Saponin-based adjuvants (SBAs) are being used in animal and human (cancer)
vaccines, as they induce protective cellular immunity. Their adjuvant potency
is a factor of inflammasome activation and enhanced antigen cross-presentation
by dendritic cells (DCs), but how antigen cross-presentation is induced is not
clear. Here we show that SBAs uniquely induce intracellular lipid bodies (LBs)
in the CD11b+ DC subset in vitro and in vivo. Using genetic and
pharmacological interference in models for vaccination and in situ tumour
ablation, we demonstrate that LB induction is causally related to the saponin-
dependent increase in cross-presentation and T-cell activation. These findings
link adjuvant activity to LB formation, aid the application of SBAs as a
cancer vaccine component, and will stimulate development of new adjuvants
enhancing T-cell-mediated immunity
