Using storage organelles for the accumulation and encapsulation of recombinant proteins

Plants have been used to produce many diverse and valuable recombinant proteins, including subunit vaccines, antibodies and antibody fragments, hormones, blood products, cytokines, and enzymes. Different plant species and platforms have been explored as production hosts, each with unique properties in terms of the gene transfer method, production time, environmental containment, scalability, downstream processing strategy, protein folding and accumulation, and overall costs. Seed-based systems have many advantages because they exploit the natural storage properties of seeds, which facilitate batch processing and distribution. Seeds possess specialized storage organelles that may be used to accumulate recombinant proteins, offering stability both in planta and after harvest in the final preparation/formulation. The post-harvest stabilizing effect of seeds allows recombinant subunit vaccines and antibodies to be delivered via the mucosal route because they are better able to withstand this harsh microenvironment when protected by the plant matrix. Native storage organelles such as starch granules and protein bodies offer this protective effect, but protein storage organelles can also be induced ectopically in vegetative tissues. In this paper, we discuss the technical capabilities of storage organelle-based expression platforms and their potential applications.