The clinical and mechanistic intersection of primary atopic disorders and inborn errors of growth and metabolism

Severe allergic dysregulation due to a gain of function mutation in the transcription factor STAT6

BACKGROUND

Inborn errors of immunity have been implicated in causing immune dysregulation, including allergic diseases. STAT6 is a key regulator of allergic responses.

OBJECTIVES

This study sought to characterize a novel gain-of-function STAT6 mutation identified in a child with severe allergic manifestations.

METHODS

Whole-exome and targeted gene sequencing, lymphocyte characterization, and molecular and functional analyses of mutated STAT6 were performed.

RESULTS

This study reports a child with a missense mutation in the DNA binding domain of STAT6 (c.1114G>A, p.E372K) who presented with severe atopic dermatitis, eosinophilia, and elevated IgE. Naive lymphocytes from the affected patient displayed increased TH2- and suppressed TH1- and TH17-cell responses. The mutation augmented both basal and cytokine-induced STAT6 phosphorylation without affecting dephosphorylation kinetics. Treatment with the Janus kinase 1/2 inhibitor ruxolitinib reversed STAT6 hyperresponsiveness to IL-4, normalized TH1 and TH17 cells, suppressed the eosinophilia, and improved the patient's atopic dermatitis.

CONCLUSIONS

This study identified a novel inborn error of immunity due to a STAT6 gain-of-function mutation that gave rise to severe allergic dysregulation. Janus kinase inhibitor therapy could represent an effective targeted treatment for this disorder.

Elevated IgE from attenuated CARD11 signaling: lessons from atopic mice and humans

CARD11 encodes a large scaffold protein responsible for integrating antigen-receptor engagement with downstream signaling to NF-kB and other outputs in lymphocytes. Over the past 10 years, several human-inborn errors of immunity have been linked to pathogenic CARD11 mutations. Most recently, severe atopic patients were discovered that carried heterozygous dominant-negative CARD11 mutations. Here, we review the mechanistic connections between attenuated CARD11 signaling, elevated IgE, and atopy, comparing and contrasting key insights from both human patients and murine models. Continued investigation of abnormal CARD11 signaling in both contexts should inform novel therapeutic strategies to combat allergic pathogenesis.

Rapamycin Dampens Inflammatory Properties of Bone Marrow ILC2s in IL-33-Induced Eosinophilic Airway Inflammation

The alarmin cytokine interleukin (IL)-33 plays an important proinflammatory role in type 2 immunity and can act on type 2 innate lymphoid cells (ILC2s) and type 2 T helper (T_H2) cells in eosinophilic inflammation and asthma. The mechanistic target of rapamycin (mTOR) signaling pathway drives immune responses in several inflammatory diseases, but its role in regulating bone marrow responses to IL-33 is unclear. The aim of this study was to determine the role of the mTORC1 signaling pathway in IL-33-induced bone marrow ILC2 responses and its impact on IL-33-induced eosinophilia. Wild-type mice were intranasally exposed to IL-33 only or in combination with the mTORC1 inhibitor, rapamycin, intraperitoneally. Four groups were included in the study: saline-treated (PBS)+PBS, rapamycin+PBS, PBS+IL-33 and rapamycin+IL-33. Bronchoalveolar lavage fluid (BALF), serum and bone marrow cells were collected and analyzed by differential cell count, enzyme-linked immunosorbent assay and flow cytometry. IL-33 induced phosphorylation of the mTORC1 protein rpS6 in bone marrow ILC2s both ex vivo and in vivo. The observed mTOR signal was reduced by rapamycin treatment, indicating the sensitivity of bone marrow ILC2s to mTORC1 inhibition. IL-5 production by ILC2s was reduced in cultures treated with rapamycin before stimulation with IL-33 compared to IL-33 only. Bone marrow and airway eosinophils were reduced in mice given rapamycin before IL-33-exposure compared to mice given IL-33 only. Bone marrow ILC2s responded to IL-33 in vivo with increased mTORC1 activity and rapamycin treatment successfully decreased IL-33-induced eosinophilic inflammation, possibly by inhibition of IL-5-producing bone marrow ILC2s. These findings highlight the importance of investigating specific cells and proinflammatory pathways as potential drivers of inflammatory diseases, including asthma.

Case Report: Eosinophilic Esophagitis in a Patient With a Novel STAT1 Gain-of-Function Pathogenic Variant

Background

STAT1 gain-of-function (GOF) is a primary immune dysregulatory disorder marked by wide infectious predisposition (most notably chronic mucocutaneous Candidiasis), autoimmunity, vascular disease and malignant predisposition. While atopic features have been described in some STAT1 GOF patients, they are not considered a predominant feature of the disease. Additionally, while eosinophilic gastrointestinal infiltration has been reported in some cases, this has always been described in the context of pre-existing oropharyngeal and/or esophageal Candidiasis.

Clinical cases

Herein, we report 3 members of a multi-generational family diagnosed with STAT1 GOF caused by a novel mutation in the N-terminal domain, c.194A>C (p.D65A). The proband presented initially with a long-standing history of treatment-refractory eosinophilic esophagitis (EoE) without preceding gastrointestinal tract fungal infections, and her mother was diagnosed with esophagitis as well.

Conclusion

EoE has been previously associated with alterations to STAT6 and STAT3 signaling pathways. The current report expands the possible association between JAK/STAT-related disorders and EoE, suggesting that EoE could be a primary disease manifestation of STAT1 GOF, even in the absence of oropharyngeal and/or esophageal Candidiasis.

