Drug Hypersensitivity

Cephalosporin antibiotics are commonly used but can result in allergic reactions and anaphylaxis. There is no clear diagnostic approach for cephalosporin-allergic patients, and guidance for the use of other antibiotics in allergic patients is based on side chain chemical similarity and limited skin testing evidence. This project includes a clinical trial and mechanistic studies to optimize the approach to cephalosporin allergy and advance future diagnostics.

Drug Hypersensitivity Syndrome or DRESS for "Drug Reaction with Eosinophilia and Systemic Symptoms" is a serious drug allergy which can be life-threatening for patients with serious organ damage. The pathophysiology of DRESS is still not fully understood. In particular, no study has focused on the characterization of eosinophils, while paradoxically eosinophilia is one of the diagnostic criteria. Likewise, there is no data about the origin of eosinophils and few data are available concerning immune polarization of T-cells or the involvement of innate lymphoid cells type 2 in the recruitment of eosinophils. Our preliminary data on increase activation markers membrane expression of cutaneous eosinophils suggest that this approach could allow the identification of endotypes in which eosinophils are involved and contribute to organ damages. The correlation between tissue infiltration of eosinophils and their degree of activation would then justify the development of targeted therapeutic strategies in DRESS syndrome (anti-IL-5 therapy?). The aim of the project is: 1) Evaluate the activation status of circulating and cutaneous eosinophils in patients with DRESS compared with drug induced maculopapular exanthema without or with eosinophilia (but do not fulfill DRESS criteria) and healthy subjects; 2) Understand the pathophysiological mechanisms at the origin of this eosinophilia.

Immediate drug hypersensitivity reactions are acute adverse reactions that occur within one hour of drug administration and can result in life-threatening symptoms such as urticaria, angioedema, and anaphylaxis. Current diagnostic methods have high false-negative and false-positive rates, and standardized testing for non-IgE-mediated reactions (e.g., MRGPRX2) is lacking. This creates significant gaps in patient safety and clinical decision-making. The study aims to establish a registry of patients with immediate drug hypersensitivity reactions to analyze clinical characteristics and investigate the underlying mechanisms of IgE-mediated and non-IgE-mediated reactions. Blood samples will be collected prospectively, using residual serum from routine clinical tests where available, to minimize additional blood draws. Mechanistic analyses will focus on IgE-mediated and non-IgE-mediated pathways, including MRGPRX2 expression in mast cells and basophils, and measurement of active β-tryptase as a biomarker for anaphylaxis. In addition, a retrospective review will be conducted of medical records from the last 10 years to identify causative drugs and classify the underlying mechanisms of hypersensitivity. Based on this, specific target drugs will be selected for further prospective analysis. Data and biospecimens from participants in an existing allergy registry, who consent to secondary use, will also be included in the study. Through the integration of clinical data and multi-layered biomarker analysis, the study aims to improve understanding of immediate drug hypersensitivity mechanisms and develop predictive models. Ultimately, this research will contribute to the establishment of personalized diagnosis, prevention, and treatment strategies for drug allergies.