Give the procedure of development of recombinant subunit vaccines.
Recombinant subunit vaccines contain only a part of the whole pathogenic organism, which can be either a synthetic peptide or an expressed whole protein. These vaccines are developed using tools of rDNA technology to avoid potential concerns associated with conventional vaccines, such as the reversal of toxoids to their toxigenic forms or the co-purification of undesirable components.
The procedure involves expressing the antigenic protein from cloned genes in the laboratory. Prokaryotic systems, such as Escherichia coli, or eukaryotic systems, such as yeast, are used to express these recombinant proteins. This method facilitates the large-scale biological production of therapeutic agents that are safe, pure, and efficient.
A key example is the development of the vaccine against Hepatitis B. The virus consists of a core containing the viral genome surrounded by a phospholipid envelope carrying surface antigens called HBsAg. This surface antigen is the key element for the vaccine. Because culturing the Hepatitis B virus is very complicated, the antigen is produced using recombinant technology rather than traditional methods.
The advantages of these vaccines include high purity, stability, and safe use. By utilizing only a part of the pathogen, specifically the antigenic component, these vaccines provide an effective immune response without the risks associated with the whole organism.
Explanation
The answer is derived from the textbook context which defines subunit vaccines as containing only a part of the pathogen (synthetic peptide or expressed protein). It highlights the use of prokaryotic (E. coli) and eukaryotic (yeast) systems for expression. The context uses the Hepatitis B vaccine as the primary example, noting that HBsAg is the key surface antigen used and explaining that culturing the virus is complicated, necessitating recombinant methods. The advantages listed (purity, stability, safety) and the rationale (avoiding toxoid reversal) are also explicitly stated in the provided text.