Inhalation of Nebulized Perfluorochemical Enhances Recombinant Adenovirus and Adeno-Associated Virus-Mediated Gene Expression in Lung Epithelium

Abstract

Use of perfluorochemical liquids during intratracheal vector administration enhances recombinant adenovirus and adeno-associated virus (AAV)-mediated lung epithelial gene expression. We hypothesized that inhalation of nebulized perfluorochemical vapor would also enhance epithelial gene expression after subsequent intratracheal vector administration. Freely breathing adult C57BL/6 mice were exposed for selected times to nebulized perflubron or sterile saline in a sealed Plexiglas chamber. Recombinant adenoviral vector was administered by transtracheal puncture at selected times afterward and mice were killed 3 days after vector administration to assess transgene expression. Mice tolerated the nebulized perflubron without obvious ill effects. Vector administration 6 hr after nebulized perflubron exposure resulted in an average 540% increase in gene expression in airway and alveolar epithelium, compared with that with vector alone or saline plus vector control ( p < 0.05). However, vector administration 1 hr, 1 day, or 3 days after perflubron exposure was not different from either nebulized saline with vector or vector alone and a 60-min exposure to nebulized perflubron is required. In parallel pilot studies in macaques, inhalation of nebulized perflubron enhanced recombinant AAV2/5 vector expression throughout the lung. Serial chest radiographs, bronchoalveolar lavages, and results of complete blood counts and serum biochemistries demonstrated no obvious adverse effects of nebulized perflubron. Further, one macaque receiving nebulized perflubron only was monitored for 1 year with no obvious adverse effects of exposure. These results demonstrate that inhalation of nebulized perflubron, a simple, clinically more feasible technique than intratracheal administration of liquid perflubron, safely enhances lung gene expression.

Effective viral-mediated lung gene therapy: is airway surface preparation necessary?

“…Due to these properties, PFC liquid is proposed to act as a carrier to enable more efficient distribution of vector particles throughout the airways. Delivery of PFC liquid to the airways also induces transient opening of tight junctions, providing vectors improved access to basolateral receptors [ 86 , 87 ]. Other hypothesised effects of PFC administration include displacement of airway surface mucins and fluid.…”

“…Inhalation of nebulised PFC vapour has also been explored as a simpler and more clinically appealing technique compared to liquid-based delivery. Nebulisation of PFC vapour similarly enhances AdV and AAV mediated gene expression in the airway epithelium of mice and macaques, respectively [ 87 ].…”

“…It is not metabolised by the kidneys or liver, and is eliminated by evaporation during exhalation or transpiration through the skin [ 85 ]. Non-human primates produced no obvious adverse effects from delivery of liquid or nebulised PFC to the airways [ 87 , 89 ]. PFC has also proven effective at increasing gene transfer among a range of animal species with various AdV and AAV-based vectors.…”

“…It is not apparent why this is the case, but more general concerns regarding the translatability of airway preparation approaches may have contributed. Furthermore, the mechanisms of PFC action are yet to be fully elucidated, particularly in the case of nebulised formulations, which offer the same gene-transfer improvements as the liquid delivery, but do not appear to increase tight-junction permeability [ 87 ].…”

Administration of Drugs/Gene Products to the Respiratory System: A Historical Perspective of the Use of Inert Liquids

“…Many studies have also demonstrated improvement in lung mechanics and oxygenation in research models of lung injury following administration of PFC liquids in nebulized or aerosolized forms ( Bleyl et al, 1999 ; Ragaller et al, 2001 ; Kandler et al, 2004 ; von der Hardt et al, 2004 ). As such, administration of nebulized perflubron improved resulting recombinant viral vector mediated gene expression ( Beckett et al, 2012 ). By adapting and optimizing PFC liquid strategies demonstrated to be beneficial for viral vector gene delivery, PFC liquids hold promise for enhanced airway delivery of CRISPR systems as therapeutic strategy for a myriad of respiratory disorders.…”