Rice seed for delivery of vaccines to gut mucosal immune tissues

Gut‐associated lymphoid tissue (GALT) is the biggest lymphoid organ in the body. It plays a role in robust immune responses against invading pathogens while maintaining immune tolerance against nonpathogenic antigens such as foods. Oral vaccination can induce mucosal and systemic antigen‐specific immune reactions and has several advantages including ease of administration, no requirement for purification and ease of scale‐up of antigen. Thus far, taking advantage of these properties, various plant‐based oral vaccines have been developed. Seeds provide a superior production platform over other plant tissues for oral vaccines; they offer a suitable delivery vehicle to GALT due to their high stability at room temperature, ample and stable deposition space, high expression level, and protection from digestive enzymes in gut. A rice seed production system for oral vaccines was established by combining stable deposition in protein bodies or protein storage vacuoles and enhanced endosperm‐specific expression. Various types of rice‐based oral vaccines for infectious and allergic diseases were generated. Efficacy of these rice‐based vaccines was evaluated in animal models.