DNA Based Vaccine: What is it and how does work?

Ground Report | New Delhi: DNA Based Vaccine: What; While still in its early stages, this technology has been developed rapidly by experts and if approved, the vaccine developed by India's Zydus Cadila, called ZyCoV-D, will be the first DNA-based vaccine ever.

To fight the Covid outbreak, scientists are working to develop what is called a third-generation DNA-based vaccine to train our immune system to ward off the coronavirus infection before it progresses.

This kind of vaccine uses engineered DNA, which then induces a response in our system against the virus strain. This new kind of vaccine could mean improved stability of the vaccine dose and ease in large-scale manufacturing, according to the World Health Organisation.

What is DNA based Vaccine?

DNA-based vaccines, which are often referred to as the third-generation vaccines, use engineered DNA to induce an immunologic response in the host against bacteria, parasites, viruses, and potentially cancer.

The vaccines that are currently available to the global population include those for measles, mumps, rubella, seasonal influenza virus, tetanus, polio, Hepatitis B, cervical cancer, diphtheria, pertussis as well as several other diseases that are endemic to certain regions of the world.

More specifically, these vaccines expose the immune system to situations that originated from the target pathogen, which allows the immune system to develop antibodies that can recognize and attack this infectious agent if the vaccinated host encounters this pathogen in the future.

The challenges associated with the development of conventional vaccines have led to the investigation of several alternative vaccine approaches that could be used for both infectious and non-infectious diseases.

While still in early stages, this technology has been developed rapidly by experts and if approved, the vaccine developed by India's Zydus Cadila NSE 0.71 %, called ZyCoV-D, will be the first DNA-based vaccine ever.

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How do DNA based vaccines work?

Like any other type of vaccine, DNA vaccines induce an adaptive immune response. The basic working principle behind any DNA vaccine involves the use of a DNA plasmid that encodes for a protein that originated from the targeted.

Plasmid DNA (pDNA) is inexpensive, stable, and relatively safe, thereby allowing this non-viral platform to be considered an excellent option for gene delivery. Some of the different virus vectors that have been used to source pDNA include onco-retrovirus, lentiviruses, adenoviruses, adeno-associated viruses, and Herpes simplex-1.

When an intramuscular (IM) injection of a DNA vaccine is administered, the pDNA will target myocytes. DNA vaccines can also be administered through a subcutaneous or intradermal injection, both of which will target keratinocytes. Regardless of the injection site, the pDNA will transfect myocytes or keratinocytes, which will then undergo a type of programmed cell death known as apoptosis.

Antigen presentation to MHCII activates helper CD4⁺ T-cell, which contributes to B cell priming and ultimately allows for the humoral immune response to be created. This humoral immune response is required to activate the production of CD8⁺ T cells.

In addition to acting on either myocytes or keratinocytes, any DNA vaccine administration route can also transfect antigen-presenting cells (APCs) located near the injection site. This direct transfection route results in endogenous transgene expression and parallel presentation of the antigen through both MHCI and MHCII, thereby yielding both CD8⁺ and CD4⁺ T cells.

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What DNA based vaccines are currently in development?

Zydus-Cadila is not the only company working to help the countries bring down their coronavirus cases. Johnson & Johnson is currently working to develop vaccines against Covid using adenovirus tech that was used to fight HIV. It is a genetically modified cold virus that has the ability to deliver genetic cargo into the host with instructions to develop "mosaic immunogens". With human trials ongoing right now, initial results will be released this year.

Our immune system may not be provided to cure HIV, but it can cure Covid. The trials are being tested on thousands of people across sub-Saharan Africa, the US, South America, and Europe.

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