT has been proposed as a potential strategy to mitigate these risks.