Genetic Vaccines
By: Dipa Talati
The investigation of genetic vaccines dates back to the 1950's and 1960's. The experiments done proved that if genetic material was delivered to cells of animals, then it could impel the making of some encoded proteins and anitbodies. In the 1970's and 1980's, there was a setback for researchers. They found that the proteins that were encoded from the inserted genes were destroyed in the cells because it was an immune reaction to unfamiliar proteins. Currently, in the 1990's the research has been advanced to human trials. A trial in 1996 made history by physicians put new genes for HIV or influenza into healthy people.
Traditional vs. Modern
Traditionally, vaccines were weakened versions or subunits of the agents. These types of vaccines cannot be made for many disorders such as malaria, AIDS, herpes and hepatitis C. This is because in order to kill these viruses, the killer T lymphocytes, cytotoxic T lymphocytes, have to be activated and this cannot be done with the traditional vaccines. Another problem with traditional vaccines is that the protection usually wears off after sometime and the patient would need frequent booster shots for it to work.
Difference in Structures
The structures of the two vaccines are also quite different. Genetic vaccines consist of plasmids, small rings of double-stranded DNA. The plasmids used have been altered to carry specific genes and also they would ostracize genes that would cause infection or disease. The genes are inserted into he cells by either injection or by a gene gun. The injection puts the genes into the muscles, while the gene gun puts the genes onto cells near the surface of the skin, like skin membranes.
How DNA vaccines work
DNA vaccines have to do two things in order to activate the killer T lymphocytes. First, the lymphocytes have to be switched on. This is done by the lymphocytes correlating with antigen-presenting cells. In other words, they have to bind to the muscle cells and at the same time to a second molecule, a "second signal", in order to activate a cell. At first, scientists thought that the vaccines had no way of getting into the animal cell to encode the protein, but recent discoveries have proven that wrong.
There are many future possibilities for genetic vaccines. For example: Most DNA vaccines stop yielding proteins after a month. So in the future, would making a longer lasting vaccine help or backfire on us? These are the types of questions posed at clinical trials now and the future.
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