There are exciting developments in India's battle against dengue, with the country's first DNA Vaccine candidate showing encouraging results in early trials. The National Centre for Biological Sciences in Bangalore is at the forefront of this development. This article delves into the intricacies of this DNA vaccine for dengue, a topic of significant relevance for the IAS exam .
Dengue DNA Vaccine: India's First Candidate - UPSC Notes
Understanding Dengue Vaccines
Dengue is a complex disease with 4 distinct strains: DEN-1, DEN-2, DEN-3, and DEN-4. In India, the most prevalent strain is DEN-2. The complexity of dengue is such that developing a vaccine is a challenging task because it must be effective against all four strains.
Currently, only two dengue vaccines have received approval for use.
- Dengvaxia: This vaccine is a product of the French company, Sanofi. However, it has its limitations as it can only be used by individuals who have previously been infected with dengue or those living in areas where the majority of the population has been infected. For those who have never been infected, this vaccine can potentially increase the risk of severe dengue.
- Qdenga: This vaccine, developed by the Japanese company Takeda, has a broader application as it can be used by individuals without a history of infection.
Learn more about dengue in the linked article.
The NCBS Vaccine
The vaccine has shown impressive results in mice, leading to the production of both B-cells (which create antibodies) and T-cells (which protect from infection).
A challenge study was conducted, wherein blood serum from vaccinated mice was transferred to immunocompromised mice. The results were promising, with a 50% higher survival rate in the immunocompromised mice compared to the unvaccinated ones.
Following this success, the next step is to test the vaccine on non-human primates. If successful, the vaccine will then proceed to clinical trials.
Decoding DNA Vaccines
DNA vaccines, also known as the third-generation vaccines, operate on the principle of in-situ production of the target antigen. This is achieved by introducing the DNA sequence of the antigen into the cells of the person being vaccinated. The plasmid DNA then enters the nucleus of the cell, produces mRNA which travels to the cytoplasm and gets copied to create the proteins that generate the immune response.
Traditional vaccines, or "whole virus" vaccines, can have adverse effects as they contain the entire virus. DNA vaccines, on the other hand, allow researchers to select only those parts of the virus that will help generate an immune response. This makes DNA vaccines not only safer but also more cost-effective and stable than "whole-virus" vaccines.
The world's first DNA Vaccine, "ZyCoV-D", was developed in India by Zydus Cadilla for Covid-19 and received emergency use approval in 2021.
Find out more about DNA vaccines in the linked article.
Challenges with DNA Dengue Vaccines
- The immune response generated by these vaccines in humans is weaker compared to that in mice, indicating that multiple doses may be required.
- Antibody-Dependent Enhancement: This is a unique issue with dengue vaccines. Normally, vaccines stimulate the body to produce antibodies that prevent the virus from attaching to cells in future encounters. However, in the case of dengue, antibodies can sometimes facilitate the replication of the virus and trigger severe illness. This happens when the antibodies formed are not of sufficient quality or quantity, allowing them to bind to the virus and form a complex that attaches to immune cells. Once inside the cells, the virus can replicate, increasing the viral load.
The phenomenon of Antibody-Dependent Enhancement is the primary reason why Dengvaxia has not been wholly successful.
| Related Links | |||
| Different Types of Vaccines | Exploring mRNA Vaccine | ||
| COVID-19: A Global Pandemic | The Anti-immunization Propaganda | ||
| DPT (Diphtheria, Pertussis, Tetanus) Vaccines | UPSC 2023 Calendar | ||
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