Indian scientists working on 1st ever dengue DNA vaccine

NEW DELHI : The world’s first DNA vaccine was given emergency approval in India recently. Developed by the Ahmedabad-based Zydus Cadila, ZYCOV-D is a vaccine against Covid-19. Now, some researchers believe the technology -- considered superior because DNA vaccines are easier to make and store, and, most importantly store an enormous amount of information -- can be used to develop a vaccine for dengue, a viral infection transmitted by mosquitoes.

“We know that there are four serotypes of the virus, but what we found was that there were genetic variations within the serotypes -- any sequence with over 6% difference is considered to be a different genotype. So, the team created a consensus sequence that is the same across the genotypes as well,” said Dr Easwaran Sreekumar, senior scientist at Rajiv Gandhi Centre for Biotechnology-thiruvananthapuram and one of the corresponding authors of the yet-to-be peer-reviewed paper uploaded on Medrxiv.

With the DNA vaccine platform allowing them to pick pieces of genetic material that can be used in the vaccine, the researchers sequenced the virus from four regions in the country and selected the common parts.

The virus that causes dengue has four types with four different viral antigens – essentially proteins that cause the infection and against which antibodies are created.

The researchers selected a part called EDIII (short for envelope protein domain III) from all the four serotypes of the virus, which is widely considered the most important viral protein. In addition, the researchers also selected the NS1 protein from the DENV2 serotype, which is known to cause severe dengue with internal bleeding and drop in blood pressure.

“In the traditional vaccines, the whole envelope protein is used, which can lead to Antibody Dependant Enhancement (a phenomenon where the viral antigen is bound to less effective antibodies, something that actually makes the virus more effective). We have used only the domain III of the envelope protein from all four serotypes to avoid ADE. And, we have added the NS1 protein from DENV2 that is known to generate both T cell and B cell response,” said Dr Arun Sankaradoss, project lead and scientist at Tata Institute of Fundamental Research-bangalore. T and B cells are lymphocyte or white blood cells that are part of the immune system.