Gene transfer using human polyomavirus BK virus-like particles expressed in insect cells.

The major structural protein (VP1) of the BK polyomavirus (BKV) was expressed in the recombinant baculovirus expression system. Recombinant BKV VP1 was shown to self-assemble into virus-like particles (VLPs) with a diameter of 45-50 nm. As for other polyomaviruses, BKV VP1 has the capacity to bind to exogenous DNA. Furthermore, the potential of BKV VP1 VLPs was investigated for gene transfer into COS-7 cells using three methods for the formation of pseudo-virions: disassembly/reassembly, osmotic shock and direct interaction between VLPs and reporter plasmid DNA. The latter method was shown to be the most efficient when using linearized plasmid. Gene transfer efficiency with BKV pseudo-virions was of the same order as that observed with human papillomavirus type 16 L1 protein VLPs. In addition, it is demonstrated that cellular entry of BKV pseudo-virions is dependent on cell surface sialic acid.