Edible Vaccine: Fact Or Artifact

The concept of edible vaccines was developed by Arntzen (currently heads the department of plant biology at the Arizona State USA) in the 1990s.

Author : Prof Dr Abdullah G Arijo

Science, with conventional definition, is all about observations and experimentation. Facts are revealed, countered, and reproduced with novel ideas that ultimately help in human welfare. This wheel once invented keeps on rolling with both blessings and criticism.
Ever since the biotechnology has offered application in diversified fields including agriculture and health, a sort of revolution has been practiced both in working abs and fields. With knowledge of Human Genome Project findings, the cutting-edge technology has made it possible to select and knockdown the defective or poor genes using restriction enzymes and substituting with genes of interest using ligase enzyme aimed at human welfare.
For instance, banana and tomato have a very limited shelf life and some fruits and vegetables have more shelf life, and this all is due to genetic potential, which can be shifted from low performing varieties to make them high performing.
Lot has been heard about vaccines, and live vaccines, but now its era of edible vaccines that are coming as an application of biotechnology. Scientists around the globe, including Lal and his co-workers, conclude that edible vaccines hold great promise as a cost-effective, easy-to-administer, easy-to-store, fail-safe and socio-culturally readily acceptable vaccine delivery system, especially for the poor developing countries. The edible vaccines involve the introduction of genes of choice into plants and then inducing these genetically modified plants to manufacture the encoded proteins. The concept of edible vaccines was developed by Arntzen (currently heads the department of plant biology at the Arizona State USA) in the 1990s. Twenty years back it was a concept, but it has become a reality today.
Initially, edible vaccines were considered to have a limited scope and useful only for preventing infectious diseases, but, with the advancement in research, it has also found to have application in the prevention of autoimmune diseases, birth control, cancer therapy, etc.
With an increasing trend in accepting transgenic plants, Scientist is currently developing a new profitable and easy to administer vaccination through genetically modified foods. These edible vaccines will aid in delivering life-saving vaccines to developing countries where traditional medical care is not readily obtainable.

Nowadays, formally known as “Biopharming”, the edible vaccines are created by introducing the desired gene into the DNA of select fruits and vegetables. Scientists begin altering the plant’s genes as seeds allowing scientists to grow entire farms of edible vaccines. As the plant grows the cells produce whatever protein is needed for the chosen vaccine. Once the plant is ingested immunization begins, causing the body to produce the necessary antibodies to fight disease.

For now, edible vaccines are still in development phases, but as time goes on and novel research continues as a norm, the edible vaccine are going to be a potential option as an easy, low-cost substitute to outmoded vaccines.
Edible vaccines as concluded by McGregor and his co-workers offer cost-effective, easily administrable, storable and widely acceptable as bio-friendly, particularly in developing countries. Oral administration of edible vaccines proves to be promising agents for reducing the incidence of various diseases like hepatitis and diarrhoea especially in the developing world, which face the problem of storing and administering vaccines. Various foods that are used as alternative agents for injectable vaccines include cereals such as wheat, rice, corn, fruits such as bananas, lettuce, potatoes, tomatoes as vegetables. Consequently, edible vaccines are expected to overcome all the issues associated with traditional vaccines and prove to be the best alternatives to traditional vaccines.

Admitting that vaccines have proved to be useful in the prevention of infectious diseases, however, the global immunization programme for children against the six devastating diseases, 20% of infants remain unimmunized which lead to approximately two million unnecessary deaths per annum. This is because of the limitations on vaccine production, distribution and delivery.
Hence there is dire need to resolve this problem to prevent the spread of infections and epidemics by un-immunized populations in the immunized areas. Various studies have concluded that immunization for certain infectious diseases, either do not exist or they are unreliable or very expensive like; immunization via DNA vaccines is a substitute but is an expensive method, along with some undesirable immune responses. Besides being expensive, these vaccines pose the problem of storage and transportation, as many of them require refrigeration.
Therefore, as substitutes must be produced for traditional vaccines, it was envisaged that plants could be promising agents for an efficient production system for vaccines, which in turn gave rise to the novel concept of edible vaccines.

As compared to issues associated with vaccines and live vaccines, edible vaccines are known for advantages including edible vaccines have an efficient mode of action for immunization, as they do not require subsidiary elements to stimulate an immune response. Edible vaccines are comparatively cost-effective, as they do not require cold chain storage like traditional vaccines and do not need sophisticated equipment and machines as they could be easily grown on rich soils and the method is economical compared to cell culture grown in fermenters. The level of acceptance for the edible vaccine may be more as they are orally administered, not injected like traditional vaccines.

However, there are some limitations to Edible Vaccines. An individual may develop immune tolerance to the particular vaccine protein or peptide. The dosage required varies from generation to generation and, plant to plant, protein content, patient’s age, weight, ripeness of the fruit and quantity of the food eaten. Edible vaccines are dependent on plant stability as certain foods cannot be eaten raw (e.g. potato) and needs cooking that cause denaturation or weaken the protein present in it. This means that despite all prospects as a substitute for traditional vaccines, many different challenges are confronted before developing a plant-based vaccine. However, it has been proved in three successful human clinical trials that enough doses of antigen can be achieved with plant-based vaccines. Hence there is ample argument to believe that edible vaccines are the substitute for traditional vaccines with a lot of novelty to come by research.

Prof Dr Abdullah G Arijo Chairman Department of Veterinary Parasitology Sindh Agriculture University, Tandojam

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