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Edible vaccine is a vaccine that is based on the genetically engineered expression of an antigenic protein by an edible plant. Following consumption, the protein is recognized by the immune system.

The process of producing transgenic plants is known as transformation.

These vaccines are important for developing countries since they are inexpensive.

Assist in diseases such as diabetes, diarrhea, multiple sclerosis, rheumatoid arthritis.

Provide mucosal immunity responses in the body.History The first journal publication describing Edible Vaccine was published in 1992. The study was conducted by Mason, Lam, and Arntzen at Texas A&M University. A tobacco plant was successfully transformed and hepatitis B antigen was expressed.

It is crucial to determine the surface antigens to make edible vaccines against different pathogens.

Common method that used involves manipulation of bacteria in the genus Agrobacterium tumefaciens. Desirable genes encoding the pathogen are transferred into the plant utilizing the Agrobacterium.The methods of insertion consist ofchemical treatment or electroporation of protoplasts with the use of a ``gene gun``. Exposure of plants to chemical substances or to an electrical field that causes the cell membrane of the protoplast to become more porous.

Microscopic particles containing DNA, are ``shot`` utilizing a gene gun into the plant tissues.Transfer DNA from A. tumefaciens is necessary in order to integrate the DNA into the host plant genome.Transformed plantcells are grown onto a callus and into complete plants which then produce transgenic fruit that can be eaten

Prior to DNA transfer fromthe bacterium to the plant,the plasmid needs to be disarmed by deleting thegenes for auxin and cytokinin synthesis.

By disarming the two synthesisthebacterium will notproduce a tumor.

Genes for antibiotic resistance are used to select out the transformedcells and whole plants, which contain the foreign gene.

Agrobacterium Tumefaciens

To get the antibiotic gene into the potatos genome A.tumefaciens is used. A.tumefaciens is a naturally occurring soil bacterium, which has the ability to get into plants through some kind of wound.

It possesses acircular "Ti plasmid" (tumor inducing), which enables it to infect plant cells with it own DNA.

Through the previous step the tumor inducing gene is removed, and integrates the new genome producing the edible vaccine.

Formed through the production of plant cells with the Agrobacteria.

Pieces of plant tissue are dividedand developed into a collection of cells in a liquid medium(suspension culture).

Certain conditions exist for this process to occur:A suitable plant tissue must be chosenHigh concentrationsof auxinand cytokininare required in the growth mediaGrowth medium should consist of organic and inorganic compounds for the maintenance of cellsMicroorganisms must be prohibited from the medium with the Aseptic conditions, of adding antibiotics during cell culture

The callus is theaim for DNA insertion into the plant tissue

.Traditional vaccinesEdible vaccinesToo expensive to be used on large scaleComparatively less expensive if produced in large amountLack of physical infrastructure (roads and refrigeration) makes it impossible to disseminate the vaccineMay be easily availableRequire trained personnel to administer injectionsDo not require any trained personnel to administerRequire elaborate production facilities, purification, sterilization, packaging, or specialized delivery systemsNo purification strategies requiredCan not directly stimulate the immune systemVaccines when taken orally, can directly stimulate the immune system

Vaccine in GM fruit could wipe out Hepatitis B

The virus, which causes high fever and attacks the liver, is a precursor of liver cancer, the biggest single cause of cancer deaths. This new development will save hundreds of thousands of lives a year, said Charles Arntzen, the scientist who developed the technology in 2000.Successful experiments show that the vaccine worked, he added, and will cost less than one penny a dose to make. A single gene transferred into a tomato or banana plant is reproduced as a protein thousands of times inside the fruit. When eaten it passes into the intestine and then into the blood stream producing antibodies against hepatitis B - working the same way as a traditionally injected but much more expensive vaccine.A single dried banana chip or tomato paste sandwiched in a wafer contains enough protein to act as a vaccine dose.The vaccine has been held back because the US department of agriculture and the food and drug administration had no licensing mechanism for plant vaccines.

The Tomato 'vaccine' that could prevent Alzheimer's

It works by attacking the toxic beta-amyloid protein that destroys vital connections between brain cells, causing Alzheimer's. To create the vaccine, the scientists combined the gene behind the betaamyloid protein with the tomato's genetic code. They then fed mice the designer tomatoes once a week for three weeks. Blood samples taken from the mice revealed the tomatoes triggered their immune systems to release disease-fighting antibodies, although the levels of plaques in the brain were not reduced. The researchers from the Korea Research Institute of Bioscience and Biotechnology in Seoul are now trying to increase the potency of the vaccine in order to ' supercharge' the immune response. They said the tomato was a good way of getting a vaccine into the body because it was enjoyable to eat and could be eaten raw. Also tomato provide other health benefits like controlling cholesterol levels, vit. C, lycopene as an antioxidant, also guard against colon and rectal cancer.

Insulin in Plants to Combat Diabetes

Researchers have developed technologies that permit the introduction of a hybrid gene that produces human insulin in tobacco and then lettuce.Currently, insulin is given to diabetic patients by means of shots that enable the hormone to go straight into the bloodstream. But there has recently been a study that aimed to produce insulin capsules in the future. This may be possible with the help of a little genetic engineering.What makes the study have a greater significance in the advancement of diabetes treatment is an alternative means of introducing the insulin hormone in the body. By genetically engineering the hormone into the plant cells of a parent plant, the cell walls would be able to help prevent the insulin from degrading.

