Molecular integrity and usefulness of episomal expression vectors derived from BK and Epstein-Barr virus

High-level and stable production of a protein of interest is one of the mos t important parameters when considering the development of an efficient vec tor system for heterologous gene expression. In order to achieve this goal, we have used episomal vector elements derived from Epstein-Barr virus (EBV ) or BK virus (BKV) in combination with the strictly regulated interferon-i nducible Mx promoter. Here we demonstrate that EBV-derived vectors replicate efficiently in all c ell lines tested (i.e. HEK293, HeLaH21 and Vero), yielding stable transfect ants with a high, inducible expression level and almost no background. In c ontrast, BKV-derived vectors are much men restricted to particular cell typ es and hampered by DNA rearrangements, which is a serious drawback for use over a longer timespan. (C) 2000 Elsevier Science B.V. All rights reserved.