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| Production of Bacterial Vaccine |
Production
of Bacterial Vaccine
These
steps are followed in production of bacterial vaccines -
The Seed
lot system:
A suitable strain of bacteria against a
specific disease is cultured, called seed lot and it is stored at -70℃ to use
as the seed to prepare a number of batches of vaccines.
From this seed lot vaccine is prepared
following further procedures. The vaccines are tested for safety and efficacy.
In clinical trials, if the result is
satisfied, the seed lot will be approved for routinely production of bacterial
vaccines.
Fermentation:
The approved bacterial seed contained in an
ampoule is stored at -70℃ or freeze-dried.
The bacteria are cultured in media through
one or more passages. When the bacteria produced in sufficient numbers, they
are inoculated into a batch of media contained in a fermenter.
The pH, temperature and redox potential of
the medium is adjusted. The maximum bacterial yield is obtained after a day.
About one day is required for rapidly growing
bacteria and for slow growing bacteria, more than two weeks is required.
Processing
of Bacterial Harvest:
The bacterial harvest is a mixture of
bacterial cells, metabolic products and exhausted medium.
This
process involves these procedures:
a) Killing
- The
bacterial cells are killed by heating and using disinfectants.
for example, Bordetalla pertussis is killed by heating and formalin.
Vibrio cholerae is killed
by phenol.
b)
Separation - The bacterial cells are separated from the culture fluid
by centrifugation, by reduction of the pH and then precipitation of the cells.
The bacterial cells are resuspended in a
saline water and the culture fluid is discarded.
Fractionation:
The components are extracted from bacterial
cells or from the culture media and then purified for bacterial cell component
vaccine.
For example, the polysaccharide antigens are
separated from Neisseria meningitidis
cells by treating with hexadecyl trimethyl ammonium bromide, purified and then
improved by resolubilization in a suitable solvent and precipitated.
Streptococcus
pneumoniae cells are treated with ethanol.
Then the bacterial components are dried to
powder, stored and incorporated into vaccines.
Detoxification:
This step is used for toxoid vaccines, in
which bacterial toxins are detoxified.
Diphtheria toxin is detoxified with formalin. The detoxification is done
in fermenter or after fractionation on the purified toxin.
Adsorption:
It is the adsorption of components of the
vaccines to a mineral adjuvant to increase the immunogenicity and to decrease
the toxicity.
These
mineral adjuvants are commonly aluminum phosphate, aluminum hydroxide, calcium
phosphate.
Absorbed vaccines are diphtheria vaccine, DTP
vaccine and tetanus vaccine.
Conjugation:
Conjugation is the linking of a vaccine
component of poor immune response with a vaccine component of good immune
response.
Example.
The immunogenicity of the vaccine Haemophilus
influenzae type B is enhanced by
conjugation with polysaccharide of diphtheria, tetanus toxoids and the outer membrane
protein of Neisseriae meningitidis
type A and type C.
"
Production of Bacterial Vaccine"
Written By
Sadia
Akhtar
Student of
Department of Microbiology
Jagannath
University.
Email-
sadiabd810@yahoo.com
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