Practice question

Banana was specifically engineered to produce edible Hepatitis B vaccine demonstrating fruit-based oral immunization feasibility. Hepatitis B surface antigen HBsAg 226 amino acid small surface protein self-assembles into 22 nm virus like particles highly immunogenic protective against HBV infection. Early work by Thanavala 1995 expressed HBsAg in transgenic tobacco plants showing assembly. Subsequent collaboration by Arntzen, Mason and colleagues introduced HBsAg gene under fruit specific promoter E8 and constitutive CaMV 35S with endoplasmic reticulum retention signal KDEL into Cavendish banana AAA group via Agrobacterium mediated transformation of embryogenic cell suspensions and regeneration through somatic embryogenesis, slow process due to triploid sterility and generation time 12-18 months. Transgenic banana fruits accumulated HBsAg up to 0.05 percent total soluble protein in pulp, sufficient to elicit anti HBs IgG when orally consumed in mice after feeding peeled fruit, boosting after parenteral priming. Banana advantages include palatability raw without cooking preserving heat labile VLP structure, eaten by infants and children, perennial high yield in tropical regions where hepatitis B endemic, no requirement for cooking that denatures antigens, and cultural acceptance. Limitations low expression variability and delayed fruiting pushed platform toward lettuce and maize seeds, but banana remains iconic proof concept for edible.