Because tacrolimus (Tac) has a narrow therapeutic index and highly inter- and intra-individual variable pharmacokinetic (PK) characteristics, monitoring of drug exposure is recommended, but limited data are available on the kinetics of Tac in paediatric renal transplant recipients, especially of limited sampling strategies. To investigate the correlation between Tac trough level (TL) and the 0-12 h area under the curve (AUC), and the value of abbreviated AUC monitoring, we evaluated 12 h PK profiles in 27 children at least 1 year after transplantation. There was a significant discrepancy between Tac TLs and 0-12 h AUC (r = 0.60). Every time point, different from C(0), gave a better prediction for the drug exposure, with C(4) and C(6) as best predictors (r = 0.93 and r = 0.92, respectively). The 0-12 h AUC was estimated with great precision by the use of a two- or three-point sampling strategy, and the latter is more time-point independent. In paediatric renal transplant recipients on Tac maintenance therapy, whose condition is stable, Tac TL is not a reliable tool for the estimation of drug exposure. Abbreviated monitoring, especially at three points in time, give reliable predictions of the complete 0-12 h AUC. We suggest a 0-12 h AUC of around 150 ng x h/ml for stable paediatric renal transplant recipients 1 year after transplantation and around 100 ng x h/ml in the following years. Target AUC values should be further established for paediatric transplant recipients according to the time after transplantation.

Background: Hematochezia is a frequent symptom in early infancy. However, it occurs very rarely within the immediate neonatal period, and its occurrence before any oral intake is particularly rare. Because of the "congenital" presentation of hematochezia in our patient, we initially considered our case to be a non-classical, potentially severe type of food protein-induced allergic proctocolitis. This diagnosis needs to be confirmed by an abnormal oral challenge test once the hematochezia has disappeared. If such a challenge cannot demonstrate an allergic origin, then the etiology of the hematochezia could be a neonatal transient eosinophilic colitis. Only two similar cases have been described so far. Case presentation: We report the case of a black baby boy of African origin born at 36 weeks 5 days of gestational age who presented with massive hematochezia immediately after birth. A rectosigmoidoscopy revealed a severe inflammation associated with diffuse eosinophilic infiltration on biopsy. His clinical outcome was favorable after introduction of an amino acid formula diet. We initially considered our case to be a nonclassical, potentially severe type of food protein-induced allergic proctocolitis but reintroduction of standard formula milk at the age of 3 months was successful. So, our patient is the first newborn in Europe who fits the diagnosis of "neonatal transient eosinophilic colitis." Conclusions: We discuss the possible etiology of "congenital" eosinophilic inflammation of the distal colon and conclude that hematochezia in well-looking neonates, in the absence of negative challenge tests later on, is more likely to be a neonatal transient eosinophilic colitis than an allergic proctocolitis. This new entity could be more frequent than previously thought, changing our medical care strategies for this kind of neonatal symptom.

Understanding the underlying mechanisms behind IgE-mediated cow’s milk allergy (IgE-CMA) is imperative for the discovery of novel biomarkers and the design of innovative treatment and prevention strategies. Here, we report data on the gut microbiome, metabolome, and lipidome of 81 children affected by food allergies, including CMA and healthy controls. Moreover, we developed a mouse model that mimicked IgE CMA best, BALB/c mice sensitized with ß-lactoglobulin using cholera toxin. During sensitization, we observed multiple microbially derived metabolic alterations, most importantly bile acid and tryptophan metabolites, that preceded allergic inflammation, while this inflammation was reflected in a disturbed sphingomyelin and histamine metabolism. We endorsed the microbial origin of these metabolites by in vitro colonic digestions and confirmed the microbial dysbiosis in our patient cohort, which was accompanied by metabolic signatures of low-grade inflammation. Our results suggest that gut dysbiosis precedes allergic inflammation, opening new opportunities for future prevention and treatment strategies. Trial: NCT04249973.

Background: IgE-mediated cow’s milk allergy (IgE-CMA) is one of the first allergies to arise in early childhood and may result from exposure to various milk allergens, of which β-lactoglobulin (BLG) and casein are the most important. Understanding the underlying mechanisms behind IgE-CMA is imperative for the discovery of novel biomarkers and the design of innovative treatment and prevention strategies. Methods: We report a longitudinal in vivo murine model, in which 2 mice strains (BALB/c and C57Bl/6) were sensitized to BLG using either cholera toxin or an oil emulsion (n=6 per group). After sensitization, mice were challenged orally, their clinical signs monitored, antibody (IgE and IgG1) and cytokine levels (IL-4 and IFN-γ) measured, and fecal samples subjected to metabolomics. The results of the murine models were further supported by fecal microbiome-metabolome data from our population of IgE-CMA (n=24) and healthy (n=23) children (Trial: NCT04249973), on which polar metabolomics, lipidomics and 16S rRNA metasequencing were performed. In vitro gastrointestinal digestions and multi-omics corroborated the microbial origin of proposed metabolic changes. Results: During sensitization, we observed multiple microbially derived metabolic alterations, most importantly bile acid, energy and tryptophan metabolites, that preceded allergic inflammation. The latter was reflected in a disturbed sphingolipid metabolism. We confirmed microbial dysbiosis, and its causal effect on metabolic alterations in our patient cohort, which was accompanied by metabolic signatures of low-grade inflammation. Conclusion: Our results indicate that gut dysbiosis precedes allergic inflammation and nurtures a chronic low-grade inflammation in children on elimination diets, opening important new opportunities for future prevention and treatment strategies.

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