Live auxotrophic vaccines contribute to protection against chronic lung infections caused by Pseudomonas aeruginosa in C57BL/6 mice.

Pseudomonas aeruginosa causes severe, often multidrug-resistant lung infections, especially in individuals with cystic fibrosis, highlighting vaccination as a promising preventive approach. This study evaluated intranasal and intradermal immunization with a D-glutamate auxotrophic P. aeruginosa strain (PAO1 ΔmurI) and two of its derivatives, one with additional D-alanine auxotrophy and another exhibiting reduced lipopolysaccharide-associated toxicity, in C57BL/6 mice using both acute and chronic lung infection models. Mice received two or three doses at various intervals, and safety was assessed through clinical and weight monitoring. A high-dose, 2-administration intranasal regimen protected against acute infection but induced transient weight loss, while a lower-dose, 3-administration regimen minimized toxicity. Immunized mice exhibited robust IL-17A production and increased IFN-γ responses. Following challenge with mucoid strains, vaccinated mice showed reduced lung bacterial loads, suggesting a partial protection against chronic infection. These findings support the potential of auxotrophic live vaccines to mitigate disease severity in patients with cystic fibrosis.