The proposed National Biotech Strategy Development document acknowledges the potential benefits of using plant as production host but it takes a rather harsh view on edible vaccine development.
The document further says that there was no scientific basis to completely disregard the potential of plant-derived vaccine. Part of the problem with the edible vaccine is the difficulty in assessing the potency and dosage of the vaccine. However, there are ways by which potency of vaccines expressed in edible parts can be assessed. These include performing minor possessing such as drying, grinding etc. and measuring the potency of vaccine against known standards, according to a reliable source.
Complete and clear-cut negation of this promising area from Biotechnology Development Strategy is much uncalled for. Development in the technology can usher in new era very rapidly. There are several new technologies in the horizon where little is known about their efficacy. However, a prudent way is to avoid making judgmental statements about them, the source added.
One of the daunting tasks the developing countries face is to provide healthcare facilities to its people. This essentially has to be done in a two-tier approach: a. By strengthening preventive health care. b. By providing trained professionals and infrastructure to look after the sick people. One of the most effective ways by which preventive care can be administered is to immunize population for 'vaccine preventable' diseases. Since most of the developing nations suffer from poor hygiene and nutrition, infectious disease are among the front-runners causing mortality. Many of the infectious diseases can be prevented by prophylactic vaccinations.
Traditionally vaccines are manufactured by cultivating the causative organism, either identical strains (that are inactivated after growth) or using strains that have lost their disease causing ability, in a suitable host. Depending on the process of developing vaccines, the cost varies from a few rupees (Tetanus vaccine) to a thousand rupees (Hepatitis A vaccine). In conventional method of manufacturing, some of the vaccines can be upgraded to safer and cheaper alternative to increase the availability of the vaccine to resource poor countries.
The source said, plants offer an attractive platform producing vaccines in virtually unrestricted large-scale, high biological safety, and so on. One of the major drawbacks in the conventional vaccine manufacturing technology is the carry over of contamination from undesired pathogens, toxins, retroviral sequences etc. originating in the production process. As a result, each vaccine lot needs to be rigorously tested for acceptability to human or animals by demonstrating the absence of toxins, pathogens etc.
Plants can provide an immense security barrier, since no plant-pathogens are known, until date, to cause disease to human being. Low technical input in growth and maintaining high value plants would provide employment opportunity to less skilled manpower of the country. It is with these benefits in mind scientists across the world have engaged themselves in developing plants as an alternative to traditional cell culture derived vaccines. Expressing only the 'effective' portion of a bacteria or virus in edible parts of plant is also being explored with varied degree of success.
'Edible vaccine' research is currently supported by major funding agencies in the United States such as NIH, NSF, US FDA, etc., and is directed at human diseases, with a special emphasis on the developing world. The technology has an immediate value for the production of inexpensive vaccines as feed additives for agricultural animals. Since various plant tissues are fed to animals, other plants such as alfalfa, maize and wheat are promising vehicles to deliver vaccines (and perhaps other pharmaceuticals) for the betterment of animal and human health. The technology is particularly relevant to our country where maintaining long "cold-chain" adds significantly to the cost of vaccines.
Although, there has been no edible vaccine released in the market until date, several companies have started conducting clinical trials of edible vaccines. Americas Animal and Plant health inspecting agency APHIS has approved therapeutic veterinary proteins made in Alfalfa, Barley, Corn, Duckweed (Lemna), Rice, Safflower and tobacco for clinical trials, the source informed.
Reasons for slow progress on developing edible vaccines are many, low yield of the required protein being amongst the leading cause. Commercial setups offering to express recombinant proteins in plants to the tune of several grams per Kilo of fresh biomass have already emerged. This technological advance permits one to study and optimize various parameters in edible vaccine development. Issues such as dosage, immunogenicity, duration of protection etc. are basic challenges that can now be addressed with plant-produced vaccines.