Edible Vaccines

 



EDIBLE VACCINES

 

For a long time, vaccines have been used as the primary defense and protection tool to fight diseases. These diseases can be bacterial, parasitic, and viral. The vaccines' working principle can be explained easily like that; it contains an agent that resembles a disease-causing microorganism and is commonly made from weakened or killed forms of the microbe, toxins, or surface proteins. The agent stimulates the body's immune system to distinguish the foreign antigen and destroy it. [1]

 

However, the process of production and purification makes them expensive and unaffordable for many developing countries. To eliminate these kinds of problems, edible vaccines, which can be administered orally or to other mucosal surfaces, are developed. They are cost-effective in availability, storage, preparation, production, and transportation, plus they also decrease demand for skilled health care professionals in developing countries (and in developed countries, too). Edible (plant-based) vaccines produced by biotechnological methods are stable at room temperature, unlike a conventional vaccine, which needs cold chain storage; therefore, the yearly cost to preserve edible vaccines is much less than the traditional ones. [2]

 

How are they produced?

Edible vaccines are produced by introducing selected wanted genes into plants and then inducing these modified plants to form the encoded proteins. This process is known as "transformation," and the changed plants are called "transgenic plants." Like traditional subunit vaccines, edible vaccines are composed of antigenic proteins and are lacking pathogenic genes. Besides, they can be very easily scaled up. [3]

For instance, China's entire population could be vaccinated by producing edible vaccines in just 40 hectares of land. Plants mainly used for oral vaccines are tobacco, potato, banana, tomato, rice, lettuce, soybean, alfalfa, muskmelon, carrot, peanuts, wheat, and corn. It is worth considering that edible does not necessarily mean nutritious, tasty, or organoleptically pleasing because oral vaccines need only be safe (non-toxic) for human consumption. [4]

 

Edible Vaccine Disadvantages

To produce an edible vaccine, you need a living, growing plant; it means you also need absolute control exercised on the environment that plant grows; the first reason for avoiding the loss of pollen and seeds during plant removal. The second and most essential purpose is the potential for the parasites. Contact with insects or the release of contaminated water into the environment is two possible mechanisms for that. However, each risk's possibility and severity depend on plant to plant, and each vaccine's antigen in transgenic plants.

Another critical point is the allergenic and toxic potential of plant components. (e.g., glycans, nicotine). [2]

 

The Current State

You can see the current state of edible vaccines in the below table;

Table1:current state of edible vaccines [5]

Plant host

Indication

Product stage

 

Potato

 

Diarrhea

 

Phase 1

 

 

Lettuce, potato

 

 

Hepatitis B

 

Phase 1

 

Tobacco cell suspension

 

Newcastle disease

 

 

USDA approved

 

Spinach

 

 

Rabies

 

Phase 1

 

Nicotiana benthamiana

 

 

Non- Hodking’s lymphoma

 

Phase 1

 

Nicotiana benthamiana

 

H5N1 “avian” influenza

 

Phase 1 (ongoing)

Phase 1 (ongoing); phase 2 (Health Canada approved)

 

Nicotiana benthamiana

 

 

H5N1

 

 

Phase 1 (ongoing)

 

Nicotiana benthamiana

 

 

H5N1 “swine” influenza

 

Phase 1 (ongoing)

 

Nicotiana benthamiana

 

 

HIV

 

 

Pre-clinical

 

Safflower

 

 

Diabetes

 

Phase 1/2

 

Tobacco

 

 

Hepatitis B

 

On market

 

 It is important to note that edible vaccines are clinically tested according to the United States Investigational New Drug Research Application standards and acceptable agricultural practices. This study has been sponsored by the United States Agriculture Agency (USDA), the European Medicine Agency (EMA), and the Cuba Regulatory Authority. It has been stated at plant production conferences on antibodies and vaccines in France in 2004 and in the Czech Republic in 2005. After evaluating and identifying the plant's essence, the possibility of cross-contamination, and the genetic history of the plants used as a vaccine, the USDA has licensed vaccines used in the veterinary sector.  [5]

Some countries can consider edible vaccines as food and medicine at the same time. For that reason FDA has tried to correct this duality by evaluating and controlling edible vaccines as a hybrid medication. But due to their genetic and physical aspects, it is not very easy to handle.  The antigen present in edible vaccines is a chemical that does not conform with the FDA rules on dietary additives but is accepted as non-GRAS (Generally Recognized As Safe). However, these vaccines will be used in the nutritional group as genetically engineered food and are thus not known to pose a high health risk.  Because of this uncertainty, there is a legal gap regarding the control on the standardization of the commercialization of edible vaccines.  In the face of this legal confusion, it is assumed that each nation will determine whether the entrance of edible vaccines (or plants that manufacture them) is permitted [5]. To conclude, the subject of the edible vaccine is developing day by day. Therefore, researches on the subject are still ongoing.

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CONTENT: Seyda Nur Açıkgöz

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REFERENCES

[1] Gunasekaran, B., & Gothandam, K.M.. (2020). A review on edible vaccines and their prospects. Brazilian Journal of Medical and Biological Research, 53(2), e8749. Epub January 24, 2020.https://doi.org/10.1590/1414-431x20198749

[2] Concha, C., Cañas, R., Macuer, J., Torres, M., Herrada, A., Jamett, F., & Ibáñez, C. (2017). Disease Prevention: An Opportunity to Expand Edible Plant-Based Vaccines? Vaccines, 5(2), 14. https://doi.org/10.3390/vaccines5020014

[3] Goyal, R., Sharma, R., Lal, P., & Ramachandran, V. G. (2007). Edible vaccines: Current status and future. Indian Journal of Medical Microbiology, 25(2), 93. https://doi.org/10.4103/0255-0857.32713

[4] Kurup, V. M., & Thomas, J. (2019). Edible Vaccines: Promises and Challenges. Molecular Biotechnology, 62(2), 79–90. https://doi.org/10.1007/s12033-019-00222-1

[5] Sohrab, S. S. (2020). An edible vaccine development for coronavirus disease 2019: the concept. Clinical and Experimental Vaccine Research, 9(2), 164. https://doi.org/10.7774/cevr.2020.9.2.164

[6] WHO. (2005, January). Informal Consultation on Scientific basis for regulatory evaluation of candidate human vaccines from plants. Retrieved from https://www.who.int/biologicals/Plant%20Vaccine%20Final%20Mtg%20Repor%20Jan.2005.pdf