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TypesAll vaccinations work by presenting a foreign antigen to the immune system in order to evoke an immune response, but there are several ways to do this. The three main types are as follows:An inactivated vaccine consists of virus particles which are grown in culture and then killed using a method such as heat or formaldehyde. The virus particles are destroyed and cannot replicate, but the virus capsid proteins are intact enough to be recognized by the immune system and evoke a response. When manufactured correctly, the vaccine is not infectious, but improper inactivation can result in intact and infectious particles. Since the properly produced vaccine does not reproduce, booster shots are required periodically to reinforce the immune response. In an attenuated vaccine, live virus particles with very low virulence are administered. They will reproduce, but very slowly. Since they do reproduce and continue to present antigen beyond the initial vaccination, boosters are required less often. These vaccines are produced by growing the virus in tissue cultures that will select for less virulent strains, or by mutagenesis or targeted deletions in genes required for virulence. There is a small risk of reversion to virulence, this risk is smaller in vaccines with deletions. Attenuated vaccines also cannot be used by immunocompromised individuals. A subunit vaccine presents an antigen to the immune system without introducing viral particles, whole or otherwise. One method of production involves isolation of a specific protein from a virus and administering this by itself. A weakness of this technique is that isolated proteins can be denatured and will then bind to different antibodies than the proteins in the virus. A second method of subunit vaccine is the recombinant vaccine, which involves putting a protein gene from the targeted virus into another virus. The second virus will express the protein, but will not present a risk to the patient. This is the type of vaccine currently in use for hepatitis, and it is experimentally popular, being used to try to develop new vaccines for difficult to vaccinate viruses such as Ebola and HIV. Dieser Artikel basiert auf dem Artikel http://en.wikipedia.org/wiki/Vaccination aus der freien Enzyklopädie Wikipedia und steht unter der GNU-Lizenz für freie Dokumentation. In der Wikipedia ist eine Liste der Autoren verfügbar. |
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