In vitro optimization of miniature bronchoscope lentiviral vector delivery for the small animal lung

Current gene therapy delivery protocols for small animal lungs typically utilize indirect dose delivery via the nasal airways, or bolus delivery directly into the trachea. Both methods can result in variable transduction throughout the lung, as well as between animals, and cannot be applied in a targeted manner. To minimize variability and improve lung coverage we previously developed and validated a method to visualize and dose gene vectors into pre-selected lobes of rat lungs using a mini-bronchoscope. Lentiviral (LV) vectors are known to be fragile and can be inactivated easily by temperature or the application of shear stresses. There are several ways that the bronchoscope could be configured to deliver the LV vector, and these could result in different amounts of functional LV vector being delivered to the lung. This study evaluated several methods of LV vector delivery through the bronchoscope, and how flow rates and LV vector stabilizing diluents impact LV vector delivery. NIH-3T3 cells were exposed to LV vector containing the green fluorescent protein (GFP) reporter gene using various bronchoscopic delivery techniques and the number of GFP-positive cells produced by each was quantified by flow cytometry. The results showed that directly drawing the LV vector into the bronchoscope tip resulted in 80-90% recovery of viable vector, and was also the simplest method of delivery. The fluid delivery rate and the use of stabilizing serum in the vector diluent had no effect on the viability of the LV vector delivered. These findings can be used to optimize LV vector dose delivery into individual lung lobes of small animal models.