The adjuvant AS04 (used in the Cervarix HPV vaccine) combines aluminium hydroxide with monophosphoryl lipid A (MPL). The inclusion of MPL in AS04 primarily enhances the immune response through which mechanism?
- A Activation of Toll-like receptor 4 (TLR4) leading to enhanced innate immune signalling ✓
- B Slow release of antigen from the injection depot
- C Direct activation of B-cell receptor cross-linking independent of T-cell help
- D Formation of immune complexes that are phagocytosed more efficiently
Correct answer: A. Activation of Toll-like receptor 4 (TLR4) leading to enhanced innate immune signalling
Explanation
MPL is a detoxified derivative of Salmonella minnesota lipopolysaccharide and acts as a Toll-like receptor 4 (TLR4) agonist. TLR4 activation triggers innate immune signalling through the TRIF and MyD88 pathways, enhancing dendritic cell maturation, cytokine production, and ultimately the adaptive immune response. This mechanism distinguishes AS04 from plain aluminium hydroxide adjuvants, which primarily act through depot formation and NLRP3 inflammasome activation.
Reference: Janeway's Immunobiology, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.