Edible Vaccines

HOW IS IT DONE Approach 1 DNA sequences encoding antibodies (molecule which is able to recognise a disease-causing agent) are inserted into the genomes of plants. Plants produce the antibodies in their cells. These plants are then harvested and purified for therapeutic use/consumed with the rest of the plant, releasing the antibodies in the process.

How it is done Approach 2 Identification, selection and isolation of desirable genes from the pathogen that encodes the surface antigen proteins. The isolated gene can be then cloned in a suitable vector for gene transfer Introduction of selected desired genes into plants and then inducing these altered plants to manufacture the encoded proteins Edible vaccines are composed of antigenic proteins and are devoid of pathogenic genes. Thus, they have no way of establishing infection, assuring its safety When eaten, edible vaccines provoke antibody response. 

Benefits Needle-free Needles provide only weak immunity at mouth, eyes, intestines and urogential tract. Oral vaccines provide “mucosal immunity” at these sites by secreting antibodies Don’t need to worry about re-use, misuse and lack of sterilisation. Thus, low risk of infection. Cheap Mass production: Can always plant more if diminishing Estimated cost of $0.005 to grow antigen for one dose of hepatitis B vaccine in an unprocessed form. Vaccine programmes for rarer diseases or diseases which are not so financially rewarding for pharmaceutical companies (i.e. diseases which do not affect developed countries) will benefit.

Heat-stable; do not require cold-chain maintenance; can be stored near the site of use, eliminating long-distance transportation. Administering oral vaccines would require little or no training at all, which reduces the significant cost of vaccination programmes which require trained professionals. Cheap

Safety concern 1 The contamination of food crops through cross pollination and of the vaccine itself in plant debris spreading as dust and as pollutants in surface and groundwater. The vaccine antigen may affect browsing animals and humans living in the area drinking vaccine-polluted water or breathing vaccine-polluted dust. Hence such crops should be cultivated and produced in greenhouses or in plant tissue culture to prevent their environmental release. Safety concern 2 May trigger immune tolerance: Thereby making the individual susceptible to, for example, the hepatitis B virus. (Daniell, Streatfield and Wycoff 2001/5/1)

Cholera Banana Vaccine

Source http://www.genomenewsnetwork.org/articles/07_00/VACCINE_BASE2_5_8.pdf

Other examples Transgenic tobacco is successfully engineered for the production of edible vaccines against Hepatitis B antigen using‘s gene of HBV (Hepatitis B Virus). The optimum level of recombinant protein was obtained in leaves and seeds. Potato is one of the best sources for vaccine production but the raw potatoes are not palatable and cooking destroys protein antigens. Vaccine for cholera is successfully developed in potato. Banana is the ideal plant for oral vaccine production due to its excellent digestibility, palatability and availability throughout the year. Vaccine for hepatitis B is successfully made in banana. Tomato plants expressing rabies antigens