In vivo retrovirus-mediated gene transfer into lamb liver

Topic: Highly efficient retrovirus-mediated gene transfer into hepatocytes in vivo has been previously reported in the rat. Before considering human a pplications of these techniques in the treatment of inherited liver disease s, it was necessary to document its efficiency in a large animal model. Lam b was choosen because the liver was similar to human liver regarding size a nd anatomy. Materials and Methods: To induce hepatocyte division which is necessary for infection with retroviral particles, animals were subjected to a left: hep atectomy. Kinetics of liver regeneration were assessed on sequential liver biopsies after partial hepatectomy in order to provide an evaluation of the peak of maximal liver regeneration in a first animal group. Recombinant re troviruses encoding a reporter gene (E. coli beta galactosidase) were then perfused through the portal vein of the regenerating liver in a second anim al group. Results: The more intense liver regeneration occurred from one to 6 days af ter partial hepatectomy, with the highest thymidine kinase rate and MIB-1 a ntibody staining on the second day. The proportion of genetically modified lamb hepatocytes expressing the reporter gene was less than l parts per tho usand, despite the use of higher titers of retroviral particles than those described in previous reports. Conclusion: The results obtained in rodent livers with this in vivo gene tr ansfer methodology cannot currently be scaled up in a large ruminant model. The efficacy of vectors has to be tested in other large mammals before pla nning gene therapy trials for the treatment of inherited liver diseases.