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| 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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