Question

Which of the following statement is correct about DNA vaccines?

• A. They have distinct advantage when preparing subunit vaccines against viruses which frequently alter their antigens
• B. They are relatively poor at stimulating cytotoxic T lymphocytes response in mice
• C. They must be administered on gold particles if they are to be effective
• D. They are only effective if followed by a protein boost

Hint:

DNA vaccines are highly stable, require no cold chain, and stimulate both MHC Class I (cellular) and MHC Class II (humoral) pathways because the antigen is produced directly inside host cells.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
DNA vaccines consist of recombinant plasmid vectors that encode a specific protein antigen from a pathogen.
Once injected into the host, the host cells take up the plasmid, transcribe the gene, and translate it to produce the foreign antigen.
This in vivo production stimulates both humoral (antibody) and cell-mediated immune responses.

Step 2: Detailed Explanation:
DNA vaccines offer several advantages over traditional vaccine platforms.
One key advantage is the ease with which plasmid vectors can be engineered and modified in vitro.
For highly mutable viruses (such as Influenza or HIV) that undergo antigenic drift, researchers can quickly alter the plasmid sequence to match new antigenic variants.
This rapid adaptation is a major advantage over traditional subunit vaccines, which require complex protein expression, purification, and folding protocols.
Let us evaluate the other options:
- Option B is incorrect: DNA vaccines are highly effective at stimulating cytotoxic T lymphocyte (CTL) responses. Because the antigen is synthesized inside host cells, it is processed via the endogenous pathway and presented on MHC Class I molecules, which directly activates CD8+ CTLs.
- Option C is incorrect: While using a gene gun with gold particles improves delivery, DNA vaccines can also be administered via direct intramuscular or intradermal injection of naked plasmid DNA in saline.
- Option D is incorrect: A prime-boost strategy using proteins can enhance the immune response, but DNA vaccines can stimulate protective immunity on their own.

Step 3: Final Answer:
The correct statement is that DNA vaccines have a distinct advantage when preparing vaccines against rapidly mutating viruses.