Inborn errors of immunity manifesting as atopic disorders

Inborn errors of immunity are traditionally best known for enhancing susceptibility to infections. However, allergic inflammation, among other types of immune dysregulation, occurs frequently in patients with inborn errors of immunity. As such, the term primary atopic disorders (PADs) was recently coined to describe the group of heritable monogenic allergic disorders. It is becoming increasingly important for clinicians to recognize that allergic diseases such as food allergy, atopic dermatitis, and allergic asthma are expressions of misdirected immunity, and in patients who present with severe, early-onset, or coexisting allergic conditions, these can be indications of an underlying PAD. Identifying monogenic allergic disease through next-generation sequencing can dramatically improve outcomes by allowing the use of precision-based therapy targeting the patient's underlying molecular defect. It is therefore imperative that clinicians recognize PADs to be able to provide informed therapeutic options and improve patient outcomes. Here, we summarize the clinical features commonly seen with each of the currently known PADs, identify clinical warning signs that warrant assessment for PADs, and lastly, discuss the benefits of timely diagnosis and management of these conditions.

Inborn errors of immunity with atopic phenotypes: A practical guide for allergists

Inborn errors of immunity (IEI) are a heterogeneous group of disorders, mainly resulting from mutations in genes associated with immunoregulation and immune host defense. These disorders are characterized by different combinations of recurrent infections, autoimmunity, inflammatory manifestations, lymphoproliferation, and malignancy. Interestingly, it has been increasingly observed that common allergic symptoms also can represent the expression of an underlying immunodeficiency and/or immune dysregulation.

Very high IgE levels, peripheral or organ-specific hypereosinophilia, usually combined with a variety of atopic symptoms, may sometimes be the epiphenomenon of a monogenic disease. Therefore, allergists should be aware that severe and/or therapy-resistant atopic disorders might be the main clinical phenotype of some IEI. This could pave the way to target therapies, leading to better quality of life and improved survival in affected patients.

Targeted pharmacologic immunomodulation for inborn errors of immunity

Inborn errors of immunity consist of over 400 known single gene disorders that may manifest with infection susceptibility, autoimmunity, autoinflammation, hypersensitivity and cancer predisposition. Most patients are treated symptomatically with immunoglobulin replacement, prophylactic antimicrobials or broad immunosuppression pertaining to their disease phenotype. Other than haematopoietic stem cell transplantation, the aforementioned treatments do little to alter disease morbidity or mortality. Further, many patients may not be transplant candidates. In this review, we describe monogenic disorders affecting leucocyte migration, disorders of immune synapse formation and dysregulation of immune cell signal transduction. We highlight the use of off-label small molecules and biologics mechanistically targeted to altered disease pathophysiology of such diseases.

Recent advances in primary immunodeficiency: from molecular diagnosis to treatment

The technological advances in diagnostics and therapy of primary immunodeficiency are progressing at a fast pace. This review examines recent developments in the field of inborn errors of immunity, from their definition to their treatment. We will summarize the challenges posed by the growth of next-generation sequencing in the clinical setting, touch briefly on the expansion of the concept of inborn errors of immunity beyond the classic immune system realm, and finally review current developments in targeted therapies, stem cell transplantation, and gene therapy.

Exploration of the Molecular Mechanism of FUZI (Aconiti Lateralis Radix Praeparata) in Allergic Rhinitis Treatment Based on Network Pharmacology

FUZI (Aconiti Lateralis Radix Praeparata) is a traditional Chinese medicine herb used extensively for nourishing yang (regarded as the positive, male universal force), which is critical in treatment of allergic rhinitis. In this paper, FUZI was explored based on network pharmacology. The active components of FUZI were screened out, its protein targets were assessed, and the protein interaction network map was built with the differential protein of allergic rhinitis, as an attempt to determine the critical targets of FUZI for treating allergic rhinitis. Subsequently, DAVID was employed to explore the biological function and pathway enrichment to determine the biological pathway of FUZI for treating allergic rhinitis.

As suggested by the results, FUZI is likely to affect the inhibition of inflammation and the regulation of immunity, probably reducing the incidence of allergic rhinitis, or alleviating nasal discomfort attributed to allergic inflammation. The targets and pathways of FUZI for treating allergic rhinitis assessed by network pharmacology provided a direction for our subsequent studies and may be a novel therapeutic target.

Gene-environment interactions in primary atopic disorders

Environmental factors modify disease presentation and severity in allergic disorders. Primary atopic disorders (PADs) are a heterogenous group of single gene disorders that lead to significant atopic and allergic disease manifestations. However, a number of these monogenic diseases have variable penetrance suggesting that gene-gene and/or gene-environment interactions could modulate the clinical phenotype. Environmental factors such as diet, the microbiome at the epithelial-environment interface, the presence and/or extent of infection, and psychologic stress can alter disease phenotypic expression of allergic diseases, and PADs provide discrete contexts in which to understand these influences. We outline how gene-environment interactions likely contribute to a variable penetrance and expressivity in PADs. Dietary modifications of both macronutrients and/or micronutrients alter T-cell metabolism and may influence effector T-cell function. The mucosal microbiome may affect local inflammation and may remotely influence regulatory elements, while psychologic stress can affect mast cell and other allergic effector cell function. Understanding gene-environment interactions in PADs can hopefully provide a foundation for interrogating gene-environment interactions to common allergic disorders, and also present opportunities for personalized interventions based on the altered pathways and environmental influences in affected individuals.