Understanding the host immune response against Pseudomonas aeruginosa to develop novel therapeutics and vaccines

Pseudomonas aeruginosa is a Gram-negative opportunistic bacterium that causes a broad range of acute and chronic infections. The high adaptability and emergence of multidrug-resistant strains of this bacterium pose a significant threat to human health. Particularly, pneumonia caused by this pathogen is associated with high morbidity and mortality in immunocompromised patients. To prevent these infections, we aimed to develop novel vaccine strategies by characterizing the host immune response against P. aeruginosa. During respiratory infections, P. aeruginosa first contacts with epithelial cells along the respiratory tract. Using RNA-sequencing, we were able to characterize transcriptional changes of the epithelial cells in response to P. aeruginosa. We observed that epithelial cells differentially upregulate immediate early response genes, that are crucial to mediate downstream pro-inflammatory responses during P. aeruginosa infection. To validate our in vitro observations, we performed acute infection studies using a mouse model of pneumonia. We observed that P. aeruginosa challenged mice had lung edema, high level of proinflammatory cytokines and neutrophils in their lungs. To prevent acute pneumonia caused by P. aeruginosa, and develop a protective vaccine against this pathogen, we characterized vaccine-mediated immune responses using the whole-cell P. aeruginosa vaccine. We found that B cells and antigen-specific antibodies are required for protection against this bacterium. Based on this work, we developed a novel intranasal P. aeruginosa vaccine containing peptides from the ferripyoverdine receptor FpvA conjugated with the carrier protein KLH. The FpvA-KLH vaccine decreased bacterial burden and lung edema upon challenge. We observed that FpvA-KLH vaccinated mice induced Th17 type immune response, tissue-resident memory T cells, and significant antibody titers against P. aeruginosa. The antibodies elicited against this bacterium were able to mediate opsonophagocytic killing. Together, these findings establish a foundation for potential vaccine strategies and possible alternative therapeutics against this bacterium and illuminate a better understanding of the host responses elicited against P. aeruginosa