(560g) In Vivo Evaluation of AAV-Mediated Gene Transfer in Airways of Mice With Acute Or Chronic Respiratory Infection

Individuals affected by cystic fibrosis are atypically susceptible to bacteria that can colonize the lung indefinitely. These infections are not initially fatal, but their chronic nature results in prolonged inflammatory responses that can lead to serious complications, permanent damage, and eventual death. Gene therapies for cystic fibrosis are a promising treatment for the disease, yet little research has been done to evaluate gene transfer in the context of a chronic inflammatory state of the airway. In this study, two models were developed to evaluate AAV-mediated gene transfer in such environments. The bacterium Bordetella bronchiseptica RB50 was used to establish a chronic, but non-lethal, respiratory infection in C57BL/6 mice. An inoculum of ~10⁵ CFUs allowed this bacterium to persist in the upper and lower respiratory tracts for at least 16 days and decreased gene expression by almost 3-fold when compared to uninfected controls (average nasal cavity luminescence 1.98x10⁸ vs. 7.09x10⁷ photons/sec, p-value < 0.01). In another model, Pseudomonas aeruginosa PAO1 was used to infect surfactant protein D (SP-D) knockout mice. With an inoculum of 10⁵-10⁶ CFUs, the bacteria persisted for only two days in the nasal cavity but caused a similar reduction in gene expression of approximately 2.5-fold (average nasal cavity luminescence 1.98x10⁸ vs. 7.78x10⁷ photons/sec, p-value < 0.05) at day 7 post-infection when compared to uninfected controls. These results confirm that on-going or nearly resolved infections in the respiratory tract decrease efficiencies of AAV-mediated gene transfer in the airway.