Context: Sputnik V Vaccine, the vaccine against Covid-19 developed by Russia, has been cleared for emergency use by the Drugs Controller General of India, the country’s drug regulator.
- It is now the third coronavirus vaccine to get emergency use approval, after Covishield (Serum Institute of India) and Covaxin (Bharat Biotech).
- The Sputnik V vaccine uses two different viruses that cause the common cold (adenovirus) in humans.
- The adenoviruses are weakened so they cannot replicate in humans and cannot cause disease.
- They are also modified so that the vaccine delivers a code for making the coronavirus spike protein.
- This aims to ensure that when the real virus tries to infect the body, it can mount an immune response in the form of antibodies.
- Sputnik uses a different vector for each of the two shots in a course of vaccination.
- Using a different adenovirus vector may help create a more powerful immune response (compared with using the same vector twice), as it minimizes the risk of the immune system developing resistance to the initial vector.
What is a vector-based vaccine?
- 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. This has the advantage of triggering a strong cellular immune response.
What are antigens?
- Antigens are proteins which our immune system can recognize.
- Majority of antigens are proteins but some are carbohydrates, lipids, and nucleic acids.
- Any antigen that is ‘foreign to our immune system is destroyed by an antibody.
What are antibodies?
- Antibodies are attack molecules our immune system makes to protect ourselves against foreign things such as bacteria and viruses.
- Antibodies circulate throughout the body until they find and attach to the antigen.
- Once attached, they can force other parts of the immune system to destroy the cells containing the antigen.
- Antibodies can also be formed in response to different blood groups.
- Everyone is born with some antibodies.
What are epitopes?
- Whenever we refer a pathogen (disease causing organisms), we may think the entire microbe is responsible for the disease.
- But the fact is these organisms possess numerous sites called as epitopes that are recognized by antibodies or receptors on the cells in the immune system.