22. Post-Exposure Vaccination by Capsid-Modified AdC7 Vector Expressing Pseudomonas aeruginosa OprF in Chronic P. aeruginosa Lung Infection

Abstract

Chronic infections by Pseudomonas aeruginosa are a common problem in cystic fibrosis and other chronic lung diseases associated with bronchiectasis. With antimicrobial resistance of P. aeruginosa becoming more common, alternate prophylactic and therapeutic approaches are needed. Despite extensive efforts, a vaccine against P. aeruginosa is not yet available. A post-exposure vaccine that eliminates already established P. aeruginosa from the respiratory tract, could be useful in the management of chronic P. aeruginosa colonization. Replication-deficient adenoviral (Ad) vectors are an attractive platform for vaccines against respiratory pathogens. We have previously found that, in addition to circumvent pre-existing anti-human Ad immunity, a non-human primate-based AdC7 vector expressing outer membrane protein F (OprF) of P. aeruginosa (AdC7OprF) was more potent in inducing lung mucosal and protective immunity compared to a human Ad5-based vector. In addition, genetic modification of the AdC7 fiber to display an integrin-binding arginine-glycine-aspartic acid (RGD) sequence can further enhance mucosal protective immunogenicity of AdC7OprF. In this study we investigated if post-exposure vaccination by AdC7OprF. RGD can clear the already established P. aeruginosa in a mouse model. Intratracheal inoculation of P. aeruginosa (clinical strain RP73) encapsulated in agar beads (10^6 cfu/mouse) was used to establish persistent infection. Intranasal immunization of P. aeruginosa infected mice with AdC7OprF. RGD (10^10 pu/mouse) induced significantly high serum anti-OprF IgG antibodies as early as 1 week of immunization that further increased to higher levels after 2 week of immunization compared to AdC7Null or PBS inoculated mice (p<0.05; all comparisons). In addition to robust humoral response, immunization with AdC7OprF. RGD induced OprF-specific T-cell responses, as indicated by the higher secretion of IFN-γ or IL-4 from the OprF-stimulated cultured splenocytes compared to AdNull or PBS inoculated mice (p<0.05; all comparisons). Importantly, the AdC7OprF. RGD immunized mice showed significantly higher clearance of P. aeruginosa from the infected lungs after 1 week or 2 weeks of immunization (p<0.05; all comparisons). In fact, after 2 weeks of immunization, 50% of AdC7OprF. RGD immunized mice (3 out of 6) completely cleared the P. aeruginosa from the infected lungs. These data suggest that immunization with AdC7OprF. RGD induced robust humoral and cellular anti-P. aeruginosa immunity that could clear established pulmonary P. aeruginosa infections.