Gb3-Coated Bovine Milk Exosomes as a Practical Neutralizer for Shiga Toxin

Shiga toxin (Stx) is associated with foodborne infections of some Shigella spp. and Shiga toxin-producing Escherichia coli (STEC), leading to life-threatening hemolytic uremic syndrome (HUS). Target-specific therapeutics against HUS are currently unavailable in clinical practice. Herein, we reported the construction and in vitro characterization of Gb3-coated bovine milk exosomes (Gb3-mExo) as a multivalent Shiga toxin neutralizer, utilizing the natural advantages of milk exosomes (mExo) in drug delivery and multivalent interactions between Stx and its receptor Gb3. Gb3-mExo constructs were achieved by conjugating mExo with the Gb3 derivatives containing stearic acid-derived lipid tail, which was prepared through an efficient chemoenzymatic approach. The constructs were able to potently neutralize the binding of the B subunit of Stx2 (Stx2B) to receptor Gb3 immobilized on the plate or expressed on model cells. General safety of the constructs was evidenced by the cytotoxicity analysis and hemolysis assay. In addition to the excellent stability under conventional storage and handling conditions, the construct can also retain most of its neutralization potency under gastrointestinal pH extremes, showing the potential for oral administration. Considering the natural availability and excellent biocompatibility of mExo, Gb3-mExo conjugates should prove to be a practical prophylactic and therapeutic for the Shiga toxin-related infections.