STRUCTURE

• Introduction – What are vaccines (15 words)          
• Body – Explain the advantages and disadvantages of DNA vaccines (120 words)
• Conclusion – Mention a short conclusion  (15 words)

ANSWER

A vaccine is a biological preparation that offers active acquired immunity to a specific disease. Generally, a vaccine comprises of an agent that has a resemblance to the disease-causing microbe.

DNA vaccination is a technique for protecting an animal against disease by injecting it with genetically engineered DNA so cells directly produce an antigen, resulting in a protective immunological response.

ADVANTAGES OF DNA VACCINES

• Do not contain an actual infectious agent, whether dead or alive. One of the classic methods of vaccination is the introduction of a live but weakened version of a pathogen into a person. This has proven effective thus far, but does offer some distinct safety concerns. The risk of reversion for example, where the vaccination strain mutates and becomes virulent, is one such issue, as is the fact that these vaccines can’t safely be used in people who are pregnant, elderly, or suffering from any one of a number of chronic diseases. These concerns are not relevant to DNA vaccines, which could potentially be given to virtually anyone regardless of health status safely, and without any risk of reversion.
• Effectively stimulate different dimensions of the immune response, thereby providing a person long lasting immunity after a small number of doses. One of the problems with some vaccination technologies is the fact that multiple booster doses are needed for a vaccine to effectively immunise an individual, and this can pose practical problems, particularly in countries where healthcare and transport infrastructure isn’t as well established as here in the UK.
• Once tested for efficiency and safety, a DNA vaccine can be generated in large volumes at a much lower cost than some traditional vaccine types. The DNA vaccine in question would also be easier to transport as there are no particular storage requirements (live vaccines for example need to be kept refrigerated).
• Potentially be applied to a broader range of disease causing pathogens like fungi and parasitic organisms. At present most vaccination technologies are limited to viruses and bacteria.

DISADVANTAGES OF DNA VACCINES

• This type of vaccination would be limited to pathogens with a distinctive protein immunogen (molecule that triggers an immune response). Some pathogens possess non-protein immunogens , bacteria with sugar coats for example.
• DNA vaccines also present a slight risk of potentially disrupting normal cellular processes. This has yet to be shown as a major concern, however there is a chance that the introduction of foreign DNA into the body could affect a cell’s normal protein expression pathways.
• Chance of an immune response against the DNA itself, or the DNA delivery vector, which would defeat the point of the vaccine as a whole. If such a reaction were to occur, no protein immunogens would be expressed, and there would be no immune response to those immunogens, and hence no immunity against the pathogen in question.
• Chance that the body develops a resistance or tolerance towards the protein the vaccine introduces. This would again defeat the purpose of the vaccine, which is to stimulate a lasting immune response against the injection.