Tu104 - Dysregulations in L-phenylalanine Metabolism Facilitate Pro-inflammatory th2 Phenotype in Severe Allergy

Abstract Text: Changes in T cell metabolism guide and determine their fate. However, metabolism and metabolic reprogramming of CD4+T cells in allergic diseases remains poorly understood. Hence, we performed metabolomics of circulating memory CD4+Teff and Treg cells from healthy subjects which revealed significant enrichment in amino-acid and L-phenylalanine (Phe) metabolism related pathways. Consequently, we studied effect of Phe on CD4+T cell energy metabolism and observed that Phe significantly enhanced total and memory CD4+T cell glycolysis while limiting OXPHOS. Phe also limited memory CD4+T cell proliferation via an Interleukin-4-induced-1 oxidase (IL4I1)-dependent mechanism which was confirmed using siRNA experiments. Next, we studied Phe induced changes in Th2 and Treg cell energy metabolism, using recently developed Single Cell ENergetIc metabolism by profilIng Translation inhibition (SCENITH), and observed a significant increase in Th2 cell glycolytic capacity coupled with a decrease in mitochondrial dependence. In in vitro differentiated Th2 cells, Phe limited their proliferation and transcription of critical type 2 factors such as mTOR, IL-4, IL-5, and IL-13. Additionally, Phe inhibited phosphorylation of mTOR and expression of CD161, a documented pathogenic Th2a marker. Metabolomics and ex vivo assessment of CD4+Teff cells and serum of allergic patients revealed significantly lower intracellular abundance of Phe in circulating memory CD4+Teff cells of a subset of severe allergic patients, elevated serum Phe concentration, and a significant negative correlation between LAT1, an important Phe transporter, and serum Phe. Altogether, these data highlight that Phe regulates Th2 cell metabolism and development of pathogenic Th2 cells and this mechanism is impaired in severe allergy.