Q. With reference to recent developments regarding ‘Recombinant vector Vaccines’, consider the following statements:

  1. Genetic engineering is applied in the development of these vaccines.
  2. Bacteria and viruses are used as vectors.

Which of the statements given above is/are correct?

  • 1 only
  • 2 only
  • Both 1 and 2
  • Neither 1 nor 2

Answer: (c) Both 1 and 2

Recombinant Vector Vaccines
  • Genetic engineering is applied in the development of Recombinant vector vaccines. Genetic engineering involves techniques to alter the chemistry of genetic material (DNA and RNA), to introduce these into host organisms and thus change the phenotype of the host organism. 
  • The techniques of genetic engineering include creation of recombinant DNA, use of gene cloning and gene transfer. Recombinant vaccines are made of a viral or bacterial vector. 
  • Recombinant vector vaccines are live replicating viruses that are engineered to carry extra genes derived from a pathogen—and these extra genes produce proteins against which we want to generate immunity.
  • These vaccine genomes may evolve to lose the extra genes during the process of manufacture of the vaccine or during replication within an individual, and there is a concern that this evolution might severely limit the vaccine’s efficacy.
DNA Vaccine
  • 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.
  • The DNA is injected directly into the body’s cells, where it instructs the cells to produce the antigen.
    • The immune system then recognizes the antigen as foreign and mounts an immune response against it, which helps to develop immunity to the pathogen.
  • DNA vaccines are third-generation vaccines.
  • DNA vaccines have theoretical advantages over conventional vaccines, including the “ability to induce a wider range of types of immune response”.
  • These vaccines are yet not completely appropriate for human use and can only be used for animal species.
  • Advantages of DNA Vaccine:
    • The immune response focused on the antigen of interest
    • Cost-effective
    • Less risk for infection
    • Antigen presentation by MHC class I and class II molecules
    • Long-term persistence of immunogen
  • Limitations of DNA Vaccine:
    • Risk of affecting genes controlling cell growth
    • Possibility of tolerance to the antigen
    • Potential for atypical processing of bacterial and parasite proteins
    • Limited to protein immunogens
  • In August 2021, Indian authorities gave emergency approval to ZyCoV-D. Developed by Cadila Healthcare, it is the first DNA vaccine approved for humans.