Production of Viral Vaccines

Production of Viral Vaccines  


Production of Viral Vaccines 

Viral vaccines are derived from cell cultures injected with virus of the appropriate strain.

These steps are followed in production of viral vaccines-

Growth of virus:

Commonly embryonated eggs are used for the viral growth, for example in influenza and yellow fever vaccines.
Influenza viruses accumulate in the high titre of the allantoic fluid of eggs.
Yellow fever viruses accumulate in the nervous system of the embryos.

Viral harvest processing:

For Influenza viruses, allantoic fluid is centrifuged to give a concentrated and purified suspensions of virus.
The concentrated suspensions of virus is treated with disrupting agents to get the viral components.

In case of the yellow fever vaccine production, the viruses are homogenized in water to provide a puree and then centrifuged to precipitate most of the embryonic debris leaving the yellow fever viruses in an aqueous suspension.
Cell cultures are clarified by filtration to remove debris. These cell cultures are used for live attenuated vaccines without any inactivation step.


Exceptions-

a) poliomyelitis vaccine is inactivated with diluted formalin or beta-propiolactone. Then the inactivated vaccine is concentrated by adsorption and elution of the viruses.

b) Rabies virus vaccine is inactivated with beta-propiolactone.
Then the inactivated vaccines are concentrated by ultrafiltration.


Blending:

It is the process to mix various components of a vaccine to form final bulk.
It is done in a large, closed vessel with a stirrer and ports. Ports are used for the addition of constituents and withdrawal of the final blend.

In the blending of viral vaccines, maintenance of antigenicity and infectivity preclude dilution and tissue culture fluids or concentrates are used undiluted or in the case of multicomponent vaccines sometimes diluted with one another.


Filling or Drying:

Vaccines that are filled as liquids are sealed and capped in containers.
Vaccines are dried or freeze-dried before sealing.


Combined viral vaccines:

The multicomponent vaccines made by blending two or more single component vaccines.  Multicomponent vaccines are needed to meet the potency and safety for each of the components present in the vaccine.

Example of combined viral vaccines are- measles, mumps and rubella (MMR) vaccine.
Inactivated (Salk) polio vaccine and the live (sabin) polio vaccine are combined
vaccine. They are produced by mixing each of the three serotypes of polio virus.

Influnza vaccines are combined vaccines because they contain components of three virus strains from two strains of influenza A and one strain of influenza B.


"Vaccines: Introduction and Types"
Written By
Sadia Akhtar
Student of Department of Microbiology
Jagannath University.
Email- sadiabd810@yahoo.com

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