Lentiviral vector gene transfer into fetal rhesus monkeys (Macaca mulatta): Lung-targeting approaches

We previously reported the efficiency of gene transfer in fetal monkeys using retroviral vectors and an intraperitoneal (IP) approach. Here, we explored intrapulmonary administration to determine whether gene transfer can be limited to the developing lung. The HIV-1-derived lentiviral vector (VSV-G pseudotyped; 1 × 10⁷ infectious particles/fetus), using the enhanced green fluorescent protein (EGFP) as a reporter, was directly injected into fetal lung with ultrasound guidance (n = 4; 55 or 70 days gestation; term 165 ± 10 days). Fetuses were monitored sonographically, fetal/maternal blood samples collected during gestation, and four of four healthy newborns were delivered at term. All lung lobes were positive for the transgene (≤ 1%) when assessed by PCR, and transgene expression was observed by direct fluorescence microscopy and flow cytometry. The results of this study show the following: (1) successful gene transfer in fetal monkeys using an intrapulmonary approach; (2) less transduction of non-pulmonary tissues with gene transfer at 70 days gestation compared with 55 days gestation or use of an IP approach; (3) that the pulmonary epithelium was EGFP-positive by immunohistochemistry; and (4) no evidence of transplacental transport of vector sequences or antibody responses in the dams. The results of these investigations indicate the efficiency of fetal gene transfer by intrapulmonary delivery, and emphasize the importance of the fetal monkey as a preclinical model system for exploring in utero genetic treatment strategies for pulmonary disorders.