Vaccination is the process of development of immunisation against a particular disease by inoculation of haemless antigen tic material like attenuated pathogen or its toxoid into a healthy person. Immunisation develops due to formation of memory cells by the immune system. When a vaccinated person receives an infected dose of the pathogen, the existing memory T- OR B - cells recognise the antigen and induce a massive formation of T-cells, B-cells and antibodies for eliminating the invaders.
Context
- Foundation Of immunology Through Vaccination
- Types of Vaccines.
Foundation of immunology through vaccination and other procedures were laid by the following scientists.
1. Edward Jenner (1749-1823)
Jenner noted that milkmaids often develop a milder form of pox called cow-pox. They did not develop small pox. In 1796, Jenner infected an 8 year old boy James Phipps, with cowpox scab (from Sarah Nelmes) and after about two months injected live small pox material into his body.
The boy did not develop small pox. It became a standard procedure for preventing small pox.Jenner also coined the term vaccine.
2. Louis Pasteur (1822-1895).
Pasteur (1879) found that ageing cultures of cholera bacteria were too weak to cause disease. He injected them into chicken. Instead of dying of cholera, the chicken became immune to fowl cholera. Pasteur then developed the technique of weakening of pathogen by starvation, eat and cold. Pasteur (1885) also developed anti rabies vaccine and administered it successfully to Joseph Meister bitten by Rabid dog.3. Robert Koch (1843-1910)
He is famous for his postulates (Koch postulates), germ theory of disease and method of obtaining pure cultures of pathogen. Koch discovered anthrax bacteria (1876 tuberculosis bacteria (1882) and cholera bacteria (1883). He also developed the test for tuberculosis for which he was awarded Nobel Prize in 1905.4. Emil Adolph von Behring (1854-1917)
Behring proposed that blood and serum of an immunised person when injected into another subject brought about immunisation of the latter (Behring law).
Bahring (1891) injected sheep with diphtheria and tetanus, obtaining serum from their blood and induced passive immunisation against the two diseases. He was awarded Nobel Prize (first for medicine physiology) in 1901.
Subsequently, it was found that small amounts of tetanus toxin provided immunity to the disease. By the end of 1920s vaccines against several diseases became available, e.g., diphtheria, tetanus, pertussis (Whooping cough), tuberculosis.
Types Of Vaccine
Vaccine is a suspension of killed or attenuated pathogenic microorganisms or antigenic preparations made out of it which on administration provides immunity towards the pathogen.
The process of administration of vaccine is called vaccination. In certain cases a single dose is enough vide life-long immunity. In others 2-3 booster doses are required to develop longtime immunity.
Vaccines are given either as injections or oral drops. They are given separately or in combination (e.g., DPT or DPT-Hib).
1. First Generation Vaccines.
(i) Attenuated Live Vaccines. Weakened, starved, aged or less virulent form of pathogen was initially used as vaccine, e.g., small pox vaccine of Jenner, cholera vaccine of Pasteur.
(ii) Killed or Inactivated Vaccines. The pathogen is killed or inactivated by heat and other methods for preparing vaccine, e.g., Salk's polio vaccine.
(iii) Toxoids. Modified or detoxified toxins are used as vaccines, e.g. tetanus toxoid, diphtheria toxoid.
(ii) Killed or Inactivated Vaccines. The pathogen is killed or inactivated by heat and other methods for preparing vaccine, e.g., Salk's polio vaccine.
(iii) Toxoids. Modified or detoxified toxins are used as vaccines, e.g. tetanus toxoid, diphtheria toxoid.
2. Second Generation Vaccines.
They are vaccines made of pure surface antigens of the pathogens only which are multiplied through genetic engineering, or recombinant DNA technique, e.g., vaccine against hepatitis B. The latter vaccine has also been produced with the help of silk worm injected with baculovirus having hepatitis antigen.
The best way for vaccination against viral diseases is to genetically change the viral particles by adding or removing the genes so that they are unable to cause the diseases but bring about formation of antibodies. Similarly toxins and toxoids can be used as vaccines
Purified antigens are highly effective vaccines because they bring about antibody development without the presence of pathogens. The risk of pathogenicity is, therefore, zero. Antigens can also be produced synthetically for this purpose.
3. Third Generation Vaccines.
They are purest, highest potency vaccines which are synthetic in nature. Recombinant vaccines are vaccines having a protein or a gene encoding the protein that causes immunogenic reactions in the host so as to produce antibody against the disease. Instead of
" protein even recombinant polypeptides can be used. Vaccine for hepatitis-B is being produced from east through recombinant DNA technology. The latest additions are vaccines against influenza type B and H1N1. Recombinant vaccines being pure are highly efficacious with no side effects."
The last revolution in vaccines is DNA vaccines. The gene controlling the formation of immunogenic protein is isolated. It is cloned and then integrated with a vector for introduction into an individual to be immunized. Marshall et al (2011) have developed a technique of oral vaccination by attaching the antigens to harmless strains of Helicobacter pylori.
For deadly microbes, toxins and poisons, a very quick response is required. Vaccination provides immunisation after a time gap. Therefore, passive immunisation is practised in such cases. Preformed antibodies, antitoxins and antivenoms are injected to patients of such cases, e.g., tetanus, snake bite The process is called passive immunisation.
Monoclonal antibodies are identical antibodies obtained from a single source for effectively dealing with an antigen. They are best produced by hybridoma cells. Hybridoma cells are hybrid cell formed by fusion of a myeloma cell and a single antibody producing B-lymphocyte from spleen Hybridoma cell can multiply indefinitely and produce monoclonal antibodies.
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