Differences in human cell lines to support stable replication of Epstein-Barr virus-based vectors

Vectors carrying the origin of replication, ori-P, of the Epstein-Barr virus (EBV) are maintained extrachromosomally in human cells expressing the EBV nuclear antigen 1 (EBNA-1). We have studied the EBV vectors p201 and p292 in which both ori-P and EBNA-1 functions are present using the human cell lines A431 and HeLa. The two lines showed differences in their transfectability by the EBV vectors. Thousands of HeLa transfectants were obtained with either vector and these remained intact as episomes. A431 could only be efficiently transfected with p292 and a high ratio of chromosomal integrations and rearrangements were observed. The vector p292 expressed the EBNA-1 gene more efficiently than p201 and this was found to be associated with a harmful effect on the grown of both HeLa and A431 lines. These results indicate that EBV vectors behave differently, depending on the cell line and that over-expression of EBNA 1 from these vectors may be detrimental to the cells.