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Administration of lentiviral vector doses achieving high transduction efficiency is well tolerated in mice

U Griesenbach(1) G McLachlan(2) A Sinadinos(1) C Cheminay(3) J Ashour(3) C Meng(1) E Castells(4) R Dean(4) M A Viegas(4) A C Boyd(5) J C Davies(1,6) D R Gill(4) S C Hyde(4) N Strelkowa(7) E WFW Alton(1,6)

1:National Heart and Lung Institute, Imperial College London, London, UK; 2:The Roslin Institute, University of Edinburgh, Midlothian, UK; 3:Boehringer Ingelheim Pharmaceuticals, Inc., Ridgefield, CT, USA; 4:Radcliffe Department of Medicine, University of Oxford, Oxford, UK; 5:Centre for Genomic and Experimental Medicine, University of Edinburgh, Edinburgh, UK; 6:Royal Brompton Hospital, part of Guy's & St Thomas' NHS Foundation Trust, London, UK; 7:Boehringer Ingelheim Pharma GmbH & Co KG, Ingelheim am Rhein, Germany

We have developed rSIV.F/HN, a lentiviral vector pseudotyped with the F and HN proteins from Sendai virus, for cystic fibrosis gene therapy. We assessed whether acute toxicity occurred following administration of rSIV.F/HN into murine lungs at doses anticipated to transduce ~10% of airway epithelial cells.  

C57BL/6 mice received once-daily doses of rSIV.F/HN vector expressing EGFP (2x10⁸ transduction units (TU)/mouse) or diluent for 4 consecutive days via intranasal instillation (total 8x10⁸ TU/mouse). On days 2 or 7 after the last dose, mice were euthanised (18 of each sex/group/day). Body weight, blood (clinical pathology and cytokine analysis) and lung tissue (organ weight, histopathology, qRT-PCR and quantification of EGFP-expressing airway cells) were collected. 

There were no vector-related clinical observations or mortality. Increase in body weight 7 days after the last dose was lower (0.1 g, n=8) in vector-treated female mice (n=8) than in controls (0.8 g, n=9). A number of inflammatory cytokines (RANTES, MCP-1, TNFα) were modestly (maximum threefold) elevated or decreased (VEGF, MIP1α) at one and/or both of the time points. Microscopic examination of lung tissue 2 days after the last dose, indicated minimal-to-mild perivascular-to-peribronchovascular infiltrates of primarily mononuclear cells, which returned to minimal severity 7 days after the last dose. ~35% ± SD 5.7 of airway epithelial cells expressed EGFP and levels of vector-specific mRNA were more than 3 log orders higher than endogenous CFTR mRNA. 

These data demonstrate that rSIV.F/HN transduction of mouse lungs is well tolerated at doses that achieved significant transduction levels. 

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