Am80-lipid nanoparticles serve as an enteric mucosal adjuvant following parenteral immunization with inactivated polio vaccine

Enteric pathogens are a major contributor to the global disease burden, necessitating vaccines capable of inducing robust gastrointestinal mucosal immunity. Achieving this response is especially challenging with inactivated or subunit vaccines, which lack the ability of live-attenuated formulations to mimic the natural infection process needed to induce strong intestinal mucosal immunity. Specifically, the inactivated polio vaccine (IPV), administered parenterally, elicits strong systemic immunity but fails to induce the mucosal IgA responses required to fully block poliovirus transmission, a critical step toward complete eradication. To address this limitation, we developed a clinically translatable and scalable nanoparticle-based intestinal mucosal adjuvant by encapsulating Am80, a small hydrophobic molecule known to promote intestinal mucosal immunity, within nanoparticles (NPs) designed for lymph node delivery, without requiring antigen modification, encapsulation, or adsorption. Encapsulation in NPs eliminated the need for the use of organic solvents, reduced toxicity, and prevented degradation, while lipid nanoparticles (Am80-LNPs) were engineered for sustained release over 3 to 5 days with high encapsulation efficiency (78 ± 9%). Cy5-labeled Am80-LNPs localized to draining lymph nodes within 6 hours and were retained for up to 72 hours. Coadministration of Am80-LNPs with the licensed IPV-2 in a Wistar rat model significantly boosted IPV-2–specific fecal IgA by 20-fold compared to IPV-2 alone and threefold over free Am80. These findings demonstrate that Am80-LNPs significantly enhance IPV-2–specific mucosal immunity in vivo and suggest their potential as a potent mucosal adjuvant against other enteric pathogens.