Designing antiviral vaccines for cytotoxic T cell (CD8+) activation Which vaccine formulation is most likely to elicit strong cytotoxic T lymphocyte responses?

Introduction:
Cytotoxic T lymphocytes (CTLs, CD8+) recognize peptides presented on MHC class I, typically derived from endogenous proteins synthesized inside infected cells. Vaccine designs that place antigen in the cytosol efficiently prime CTLs.

Given Data / Assumptions:

• MHC I presentation favors intracellularly produced antigens.
• Live attenuated viruses replicate to limited degrees and generate endogenous antigen.
• Inactivated or purely extracellular antigens mainly drive MHC II helper responses unless cross-presentation occurs.

Concept / Approach:

Live attenuated vaccines mimic natural infection, ensuring robust MHC I presentation and strong CTL memory. While cross-presentation can occur with certain adjuvants or delivery systems, it is less reliable than true intracellular synthesis.

Step-by-Step Solution:

Verification / Alternative check:

Historically, live attenuated viral vaccines (where safe) generate durable cellular and humoral immunity, including CTL responses.

Why Other Options Are Wrong:

Option A: High dose inactivated virus favors antibody responses; CTL priming is limited without cross-presentation.

Option B: Adjuvants enhance innate signals but cannot substitute for antigen and proper presentation pathway.

Option D/E: Exogenous peptides/subunits may not reach MHC I efficiently unless specialized delivery or cross-presentation is ensured.

Common Pitfalls:

Assuming dose or adjuvant alone determines CTL responses; the intracellular location of antigen synthesis is the key determinant.

Final Answer:

Live virus (attenuated) capable of intracellular replication