DNA vaccines

DNA vaccines

Subject: Science and Technology

Context: Health Minister Mansukh Mandaviya on Tuesday said several Indian companies are increasing their production of Covid-19 vaccines and that the country may become the first in the world to develop a DNA-based vaccine.

Cadila has completed third phase trial of its DNA vaccine and has applied for emergency use authorisation before DCGI (Drugs Controller General of India). Our expert team is looking into it. When this will come in the market, India will be the only country where scientists have developed a DNA vaccine

Concept:

DNA 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.

Traditional vaccines

• The vaccines expose the immune system to epitopes 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.
• Conventional vaccines are crucial for preventing the spread of numerous highly infectious diseases, the manufacturing of these vaccines often requires that researchers handle live pathogens. Not only can the handling of these pathogens pose safety concerns for those developing the vaccine, but the risk of contamination by these pathogens is also of concern.

Cons of traditional vaccine:

• 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.
• One alternative vaccine that has gained considerable attention is a DNA-based vaccine which is considered to be more stable, cost-efficient, and easier to handle than traditional vaccines.

DNA vaccines working

• 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 pathogen in which the vaccine will be 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-retroviruses, lentiviruses, adenoviruses, adeno-associated viruses, and Herpes simplex-1.

DNA vs RNA Vaccine

• With a DNA vaccine, the virus’ genetic information is transmitted to another molecule that is called the messenger RNA (mRNA). This means with an RNA or mRNA vaccine, you’re one step ahead of a DNA vaccine.
• Another difference between a DNA and RNA vaccine is that a DNA vaccine delivers the message via a small electrical pulse, which literally pushes the message into the cell. The advantage is that this vaccine is very stable at higher temperatures. The disadvantage is that it requires a special device that provides the electrical pulse.

DNA vaccines in development

• Currently, there are no DNA vaccines that have been approved for widespread use in humans.
• Several DNA-based vaccines have been approved by both the United States Food and Drug Administration (FDA) and the United States Department of Agriculture (USDA) for veterinary use, of which include a vaccine against West Nile Virus in horses as well as a melanoma vaccine for dogs.
• Over 160 different DNA vaccines are currently being tested in human clinical trials in the United States. It is estimated that 62% of these trials are devoted to cancer vaccines and 33% are applied for vaccines against human immunodeficiency virus (HIV).
• One of the first clinical trials on a DNA vaccine investigated the potential therapeutic and prophylactic effects of a DNA vaccine against HIV.

Challenges

• One of the biggest challenges associated with DNA vaccines is their low immunogenicity in larger animals and humans.
• Researchers believe that higher amounts of DNA within the range of 5 to 20 mg would need to be injected into an average-sized human to increase the immunogenicity of DNA-based vaccines.
• Another challenge of DNA-based vaccines involves the optimization of transfection, which could be achieved through the incorporation of several parameters such as a hybrid viral/eukaryotic promotor or the optimization of antigen codons.
• An ideal DNA vaccine will avoid extracellular degradation and successfully enter the nucleus of target cells to induce a long-term immune response.