Engineered bacteria as an orally administered anti-viral treatment and immunization system.

The emergence of new viral pathogens necessitates innovative antiviral therapies and vaccines. Traditional approaches, such as monoclonal antibodies and vaccines, are often hindered by resistance, limited effectiveness, and high costs. Here, we develop an engineered probiotic-based antiviral platform using Nissle 1917 (EcN), capable of providing both mucosal and systemic immunity via oral administration. EcN was engineered to display anti-spike nanobodies or express the Spike-Receptor Binding Domain on its surface. Our findings reveal that EcN with nanobodies effectively inhibits the interaction between spike protein-expressing pseudoviruses and the ACE2 receptor. Furthermore, we observed the translocation of nanobodies to distant organs, facilitated by outer membrane vesicles (OMVs). The oral administration of EcN expressing spike proteins induced a robust immune response characterized by the production of both IgG and IgA, antibodies that blocked the pseudovirus-ACE2 interaction. While SARS-CoV-2 served as a model, this versatile probiotic platform holds potential for developing customizable biotherapeutics against a wide range of emerging pathogens such as influenza virus or respiratory syncytial virus (RSV) by engineering EcN to express viral surface protein or neutralizing nanobodies demonstrating its versatility as a next-generation mucosal vaccine strategy.