The use of transient expression systems for the rapid production of virus-like particles in plants

Advances in transient expression technologies have allowed the production of milligram quantities of proteins within a matter of days using only small amounts (tens of grams) of plant tissue. Among the proteins that have been produced using this approach are the structural proteins of viruses which are capable of forming virus-like particles (VLPs). As such particulate structures are potent stimulators of the immune system, they are excellent vaccine candidates both in their own right and as carriers of additional immunogenic sequences. VLPs of varying complexity derived from a variety of animal viruses have been successfully transiently expressed in plants and their immunological properties assessed. Generally, the plant-produced VLPs were found to have the expected antigenicity and immunogenicity. In several cases, including an M2e-based influenza vaccine candidate, the plant-expressed VLPs have been shown to be capable of stimulating protective immunity. These findings raise the prospect that low-cost plant-produced vaccines could be developed for both veterinary and human use.