Vaccination is one of the most successful developments in preventive human healthcare. In their contribution, Mor and Mason describe how edible vaccines that can be delivered in food plants may make that protection more widely accessible.Despite their efficacy, most modern vaccines, which are inactivated or attenuated strains of the pathogen delivered by injection, have limitations. This creates constraints on the use of vaccines because many pathogens are difficult, and prohibitively expensive, to culture. Second, the majority of vaccines are delivered to patients by injection. This requires skilled staff and a sophisticated medical infrastructure, which limits their use in the developing world. Therefore, alternative routes for vaccination as well as alternate sources of vaccination antigens have been explored. Orally delivered vaccines that contain a subunit of the pathogen and can elicit a protective immune response are one such alternative. Using transgenic plants for both production and delivery is the major focus of this chapter.
The authors provide a historical overview of the development of strategies for production of recombinant antigens in plants, most of which have been achieved in the laboratories of Arntzen and Mason. They describe their success in producing immune responses in humans with plant-produced hepatitis B surface antigen, the labile toxin B subunit of enterotoxigenic Escherichia coli and the capsid protein of Norwalk virus. Success with these proteins in Phase I/II trials has now prompted larger scale clinical trials. What is compelling is that their approach is successful for proteins from widely different pathogens and indicates that orally delivered vaccines may be successful against a wide range of pathogens. Mor and Mason then discuss the rapid increase of research in the edible-vaccine field and point out that plants can be used to create multicomponent vaccines that can protect against several pathogens at once. This is an aspect of the edible-vaccine approach that further strengthens its impact.
After discussing strategies for vaccine expression, the authors turn their attention to the use of orally delivered antigens both as immunocontraceptive vaccines and in the treatment of autoimmune diseases. They end their chapter with a careful discussion of where the technical challenges in edible-vaccine technology lie, and how they may be solved.
We share their view that orally delivered vaccines are a proven technology, which holds great promise for development within mainstream pharmaceuticals. By their use, entire populations in the developing world will be able to share the same protection from disease that we take for granted in industrialised countries.
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