Therapeutic levels of alpha-1-antitrypsin following gene therapy with F/HN pseudotyped simian immunodeficiency virus.

Paul-Smith M, Gelinas JF, Pytel KM, Chan M, Meng C, Cammack L, Pringle IA, Inoue M, Hasegawa M, Hyde SC, Gill DR, Alton EW, Griesenbach U

The British Society of Gene Therapy Annual Conference, Glasgow, 2015

A protease/anti-protease imbalance is a characteristic feature of inflammatory lung diseases such as cystic fibrosis (CF) and COPD. However, alpha-1-antitrypsin (AAT) enzyme replace- ment therapy (ERT) trials have not shown conclusive evidence of therapeutic benefit. Here, we assessed whether transduction of murine lungs with a pseudotyped SIV vector, rSIV.F/HN-hCEF-AAT, generates therapeutic levels of AAT.

Mice were transduced with rSIV.F/HN-hCEF-AAT (1.4e8 TU/mouse) by nasal instillation and culled 10 days post-trans- duction. AAT levels in lung homogenate and epithelial lining fluid (ELF) were 3 logs above controls (p < 0.05), and hAAT concentration in ELF was 92–28lg/ml, similar to the thera- peutic AAT level in ELF of 70lg/ml. For comparison trans- fection of mouse lung with cationic lipid GL67A complexed to hCEFI-AAT only led to 0.4–0.1lg/ml AAT in ELF. A neutrophil elastase (NE) activity assay showed that the recombinant AAT successfully neutralised NE activity (p < 0.05). In a separate experiment, mice were treated with rSIV.F/HN-hCEF-AAT (2e7 TU/mouse).

Quantification of AAT showed that expression was stable for 365 days. We also demonstrate for the first time that rSIV.F/HN lung transduction generates significant (p < 0.05) levels of hAAT protein in serum.
AAT enzyme replacement therapy is currently being assessed for the treatment of a range of diseases, but shortage of human plasma-derived protein, as well as high costs, are limiting. In conclusion, rSIV.F/HN produces therapeutically relevant and long-lasting levels of AAT in murine lung. Additionally, AAT escapes from the lung into circulation, suggesting that gene therapy may help to overcome some of the current bottlenecks of ERT.