Hepatitis is an infectious viral disease which damages the liver.
Hepatitis arises from the words “Hepato+ liver and itis+ inflammation.”
It is one of the deadly infection of virus which affects almost 7 million people a year.
It can cause acute and also chronic liver infection and damage.
Since the liver is a seat of all the body reactions and metabolism, its damage leads to death.
It is a severe disorder and very contagious. But it can be prevented by use of hepatitis-B vaccination.
The production of hepatitis B vaccine was done by use of hepatitis virus previously.
The vaccine was a live vaccine or an attenuated vaccine one.
The live vaccine is one where the live hepatitis virus is used. But due to attenuation, its virulence is removed.
So they no longer can be pathogenic when the weak virus is introduced into the body.
But these vaccines are unsafe and non-reliable due to problems of virulence in immune-compromised patients. Also, there is a trend of decline in immunity of humans.
So once administered the vaccines can turn virulent and cause infection.
So to avoid this, and provide effective prevention, hepatitis-B subunit vaccines are used.
These vaccines are manufactured by using genetic engineering technology.
The subunits vaccines are the antigens of the virus and can evoke an immune reaction.
Further, these subunits are not the virus as a whole so no chances of virulence.
But the subunits are hard to collect and even multiply as they are not organisms. Further their size is also very small.
So the steps in the production of hepatitis B vaccine is quite lengthier than routine steps of five steps of genetic engineering.
Production of Hepatitis B Vaccine
1. Isolation of the Whole genome of the hepatitis-B virus:
2. Cloning of the genome with plasmid and its multiplication
3. The release of the sequence coding for HBs antigen.
4. Ligate with yeast expression vector
5. Transform in Saccharomyces and allow for vaccine formation.
Isolation of genome from the virus is the first step. An entire genome of 2kb is isolated which codes for HB ag on the virus body. But the quantity can be less and virus are also not readily multiplied in labs. So the gene is multiplied by the use of plasmid. The plasmid has the inherent tendency to multiply. These plasmids with genome are introduced into bacteria for replication and multiplication. Many plasmids with the gene are produced.
From these sufficient genomes, the required gene coding for HBs is cleaved by use of restriction endonucleases.
These are the enzymes which cut DNA molecules at precise points.
Once the required gene is formed, it is again taken and cloned with another vector namely yeast expression vector.
Here the yeast expression vector has alcohol dehydrogenase-1 (a strong promoter gene) by the side. Also, there is leucine 2 as a marker.
The enzyme DNA ligase is used for ligation (cloning) of the gene with yeast vector.
Then this newly formed vector is transformed into Saccharomyces cerevisiae bacteria.
The transformed cells are allowed to grow in culture media and promote the gene expression. The vaccine is formed and is present in the body of the bacterial cell.
The bacterial cells are lysed, and the solution is centrifuged.
By this, the HBs gene is obtained in the supernatant. This vaccine is isolated and allowed to form aggregates with silver.
Unlike routine steps of rDNA technology, here we use two vectors. One for the multiplication of viral genes. The other is to transfer the HBs gene into bacteria from where it is expressed.
The hepatitis B vaccine is given as an intramuscular injection. It is administered as three doses and the second and third doses are given after one month and six months respectively.