Which of the following statements best describes the design, working mechanism, and challenges associated with recombinant vector vaccines?
Show answer & explanation
Correct answer: B
Explanation
Solution: The correct answer is These vaccines utilize a harmless viral or bacterial vector genetically engineered to express antigenic proteins of a target pathogen, eliciting a strong cellular and humoral immune response, but face challenges like vector immunity and stability issues.
Explanation:
☛ Recombinant Vector Vaccines: These vaccines use a modified, harmless carrier organism (a viral or bacterial vector) to deliver genetic material encoding the protective antigen of a target pathogen into human host cells.
☛ Working Mechanism: Inside the host cells, the vector delivers the genetic code to produce the target antigen. This mimics a natural infection, robustly activating both humoral immunity (B-cell antibody production) and cell-mediated immunity (cytotoxic T-cells).
☛ Challenges: A primary limitation is pre-existing vector immunity, where the recipient's immune system may recognize and eliminate the delivery vector before it can express the antigen. Ensuring cold-chain stability and complex manufacturing are additional challenges.
Extra Exam-Relevant Facts:
☛ Adenoviral Vectors: Widely used viral vectors that include the chimpanzee adenovirus (used in Covishield / Oxford-AstraZeneca) and human adenovirus types 26 and 5 (used in Sputnik V).
☛ Inactivated Vaccines: Utilize whole killed pathogens that cannot replicate (e.g., Covaxin, Salk Polio Vaccine) and often require adjuvants and booster doses.
☛ Subunit / Peptide Vaccines: Present only purified antigenic fragments of the pathogen rather than whole organisms (e.g., Hepatitis B vaccine, Novavax).
☛ Plasmid DNA Vaccines: Deliver genetically engineered circular DNA molecules directly into host cells (e.g., ZyCoV-D).
Important One-Liners for Upcoming Exams:
☛ Which viral vector was used to develop the Covishield vaccine? → Chimpanzee Adenovirus (ChAdOx1)
☛ Which vaccine became the world's first approved recombinant vector vaccine against Ebola? → Ervebo (rVSV-ZEBOV)
☛ Which branch of the immune system relies primarily on antibodies produced by B cells? → Humoral immunity
☛ Which is the world's first needle-free plasmid DNA vaccine approved for COVID-19? → ZyCoV-D
☛ Who is widely recognized as the 'Father of Immunology' for developing the smallpox vaccine? → Edward Jenner