The British Society of Gene Therapy Annual Conference, London, 2014
Alpha-1-antitrypsin (AAT) is an anti-protease that inhibits neutrophil elastase. Therefore, a gene therapy treatment strategy delivering alpha-1-antitrypsin to the lung could be beneficial in a number of diseases including cystic fibrosis, COPD and alpha-1-antitrypsin deficiency.
A preliminary analysis of sputum samples from stable patients with cystic fibrosis has suggested that in patients with poorer lung function (determined by FEV1 % predicted and lung clearance index) the concentration of both AAT and neutrophil elastase is higher. This fits with a picture of an ongoing inflammatory processes in the CF lung, suggesting that the endogenous AAT is insufficient to protect the lung from the effects of neutrophil elastase.
The UK Cystic Fibrosis Gene Therapy Consortium has developed non-viral and viral gene delivery strategies, which have been assessed in vivo using the secreted Gaussia luciferase reporter gene.
Nasal instillation of pCMV-GLux complexed to lipid GL67A led to expression of Gaussia luciferase detectable at 2 days in lung tissue homogenate (36042 RLU/mg protein in treated animals v. 18 RLU/mg protein in negative controls, p < 0.01) and bronco-alveolar lavage fluid (9088 RLU/ul in treated animals v. 138 RLU/ul in negative controls, p < 0.05). As anticipated, Gaussia lucifierase expression in lung tissue homogenate fell to close to background levels by 14 days post treatment.
Similar experiments are now ongoing to assess expression of alpha-1-antitrypsin following gene therapy in mice, using CpG-depleted plasmids constructs with enhanced duration of expression complexed with GL67A and a novel lentivirus pseudotyped with the F/HN proteins from Sendai virus.