Papillomavirus pseudoviruses that comprise the L1/L2 capsid proteins can package a wide variety of non-viral DNA plasmids and deliver the packaged genetic material to cells. This function makes them attractive candidates as targeted gene delivery vehicles. Current methods for the efficient production of papillomavirus pseudoviruses require the use of 293TT cells. One key drawback to this production method is SV40 T antigen gene contamination introduced by the 293TT cells. Because T antigen is a known oncoprotein, pseudoviruses generated using this methodology are unsuitable for clinical applications. A second drawback is that intracellular production precludes production of toxin gene-transducing pseudovirions. A third drawback is that intracellular production cannot be used to generate mRNA transducing vectors.
Scientists at the NCI have developed a novel, chemically defined, cell-free, papillomavirus-based vector production system that allows the incorporation of purified plasmid DNA (pseudogenome) or mRNA into high-titer papillomavirus L1/L2 capsids without the use of 293TT cells. Titers as high as 1011 infectious units/mg of L1 were generated. Pseudoviruses were infectious both in vitro and in vivo, and should be compatible with good manufacturing practice (GMP) requirements.