Complete correction of hyperbilirubinemia in the Gunn rat model of Crigler-Najjar syndrome type I following transient in vivo adenovirus-mediated expression of human bilirubin UDP-glucuronosyltransferase.

Recombinant adenoviral vectors are useful for the in vivo expression of genes in hepatocytes. Adenoviral vectors deleted in E1a, E1b, and E3b were constructed and used to study in vivo expression of the major human bilirubin UDP-glucuronosyltransferase isoform (HUG Br1) under the transcriptional control of the cytomegalovirus (CMV) immediate-early promoter-enhancer (H5.010CMV hugBr1). As a control, a recombinant adenoviral vector containing the beta-galactosidase reporter gene driven by the CMV promoter-enhancer was employed (H5. 010CMVlacZ). Recombinant virus was expanded following exposure to E1 transcomplementing (293) cells and concentrated to t titer of approximately 10(13) particles per milliliter. A rat model for Crigler-Najjar syndrome type I deficient in HUG Br1 (ie the Gunn rat) was injected with 5 X 10(9) plaque-forming units (p.f.u.) via the portal vein of either H5.010CMVhugBr1 or H5. 010CMVlacZ. Rats from each set were killed at 3 days, 11 days and 22 days after infusion. Liver total cellular DNA, RNA and protein were analyzed for the transgene and the transgene product at the specified times. Analysis of livers by Southern blot hybridization demonstrates sequence-specific hybridization to adenoviral vector DNA, and Northern blot hybridization demonstrates sequence-specific hybridization to transgene-derived RNA. DNA levels peak at approximately one copy number at 3 days and decline over 22 days. RNA and Western blot analyses demonstrate overexpression of message and protein at 3 days, declining over 22 days. In virto functional assay for bilirubin glucuronosyl-transferase activity demonstrates overexpression of bilirubin UDP-glucurosyltransferase function. In situ hybridization of frozen sections to detect expressed mRNA using beta-galactosidasederived 35S-labeled riboprobes demonstrates adenovirus-derived transgene expression in hepatocytes. Significant drops in serum bilirubin levels were noted following expression of HUG Br1 but not beta-galactosidase. The drop in serum bilirubin correlates with the appearance of bilirubin glucuronides in bile. In summary, recombinant adenoviral vectors were used to demonstrate in vivo complementation of the genetic defect in Gunn rat livers with the HUG Br1 cDNA leading to a resolution of hyperbilirubinemia lasting approximately 7 weeks. These studies suggest that delivery of the HUG Br1 cDNA might provide a reasonable therapeutic benefit for Crigler-Najjar syndrome type I patients, as safe and efficacious gene delivery systems are developed.