A new meningococcal vaccine is described as a 'glycoconjugate vaccine' where the polysaccharide is covalently linked to a carrier protein. What is the primary immunological advantage of conjugation compared to plain polysaccharide vaccines?
- A Converts T-independent (TI-2) immune response to a T-dependent response, generating memory B cells and boostable immunity ✓
- B Eliminates the need for adjuvants by directly activating cytotoxic T lymphocytes
- C Allows cross-placental transfer of vaccine antibodies to protect neonates immediately after maternal vaccination
- D Prevents molecular mimicry-based autoimmune reactions by carrier protein masking
Correct answer: A. Converts T-independent (TI-2) immune response to a T-dependent response, generating memory B cells and boostable immunity
Explanation
Plain polysaccharide antigens are T-independent type 2 (TI-2) antigens — they cannot engage T helper cells, produce only IgM (no class switching), no immunological memory, and are ineffective in children <2 years. Conjugation to a carrier protein (e.g., tetanus toxoid, CRM197) makes the antigen T-dependent, allowing T-cell help, class switching to IgG, germinal centre reactions, memory B-cell formation, and boostable responses on re-exposure. This is the basis of Hib, meningococcal, and pneumococcal conjugate vaccines.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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