Mucosal immunization with the lung Lactobacillus-derived amphiphilic exopolysaccharide adjuvanted recombinant vaccine improved protection against P. aeruginosa infection.

Respiratory infections caused by Pseudomonas aeruginosa are a major health problem globally. Current treatment for P. aeruginosa infections relies solely on antibiotics, but the rise of antibiotic-resistant strains necessitates an urgent need for a protective vaccine. Traditional parenteral vaccines, despite employing potent adjuvants aimed at serotype-dependent immunity, often fail to elicit the desired mucosal immune response. Thus, developing vaccines that target both localized mucosal and systemic immune responses represents a promising direction for future research on P. aeruginosa vaccination. In this study, we explored EPS301, the exopolysaccharide derived from the lung microbiota strain Lactobacillus plantarum WXD301, which exhibits excellent self-assembly properties, enabling the formation of homogeneous nanoparticles when encapsulating recombinant PcrV of P. aeruginosa, designated as EPS301@rPcrV. Notably, the EPS301 vector effectively enhanced antigen adhesion to the nasal and pulmonary mucosal tissues and prolonged antigen retention. Moreover, EPS301@rPcrV provided effective and sustained protection against P. aeruginosa pneumonia, surpassing the durability achieved with the "gold standard" cholera toxin adjuvant. The EPS301-adjuvanted vaccine formulation elicited robust mucosal IgA and Th17/γδ17 T cell responses, which exceeded those induced by the CTB-adjuvanted vaccination and were sustained for over 112 days. Additionally, Th 17 and γδ 17 resident memory T cells induced by EPS301@rPcrV were crucial for protection against P. aeruginosa challenge. Intriguingly, IL-17A knockout mice exhibited lower survival rates, impaired bacterial clearance ability, and exacerbated lung tissue damage upon EPS301 adjuvanted vaccination against P. aeruginosa-induced pneumonia, indicating an IL-17A-dependent protective mechanism. In conclusion, our findings provided direct evidence that EPS301@rPcrV mucosal vaccine is a promising candidate for future clinical application against P. aeruginosa-induced pulmonary infection.