Killed but metabolically active Pseudomonas aeruginosa-based vaccine induces protective humoral- and cell-mediated immunity against Pseudomonas aeruginosa pulmonary infections.

Pseudomonas aeruginosa (Pa) is a significant cause of morbidity and mortality, especially in cystic fibrosis patients. Its eradication is difficult due to a wide phenotypic adaptability and an increase of its resistance to antibiotics. After the failure of several recombinant vaccines which mainly triggered humoral response, live-attenuated vaccines received attention thanks to their ability to elicit a broad immunity with both humoral- and cell-mediated responses, essential to fight this pathogen. In this study, we developed an innovative and safer live-attenuated Pa vaccine based on a Killed But Metabolically Active (KBMA) attenuation method. KBMA Pa has been further rationally designed to overexpress beneficial effectors like the type 3 secretion system apparatus. We demonstrated that KBMA Pa elicits a high and broad humoral response in mice against several antigens of particular interest such as OprF and PcrV proteins. Moreover, we assessed cytokines in the serum of immunized mice and showed that KBMA Pa elicits Th1, Th2 and especially Th17 pathways of cell-mediated immune responses. Th17 pathway involvement was also confirmed after specific stimulation of helper T cells in immunized mice. Finally, we showed that this vaccine is safe and has a protective effect in a murine acute pulmonary infectious challenge. In conclusion, KBMA Pa is a new platform with high potential for the development of a vaccine against Pa.