689. Protection Against Pulmonary Infection with P. aeruginosa Following Immunization with an Adenovirus Vector Expressing a P. aeruginosa OprF Epitope

Abstract

Top of pageAbstract Pseudomonas aeruginosa is an important opportunistic pathogen that can cause severe infections of the respiratory tract, particularly in immunocompromised patients and individuals with cystic fibrosis (CF). In the context that infections with P. aeruginosa remain the major cause for the high morbidity and mortality in CF, a vaccine against P. aeruginosa would be very useful in this disorder. The outer membrane protein F (OprF) of P. aeruginosa is currently being investigated as a promising vaccine candidate and various immunogenic and protective epitopes within the OprF protein have been identified. In the context that adenovirus (Ad) vectors have strong immunogenic potential, and thus are useful as adjuvants for genetic vaccines. The present study evaluates the immunogenic and protective properties of a novel Ad vector expressing a 14-mer epitope of the P. aeruginosa OprF protein (Epi8) in the Ad hexon protein (AdZ.Epi8). The potential of AdZ.Epi8 to induce an anti-P. aeruginosa humoral response was evaluated first. Immunization of C57Bl/6 mice with AdZ.Epi8 at a dose of 109 and 1010 particle units (pu) resulted in detectable serum anti-P. aeruginosa IgG and IgM antibodies following intramuscular, subcutaneous and intratracheal administration. No anti-P. aeruginosa were detected in naive mice or mice infected with a control wild-type capsid Ad vector (AdZ). To evaluate cellular immune responses following immunization with AdZ.Epi8, spleen CD4 and CD8 T cells of immunized mice were evaluated by intracellular cytokine staining for the Epi8-specific interferon (INF) γ and IL-4 response 12 days following subcutaneous immunization with AdZ.Epi8 or AdZ at a dose of 1010 pu. Mice immunized with AdZ.Epi8 demonstrated an increased number of Epi8-specific INF-γ positive CD4 (18%) and CD8 (36%) T cells, compared to AdZ-immunized or unimmunized mice (10% CD4, 13% CD8, 5% CD4, 6% CD8, respectively). No significant Epi8-specific staining was detected for IL-4 in CD4 or CD8 cells. To evaluate the protective effect of immunization with AdZ.Epi8 against pulmonary infection with P. aeruginosa, mice were challenged with a lethal dose (8×105 colony-forming units) of agar-encapsulated P. aeruginosa (strain PAO1) 5 wk following subcutaneous immunization. Unimmunized mice or mice infected with AdZ died within the 1st 3 days, whereas 80% of the mice immunized with AdZ.Epi8 survived more than 3 wk. The data indicates that incorporation of an epitope of the P. aeruginosa OprF protein into an Ad vector can induce cellular and humoral anti-P. aeruginosa immune responses and can protect against pulmonary infections with P. aeruginosa. We conclude that Ad vectors expressing P. aeruginosa epitopes may serve as an efficient vaccine carrier and may thus be useful in the development of a vaccine to prevent pulmonary infections caused by P. aeruginosa.