Efficiency of delivery of DNA to cells by bovine papillomavirus type-1 L1/L2 pseudovirions

To investigate the efficiency of encapsidation of plasmid by papillomavirus virus-like particles (PV VLPs), and the infectivity of the resultant PV ps eudovirions, Cos-1 cells were transfected with an 8-kb plasmid incorporatin g a green fluorescent protein (GFP) reporter gene (pGSV), and infected with bovine PV (BPV-1) L1/L2 recombinant vaccinia virus to produce BPV1 pseudov irions. Approximately 1 in 1.5x10(4) of dense (1.35 g/ml) PV pseudovirions and 0.3 in 10(4) Of less-dense (1.29 g/ml) pseudovirions packaged an intact pGSV plasmid. The majority (>75%) of packaged plasmids contained deletions , and the deletions affected all tested genes. After exposure of Cos-1 cell s to BPV-1 pseudovirions at an MOI of 40,000:1, 6% of cells expressed GFP g iving a calculated efficiency of delivery of the pGSV plasmid, by pseudovir ions which had packaged an intact plasmid, of approximately 5%. Plasmid del ivery was not effected by purified pGSV plasmid, was blocked by antiserum a gainst BPV-1, and was not blocked by DNase treatment of pseudovirions, conf irming that delivery was mediated by DNA within the pseudovirion. We conclu de that a major limitation to the use of PV pseudovirions as a gene deliver y system is that intact plasmid DNA is not efficiently selected for packagi ng by VLPs in cell-based pseudovirions production systems.