Role of eosinophils in DRESS

Drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome is a severe and potentially life-threatening adverse reaction to a medication with an estimated mortality rate of 5-10%. Tissue infiltration of eosinophils into the heart, lung, liver, and kidney can lead to fatal organ dysfunction. Current thinking is that drug-specific T cells, activation of JAK-STAT pathways and perhaps latent viral reactivation underly this Type IVb drug hypersensitivity. However, little is known about the role of eosinophils in this disease, even though blood eosinophilia (>700 cells/µL) is a hallmark of DRESS, occurring in >80% of patients. Analyses of drug-induced hypersensitivity reactions have typically failed to capture the eosinophil transcriptome, mainly due to technical limitations. The current standard of treatment for DRESS, systemic corticosteroids, is often accompanied by significant side effects. Development of targeted therapy for patients with DRESS syndrome would address a tremendous unmet medical need, as up to 60% of patients have a recurrence. Eosinophil-targeting therapies have enhanced our ability to treat eosinophil-driven diseases such as asthma and led to the discovery of asthma endotypes. Similarly, in patients with hypereosinophilic syndrome (HES), variable response to anti-IL-5 and anti-IL-5Ra therapies has been correlated to HES clinical subtypes, suggesting eosinophils are more heterogeneous than previously recognized. Case reports of successful treatment of DRESS with anti-IL-5 or anti-IL5R? biologics suggest that eosinophils are directly pathogenic in this condition. Thus it is critical to understand the phenotype and importance of eosinophils in DRESS pathogenesis to inform future clinical studies including those using eosinophil-targeted therapies. We have optimized the process of RNA isolation from circulating activated human eosinophils with sufficient quantity and quality for next-generation sequencing. With direct access to acutely ill patients in the allergy clinic and the inpatient setting, we successfully performed RNA sequencing on blood eosinophils from patients with various eosinophilic disorders, including DRESS and healthy controls. Our preliminary data show that the transcriptional signatures of eosinophils from patients with DRESS are unique and distinct from those of patients with other diseases associated with peripheral eosinophilia, such as eosinophilic gastrointestinal disorders (EGID) and HES with skin manifestations. This gives rise to our central hypothesis that circulating eosinophils in patients with DRESS exhibit a unique transcriptional phenotype and immunophenotype compared to other forms of eosinophilia (Fig. 1). Aim 1: To determine the transcriptional and immunophenotype signatures of blood eosinophils derived from patients with DRESS. Clinical history and peripheral blood from patients acutely ill with DRESS (n=8) as defined by RegiSCAR score =4 seen in the outpatient clinic or inpatient allergy or dermatology consult services will be collected before DRESS-directed therapy when possible. RNA isolated from these purified eosinophils will be used for next-generation bulk RNA sequencing. High-parameter eosinophil flow cytometry on fresh blood samples will be performed and correlated with expression data. These data will be compared to transcriptomic and immunophenotypic data of eosinophils isolated from healthy volunteers (n=8) and hypereosinophilic patients such as HES or EGID (n=8). For additional comparison, we will recruit patients with allergic contact dermatitis (n=8),