Background/purpose: Fetal gene replacement is a novel, potential therapy for antenatally diagnosed monogenic disorders. The purpose of this study was to evaluate in vivo techniques of lentiviral (LV) vector-mediated gene transfer to the tracheobronchial tree in a rabbit model of fetal gene therapy.
Methods: Via triple plasmid transfection, vesicular stomatitis virus-G-pseudotyped LV vector containing green fluorescent protein (GFP) reporter gene under the control of a cytomegalovirus promoter was constructed. In vivo gene transfer of 5 x 10(6) LV particles to fetuses of time-mated NZW rabbits (term = 31 days) was attempted using 2 techniques: (1) direct amniotic injection (gestation = 24-26 days) and (2) direct tracheal injection (gestation = 26 days). Injected fetuses and saline-injected littermate controls were delivered and killed on gestational day 30. Fetal and maternal tissues were analyzed.
Results: Both in vivo techniques produced gene transfer to fetal tissues (trachea, lung, liver, intestine), including those of some controls. In one prep, GFP DNA was identified in maternal lung.
Conclusions: Lentiviral vector-mediated GFP gene transfer to fetal rabbit tracheobronchial epithelium occurs within 4 days of transfection by both amniotic injection or direct fetal tracheal injection. This in vivo model confirms bioavailability of vector through amniotic fluid with some cross-infection of adjacent fetuses. Vector access to fetal tissues appears to be by both luminal and hematogenous routes. Transplacental gene transfer from fetus to mother may occur in this model.