Journal of Cystic Fibrosis, 3 S1 S29
The European Cystic Fibrosis Conference, Birmingham, 2004
In recent years, research into viral vectors for gene transfer to the airways has focussed on adenoassociated virus (AAV). Recombinant AAV demonstrates long term expression in a variety of tissues. This is thought to be due to a combination of the absence of any viral coding sequences that may otherwise induce an immune response to transduced cells, and the persistence of recombinant genomes episomally or integrated into chromosomal DNA. rAAV5 in particular has emerged as an interesting candidate for lung gene therapy by virtue of the fact that it binds to sialic acid, which is found on the apical surface of epithelial cells. We, and others, have shown that rAAV5 transduction in murine lungs persists for at least 32 weeks (9.69±3.17 RLU/mg protein) close to peak levels (week 4: 15.1±4.43 RLU/mg protein, ANOVA on log-transformed data: p=0.023). However it is likely that the life-long expression of a therapeutic gene needed for diseases such as cystic fibrosis will require repeat administration, since the target cells in the airways are terminally differentiated. A number of studies have attempted to establish the parameters affecting repeat administration of different AAV serotypes. Little research though has focussed on the repeat administration of rAAV5. Analysis of serum antibodies over our 32-week time course study shows that anti-AAV antibody levels in the blood reach peak levels by 4 weeks and remain high throughout the following 28 weeks. We will present data demonstrating that repeat administration of rAAV5 carrying different reporter genes, with an 8-week gap between instillations to the lung, leads to some Lux expression on second administration (0.23±0.06 RLU/mg protein, ANOVA on log-transformed data, p=0.016 compared with naÔve mice), but no detectable transduction with a third dose. We are also investigating the effect of an increased gap between administrations, and of a soluble CTLA4-expressing rAAV5 in separate repeat administration studies.