The vaccine in the vegetable salad: plants that provide ``natural'' vaccines

In a laboratory in Florida, genetically modified plants are currently being developed, which are able to provide mice with protection against malaria parasites and cholera toxins - diseases that kill more than a million people every year

Who is the greatest killer of all time? Attila the Hun, who almost destroyed the Eastern Roman Empire? The dictator Stalin, who led to the execution of millions of his people? And maybe it was World War II, which resulted in the death of more than twenty million young soldiers? The real answer is none of them. The main cause of death throughout human history was one and only: diseases. Analysts believe that the smallpox epidemic alone killed 500 million people during the XNUMXth century, malaria still kills over a million people every year, and cholera causes the agonizing death of between one hundred and one hundred and fifty thousand people a year.

In the last hundred years the wheel started turning in the opposite direction. We fight infectious diseases with great success, and a large part of childhood diseases that were common a hundred years ago, have almost disappeared from the West thanks to vaccinations and strict sanitary conditions. Smallpox also completely disappeared from the world thanks to the vaccine that was invented two hundred and ten years ago. But there are other diseases for which we still do not have an answer, and they can be found mainly in the Far East and Africa. Among them are AIDS, malaria and cholera.

The sad truth is that we have a vaccine for children capable of stopping the spread of cholera, but it is effective for only three years, and is too expensive to be used on the entire population. Even if there were effective vaccines for malaria and AIDS, it is likely that their prices would be too high for the poor population of Africa, many of whose citizens do not earn more than a few dollars a day at best.

The solution, therefore, must be cheap and convenient to use, and conventional vaccines clearly are not. But a new hope is emerging on the horizon. Hope for a better world, where we can use nature's own resources to defend ourselves from its disturbances. Biomedical researcher Henry Daniel of the University of Central Florida, who recently developed in his laboratory a new strain of vaccines that can be grown in the field and eaten, believes in this hope. These are the herbal vaccines, which may protect us in the future from many infectious diseases.

The herbal vaccines work similarly to regular vaccines, through the education of the body. A vaccine shot against hepatitis contains millions of killed hepatitis viruses that cannot cause harm to the body. The immune system recognizes the dead viruses and learns their characteristics. The next time a hepatitis virus enters the body, the immune system will be able to deal with it quickly and efficiently. Daniel took the same idea, and genetically engineered unusual lettuce and tobacco plants. These plants produce in their leaves a large amount of two different proteins: one that is also found in the parasites that cause malaria, and the other that is similar to the toxin secreted by the cholera bacterium.

Is it possible to eat the leaves of the plants, and expect the proteins to reach the bloodstream from the stomach, giving the immune system a crash course in defending against malaria and cholera? probably not. The stomach contains strong hydrochloric acid, which is necessary for the initial digestion of the food, and most of the proteins that reach the stomach undergo a very rapid breakdown before continuing to the intestine and being absorbed into the bloodstream. To deal with the problem, Daniel developed a unique mechanism in his plants: they assimilate the immune proteins in their chloroplasts - small bodies where photosynthesis takes place. The rigid cell walls provide primary protection against the acid in the stomach, and the chloroplast membranes provide additional shelter for the sensitive proteins. In this way, the proteins survive the traumatic passage through the stomach and manage to reach the intestine - and from there into the bloodstream.

In a study published this month in the scientific journal ``Plant Biotechnology,'' Daniel describes the plants he created, and how he fed mice a mixture produced from the leaves of the plants. The immune system understood the hint and started producing antibodies against cholera toxins and malaria parasites. The same antibodies were able to prevent the malaria parasites from penetrating the red blood cells of the mice very effectively, and provided protection against the toxin secreted by the cholera bacteria.

Sounds good? This is truly innovative research that may lead to the fact that we will receive the vaccines of the future together with our morning salad. But there are still two main problems. The first is that although the mice definitely produced antibodies against malaria, the tests of the effectiveness of the antibodies were only done on blood samples taken from the small rodents. That is, it has not yet been proven with certainty that the malaria antibodies provide effective protection against the invasion of the pests into the body. The second problem is that the vaccine does not last long: the mice acquired immunity for a little over 300 days, even when the vaccine was ``boosted'' with additional doses of plants in the food. On the other hand, 300 mouse days are equivalent to 40-50 human years, and it is permissible to hope that in humans the vaccine will survive such a long period.

The research provides new hope that in the future we can get the vaccines for many diseases in the food we eat every day. Perhaps in this way we will also be able to overcome the last of the great murderers of history, and bring about the fact that future generations will be protected from serious diseases even without medical intervention.

The original scientific article: http://www3.interscience.wiley.com/cgi-bin/fulltext/123226774/PDFSTART