Edible vaccines should preferably be consumed:
Edible vaccines rely on oral exposure to gut associated lymphoid tissue, so preservation of antigen structural integrity is crucial. Cooking, drying at high temperature, roasting, fermentation involving microbial proteases and acidic boiling denatures protein tertiary structure, unfolding alpha helices and beta sheets, disrupting disulfide bonds essential for conformational B cell epitopes required for neutralizing antibody induction, aggregating proteins into insoluble forms, destroying T cell epitopes via hydrolysis. For example HBsAg virus like particles dissociate into monomers losing particulate presentation critical for B cell receptor crosslinking if heated above 60C. Maillard reaction between sugars and lysine alters antigenicity. Therefore transgenic expression targeted to raw edible tissues like banana fruit pulp eaten fresh peeled, tomato fruit consumed raw in salads, lettuce leaves, baby carrots, rice seeds eaten without extensive heating although rice normally cooked may retain some antigen if heat stable variants engineered. If cooking mandatory, alternative freeze-drying retaining structure followed by consumption as powder capsules or incorporation into chocolate considered. Guidance emphasizes consumption raw without processing after harvest with minimal refrigeration to maintain native conformation for maximal mucosal IgA and avoid tolerance.
Ref: Mason et al. 2002 Trends Biotech Edible consumption raw; Streatfield Kwon 2007 Should be raw.