The effect of age on hepatic gene transfer with self-inactivating lentiviral vectors in vivo

Abstract

It is known that cellular proliferation, by either compensatory regeneration or direct hyperplasia, can augment lentiviral vector transduction into hepatocytes in vivo. For this reason, the present study was designed to determine if adolescent mice (3½ weeks of age), which still have relatively proliferating livers, would have differential transduction compared to older (7 weeks of age) mice. Self-inactivating lentiviral vectors containing the human α1-antitrypsin (hAAT) promoter driving the expression of either the bacterial lacZ gene or the hAAT cDNA were generated for these studies. We found that adolescent mice given lentiviral vectors expressing lacZ (50 μg p24/mouse) via intravenous administration had a significantly higher level of hepatocyte transduction as measured by X-gal staining of liver sections compared to the 7-week-old mice. In addition, serum hAAT levels were nearly 40-fold higher in 3½-week-old mice administered lentiviral vectors expressing hAAT (50 μg p24/mouse) compared to the 7-week-old mice. Moreover, the incorporation of a matrix attachment region from immunoglobulin κ significantly increased transduction of hepatocytes in vivo. Although there was a small reduction in the circulating levels of hAAT, likely due to an immune response against the transgene product, gene expression was sustained for the duration of the study (30 weeks in total). In conclusion, the present study strongly demonstrates that lentiviral vector transduction efficiency and transgene expression were significantly enhanced in adolescent compared to older mice.