An mRNA-based COVID-19 vaccine (BNT162b2) uses modified uridine in place of uridine in the mRNA sequence. What is the primary reason for this modification?
- A Modified uridine increases the half-life of the lipid nanoparticle carrier
- B N1-methylpseudouridine substitution reduces innate immune detection by TLR7/TLR8, preventing translational suppression and increasing protein yield ✓
- C Pseudouridine insertion prevents reverse transcription and integration of vaccine mRNA into host genome
- D Uridine modification enables cold-chain-independent storage at room temperature
Correct answer: B. N1-methylpseudouridine substitution reduces innate immune detection by TLR7/TLR8, preventing translational suppression and increasing protein yield
Explanation
The key modification in BNT162b2 (Pfizer-BioNTech) and mRNA-1273 (Moderna) is substitution of uridine with N1-methylpseudouridine (m1Ψ), which prevents recognition by innate immune sensors (particularly endosomal TLR7 and TLR8) that would otherwise trigger interferon responses and translational suppression. This modification increases mRNA stability and dramatically improves protein (spike antigen) translation efficiency. Lipid nanoparticle stability and cold-chain requirements are separate physicochemical issues not addressed by nucleoside modification.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.