Fig. 1: Mechanisms of action of oil-in-water emulsion-adjuvanted vaccines.
From: “World in motion” – emulsion adjuvants rising to meet the pandemic challenges
Intramuscular injection of oil-in-water emulsion-adjuvanted vaccines generates an immunocompetent environment at the muscle injection site characterized by secretion of pro-inflammatory cytokines and chemokines, induction of damage-associated molecular patterns (DAMP)-signaling, and recruitment of innate immune cells such as neutrophils, eosinophils, dendritic cells, monocytes, and macrophages. Innate immune cells capture the antigen and migrate to the draining lymph node. Antigen and the emulsion adjuvant co-localize with subcapsular sinus macrophages right outside the B cell follicles, as well as with dendritic cells in the medulla. The antigen is transferred to the B cell follicles where germinal center B cells, helped by T follicular helper cells, undergo the processes of extensive somatic hypermutation and affinity maturation, and differentiate into plasmablasts or memory B cells. Antigen-loaded dendritic cells activate T cells which develop a mixed Th0/Th1/Th2 phenotype. Overall, these immunological mechanisms result in increased circulating vaccine-specific T cells, a broadly diverse repertoire of memory B cells as well as high titers of polyfunctional and cross-neutralizing serum antibodies.
