DNA vaccines can either be purified from the disease-causing organism itself or genetically engineered. DNA vaccination differs from traditional vaccines in that just the DNA coding for a specific component of a disease-causing organism is injected into the body. The injection or oral administration of these non-disease-
Instead of taking a damaged pathogen, a single gene from that pathogen is artificially copied and multiplied. That gene is then injected into a muscle. For unknown reasons, muscle cells tend to take up this gene and use it as one of their own genes, making the product the gene describes. The immune system will recognize that product as foreign, and remember it, just like it does in conventional vaccination. Since the gene is produced artificially, it can be made much more pure than any vaccine produced directly from pathogens. Several different genes can be mixed and injected simultaneously, making it possible to vaccinate against many variants of a pathogen, or against several different pathogens, at the same time. Because DNA vaccines generate cell-mediated immunity, the hope is that they will be effective against difficult viruses, even in cases where standard vaccines have failed to work. Additionally, the genes are cheap to produce, don't require cooling, and can be stored for years.
The main thrust of DNA vaccine technology currently lies in creating vaccines for viral, bacterial, or parasitic infections, such as hepatitis C virus, herpes simplex virus, HIV, human papilloma virus, malaria, influenza, and tuberculosis, which do not appear to induce neutralizing antibodies. It is also hoped that this technology could be used to control cancer and treat established chronic viral infections.
This group of vaccines may benefit from research published in a February 2008 issue of Genetic Vaccines and Therapy. According to scientists in Heidelberg, Germany, tattooing may be a more effective way of delivering DNA vaccines than intramuscular injection, thereby offering a more effective means of delivery. Using a coat protein from the human papillomavirus (HPV) as a model DNA vaccine antigen, they compared delivery by tattooing the skin of mice with standard intramuscular injection with, and without the molecular adjuvants that are often given to boost immune response. The tattoo method resulted in a stronger antibody and cellular response than intramuscular injection, even when adjuvants were included. Three doses of DNA vaccine given by tattooing produced at least 16 times higher antibody levels than three intramuscular injections with adjuvant. The adjuvants enhanced the effect of intramuscular injection, but not of tattooing. The researchers postulated that these results might be due to the fact that tattooing causes a wound and sufficient inflammation to prime the immune system, and also covers a larger area of the skin than an injection, so the DNA vaccine can enter more cells.
As of mid 2010, however, no DNA vaccines have yet been approved for use and it is unlikely that any will be approved before 2015. More information can be obtained at http://www.kaloramainformation.com/
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