Hepatitis is a 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 an year.
It can cause acute and also chronic liver infection and damage.
Since 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.
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 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 trend of decline in immunity of humans.
So once administered the vaccines can turn virulent and cause infection.
So to avoid this, and provide efficient 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 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 Whole genome of hepatitis-B virus:
2. Cloning of the genome with plasmid and its multiplication
3. Release of sequence coding for HBs antigen.
4. Ligate with yeast expression vector
5. Transform in sachromycis and allow for vaccine formation.
Isolation of genome from 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 use of plasmid. Plasmid have the inherent tendency to multiply. These plasmid with genome is 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 leucin 2 as marker.
The enzyme DNA ligase is used for ligation (cloning) of gene with yeast vector.
Then this newly formed vector is transformed into sachromycis cervatia 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 bacterial cell.
The bacterial cells are lysed and the solution is centrifuged.
By this the HBs gene is obtained in 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 3 doses and the second and third doses are given after 1 month and six months respectively.