A Novel Mucosal Vaccine for Pseudomonas aeruginosa Infection

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Project Summary Pseudomonas aeruginosa (PA) is an opportunistic pathogen that causes a diverse array of disease manifestations. It is a major cause of healthcare associated infections worldwide, chronic lung infection in patients with cystic fibrosis (CF), and burn wound infections. There is a high rate of antimicrobial resistance in PA, leading to significant morbidity and mortality from infection. The World Health Organization has classified multidrug resistant (MDR) PA as a priority 1 pathogen for research. As infections with MDR strains of PA have become commonplace, treatment options have become limited. We propose to develop a vaccine to prevent PA infection in high-risk individuals. Prior attempts to develop a PA vaccine have focused on protection from respiratory infection, most notably ventilator-associated pneumonia and lung infection in CF patients. These attempts have been unsuccessful despite the induction of detectable vaccine-specific antibody responses in immunized patients. We and others hypothesize that the parenteral immunization scheme and adjuvants used in these studies do not produce the full spectrum of balanced humoral and cellular immunity necessary for effective protection from PA in the respiratory tract. This can be overcome through direct immunization at the mucosal surface with an adjuvant that can induce Th17 immunity, as Th17 immunity has been shown to be a critical component for protection to PA. Furthermore, vaccines administered at mucosal surfaces have also been shown to generate protective systemic immune responses. We are developing a vaccine that can be administered mucosally, providing complete protection not only against respiratory infection with PA, but also against non-mucosal disease manifestations; thus, providing complete immunity to the pathogen. The vaccine will consist of a minimum of four virulence factors to provide broad protection against the large number of PA serotypes present in nature. In this application, we will evaluate PcrV, OprF, OprI, and Exotoxin A toxoid as vaccine targets. These antigens will be conjugated to Tobacco Mosaic Virus, which we have previously demonstrated to be an effective delivery platform for the mucosal delivery of subunit vaccine antigens. In a pilot study, we demonstrated that IN delivery of TMV-PcrV protected 66% of mice from lethal challenge with 10xLD50 of PA in an acute lung infection model, whereas all uninfected mice succumbed to infection. In the present study we will optimize vaccine immunogenicity for each of the four TMV conjugates, evaluating functional antibody and T cell responses following IN vaccination, and testing protective efficacy in an acute lung infection model of PA. We will then test the ability of a combined multivalent vaccine against five different strains of PA using both the lung infection model, and a foreign implant biofilm model. Using this we will establish proof of principle for our approach and develop a prototype vaccine to move into preclinical development in a subsequent R01 application.