Which of the following correctly describes the mechanism of action of mRNA-based COVID-19 vaccines?

• A The mRNA integrates into the host cell genome and permanently expresses spike protein
• B Lipid nanoparticle-encapsulated mRNA is translated by host ribosomes to produce spike protein, which is presented to the immune system ✓
• C The mRNA directly activates toll-like receptors to produce non-specific innate immunity only
• D Reverse transcriptase converts vaccine mRNA to cDNA for stable expression

Explanation

mRNA vaccines (Pfizer-BioNTech BNT162b2, Moderna mRNA-1273) use lipid nanoparticles (LNPs) to deliver modified mRNA encoding the SARS-CoV-2 spike protein into host cells. Host ribosomes translate the mRNA into spike protein, which is displayed on cell surfaces and processed through MHC pathways to activate both humoral (neutralising antibody) and cellular (CD4+/CD8+ T cell) immunity. The mRNA cannot integrate into the genome (no reverse transcriptase activity) and is degraded within days. LNP formulation also provides adjuvant-like innate immune stimulation through NLRP3 inflammasome activation.

Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.