Rapid clearance of syngeneic transplanted hepatocytes following transduction with E-1-deleted adenovirus indicates early host immune responses and offers novel ways for studying viral vector target cell and host interactions

To distinguish between transduced cell clearance and transgene regulation following adenoviral gene transfer, we infected F344 rat hepatocytes with an E-1-deleted adenovirus (Adβgal) and studied cell survival in the liver of dipeptidyl peptidase IV-deficient (DPPIV-) F344 rats. Transplanted cells were localized with histochemical staining for β-galactosidase (lacZ). The transgene was expressed in 90-100% hepatocytes without impairment in cell viability in vitro, although transplanted cells were cleared mostly within 1 day by infiltrates containing activated macrophages, CD4⁺ or CD8⁺ lymphocytes, and phagocytes. When ADβgal-transduced hepatocytes were transplanted repeatedly at 14-day intervals, transplanted cells were cleared rapidly each time. LacZ expression following Adβgal administration to intact animals was associated with apoptosis and unscheduled DNA synthesis in the liver. To determine whether adenoviral antigen expression activated consequential MHC-restricted liver injury, we transplanted Adβgal-hepatocytes followed subsequently by transplantation of nontransduced hepatocytes engrafted with progressive liver repopulation. The findings indicated that adenovirally transduced cells are cleared early in the host liver. Use of ex vivo strategies will facilitate analysis of modified adenoviral vectors in the context of immunoregulatory, cellular and viral mechanisms.