167. Development of Non-Viral Gene Delivery Systems Deliverable Via Aerosol and Displaying Broad-Spectrum Antibacterial Activity for Cystic Fibrosis Gene Therapy
Authors: Tony Le Gall, Angélique Mottais, Mathieu Berchel, Pierre Lehn, Paul-Alain Jaffres, Tristan Montier
Journal: Molecular Therapy (2015)

In cystic fibrosis (CF) patients, bronchopulmonar infections are due to various micro-organisms including Gram(+) (e.g. Staphylococcus aureus) and Gram(-) (e.g. Pseudomonas aeruginosa) bacteria. These can alter CF gene transfer, especially by impairing the DNA to be delivered and the epithelial cells to be transfected. Gene delivery vectors can show some antibacterial activity, an additive property that could be useful for transfecting cells in spite of the presence of bacteria. To date, most of the vectors that we have evaluated can demonstrate strong antibacterial activity against Gram(+) bacteria but little or no against Gram(-) bacteria. The preferred method to target the respiratory epithelium being the nebulization, this project aims at identifying formulation(s) deliverable as an aerosol that might display, at the same time, gene delivery ability together with broad-spectrum antibacterial activity. Several original combinations of (1) one of our cationic lipids with (2) a benchmark stable complex of silver are performed at different molar ratios before being tested under various in vitro experimental conditions. First, the antibacterial activity is evaluated using co-cultures of a S. aureus strain and a P. aeruginosa strain. Second, the transfection efficiency and the cytotoxicity are determined following direct deposition into the culture medium of human bronchial epithelial cells. This allows identifying combination(s) showing good activities. Finally, the best formulation is tested by nebulization, transfection and antibacterial activities being determined in a single assay. The combination of a cationic lipid with a silver salt mixed at 1/1 molar ratio can demonstrate some synergistic biocide effects towards a co-culture of two bacterial species of different Gram. This combination exhibits little or no cytotoxic effects and some ability to transfect cells as efficiently as the cationic lipid used alone. Nebulization of this formulation yields results compatible with those obtained by direct deposition i.e. transfection and antibacterial activities can be obtained at the same time. It may be useful to combine a cationic lipid with a silver salt with the aim of cumulating their respective bio-properties. This study allows verifying this assumption showing that an equimolar combination of such two compounds (1) can be simultaneously active against Gram(+) and Gram(-) bacteria that frequently contaminate the lungs of CF patients, (2) induces no noticeable toxicity towards bronchial epithelial cells, and (3) retains antibacterial and transfection activities even when nebulized. Contrary to a gene delivery system ineffective against bacteria, such a combination might thus participate in the eradication of contaminating bacteria while efficiently transfecting bronchial epithelial cells, thereby reducing the stress experienced by these cells and promoting the gene medicine expression.