Vaccines are for dinner

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Abstract
Transgenic plants have been sought not only as bioreactors but also as potential scaffolds for oral vaccines. Tobacco was initially exploited for the successful expression of Streptococcus mutans surface protein A as a potential dental caries vaccine (1) and for hepatitis B surface antigen (2) as a vaccine bioreactor alternative for viral hepatitis B. Today, a number of edible plants (Table 1), including potatoes, tomatoes, maize, and soybeans, have been genetically modified to express a variety of vaccine targets, including hepatitis B surface antigen (2), Norwalk virus particles (3, 4), heat-labile enterotoxin B subunit (5, 6), and others (7–11) that can benefit both humans (6–8) and livestock (9–11). The advantage of edible vaccines is that often the plant products, whether leaves, fruit, or seed, can be readily consumed with limited or no processing. Viable oral platforms such as edible products suitable for human use are in demand to deliver vaccines (12). Obviously, the fact that food products are consumed obviates many of the health concerns that arise in the oral vaccination of humans (as reviewed in ref. 13). Edible vaccines can also have the advantage of circumventing cold-storage issues (the “cold chain”), because plant tissues can be dried or, as when the seeds are targeted, have low moisture content. Likewise, water- or oil-based plant extracts can provide additional storage convenience. In this issue of PNAS, Nochi et al. (14) describe a rice-based oral vaccine that potentially addresses many of these topics. At hand is the need for vaccine development and strategies to aid underserved nations with the ability to produce vaccines locally in a cost-effective manner. Because rice is produced in many such areas, this current work shows the feasibility of propagating rice-based vaccines that are truly edible vaccines, unlike in the …