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JC virus-like particles based on VP1: an effective gene-therapeutic and retargeting delivery system

Reference Number TO 07-00049

Challenge

A variety of delivery methods have been developed to enable nucleic acids to be delivered into cells for therapeutic applications. Tissue specific transfer of nucleic acids in vivo so far mostly rely on viral transfer systems. Due to the potential danger of recombination with cellular sequences, these bear a safety risk that is very difficult to predict. Repeated in vivo administration of e.g. adenoviruses and adeno-associated viruses is hampered because of their high immunogenicity in most individuals. In addition, due to the complex structure of the viruses it is only possible with considerable effort to deliver therapeutic nucleic acids to the target site at sufficient concentrations/levels and in suitable form. Another aspect is that viruses usually infect more than one type of cells. As an alternative, non-viral systems avoid most of these disadvantages but, in turn, and similar to retroviral systems, exhibit much lower transfer efficiencies and target cell specificities.

A: Production and assembly of siRNA-filled polyoma JCV VP1 VLPs.
   B: Retargeting of VLP by crosslinking antigen-specific scFv molecules.
A: Production and assembly of siRNA-filled polyoma JCV VP1 VLPs. B: Retargeting of VLP by crosslinking antigen-specific scFv molecules.

Technology

The German Primate Center (DPZ) has a long history in the research of polyoma JC virus (JCV) and the successful development of virus-like particles (VLPs). The need to provide clinically applicable effector molecules has been the motivation of the researchers to generate VLPs based on human JCV VP1 protein. JCV has been described as a suitable tool for transduction of genetic material in a variety of cell lines.

Purified VP1 protein spontaneously forms stable homo-pentameric capsomers, which in turn assemble into VLPs. VLPs can be loaded in a single dissociation-reassociation cycle in which the cargo nucleic acids (here: siRNA or miRNA) can be added in the dissociated stage. VLPs can then form around the nucleic acid cargo during slow dialysis versus physiological, non-reducing buffer conditions (see figure A). Using a siRNA to target the nuclear kappaB factor ligand RANKL in a rat osteoporosis model, significant silencing of RANKL with very low quantities of VLP could be achieved. Moreover, recovery of silencing by repeated VLP injections has been shown.

In addition, the VLPs serotonergic tropism could be specifically altered by covalently linking a HER2/neu single chain antibody fragment onto the surface of the particles by different methods (see figure B). Thereby, transduction of HER2/neu positive breast- and colorectal- cancer cells could be achieved and moreover, the natural tropism of the VLPs could be blocked.

Commercial Opportunity

The VLPs represent an alternative way of transiently transducing genetic material into desired target cells, without the presence of any viral derived genetic material and unwanted integration of genetic information into the cells’ genome. Moreover, JCV-VP1 VLPs are an effective platform for presentation of targeting molecules on the surface of the virus capsid enhancing tissue-/cell-specific gene therapeutic efforts.

The technology is available for exclusive or non-exclusive licensing as well as for joint collaboration for further pre-clinical validation and/or clinical development.

Developmental Status

A proof of concept study for the VLP technology was performed with siRNA delivery in a rodent model and with both RNA and DNA delivery in multiple cell types. The technology is ready for in vitro and in vivo delivery of nucleic acids (e.g. siRNA, miRNA or DNA expression cassettes). A limited repertoire of targeting molecules including scFv for Her2/neu is available for testing. Production and purification protocols for VP1 and targeting molecules in the double-digit milligram range have been established.

Patent Situation

Patents protecting the nucleic-acid loaded JCV-VLP are granted in US and JP, and pending in EP and CA.

Further Reading

Hoffmann et al. (2016), Mol. Ther. Nucleic Acids 5, e298.