Vaccination is a disease preventive measure, where the immune system of a person is boosted against a particular disease (Behbehani, 445). Disease prevention could either be acquired via challenging the immune system with attenuated strains of the disease maker or passive by receiving antibody against the disease pathogen (Wolfe, 430). Vaccination generally falls under the category of acquired immunity.
Initially live pathogens at lower doses were used as vaccines to prevent the disease (example: small pox), followed by usage of attenuated strains of pathogen to produce immune response against the disease (example: BCG vaccine used in the treatment of tuberculosis). In recent days, various other vaccine strategies like DNA vaccine (gene shot) and edible vaccines are being developed. Edible vaccines are a new breakthrough in the field of vaccine administration.
In these vaccines, a gene specific for an antigen causing disease is cloned into a vector which is then introduced into the plant forming transgenic plants expressing the antigen in low levels. When these transgenic plants are consumed they are they confer protection against the disease caused by the introduced antigen which is similar to a regular vaccine (Thanavala, 3358). A diagrammatic representation of steps involved in the production of edible vaccine is included as supplementary figure.
These edible vaccines can cut the cost of vaccine production and increase to ease of vaccine administration thus making it more affordable in developing countries (www. nexgenbiotech. com). A recent example of edible vaccine under trial includes Hepatitis B vaccine in transgenic potatoes (Kong, 11539). Hepatitis B is a major health problem affecting nearly two billion people worldwide every year (Alter, 40).
Despite the availability of safe and effective vaccine against the Hepatitis B virus (HBsAg in particular which causes the disease), the vaccine usage is highly restricted due to the high cost involved in producing it (Kong, 11540). Thus using plant based vaccine proves to be a better and cheaper alternative to make these vaccines available. Here the method involves cloning of HBsAg antigen gene into a vector which is made to express in bacteria like Agarobacterium. These are then transformed into Solanum tuberosum cell lines which are then plated on pots to produced transgenic potatoes.
The efficiency of vaccine was first tested in mice by feeding it with these transgenic potatoes in comparison to oral hepatitis vaccine obtained from yeast. Also the level of protection conferred by the transgenic potatoes to these HBsAg was also tested. All these tests revealed that oral administration of Hepatitis B antigen using transgenic potatoes conferred increased protection against antigen degradation in the gut and produce increased immunogenic response from the mice (Kong, 11542 and Tacket, 607).
Immunogenic response was quantified by analyzing the amount of antibody against HBsAg found in the mouse serum using ELISA. Apart from the cost factor and ease of administration, oral vaccines that include edible vaccines, are more preferred form of vaccination in case of disease whose route of entrance into the host includes mucosal layer (like enteric or pulmonary diseases). These edible vaccines can elicit humoral immunity and increased response from the mucosal membrane which the first line of defense.
Also the digestion of plant tissue happens in a particular part of the gut (large intestine) which is ideal for priming T cells and bring about protective response (near to payers patch) (Walmsley, 13). Other such edible vaccines include enterotoxic Escherichia coli in transgenic potatoes which is a main causative of diarrheal disease which kills around 10 million children every year (Masson, 1336). Fruits like banana and tomatoes can also been used in the development of vaccines since they do not need to be cooked before human consumption. Figure: 1 www.nexgenbiotech. com
Work Cited Behbehani AM. “The smallpox story: life and death of an old disease”. Microbiol Rev. 47 (1983): 455–509 Wolfe R, Sharp L. “Anti-vaccinationists past and present”. BMJ 32JKrishnamurthy 7361(2002): 430–2. Thanavala Y, Lyons P, Mason HS, Arntzen C. Immunogenicity of transgenic plant-derived hepatitis B surface antigen.. Proc Natl Acad Sci U S A. 92 (1995): 3358-61 www. nexgenbiotech. com Kong Q, Richter L, Yang YF, Arntzen CJ, Mason HS, Thanavala Y. Oral immunization with hepatitis B surface antigen expressed in transgenic plants..
Proc Natl Acad Sci U S A. 98 (2001):11539-44 Alter MJ. Epidemiology and prevention of hepatitis B. Semin. Liver Dis. 23 (2003): 39–46. Tacket CO, Mason HS, Losonsky G, Arntzen CJ. Immunogenicity in humans of a recombinant bacterial antigen delivered in a transgenic potato. Nat Med. 4(1998):607 Walmsley A M, Mason H S, Arntzen C J. Mucosal Immunol Update. 7(1999):12–14 Mason HS, Haq TA, Clements JD, Arntzen CJ. Edible vaccine protects mice against Escherichia coli heat-labile enterotoxin (LT): potatoes expressing a synthetic LT-B gene. Vaccine. 16(1998):1336-43.