Plant molecular farming of virus-like nanoparticles as vaccines and reagents

The use of plants for the production of virus-like nanoparticles (VNPs) dates back to separating natural empty capsids of plant viruses from whole virions nearly 70 years ago, through to the present use of transgenic plants or recombinant Agrobacterium tumefaciens and/or plant virus-derived vectors for the transient expression of engineered viral or other structural proteins in plants-a production system also known as molecular farming. Plant production of heterologous proteins has major advantages in terms of convenience-whole plants are generally used, and processes do not need to be sterile-and cost, as bulk biomass production is significantly cheaper than by any other method. Plant-made VNPs in current use for nanotechnology include whole virions and naturally occurring empty capsids of plant viruses, and particles made by reassembly of coat protein (CP) purified from virions or by recombinant expression. Engineered VNP-forming animal or human virus CPs expressed in plants include L1 protein from human papillomaviruses, human norovirus CP, hepatitis B surface and core antigens, influenza virus HA protein and HIV Gag polyprotein forming large enveloped particles by budding, orbi- and rotavirus particles that require assembly of four co-expressed proteins, and polio- and foot and mouth disease viruses which require proteolytic processing of a polyprotein precursor to form 4-component VNPs. Both plant and animal virus-derived plant-made VNPs can be used for surface and internal display of heterologous peptides or even whole proteins. A significant recent development has been the production of pseudovirions in plants, comprising plant or animal virus CPs and RNA or DNA pseudogenomes that can be used to deliver nucleic acid payloads into cultured cells or specific tissues or tumors in whole animals. This article is characterized under: Biology-Inspired Nanomaterials > Protein and Virus-Based Structures Therapeutic Approaches and Drug Discovery > Emerging Technologies Diagnostic Tools > in vivo Nanodiagnostics and Imaging