Inborn Error of STAT2-Dependent IFN-I Immunity in a Patient Presented with Hemophagocytic Lymphohistiocytosis and Multisystem Inflammatory Syndrome in Children

The lack of either IRF9, or STAT2, has surprisingly little effect on human natural killer cell development and function

Analysis of genetically defined immunodeficient patients allows study of the effect of the absence of specific proteins on human immune function in real-world conditions. Here we have addressed the importance of type I interferon signalling for human NK cell development by studying the phenotype and function of circulating NK cells isolated from patients suffering primary immunodeficiency disease due to mutation of either the human interferon regulatory factor 9 (IRF9) or the signal transducer and activator of transcription 2 (STAT2) genes. IRF9, together with phosphorylated STAT1 and STAT2, form a heterotrimer called interferon stimulated gene factor 3 (ISGF3) which promotes the expression of hundreds of IFN-stimulated genes that mediate antiviral function triggered by exposure to type I interferons. IRF9- and STAT2-deficient patients are unable to respond efficiently to stimulation by type I interferons and so our experiments provide insights into the importance of type I interferon signalling and the consequences of its impairment on human NK cell biology. Surprisingly, the NK cells of these patients display essentially normal phenotype and function.

HLH Syndrome in a Community Hospital: The Challenge of an Early Diagnosis

Introduction

Hemophagocytic lymphohistiocytosis (HLH) is a potentially fatal hyperinflammatory cytokine storm. It can be secondary to infections, malignancies, autoimmune diseases, or the manifestation of genetic disorders, including primary immune deficiency. HLH requires a high index of suspicion and is challenging for community hospitals.

Methods

Medical records of children with HLH admitted to the Meir Medical Center in Israel between 2014 and 2017 were reviewed.

Results

Nine children met ≥5/8 HLH-2004 criteria. The median age was 1.1 year, and 78% of the patients were aged <2 years. All patients had prolonged fever, cytopenia, and elevated soluble interleukin-2 receptor, and 89% had elevated ferritin levels. Of three children who underwent gene panel evaluation, one had heterozygote genetic variants of UNC13D and STXBP2 of unclear significance, whereas the other two had no variants. Infection was identified in 8 of 9 patients: adenovirus, HHV6, EBV, and Streptococcus Group A. Only 2 patients received HLH-2004 therapy (dexamethasone, etoposide, cyclosporin-A) and the others received dexamethasone and/or intravenous gamma globulins (IVIG), with rapid resolution of fever (median 2 days). One patient (11%) died of Pseudomonas septicemia and multiorgan failure. At a median follow-up of 7 years (range 2.6-8.1 years), all others (8/9) are long-term survivors with no recurrent HLH, but 2 patients developed adenovirus-related bronchiolitis obliterans.

Conclusion

Children presenting with prolonged fever and abnormal blood counts should be evaluated with ferritin, triglycerides, and fibrinogen levels which indicate possible HLH. Early intervention with corticosteroids and/or IVIG may prevent deterioration, spare them from chemotherapy and provide time for more elaborate testing to identify true HLH. Unfortunately, mortality remains a significant risk for these children.

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.

Integrative bioinformatics analysis reveals STAT2 as a novel biomarker of inflammation-related cardiac dysfunction in atrial fibrillation

Atrial fibrillation (AF) is a common critical cause of stroke and cardiac dysfunction worldwide with lifetime risks. Viral infection and inflammatory response with myocardial involvement may lead to an increase in AF-related mortality. To dissect the potential sequelae of viral infection in AF patients, especially the coronavirus disease 2019 (COVID-19), based on AF and COVID-19 databases from Gene Expression Omnibus, weighted gene co-expression network analysis was used to identify key genes in heart tissues and peripheral blood mononuclear cells. Here, HSCT, PSMB9, STAT2, and TNFSF13B were identified as common risk genes of AF and COVID-19 patients. Correlation analysis of these genes with AF and COVID-19 showed a positive disease relevance. silencing of STAT2 by small interfering RNA significantly rescued SARS-CoV-2 XBB1.5 pseudovirus-induced cardiac cell contraction dysfunction in vitro. In conclusion, we identified STAT2 may be a novel biomarker of inflammation-related cardiac dysfunction in AF.