Optimizing human Treg immunotherapy by Treg subset selection and E-selectin ligand expression

While human Tregs hold immense promise for immunotherapy, their biologic variability poses challenges for clinical use. Here, we examined clinically-relevant activities of defined subsets of freshly-isolated and culture-expanded human PBMC-derived Tregs. Unlike highly suppressive but plastic memory Tregs (memTreg), naïve Tregs (nvTreg) exhibited the greatest proliferation, suppressive capacity after stimulation, and Treg lineage fidelity. Yet, unlike memTregs, nvTregs lack Fucosyltransferase VII and display low sLe^X expression, with concomitant poor homing capacity. In vitro nvTreg expansion augmented their suppressive function, but did not alter the nvTreg sLe^X-l°w glycome. However, exofucosylation of the nvTreg surface yielded high sLe^X expression, promoting endothelial adhesion and enhanced inhibition of xenogeneic aGVHD. These data indicate that the immature Treg glycome is under unique regulation and that adult PBMCs can be an ideal source of autologous-derived therapeutic Tregs, provided that subset selection and glycan engineering are engaged to optimize both their immunomodulation and tropism for inflammatory sites.