Engineering of synthetic bacterium surface for glucan nanofilm assembly against invasive fungal infection

Invasive fungal infections induced by Candida species are becoming an urgent threat to global health. While a series of antifungal vaccines have been developed, their efficiency is frequently compromised by the failure of immune stimulation. In this study, a novel antifungal vaccine was constructed by assembling β-glucan with the Candida albicans antigen candidalysin on the surface of the genetically engineered Escherichia coli strain EcS. This co-assembly was mediated by the cell surface-exposed artificial glucan-binding protein CipC-mCherry-CipC, leading to the formation of the surface glucan nanofilm with the thickness of ~80 nm. Upon co-incubation with macrophages, the vaccine efficiently escapes from the lysosomes, leading to enhanced production of reactive oxygen species and macrophage maturation. After mouse immunization, the vaccine persists longer in lymph nodes longer than free candidalysin or the glucan-free complex, and induces higher levels of CD4⁺, CD8⁺, TNFα⁺CD4⁺ and IFNγ⁺CD4⁺ T cells in the spleen. In a murine model of invasive fungal infection, immunization with this vaccine remarkably increases the survival rate, reduces the kidney fungal burdens and attenuates inflammatory responses. This bioengineering strategy offers a potentially viable approach for developing co-assembled whole-cell vaccines and can be extended to leverage bacterial carriers for surface antigen display. The vaccine acts not only as antigens but also as adjuvants, thereby eliciting strong and specific protective immunity against invasive fungal infections.