Engineered Dendritic Cells Imprint Dual Gut-Homing Specificity on Human Tregs for Pan-Intestinal Immunotolerance.

Current therapeutic strategies for inflammatory bowel disease often rely on systemic immunosuppression or single-target biologics, which can lead to significant side effects or incomplete remission. To overcome this therapeutic hurdle, we recently proposed engineering dendritic cells (DCs) to de novo synthesize high concentrations of the active vitamin D (1,25[OH]2D) and A (retinoic acid or RA) because 1,25(OH)2D directly stimulates the expression of Foxp3 (the master regulator of CD4+ Tregs) and RA induces gut-homing receptor expression. In our previous studies, we engineered mouse DCs using a lentiviral vector to overexpress CYP27B1 (encoding 1α-hydroxylase) and ALDH1A2 (encoding RALDH2) to synthesize 1,25(OH)2D and RA, respectively. The engineered DCs stimulated CD4+Foxp3+ Tregs expressing CCR9 (a gut-homing receptor) both in vitro and in vivo. In addition, the engineered DCs robustly suppressed experimental colitis, a process that depended on CD4+Foxp3+ Tregs. In addition, the engineered DCs did not cause hypercalcemia, the major side effect associated with systemically high 1,25(OH)2D concentrations, suggesting a safety profile. Moreover, the engineered DCs upregulated tissue expression of CYP27B1 and ALDH1A2 genes for thirty days of the observational period. To evaluate the potential clinical translation of the engineered DCs, this study extended our previous animal studies to humans. Our data demonstrated that engineered human DCs, like their mouse counterparts, stimulated CCR9+CD4+Foxp3+ Tregs. Notably, our human data revealed that the engineered human DCs also stimulated α4β7+ and α4β7+CCR9+ CD4+Foxp3+ Tregs, a finding validated in vivo in mice. This finding is clinically significant because CCR9 mediates homing to the small intestine, while a4b7 targets both the small and large intestines, thereby offering "pan-intestinal" therapeutic coverage. Our human data thus further support the engineered DCs as a promising therapy for inflammatory bowel disease. Additionally, because CCR9 is a homing receptor for inflammation, the engineered DCs can potentially be a solution for a broad range of inflammatory diseases.