Siderophore-based targeted antibody recruitment for promoting immune responses towards Gram-negative pathogens.

Antibody-recruiting molecules (ARMs) have emerged as a promising strategy for enhancing immune responses against pathogens and cancer cells. In this study, we developed a novel class of antibacterial ARMs utilizing siderophores, small iron-chelating compounds, as targeting motifs. Siderophores naturally exhibit high specificity for bacterial pathogens due to their role in iron acquisition, making them ideal candidates for selective targeting. We identified a potent ARM, GNP3, comprising MECAM, a siderophore mimetic, and 2,4-dinitrophenyl (DNP), a motif recognized by endogenous antibodies, connected via a flexible linker. GNP3 binds simultaneously to both anti-DNP antibody and the siderophore receptor, FepA, facilitating the targeted deposition of antibodies on the surface of FepA-expressing bacterial cells, such as Escherichia coli and Pseudomonas aeruginosa. This GNP3-induced opsonization promoted robust immune responses, including complement-dependent cytotoxicity (CDC) in the presence of serum and macrophage-mediated phagocytosis. Moreover, GNP3 effectively triggered CDC activity against serum-resistant uropathogenic E. coli. The results suggest that siderophore-based ARMs, by harnessing the immune defense system, represent a promising complementary approach to traditional antibiotics for overcoming recalcitrant bacterial infections.