Stomach Virus Vaccine Could Come From Tobacco

Tobacco and vaccine
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The much-maligned tobacco plant may have a silver lining: scientists have found a way to make the plant manufacture a protein that can be used to make a vaccine against the common stomach virus known as norovirus. This highly contagious virus is also known as Norwalk-like virus, gastroenteritis, and stomach flu.

This is not the first time tobacco has been used as a factory to produce vaccines. Scientists at Stanford University in California reported in July 2008 that they were using the plants to grow the key ingredients of a cancer vaccine for a type of non-Hodgkin’s lymphoma. The advantages of using a plant-grown vaccine over an animal-grown vaccine, which has been the standard, is that vaccines from plants would be cheaper and, at least in theory, harbor less risk of passing along unknown viruses from animals.

According to Charles Arntzen, a plant biologist at Arizona State University, he and his research team used a genetically engineered virus called the tobacco mosaic virus to force the tobacco plant to make the protein. The protein forms into a ball, also known as a virus-like particle or capsid, which the immune system “thinks” is a virus and attacks it. The capsid is benign, however, and cannot cause disease.

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Stomach virus affects an estimated 23 million people every year, according to the US Centers for Disease Control and Prevention (CDC). Symptoms include nausea, vomiting, diarrhea, and stomach cramps. Some people also experience low-grade fever, chills, headache, and tiredness. Children generally experience more vomiting than adults. In most people, symptoms disappear in about two days.

Although symptoms disappear in most people within two days, the stomach virus can be more serious for the very young, the elderly, and people who have a compromised immune system or other illnesses, as they are more prone to dehydration. These individuals can often be found in group settings, such as day care centers, nursery schools, nursing homes, and hospitals, which lend themselves to easy contamination.

Norovirus is spread easily if people eat food or drink beverages that have been contaminated, touch contaminated surfaces or objects and then place their hands in their mouth, or have direct contact with people who are infected and who show symptoms. Once people become infected with norovirus, they are contagious from the time they begin to feel ill until at least three days after they have recovered, although they can be contagious for as long as two weeks.

Thus far scientists have not conducted any human trials of the tobacco-based vaccine for stomach virus. Researchers have noted, however, that the vaccine may be more effective if it is administered intranasally rather than orally, because the immune cells in the nasal passages are more likely to accept the vaccine.

SOURCES:
Centers for Disease Control and Prevention
McCormick AA et al. Proceedings of the National Academy of Science USA 2008 Jul 22; 105(29): 10131-36
Reuters 8/19/09

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