PcrV in an intranasal adjuvanted tobacco mosaic virus conjugate vaccine mediates protection from Pseudomonas aeruginosa via an early Th1/Th17 skewed localized and systemic immune response.

Multi-drug-resistant Pseudomonas aeruginosa (PA) infections are a growing problem for at-risk populations, causing thousands of deaths per year, and novel therapies to treat or prevent severe PA infection are desperately needed. We developed a novel intranasal (IN) protein subunit vaccine using tobacco mosaic virus (TMV) as a vaccine delivery platform. Recombinant PcrV (rPcrV) was covalently linked to TMV and delivered IN with the adjuvant curdlan (TMV-PcrV+c). IN delivery of TMV-PcrV+c elicited significantly higher anti-PcrV antibody titers than unadjuvanted TMV-PcrV and rPcrV with or without adjuvant, and it provided significantly greater protection from lethal pneumonic infection with PA compared to all other groups. The protective vaccine formulation elicited anti-PcrV IgA in the lungs, while anti-PcrV IgG1 in the serum was associated with survival after infection. Following infection, TMV-PcrV+c immunization was associated with early IL-17 and IFN-γ secretion in the lungs and later IL-17 secretion in the spleen. This corresponded with a rapid, but transient recruitment of neutrophils to the lungs of vaccinated mice compared to unvaccinated controls, which was followed by an increase in the number of lung macrophages. This is indicative of a Th1/Th17 response mediating localized and systemic inflammation to clear the PA infection while limiting host-derived tissue damage, ultimately enhancing protection. As a vaccine antigen, PcrV did not confer complete protection, so we evaluated OprF and OprI as part of a multivalent vaccine. However, these additional antigens did not enhance protective efficacy despite generating high antibody titers. Overall, TMV-PcrV+c is a promising vaccine candidate that elicits specific antibodies, localized IFN-γ secretion and IL-17 secretion both locally and systemically after PA challenge, phagocyte recruitment to the infection site, and protection against a lethal dose of PA in a pneumonic disease model.