Therapeutic gene delivery in human B-lymphoblastoid cells by engineered non-transforming infectious Epstein-Barr...

The B-lymphotrophic human herpes Epstein-Barr virus (EBV) is a 160-kilobase double-stranded DNA episomal virus carried in a persistent asymptomatic state by more than 90% of the worldwide adult population. We engineered a helper-dependent mini-EBV, with the minimal cis-EBV elements for episomal replication, viral amplification and packaging, for use as a gene delivery system. The therapeutic potential of this system was established by stably transducing B-lymphoblastoid cells from a Fanconi anaemia group C (FA-C) patient with a mini-EBV constitutively expressing the normal FACC cDNA and showing in vitro correction of the FA phenotype. In the absence of selective pressure, episomal expression persisted with a half-life of 30 days in actively growing transduced cells, indicating a retention rate of 98% expression per cell doubling. This work demonstrates the generation of an infectious non-transforming viral vector that can potentially deliver large therapeutic genes efficiently and selectively into human B cells.