Methotrexate and Cyclosporin Improve Skin Biomarkers in Paediatric Atopic Dermatitis: Results from the TREAT TrialTo the Editor,Methotrexate (MTX) and cyclosporin (CyA) are the main conventional systemic treatments for severe atopic dermatitis (AD) globally.1,2 The complex interaction of cutaneous immune biomarkers and their modulation during therapy with these drugs is poorly understood.3 In the Treatment of severe Atopic Eczema in children Trial (TREAT) CyA led to faster disease control, while MTX showed sustained disease control post-therapy.4 Here we explore skin immune biomarkers in TREAT participants randomised to either CyA (4mg/kg/day) or MTX (0.4mg per week) for 36 weeks with 24 weeks follow-up after therapy cessation.4 43 participants were included (22 CyA; 21MTX). Tapestrips were taken from the volar forearm at baseline, 12, 36 and 60 weeks. Concentrations of NMF and immune biomarkers were measured. Please see supplementary materials for sampling, laboratory and statistical methods.Baseline demographics were well balanced across study groups, including disease severity, measured by Eczema Area and Severity Index (EASI; Table S1). Changes in EASI scores at the biomarker sampling time points reflect the disease severity changes in the full TREAT trial population (Fig. S1).MTX and CyA drove significant changes in stratum corneum cytokine levels. While there were no statistically significant biomarker differences between the treatment groups, it is noteworthy that the number of biomarkers showing significant change from baseline was higher with MTX than for CyA (Fig. 1, Table S2). Innate cytokines, CXCL8 and IL-18 were altered with both treatments. CXCL8 decreased from baseline at 12 weeks with MTX and CyA, at 36 weeks with MTX only and at 60 weeks with both drugs. IL-18 decreased at 12 weeks with CyA, at 36 weeks with both drugs and at 60 weeks with MTX only. The innate cytokine IL-1α increased at all timepoints compared to baseline only with MTX. Similarly, the skin barrier biomarker NMF increased at weeks 12 and 36 only with MTX. Th2 cytokines decreased with both treatments: CCL17 at 12 and 36 weeks with MTX only and at 60 weeks with both treatments, while CCL27 decreased at 12 weeks with CyA only, at week 36 with both drugs and at 60 weeks with MTX only. IL-17 decreased with both drugs at week 36 and the Th1 biomarker CXCL10 decreased at week 60 with CyA only. All biomarkers except NMF and IL-1α positively correlated with EASI score (Fig. 2). CXCL8/TARC showed the strongest correlation (r=0.50; P<0.0001).Systemic treatment with both MTX and CyA led to clinical improvement with differential cytokine signatures, indicating that MTX and CyA not only suppress inflammation, but also normalize immune responses mediated by cytokines involved in innate (IL-1α, IL-18, CXCL8), Th1 (CXCL10), Th17 (IL-17A) and Th2 (CCL17 and CCL27) immunity. Significant changes from baseline were found for the skin barrier biomarker NMF, but only with MTX.Normalization of NMF levels can also be attributed to a decrease in Th2 cytokines, which inversely regulate filaggrin gene expression. CCL17 and CCL27, Th2 mediators in AD, normalized to a larger extent after MTX compared to CyA, suggesting MTX may modulate Th-2 suppression pathways and normalize skin barrier function. The strong correlation of CXCL8 and CCL27 with EASI score is consistent with previous stratum corneum biomarker studies.5-6In conclusion, MTX and CyA improve clinical outcomes in AD and modulate the cutaneous immune response. MTX has a more pronounced effect on certain immunological and skin barrier biomarkers compared to CyA, indicating potential differences in their mechanisms of action, and suggesting that MTX may offer additional benefits in the treatment of AD, even after treatment cessation.

Background: Various biomarkers are used to define peanut allergy (PA). We aimed to observe changes in PA resolution and persistence over time comparing biomarkers in PA and peanut sensitised but tolerant (PS) children in a population-based cohort. Methods: Participants were recruited from the EAT and EAT-On studies, conducted across England and Wales and were generally well exclusively breastfed babies recruited at 3 months old and followed up until 11 years old. Clinical characteristics, skin prick test (SPT), sIgE to peanut and peanut components and mast cell activation tests (MAT) were assessed at 12m, 36m and 7-11y. Results: The prevalence of PA was 2.1% with only 1 child having PA resolution at 7-11y. PA children had larger SPT size, higher peanut-sIgE, Ara h 2-sIgE and MAT (all p<0.001) compared to PS children at 36m and 7-11y. SPT, peanut-sIgE, Ara h 2-sIgE and MAT between children with persistent PA, new PA, outgrown PA and PS were statistically significant at both 36m and 7-11y (p<0.001). Those with persistent PA had SPT, peanut-sIgE and Ara h 2-sIgE that increased over time and MAT which was highest at 36m. New PA children had increased SPT and peanut-sIgE from 36m to 7-11y, but MAT remained low. PS children had low biomarkers across time. Conclusions: In this cohort, few children outgrow or develop new PA between 36m and 7-11y. Children with PA have significantly higher SPT, peanut-sIgE, Ara h 2-sIgE and MAT compared to PS children, evident from 12-36m of age.

Background: Although well described in adults, there are scarce and heterogeneous data on the diagnosis and management of chronic urticaria (CU) in children (0-18 years) throughout Europe. Our aim was to explore country differences and identify the extent to which the EAACI/GA²LEN/EDF/WAO guideline recommendations for paediatric urticaria are implemented. Methods: The EAACI Taskforce for paediatric CU disseminated an online clinical survey among EAACI paediatric section members. Members were asked to answer 35 multiple choice questions on current practices in their respective centres. Results: The survey was sent to 2,773 physicians of whom 358 (13.8%) responded, mainly paediatric allergists (80%) and paediatricians (49.7%), working in 69 countries. For diagnosis, Southern European countries used significantly more routine tests (e.g., autoimmune testing, allergological tests, and parasitic investigation) than Northern European countries. Most respondents (60.3%) used a 2nd generation antihistamine as first- line treatment of whom 64.8% up dosed as a second- line. Omalizumab, was used as a second line treatment by 1.7% and third-line by 20.7% of respondents. Most clinicians (65%) follow EAACI/WAO/GA2LEN/EDF guidelines when diagnosing CU, and only 7.3% follow no specific guidelines. Some clinicians prefer to follow national guidelines (18.4%, mainly Northern European) or the AAAAI practice parameter (1.7%). Conclusions: Even though most members of the Paediatric Section of EAACI are familiar with the EAACI/WAO/GA2LEN/EDF guidelines, a significant number do not follow them. Also, the large variation in diagnosis and treatment strengthens the need to re-evaluate, update and standardize guidelines on the diagnosis and management of CU in children.