Towards human translation of lentiviral airway gene delivery for cystic fibrosis: A one-month CFTR and reporter gene study in marmosets

Gene therapy continues to be a promising contender for the treatment of cystic fibrosis (CF) airway disease. We have previously demonstrated that airway conditioning with lysophosphatidylcholine (LPC) followed by delivery of a HIV-1 based lentiviral vector (LV) functionally corrects the CF transmembrane conductance regulator (CFTR) defect in the nasal airways of CF mice. In our earlier pilot study we showed that our technique can transduce marmoset lungs acutely; this study extends that work to examine gene expression in this non-human primate (NHP) 1 month after gene vector treatment. A mixture of three separate HIV-1 VSV-G pseudotyped LV vectors containing the luciferase (Luc), LacZ and hCFTR transgenes was delivered into the trachea via a miniature bronchoscope. We examined whether a single-dose delivery of lentiviral vector after LPC conditioning could increase levels of transgene expression in the trachea and lungs compared to control (PBS) conditioning. At one month, bioluminescence was detected in vivo in the trachea of 3 of the 6 animals within the PBS control group, compared to 5 of the 6 LPC-treated animals. When examined ex vivo there was weak evidence that LPC improves tracheal Luc expression levels. In the lungs, bioluminescence was detected in vivo in 4 of the 6 PBS treated animals, compared to 5 of the 6 LPC treated animals; however, bioluminescence was present in all lungs when imaged ex vivo. LacZ expression was predominantly observed in the alveolar regions of the lung. hCFTR was detected by qPCR in the lungs of 5 of the 11 animals. Basal cells were successfully isolated and expanded from marmoset tracheas, but no LacZ positive colonies were detected. There was no evidence of an inflammatory response towards the LV vector at one month post-delivery, with cytokines remaining at baseline levels. In conclusion, we found weak evidence that LPC conditioning improved gene transduction in the trachea, but not in the marmoset lungs. We also highlight some of the challenges associated with translational lung gene therapy studies in NHPs.Nigel Farrow, Patricia Cmielewski, Juliette Delhove, Nathan Rout-Pitt, Lewis Vaughan, Tim Kuchel, Chris Christou, John Finnie, Matthew Smith, Emma Knight, Martin Donnelley and David Parson