The basic principle of any vaccine is to fool the body into thinking that it’s been infected by the virus (or bacterium) that causes the disease. in response, the immune system creates proteins called antibodies. if you get infected by the real virus, memory cells in the immune system called ‘B lymphocytes’ produce the antibodies again, helping you to fight the infection.
All of the potential COVID-19 vaccines fundamentally achieve this in the same way, by exposing the immune system to the club-shaped protein spikes that cover the virus’s spherical shell. (This shell, made of fatty lipid molecules, encloses the virus’s genetic material.) When the virus invades our body, the spikes connect with a receptor on the surface of cells lining the throat and lungs to gain access to these cells, allowing the virus to enter and replicate. But exposing the immune system to these spikes, which are harmless on their own, trains our body to quickly churn out antibodies that smother the spikes and stop them from connecting.
Each team has its own twist on this approach. the vaccine being developed at Oxford University involves injecting the genetic sequence (the DNA) of the protein spike into the blood. our cells will use this DNA to manufacture the spike, triggering the immune response. Moderna’s approach involves injecting the spike’s genetic material in a different form (RNA instead of DNA). A vaccine being developed at the University of Pittsburgh injects the spike protein itself on a patch of microneedles – the patch would be stuck on like a plaster, and the tiny needles would dissolve once they had pierced the skin.
To deliver the spike’s DNA to our cells, the Oxford researchers are packaging it inside a ‘viral vector’ – essentially a delivery virus. this is a modified chimpanzee virus belonging to a group of viruses called the ‘adenoviruses’. ‘The vector has been crippled’ says Lambe. ‘It doesn’t replicate and it doesn’t cause disease.’
Author: Seoyeon Stephanie Chung
Source: BBC Science Focus Magazine
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