[Gene therapy for acute hepatitis using CrmA gene transduction]

Fas-Fas ligand interactions between adenovirus-infected hepatocytes and cytotoxic T lymphocytes (CTLs) play a major role in killing of vector-transduced hepatocytes. Cytokine response modifier A (CrmA) is known to protect lymphoid cells from Fas-mediated apoptosis by inhibiting caspase 8. In this study, we generated an E1-deleted adenovirus expressing CrmA, and investigated the effect of exogenous CrmA expression on the inhibition of Fas-mediated apoptosis in murine hepatocytes in vitro and on the prolongation of the transgene expression in adenovirus-transduced hepatocytes in vivo. Agonistic anti-Fas antibody induced massive apoptosis into hepatocytes, however, most of the cells expressing CrmA were escaped from apoptosis and survived. This result showed that anti-apoptic function was obtained in murine hepatocytes by expressing CrmA. The prolongation of the transgene expression was studied using mice with congenital deficiency of lysosomal beta-glucuronidase (GUSB). The serum GUSB activity from the mice injected only an adenovirus expressing human beta-glucuronidase disappeared within 70 days, however, significant GUSB activity was observed for more than 130 days in the mice co-transduced with adenoviruses expressing both GUSB and CrmA. Moreover, histochemical analysis showed GUSB expressions in the liver even at 130 days after the viral administration. These observations demonstrate that the prolongation of the transgene expression can be achieved in rodent liver by CrmA co-expression using adenoviral gene transfer.