Non-viral delivery of the porphobilinogen deaminase cDNA into a mouse model of acute intermittent porphyria.

Acute intermittent porphyria (AIP), an inborn error of metabolism, results from the deficient activity of the third enzyme in the heme biosynthetic pathway, porphobilinogen deaminase (PBGD). Clinical symptoms of this autosomal dominant hepatic porphyria include episodic acute attacks of abdominal pain, neuropathy, and psychiatric disturbances. Current therapy based on intravenous heme administration is palliative and there is no way to prevent the attacks. Thus, efforts are focused on methods to replace the deficient activity in the liver to prevent the acute attacks of this hepatic porphyria. Here we explore the efficiency of a non-viral gene delivery to obtain PBGD expression in the liver of AIP transgenic mice. Four vectors were evaluated: naked DNA and DNA complexed to liposomes, polyethylenimine (PEI), and PEI-galactose, using a luciferase construct as reporter gene. The vectors were administered intravenously or directly into the portal vein with transient blood flow blockage. After tail vein injection of the DNA complexes, the liposome vector had the highest luciferase expression in lung and less in liver. When injected into the portal vein, the naked DNA had considerably higher hepatic reporter gene expression; 100 microg of naked DNA had the highest hepatic luciferase expression 24h after portal vein injection. When these vectors were used to deliver the PBGD gene into the AIP mouse model no enhancement of the endogenous PBGD activity in liver was detectable, despite the presence of the PBGD-plasmids as verified by PCR. Thus, more efficient non-viral vectors are needed to express sufficient PBGD activity over the endogenous hepatic level (approximately 30% of normal) in this murine system.