RENBP inhibition amplifies metabolic glycan labeling efficiency of antigen-presenting cells in vitro and in vivo

Metabolic glycoengineering of unnatural sugars provides a powerful tool to introduce unique chemical tags onto cell membrane for subsequent conjugation of cargos. However, the metabolic glycan labeling efficiency of antigen-presenting cells (APCs), the key mediators of adaptive immunity, is often low. Here, we report that APCs upregulate GlcNAc 2-epimerase (RENBP) and that RENBP inhibition leads to improved labeling efficiency of tetraacetyl-N-azidoacetylmannosamine (AAM) in APCs, including dendritic cells (1.2-fold), macrophages (1.3-fold), and B cells (1.4-fold) in vitro. RENBP inhibition can preferentially enhance AAM labeling efficiency in APCs than in non-APCs and selectively enhance the labeling efficiency of AAM over azido-galactosamine. We further demonstrate that RENBP inhibitors can improve AAM-mediated labeling of B cells and other APCs in vivo, with the largest enhancement for B cells (>3-fold) for 7 days. Our study uncovers a facile approach to improving metabolic glycan labeling of APCs, enabling the development of APC-targeted immunotherapies.