DNA-based Vaccines

DNA-based Vaccines

Subject – Science and Tech

Context – Zycov­D, first vaccine for those above 12, gets nod. It is also the only DNA based vaccine in the world and can be administered without a needle, purportedly minimising chances of reactions.

Concept –

• Viral vector-based vaccines differ from most conventional vaccines in that they don’t actually contain antigens, but rather use the body’s own cells to produce them. They do this by using a modified virus (the vector) to deliver genetic code for antigen, in the case of COVID-19 spike proteins found on the surface of the virus, into human cells.
• By infecting cells and instructing them to make large amounts of antigen, which then trigger an immune response, the vaccine mimics what happens during natural infection with certain pathogens – especially viruses.
• A DNA or RNA vaccine has the same goal as traditional vaccines, but they work slightly differently. Instead of injecting a weakened form of a virus or bacteria into the body, DNA and RNA vaccines use part of the virus’ own genes to stimulate an immune response. In other words, they carry the genetic instructions for the host’s cells to make antigens.
• This has the advantage of triggering a strong cellular immune response by T cells as well the production of antibodies by B cells.

The Difference Between DNA and RNA Vaccines

• DNA and RNA vaccines work the same way as each other, but have some differences. With a DNA vaccine, the virus’ genetic information “is transmitted to another molecule that is called the messenger RNA (mRNA),”.
• This means with an RNA or mRNA vaccine, you’re one step ahead of a DNA vaccine. 
• The mRNA goes into the cell, and the cell translates it into proteins, which are the ones that the organism sees and induces the immune response.
• Another difference between a DNA and RNA vaccine is that a DNA vaccine delivers the message via a small electrical pulse, which “literally pushes the message into the cell.”
• DNA Vaccine – “The advantage is that this vaccine is very stable at higher temperatures. The disadvantage is that it requires a special device that provides the electrical pulse.”

Advantages of DNA Vaccine

• The immune response focused on the antigen of interest
• Cost-effective
• Less risk for infection
• Antigen presentation by MHC class I and class II molecules
• Long-term persistence of immunogen

Limitations of DNA Vaccine

• Risk of affecting genes controlling cell growth
• Possibility of tolerance to the antigen
• Potential for atypical processing of bacterial and parasite proteins
• Limited to protein immunogens