358. Route of Administration of sec-R Targeted Compacted DNA Influences Both the Site of Expression and Host Immune Response to the Vector

Abstract

DNA can be condensed, using poly-L-lysine, under high salt conditions, into discrete unimolecular (with respect to DNA) particles, 12–30 nm in diameter. We have shown that modification of these complexes with a peptide ligand (C105Y) that binds the serpin enzyme complex receptor (sec-R) targets them to lung, liver and spleen after intravenous administration and to airway epithelial cells after intratracheal administration in mice. The receptor is present on the apical surface of airway epithelia in mice and humans. We tested the effect of different routes of administration, luminal or intravenous (IV), on host antibody response to vector and delivery of a secreted protein, Factor IX, into the blood. C57BL/6 mice (n = 10) received a transtracheal application of a 50 μl bolus of a 0.5 M NaCl solution containing 5 μg of sec-R targeted compacted pCMV FIX plasmid (codes for secretable human Factor IX driven by the CMV promoter). Control groups included animals that received 5 μg non-targeted compacted pCMV FIX in 0.5 M NaCl (n = 5), 0.5 M NaCl alone (n = 5), and 5 μg sec-R targeted pCMV FIX injected intravenously via the tail vein (n = 10). Blood was sampled on days 2, 10, and 28. Human Factor IX was detected only in the plasma of animals that received sec-R targeted complexes. The luminal application group achieving expression levels of 65–90 ng/ml plasma while the IV group achieved 59–145 ng/ml plasma. Expression persisted for 10 days but diminished by 28 days, which may be due in part to development of anti-Factor IX-antibodies. When the complexes were administered IV (n = 36), 19 of 36 immuno-competent mice dosed with sec-R targeted human Factor IX, following initial dosing with sec-R targeted lac Z complexes 3 weeks earlier, developed antibodies against the vector by 28 days, but the antibodies did not affect the efficacy of re-administration. Animals treated with saline alone or non-targeted complexes did not produce antibodies to targeted complexes. When luminal administration was used, no antibody response is observed even in animals that receive targeted complexes. In conclusion, compacted DNA, targeted to the sec-R, is effective in delivering genes in vivo following luminal or intravenous administration. The route of administration influences both the site of expression as well as the production of antibodies against the complex. Furthermore, luminal administration achieves levels of secreted protein expression and delivery to the blood comparable to what is achieved by the intravenous route.