A pathogen upon infection produces proteins, vital for its functions, which elicit an immune response from the infected body. The gene encoding such a protein is isolated from the causative organism and used to develop a recombinant DNA. This DNA is expressed in another host organism, like genetically engineered microbes; animal cells; plant cells; insect larvae etc, resulting in the release of the appropriate proteins which are then isolated and purified. These when injected into the body, causes immunogenic response to be active against the corresponding disease providing immunity against future attack of the pathogen.
Based on the proteins involved in evoking immune response recombinant protein vaccines are of two types:
Whole protein vaccines: The whole immunogenic protein is produced in another host organism which is isolated and purified to act as vaccines.
Polypeptide vaccines: It is known that in the immunogenic protein produced, the actual immunogenic property is limited to one or two polypeptides forming the protein. The other parts of the protein may be successful in evoking an immune response but do not actually cause the disease. For eg: in the case of cholera caused by Vibrio cholerae, consists of three polypeptide chains like A1
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