SV40 in vitro packaging: a pseudovirion gene delivery system

Nuclear extracts of Spodoptera frugiperda (Sf9) insect cells infected with baculoviruses encode the simian virus 40 (SV40) major coat protein (VP1). As described in this protocol, these extracts are able to package supercoiled plasmid DNA or RNA interference (RNAi) sequences in the presence of MgCl(2), CaCl(2), and ATP, thus forming SV40 pseudovirions in vitro. Such packaging has numerous advantages over other viral and nonviral delivery systems. Specifically, it provides a wide host range and high transduction efficiency. The only major disadvantage of this system is low expression per transduced cell observed in vitro, likely a result of DNA trapped in the cytoplasmic compartment of the cell that does not enter the cell nucleus.