How are Vaccines Developed?


Vaccines
Everyone has heard of vaccines. Most people have been vaccinated one or more times in their lifetime. Vaccines are preparations that are designed to improve immunity to a particular disease. Vaccines usually contain either killed or weakened forms of pathogenic microorganisms, parts of those microorganisms, or agents that resemble those microorganisms. The process by which vaccines work involve stimulation of the adaptive immune system of the recipient of the vaccination. The adaptive immune system is characterized by two important points: memory and specificity. Adaptive immunity is used by the immune system to mount a defense that is specific to the pathogen that is attacking it. Once the initial attack is over, the adaptive immune system has processes by which it can remember those pathogens in order to mount a faster and stronger defense if they are encountered again.

Vaccines are developed in a number of ways and can be comprised of a number of different constituent parts. The history of the development of vaccines is long, but it originated with Edward Jenner. In Europe, milkmaids would often use the scabs of cows that were suffering from cowpox in order to vaccinate themselves against smallpox, a member of the same viral family. Though they did not initially understand why this worked, Edward Jenner surmised his vaccination theory upon learning of this technique and subsequently developed a vaccine to smallpox.

There are a few main types of vaccines. Killed vaccines are vaccines which contain dead microorganisms that were previously virulent. These microorganisms were often killed using heat or chemicals. Attenuated vaccines contain live microorganisms that have been modified to destroy most of their virulent or pathogenic properties but still trigger an adaptive immune response. Toxoid vaccines are produced from inactive toxic compounds that are produced by microorganisms rather than the microorganisms themselves. This would trigger a response designed to prevent toxic compounds from having an effect on the host rather than preventing infection entirely. Subunit vaccines are vaccines produced from subunits (such as fragments of microorganisms, proteins produced by those microorganisms, surface proteins, or parts of viral capsids) of pathogenic microorganisms. Conjugate vaccines are produced using pathogenic polysaccharide coats of bacteria and linking them with other pathogenic proteins to produce an immune response.

Though constantly changing, techniques that are used to develop vaccines have become somewhat standard. The antigen must be generated first. This is either grown in culture or in cells contained within chicken eggs. After production, the specific antigen must be modified to fit whatever vaccine type it is meant to be used for. Often, extra ingredients (excipients) are added to vaccines in order to either preserve the antigens found within the vaccine or to act as adjuvents (substances which will promote a faster and stronger response from the immune system).

Often, aluminum containing compounds are added. Other excipients include various antibiotics (to prevent growth of bacteria within the vaccine), egg protein (often found within flu vaccines due to the fact that they are grown using chicken eggs), formaldehyde (to inactivate toxic compounds or to prevent contamination by bacteria or other viruses), and monosodium glutamate (which can act as a vaccine stabilizer). Preservatives are necessary for vaccines in order to prevent possible infection or side effects, such as infection of the vaccine by bacteria or re-activation of the pathogenic components of attenuated viruses.

Vaccination plays an important role in modern medicine. It is used to prevent, or in some cases completely eliminate, the threat posed by many viruses and bacteria that are harmful to human health. With vaccines, the adaptive immune system is able to get a handle on infections before they get out of control and to prevent the spreading of infections to other systems. With vaccination, the adaptive immune system is able to mount a response that would otherwise take days or weeks. The production of vaccines boils down to the production of safe antigens that can be used to trigger an adaptive immune response in a safe way in order to prime the system for the potential of a real threat in the future.

Written By : Alexander Maness, United States (M.S. in Biotechnology)

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Edited by: Rajesh Bihani ( Find me on Google+ )

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