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- In a significant development in DNA vaccination research, India’s first and only DNA vaccine candidate for dengue has shown promising results.
- Dengue is a mosquito-borne viral infection, found in tropical and sub-tropical climates worldwide, mostly in urban and semi-urban areas.
- The virus responsible for causing dengue, is called dengue virus (DENV).
- There are four DENV serotypes, meaning that it is possible to be infected four times.
Transmission and Symptoms
- Dengue is transmitted by several species of mosquitoes within the genus Aedes.
- Symptoms include fever, headache, muscle, and joint pain, and a characteristic skin rash that is similar to measles. There is a drop in platelets.
- There are four types of dengue strains, and type II and IV are considered to be more severe and normally require hospitalization.
- The Aedes mosquito breeds in clean stagnant water.
- There is no specific medicine to treat dengue.
- Platelets are pieces of very large cells in the bone marrow called megakaryocytes.
- They help form blood clots to slow or stop bleeding and to help wounds heal.
- Having too many or too few platelets or having platelets that don't work as they should can cause problems.
Normal platelet count in a body
- In the normal human body, the platelet count in dengue ranges from 1.5 lakh to 4 lakh.
Reasons behind drop in platelet count in Dengue
- Platelet count in dengue decreases as it suppresses bone marrow, which is the platelet-producing area.
- Platelet count in dengue decreases because of blood cells affected by the disease.
- Antibodies that are produced during this period lead to massive destruction of platelets in dengue.
Impact of drop in platelet count in cases of dengue
Patient can be asymptomatic or may have bleeding manifestations, such as:
- Bleeding from gums or nose.
- Blood in urine, stools or vomit.
- Bleeding under the skin, which might look like bruising.
- Major internal organ bleeds in few cases.
- In cases where platelets drop to below 10,000, platelet transfusion is required but in case of bleeding manifestations, platelet transfusions can even be given at more than the cut-off value of 10,000 too.
Donor eligibility criteria
- Donor eligibility criteria are the same for both platelet and whole blood donors.
- Any healthy adult who clears the screening process of the blood bank for platelet donation can donate the platelets.
Need for an effective Vaccine for Dengue
- Developing an effective vaccine against dengue is tricky because it is caused by four closely related viruses—DEN-1, DEN-2, DEN-3 and DEN-4—called serotypes. Each one interacts differently with antibodies in human blood.
- A person infected with DEN-1 is then protected against it for life, but not against the other three serotypes.
- An ideal vaccine must target all serotypes.
The world’s first DNA vaccine—ZyCoV-D, developed by Ahemdabad-based pharmaceutical firm Zydus Cadila—was approved in 2021 for emergency use against COVID-19. Globally, DNA vaccines are being developed for diseases like tuberculosis and chikungunya. Some 19 DNA dengue vaccines are being evaluated, but yet to reach final clinical trials.
A DNA vaccine is a type of vaccine that transfects a specific antigen-coding DNA sequence into the cells of an organism as a mechanism to induce an immune response.
DNA vaccines work by injecting genetically engineered plasmid containing the DNA sequence encoding the antigen(s) against which an immune response is sought, so the cells directly produce the antigen, thus causing a protective immunological response. DNA vaccines have theoretical advantages over conventional vaccines, including the "ability to induce a wider range of types of immune response".
Q) Which of the following statements is/are correct?
a. The world’s first DNA vaccine—ZyCoV-D, developed by Ahemdabad-based pharmaceutical firm Zydus Cadila—was approved in 2021 for emergency use against COVID-19.
b. Dengue is caused by four closely related viruses—DEN-1, DEN-2, DEN-3 and DEN-4—called serotypes.
i. Only a
ii. Only b
iii. Both a and b
iv. None of the above.
Answer: Option iii