Gene transfer using recombinant rabbit hemorrhagic disease virus capsids with genetically modified DNA encapsidation capacity by addition of packaging sequences from the L1 or L2 protein of human papillomavirus type 16

The aim of this study was to produce gene transfer vectors consisting of pl asmid DNA packaged into virus-like particles (VLPs) with different cell tro pisms. For this purpose, we have fused the N-terminally truncated VP60 caps id protein of the rabbit hemorrhagic disease virus (RHDV) with sequences wh ich are expected to be sufficient to confer DNA packaging and gene transfer properties to the chimeric VLPs. Each of the two putative DNA-binding sequ ences of major L1 and minor L2 capsid proteins of human papillomavirus type 16 (HPV-16) were fused at the N terminus of the truncated VP60 protein. Th e two recombinant chimeric proteins expressed in insect cells self-assemble d into VLPs similar in size and appearance to authentic RHDV virions. The c himeric proteins had acquired the ability to bind DNA. The two chimeric VLP s were therefore able to package plasmid DNA. However, only the chimeric VL Ps containing the DNA packaging signal of the L1 protein were able efficien tly to transfer genes into Cos-7 cells at a rate similar to that observed w ith papillomavirus L1 VLPs. It was possible to transfect only a very limite d number of RK13 rabbit cells with the chimeric RHDV capsids containing the L2-binding sequence. The chimeric RHDV capsids containing the L1-binding s equence transfer genes into rabbit and hare cells at a higher rate than do HPV-16 L1 VLPs. However, no gene transfer was observed in human cell lines. The findings of this study demonstrate that the insertion of a DNA packagi ng sequence into a VLP which is not able to encapsidate DNA transforms this capsid into an artificial virus that could be used as a gene transfer vect or. This possibility opens the way to designing new vectors with different cell tropisms by inserting such DNA packaging sequences into the major caps id proteins of other viruses.