Description
Application of rDNA Technology and Genetic
Engineering in the Production of Hepatitis Vaccine
The Recombivax HB (Merck) is a hepatitis B vaccine and one of the most
significant developments in recombinant DNA technology field. This vaccine
comprises of highly specific antibodies. Hepatitis causes a severe acute infection
that ulti mately results in chronic infection and permanen t liver damage. It is
caused by Hepatitis B Virus (HBV) which is an enveloped and double -stranded
DNA virus. Hepatitis B infection can be prevented with a vaccine made using
recombinant DNA technology.
In figure 3. 22, the steps followed in the production of Hepatitis B vaccine
using recombinant DNA technology are enlisted:
1) The DNA (genetic material) of the hepatitis virus is extracted. At this stage
the surface proteins incite an immune response.
2) The individual genes are analysed and identified.
3) The specific gene which directs production of surface protein is located.
4) The gene is then removed from the viral DNA and inserted into the plasmid.
5) The plasmids are accurately inserted into the corresponding yeast cells.
6) This cell is then allowed to grow via ferm entation. Thus, the cells reproduce
and generate more quanta of surface proteins.
7) After 2 days the yeast cells are ruptured to release the surface proteins.
8) The resulting mixture is processed to extract and purify the surface proteins.
9) A large amount of p ure surface proteins are obtained which provoke an
immune response.
10) The resulting surface proteins are mixed with other ingredients under
optimum conditions to obtain the vaccine.
Antigenic Markers for HBV-Infection
The fol lowing three antigenic markers have been identified for the HBV
infection:
1) HBsAg: It is a surface antigen found on the viral envelope. It represents one
of the earliest marks and appears in the blood during incubation.
9) Result is a
large quantity of
pure surface
protein particles
that provoke an
immune
response
10) Surface
proteins are
combined
with
preserving
agent and
other
ingredients to
make vaccine
7) After 48
hours yeast
cells are
ruptured to
free surface
protein. 8)
Mixture is
processed to
extract and
purify surface
protein
6) Yeast is grown by
fermentation. Cells
reproduce and
generate more
surface protein
Hepatitis
virus
Genetic
material
(DNA)
1) Genetic material
is extracted from
hepatitis virus
3) Gene that
directs
production of
surface protein
is located
4) Gene is
removed from
viral DNA and
inserted into
plasmid
5) Plasmids
are inserted
into yeast
cells
Yeast
cell
Plasmids
containing
gene for
surface
protein
Surface
proteins
that
provoke an
immune
response
2) Individual
genes are
analysed and
identified
Figure 3.21: Production of Hepatitis B Vaccine
Source: Adapted from Remington: The Science and Practice of
Pharmacy Volume I (20th ed.), by Alfonso G. (2000), (Lippincott
Williams & Wilkins).
2) HBeAg: It is obtained from the prote in capsid surrounding the DNA. It is a
marker for causing active infection.
3) HBc: It is a core antigen which does not circulate in the blood, and
stimulates the production of the primary antibodies against HBV. These
antibodies are not protective, and hence, do not provide immunity.
