The ZyCoV-D vaccine heralds a wave of DNA vaccines for various diseases that are undergoing clinical trials around the world.
India has approved a new COVID vaccine that uses circular strands of DNA to prime the immune system against the virus SARS-CoV-2. Researchers have welcomed news of the first DNA vaccine for people to receive approval anywhere in the world, and say many other DNA vaccines may soon be hot on its heels.
ZyCoV-D, which is administered into the skin without an injection, has been found to be 67% protective against symptomatic COVID-19 in clinical trials, and will likely start to be administered in India this month. Although the efficacy is not particularly high compared to that of many other COVID-19 vaccines, the fact that it is a DNA vaccine is significant, say researchers.
It is proof of the principle that DNA vaccines work and can help in controlling the pandemic, says Peter Richmond, a pediatric immunologist at the University of Western Australia in Perth. “This is a really important step forward in the fight to defeat COVID-19 globally, because it demonstrates that we have another class of vaccines that we can use.”
ZyCoV-D contains circular strands of DNA known as plasmids, which encode the spike protein of SARS-CoV-2, together with a promoter sequence for turning the gene on. Once the plasmids enter the nuclei of cells, they are converted into mRNA, which travels to the main body of the cell, the cytoplasm, and is translated into the spike protein itself. The body’s immune system then mounts a response against the protein and produces tailored immune cells that can clear future infections. Plasmids typically degrade within weeks to months, but the immunity remains.
RNA vaccines were quicker to show strong immune responses in clinical trials; they have now been delivered to hundreds of millions of people around the world. But DNA vaccines have a number of benefits because they are easy to produce and the finished products are more stable than mRNA vaccines, which typically require storage at very low temperatures.
More than half a dozen DNA vaccines for COVID-19 are in early-stage trials, including one by the South Korean biotech company GeneOne Life Science in Seoul, and also the Italian one COVID-eVax Takis, Rottapharm Biotech, which is undergoing phase I/II
But Richmond expects many more DNA vaccines to emerge, targeting diseases for which there are currently no vaccines — from cytomegalovirus, which can be passed on to babies during pregnancy, to respiratory syncytial virus. DNA vaccines are also being trialled or developed for influenza, human papillomavirus, HIV and Zika.
Article issued By Giorgina Mangano
Picture source: https://www.eiu.com/n/africa-faces-major-obstacles-to-accessing-covid-vaccines/