Principles of vaccination

How immunity counters such or such disease develop does? Our immune system has memory: when it is confronted for the first time with a pathogenic agent, i.e. to a virus or a bacterium, the organization reacts by specializing certain cells to produce specific antibodies against this agent. These cells "memories" will be stored during years in our body, and will quickly be reactivated with the least contact with the pathogenic one. By accelerating and reinforcing specific mechanisms of defence.What makes it possible the organization to quickly eliminate the intruder before developing the disease. 

In 2000 years, the techniques somewhat evolved/moved, and the recent contributions of the genetics and molecular biology made it possible to fight new diseases. There are three great families of vaccines: attenuated vaccines, inactivated vaccines, and those resulting from the genetic engineering.

Attenuated vaccines

The attenuated vaccines are manufactured starting from bacteria or of alive viruses which one made transfer so that they lose their infectious character. But not their antigenic character, i.e. their role of release of the production of cells "memories". The organization thus constitutes a stock of antibody of which it will be useful effectively when it comes into contact with the wild bacteria or viruses (natural). The oral vaccine against the poliomyelitis, for example, is obtained by successive passage of the virus in culture of cells and in animals. What induces changes, and thus the attenuation. After administration by simple oral way, the organization develops the antibodies necessary to the immunization against the disease.

Inactivated vaccines

The inactivated vaccines, called so killed, function on the same principle. The organization recognizes the bacterium or the virus (whole but inactive), and develops against them antibodies. They are prepared starting from inactivated microbe cultures by various processes. The vaccine against the whooping-cough consists in preparing a suspension of whole germs, inactivated by heat and formol. Remain to produce these vaccines in great number, therefore to produce many inactivated viruses. The scientists for that developed of the "cellular lines", made cells coming from various animals which divide ad infinitum. Each microbe or virus develops more or less well according to the origin of the cellular lines. The flu virus develops with wonder on cellular lines coming from chicken foetus.

Vaccines resulting from the genetic engineering

The vaccines resulting from the genetic engineering, them, are inactivated either physically, but by genetic way. By inactivant genes responsible for the virulence of a germ, one creates a nonpathogenic mutant. It is then enough to obtain the multiplication of the mutant, and there are new stocks, "immunogenic" but inoffensive. 

Another method consists in not using either whole germs for vaccination, but only the "antigenic" molecules of these genes. It is enough to make manufacture by a yeast, a bacterium or an animal cell, the portion of the virus recognized like antigen by the organization to vaccinate. How? In "grafting" in this yeast or bacterium the gene coding for the antigen, i.e. for viral protein starting at the host the production of antibody. The vaccine is thus here manufactured by other living organisms. The produced antigens are then insulated by purification, and can be used as a basis for vaccines, called "molecular". It is seen, one is well far from the broyats of pustules of patients.

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