GENERAL STEPS EMPLOYED IN THE PRODUCTION OF VACCINES

The basic steps involved in vaccine production are summarized in this section.

  1. Generation of the antigen: The first step in order to produce a vaccine is generating the antigen that will trigger the immune response in the host organism. For this purpose, the pathogen’s proteins or DNA molecules need to be grown and harvested in their  pure forms; and some of the techniques used in cultivating these organisms are elaborated as follows:
  • Viruses are grown on primary cells from chicken embryo or fertilized eggs or cell lines that reproduce repeatedly. Hepatitis A vaccine and influenza vaccine are generated this way.
  • Bacteria are grown in bioreactors which are devices that use a particular growth medium that optimizes the production of antigens. Haemophilus influenza vaccines are produced this way.
  • Recombinant proteins derived from the pathogen can be generated either in yeast bacteria or cell cultures.
  1. Isolation of the antigens: The aim of isolating the antigen from the pathogen is to release as much viral or bacterial particles as possible for the development of the vaccine. To achieve this, the antigen will be separated from the microbial cells used to generate it and isolated from the proteins and other parts of the growth medium that are still present. After this stage, the isolated molecules are purified prior to further development.
  2. Purification: Here, the antigens isolated are then purified in order to produce a high quality purified product. Purification can be done using different techniques for protein purification such as high performance liquid chromatography (HPLC). Recombinant proteins need many operations involving ultrafiltration and column chromatography for its purification.
  3. Addition of other supporting/carrier molecules: This step involves addition of other supporting components to the purified antigenic molecules. The supporting components usually added to the purified protein or microbial substances required for vaccine production include: adjuvants, stabilizers, and preservatives. These substances are added to vaccines being produced in order to boost their activity in vivo as well as preserve them prior to usage. Adjuvants enhance the recipient’s immune response to an antigen while stabilizers increase the storage life of the vaccines. Preservatives allow the use of multidose vials of a vaccine as required (i.e. it allows a particular vaccine to be used over certain period of time because it contains substances that prevent their spoilage). All the supporting components that constitute the final vaccine are combined and mixed uniformly in a single vial or syringe that can be administered to humans for the prevention of a particular infectious disease.
  4. Vaccine packaging: Once the vaccine is put in the recipient vessel (either a vial or a syringe), it is sealed with sterile stoppers, and thus ready for usage. The vaccine is finally labeled and distributed worldwide. Several quality control and quality assurance practices (as part of the good manufacturing practices, GMPs employed in vaccine development) are put in place in the production of vaccines since these molecules are biological substances that interact with the internal organs, cells and tissues of living organisms. The safety, efficacy and quality of every vaccine are thoroughly checked and approved by the relevant health authorities before they are released for usage by the general public or in clinical medicine.

References

Acheson N.H (2011). Fundamentals of Molecular Virology. Second edition. John Wiley and Sons Limited, West Sussex, United Kingdom.

Alan J. Cann (2005). Principles of Molecular Virology. 4th edition. Elsevier Academic Press,   Burlington, MA, USA.

Alberts B, Bray D, Johnson A, Lewis J, Raff M, Roberts K and Walter P (1998). Essential Cell Biology: An Introduction to the Molecular Biology of the Cell. Third edition. Garland Publishing Inc., New York.

Balows A, Hausler W, Herrmann K.L, Isenberg H.D and Shadomy H.J (1991). Manual of clinical microbiology. 5th ed. American Society of Microbiology Press, USA.

Barrett   J.T (1998).  Microbiology and Immunology Concepts.  Philadelphia,   PA: Lippincott-Raven Publishers. USA.

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