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 f ollowing adenoviral gene transfer, we infected F344 rat hepatocytes with an E-1-deleted adenovirus (Ad beta gal) and studied cell survival in the live r of dipeptidyl peptidase IV-deficient (DPPIV-) F344 rats. Transplanted cel ls were localized with histochemical staining for DPPIV and transgene expre ssion localized with staining for beta-galactosidase (lacZ). The transgene was expressed in 90-100% hepatocytes without impairment in cell viability i n vitro, although transplanted cells were cleared mostly within I day by in filtrates containing activated macrophages, CD4(+) or CD8(+) lymphocytes, a nd phagocytes. When ad beta gal-transduced hepatocytes were transplanted re peatedly at 14-day intervals, transplanted cells were cleared rapidly each time. LacZ expression following Ad beta gal administration to intact animal s 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 Ad beta sal-hepatocytes follo wed subsequently by transplantation of nontransduced hepatocytes. Transplan ted cells expressing Ad beta gal were rapidly cleared as before, whereas no ntransduced 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 modif ied adenoviral vectors in the context of immunoregulatory, cellular and vir al mechanisms.