The Hindu

Potato, The New Vaccine?

A jab in the arm to take a vaccine may soon become history. In a few years, you could be eating potatoes to take your Hepatitis B vaccine.

A group in the United States has taken the first steps towards creating a genetically-modified (GM) potato, which can act as a vaccine against the virus that infects millions of people each year and threatens them with a potentially-fatal liver disease.

Edible vaccines have a number of advantages, especially in developing countries. For one, they can be easily administered, unlike an injection which requires a trained health worker. At present, only the polio vaccine is given orally, using a weakened strain of the organism.

If plants can be genetically modified to produce proteins which, when eaten, are absorbed into the body and activate the human immune system, the cost of making the vaccine and storing it can be reduced.

In 1992, tobacco was genetically modified to produce a protein found on the outer surface of the Hepatitis B virus. The viral protein produced by such plants was shown to evoke an immune response when injected into mice.

Now the same Cornell University-based group has reported in the November issue of Nature Biotechnology, that it had successfully modified potato genetically to make this viral protein. Mice fed with the potato soon developed protective antibodies against the viral protein. Preliminary testing of this edible vaccine on human subjects has begun.

But some issues need to be resolved before the ``vaccine potato'' becomes a commercial reality. The Cornell University group has successfully increased the viral protein levels in the GM potato 15 fold, but found that the potato lines producing the most protein did not grow well. In the mice trials, a potato strain that produced less viral protein was used.

It was given to the animals along with the non-toxic part of the cholera toxin as an adjuvant to boost the immune response. If a potato strain which produces good tubers with sufficient levels of the viral protein can be developed, then the use of such adjuvant can be avoided. Alternatively, the potato can be genetically modified to produce both the viral protein and the adjuvant.

In addition, the production levels of the viral protein in the GM plants have to be standardised so that a uniform dosage becomes possible.

Given the problems of stability and shelf-life, eating fresh produce may not be the way such edible vaccines can be administered. Simple food-processing methods, such as dehydration or freeze-drying, may be needed to produce a uniform product.