LONDON - Scientists have for the first time used a vaccine manufactured in a factory to protect animals-- Minks in this case - against a viral disease. The achievement, reported in the number of next month Nature Biotechnology , may mark the beginning of a new industry to use plants as Minifactories to produce vaccines for pets and people.
A four country team led by Kristian Dalsgaard of the Danish Veterinary Institute for Virus Research in Lindholm, Denmark, designed the mosaic virus cowpeas, which infects plants to contain a short peptide of 17 amino acids of canine parvovirus. The trick to making this chimera in a good antigen - a foreign body that will stimulate an immune response in the host - is having the peptide copied several times on the surface of each virus particle. This is without perspiration to the mosaic virus cowpea: His icosahedron surface is composed of 60 copies of each of the two envelope proteins. It has a projecting loop which is easily discerned by passing the cells. Researchers designed viral DNA to include the foreign sequence in the loop, which is then replicated 60 times on each virus particle.
Dalsgaard team injected the virus designed in the leaves of its natural host, the plant cowpea, also known as bean name with black eyes. After about 3 weeks, the population of prosperous virus - about 1 to 2 grams of chimeric virus particles per kilogram of plant - was harvested from the juice of chopped-up leaves. Because the peptide sequence of canine parvovirus is also found in two other pathogens, viruses mink enteritis virus and feline panleukopenia, researchers expected that injection of chimeric particles would protect those species - dog, mink and the cat - against viral diseases. Good vaccines already exist for these diseases, but it might be cheaper to produce other vaccines in plants.
Two mink groups were vaccinated with viral particles, six low dose (100 micrograms) and eight high-dose (1 mg). Approximately one month later, the animals were exposed to infectious contents of the intestine of a mink animal acute viral disease enteritic, a debilitating diarrheal disease. One mink in the vaccine group low dose, fell ill. Seven of the 10 unvaccinated controls, meanwhile, contracted the disease. The vaccine so that the researchers did not find even traces of virus in faeces than half the immunized mink. Dalsgaard plans to repeat the experience in cats.
Experts applaud the study. Said Michael Wilson, deputy director of the Scottish Crop Research Institute in Dundee, UK, which is developing a similar approach with the virus of potato X, "It is very encouraging that they have to work."
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