Figure 4.

Transduction efficiency of rAAV2/6.2 in murine airway epithelium after fetal intratracheal injection. (a,b) Quantification of the percentage of transduced cells in conducting airways and alveoli after fetal i.t. injection of low (2 × 10⁹ GC/fetus) and high titer (3 × 10¹⁰ GC/fetus) rAAV2/6.2, respectively. Transduction efficiency of conducting airways was determined by counting the total number of β-gal positive cells in the large airways (trachea and mainstem bronchi) relative to the total number of epithelial cells present on three cross-sections spaced 200 µm apart at ×20 magnification. Alveolar cell transduction was estimated in three cross-sections spaced 200 µm apart using a 400 × 400 µm counting frame at ×20 magnification to systematically sample the lung parenchyma of the entire lung cross-section. To determine the percentage of β-gal positive alveolar cells, the ratio of the average number of β-gal positive cells to the average cell density was made per counting frame. Transduction levels are compared between 1 and 4 weeks after vector administration. (c) Transduction efficiency of the conducting airways was further subdivided and quantified in the trachea, bronchi, and bronchioles, respectively, at 1 and 4 weeks after fetal i.t. injection of high-titer rAAV2/6.2. Mean ± SD, analysis of variance, Student's t-test, *P < 0.05.