AdvantagesEdible plants are very effective as a delivery vehicle for inducing oral immunization Excellent , feasibility of oral administration compared to injection. Easy for separation and purification of vaccines from plant materials. Effective prevention of pathogenic contamination from animal cells. Convenience and safety in storing and transporting vaccines.Effective maintenance of vaccine activity by controlling the temperature in plant cultivation.

Contd.Possible production of vaccines with low costs.Reduced need for medical personnel and sterile injection conditions.Economical to mass produce and transport.Reduced dependence on foreign supply.Storage near the site of use. Heat stable, eliminating the need for refrigeration.Antigen protection through bioencapsulation.

DisadvantagesOptimization of dose of vaccine: A low dose may not be sufficiently immunogenic while high doses may cause tolerance. The dose of edible vaccine shall vary with the fruit, plant, size, ripeness and protein content of the edible part.Protein content of transgenic organisms: The immunogenic protein may not accumulate in high concentrations in the transgenic organismsImmunogenicity: Edible vaccines show low immunogenicity. To enhance immunogenicity, mucosal adjuvants, better targeted to the immune system, may be used. Cholera toxin is used as an engineered adjuvant.Antigenic variability:It would be difficult to develop edible vaccines against diseases caused by anti gen e i ti cally variable groups of pathogens as well as those caused by multiple varieties of organisms (dengue) or by complex parts from different life cycles of parasites (malaria) or by rapidly mutating organisms like HIV.Thermal Stability:Proteins in food are heat labile. Cooking results in destruction of protein the material shall destroy the immunogenicity nature of the protein.

Contd.Lack of Awareness and Funds:Small companies are undertaking most research as edible vaccines are targeted to markets of developing nations. Large companies are more interested in developing vaccines for farm animals as compared to human beings.Regulatory Issues:It has to be decided whether edible vaccines would be regulated under food, drugs or agricultural products.Ethical considerations usually restrict clinical trials from directly assessing protection in humans. Not convenient for infants.

Current Status of Edible VaccinesEdible vaccines are currently being developed for a number of human and animal diseases, including measles, cholera, foot and mouth disease, and Hepatitis-B and C. Many of these diseases are likely to require booster vaccinations or multiple antigens to induce and maintain protective immunity.At least 350 genetically engineered pharmaceutical products are currently in clinical development in the United States and Canada . Scientists believe that potent drugs and vaccines will soon be harvested just like wheat and corn.In Canada , a genetically engineered tobacco plant made to produce Interleukin 10 will be tested to treat Crohn's disease, an intestinal disorder.Scientists have also discovered that fruits with high water content could result in proteolysis. Experimentation with freeze-dried food to create pellets or powder is now being investigated to help avoid proteolysis and overall efficacy.

Contd.Arntzen and his colleagues plan to develop banana-based vaccines. They're also targeting papilloma virus, which can lead to cervical cancer, as well as Hepatitis-B virus. A reliable injectable vaccine already exists for Hepatitis-B, but a less expensive, edible vaccine would be better, particularly for use in the developing world.Current measles vaccines are made from the actual virus and work by priming the immune system to attack if it becomes exposed to a full assault of the measles virus. In contrast, plant-based vaccines rely on the measles virus gene for the H protein being genetically cloned into the plant.

Second Generation Edible VaccinesMulti-component vaccines can be obtained by crossing two plant or animal lines harboring different antigens.B subunit ofVibrio choleraetoxin (VC-B) tends to associate with its copies of itself, forming a doughnut-shaped five-member ring with a hole in the middle.Using this strategy, several different antigens can be exposed to immune cells simultaneously, for example, a trivalent edible vaccine can be developed that shall be effective against cholera, enterotoxigenicE. coliand rotavirus.Global alliance for vaccines and immunization (GAVI) gives very high priority to such combination vaccines for developing countries.

Future of Edible VaccinesAlthough still at an early stage of development, the experimental know-how and results strongly suggest that plant-derived edible vaccines are likely to become a reality, in the next few years. Future research will demonstrate if these vaccines meet the standards of quality (purity, potency, safety and efficacy) defined for vaccines by theWorld Health Organization.Its economic production will lower down the cost of immunizationIn most countries of the world, plants engineered to produce vaccines fall under the very restrictive rules set up to control GM-crop plants. The present concern, especially in Europe , over the use of biotechnology for the genetic improvement of crop plants also negatively affects the acceptance of GM-plants for medicinal use.It is hoped that simpler rules will be set up for GM-plants producing vaccines and that they are seen as clearly and legally distinct from GM-plants grown for nutrition purposes.

Conclusion Edible plant vaccines offer significant new opportunities for making safe and effective oral vaccines would be more widely used especially in developing countries. Due to some positive aspects like they are economical, safe, easy to administered and can be stored without refrigeration so that these vaccines are prominent over typical traditional vaccines. Plant-based vaccines are obtained from specific transition plants. This technique can be utilized for the treatment of Hepatitis-B, measles, cholera, foot and mouth disease but still diseases like cancer, malaria, HIV, asthma, etc. are major health problems in developing countries. By means of edible vaccines these problems can be solved.

Plant based medicines- Science not Fiction

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