Critical assessment of lifelong phenotype correction in hyperbilirubinemic Gunn rats after retroviral mediated gene transfer

Abstract

Among inherited diseases of the liver, Crigler-Najjar type 1 disease (CN-1), which results from complete deficiency in bilirubin UDP-glucuronosyltransferase activity (B-UGT1), is an attractive target for gene therapy studies. Hyperbilirubinemic Gunn rats, a model of CN-1, were injected at 2 days of age with lentiviral or oncoretroviral vectors encoding the human B-UGT1. After injection, bilirubinemia was normalized for up to 95 weeks. Bilirubin conjugates were present in the bile, demonstrating liver transduction. PCR and enzyme activity analysis confirmed gene and phenotype correction in liver. We observed that when using a strong viral promoter, a complete correction was achieved with less than 5% of B-UGT1 copy per haploid genome and after a reconstitution of 12% B-UGT1 normal activity. Liver histology remained normal throughout the experiment and tissue distribution analysis revealed preferential hepatocyte transduction after systemic delivery. Finally, no adverse immune response occurred even after induction of nonspecific liver inflammation, suggesting immune ignorance to the therapeutic protein. Our present results document the lifelong safety of gene therapy for CN-1 with retroviral vectors. They offer a better delineation of liver gene correction level required to achieve complete correction of bilirubinemia and pave the way for future clinical application of gene therapy for inherited liver disorders.

Perinatal Gene Transfer to the Liver

“…In contrast to Seppen and colleagues, the vector was injected intravenously via the superior temporal vein and hepatocytes were observed to be the main source of expression. In this study, normalisation of bilirubin was achieved for up to at least 95 weeks [145]. The same group used an AAV8 vector to treat neonatal Gunn rats.…”

Sustained Reduction of Hyperbilirubinemia in Gunn Rats After Adeno-Associated Virus-Mediated Gene Transfer of Bilirubin UDP-Glucuronosyltransferase Isozyme 1A1 to Skeletal Muscle

“…However, given the mortality, morbidity, and cost of transplant procedures, there is high motivation to develop alternative approaches including gene therapy (Miranda and Bosma, 2009). A number of preclinical gene therapy studies in the Gunn rat, a natural mutant that has no UGT1A1 activity, have achieved correction in vivo by hepatic gene transfer of the UGT1A1 gene using various vectors, such as viral vectors based on retrovirus (Nguyen et al, 2007), lentivirus (van der Wegen et al, 2006;Schmitt et al, 2010), recombinant simian virus 40 (SV40) virus (Sauter et al, 2000), adenovirus (Askari et al, 1996;Toietta et al, 2005;Dimmock et al, 2011), adeno-associated virus (AAV) (Seppen et al, 2006), and naked plasmid DNA (pDNA) (Danko et al, 2004;Jia and Danko, 2005b).…”

A new surgical approach to improve gene transfer in liver using lentiviral vectors

“…The existence of a rat model of the disease, the Gunn rat, has made possible to test various gene transfer strategies to correct the phenotype. We previously demonstrated that using lentiviral vectors more than 10% of transduction efficiency was required to correct completely the hepatic disorder [3,4]. In this study, lentiviral vectors were injected in newborn animals in which hepatocytes are cycling.…”