832. Radioscintigraphy of sec-R Directed CFTR Gene Transfer in CF Mice Following Intranasal Administration

Abstract

Previously, we have shown that compacted DNA targeted to the serpin enzyme complex receptor (sec-R) can deliver amounts of a human CFTR vector sufficient for partial correction of the chloride transport defect and NOS-2 downregulation in the CF knock out mouse nose. To examine the distribution of these compacted DNA particles in vivo following administration, we used radioscintigraphy imaging. We modified our DNA compacting agent (a polymer of poly-L-lysine, chemically conjugated to the C105Y sec-R targeting ligand) with radiolabeled I-125. Prior to dosing, 12 S489X/FABP-hCFTR were imaged by X-ray for proper anatomical alignment with radiograph images. Following complex formulation, 9 mice were dosed intranasally (IN) with 25 μg of sec-R targeted radiolabeled hCFTR DNA (specific activity 50 μCi each), while 3 control mice received administration of free I-125 (specific activity 50 μCi each). We used a small animal gamma scanner produced at Thomas Jefferson National Lab to analyze radio images at 2, 4, 24, and 48 hrs following nasal administration of the dose. At each time 3 animals were sacrificed, frozen and stored for subsequent sectioning. For each mouse, I-125 scintigraphic images, x-ray images, and autoradiographs were aligned and analyzed. Targeted delivery resulted in higher total retained activity than the carrier control at the assayed time points. Both test and control groups begin to exhibit thyroid uptake by 2 hrs. By 2 hrs, scintigraphic and autoradiographic data indicated high activities in the nasal and lower airways in animals that received the targeted complexes compared to controls. The highest observed activity was in thyroid, liver and bladder. Autoradiographic images correlated well with their corresponding in vivo scintigraphic images. For mice that received targeted complexes, strong signals were measured in both abdominal (stomach and liver) and bladder regions indicating possible ingestion during or aspiration following administration, as well as secretion into the bladder. This rapid clearance by 2 hrs was observed for all mice. Regional analysis showed significantly (p < 0.05) higher activities for the targeted delivery in nose, lung and liver compared with controls, 2 and 4 hrs post administration. By 24 hrs, activities in the upper airways (nasal region) and lungs were back to the background level, while activity in the thyroid remained significant at 24 and 48 hrs. The data indicate a rapid clearance of sec-R targeted compacted DNA (by 2 hrs), followed by the appearance of at least the labeled component of the complex (the ligand) in the thyroid and bladder by 4 hrs. Intranasal administration may also result in aspiration or ingestion of the targeted complexes. Alternatively, these complexes or their components may have access to and enter the circulation and accumulate in the liver.