Gene transfer in vitro and in vivo with Epstein-Barr virus-based episomal vector results in markedly high transient expression in rodent cells.

The EBV-based plasmid vectors, which carry oriP and EBNA1 gene from EBV genome, can be retained in the nucleus and replicate in human cells. Rodent cells are not permissive for the EBV plasmids, in terms of the plasmid replication. However, the EBV vector facilitates not only the long term maintenance of the plasmid but also high level gene expression at a transient phase after transfection. It has not been elucidated if rodent cells show this high level transient expression. We demonstrate that rodent cells transfected with an EBV vector expressed a marker gene more intensively than those with a conventional plasmid vector did. The high marker gene expression was also seen in rat myocardium injected in vivo with the EBV plasmid. The present data indicate that the EBNA1-oriP system functions in "non-permissive" rodent cells at transient phase, and may require different cellular factor(s) for the transient expression and plasmid replication.