Carbomer-based Nano-Emulsion Adjuvant Enhances Dendritic Cell Cross-presentation via Lipid Body Formation Independent of Glycolysis

Abstract

ADJ induces inflammasome activation in DCs, but deficiency for NLRP3, ASC or caspase 1 did not affect ADJ-mediated cross-presentationNext, we examined the effects of ADJ on the expression profiles of cytokines, chemokines and canonical cell surface markers of DC activation. Compared to untreated DCs, ADJ-treated DCs showed statistically significant, yet modest increases in expression of CD40, CD80, and CD86; no significant differences in expression were observed for MHC-I, MHC-II, or CCR7 (Fig. 1C).ADJ-treated DCs produced higher levels of IL-12 (p70), TNF-, IL-1, CCL3, CCL4, CXCL1, and RANTES, as compared to untreated DCs; no significant differences in expression were observed for IL-6, IL-10, and IFN- (Fig. 1D). Particularly, ADJ-stimulated DCs also produced significantly elevated levels of IL-1 and IL-18 (Fig. 1D), which is suggestive of inflammasome activation. Since inflammasome activation has been implicated in modulation of antigen presentation by DCs (Sokolovska et al., 2013, Li et al., 2019, we performed B3Z assays using DCs deficient in NLRP3, ASC, or caspase 1 to interrogate whether inflammasome activation is required for ADJ-induced cross-presentation in BMDCs. Surprisingly, loss of NLRP3, ASC or caspase 1 activity did not affect ADJ-induced cross-presentation by DCs, in vitro (Fig. 1E). To validate whether caspase 1 is required for cross-presentation in vivo, we immunized cohorts of wild type (WT) and caspase 1-deficient mice with ADJ+OVA, and quantified OVA SIINFEKLspecific CD8 T cells in spleens using MHC I tetramers at day 8 after immunization. Consistent with our results from B3Z assays, caspase 1 deficiency did not significantly affect the activation of SIINFEKL-specific CD8 T cells in spleens (Fig. 1F), suggesting that caspase 1 is not essential for ADJ-driven cross-presentation to CD8 T cells in vivo.

Lipid peroxidation of immune cells in cancer

“…Leakage of endosomal antigens into the cytosol is a crucial step in the process of cross-presentation in DCs. Elevated production of reactive oxygen species (ROS) and lipid peroxidation induces the escape of antigens from endosomes to the cytosol, facilitating their degradation and promoting antigen presentation by DCs (93). Consistent with this study, it was observed that increased cellular lipid bodies enhance the antigen crosspresentation of human cDC2s (94), however, whether this process is related to the accumulation of lipid peroxidation remains unclear.…”

Review: Current trends, challenges, and success stories in adjuvant research

“…The field of either immunologically silent or immunostimulatory vaccine delivery systems is large and complex (39), and goes far beyond the scope of this article. It includesto name just a few -virosomes (reviewed in (40)) that are among the few adjuvants in a licensed vaccine (41), a wide variety of liposomes, polymers such as carbomer-lecithin adjuvant Adjuplex (42) and PLGA nanoparticles that have been used to deliver various payloads (such as immunostimulatory vaccines for cancer (43) or tolerogenic vaccines for the treatment of autoimmune disease (44), and even immunologically inert materials such as gold particles for the biolistic delivery of DNA vaccines by gene gun (45) (which exert their adjuvant effect through the cellular trauma caused by high-velocity microparticle bombardment of the skin). A delivery system that has recently received unprecedented attention due to the COVID pandemic is lipid nanoparticles (LNPs) that are used in the approved mRNA vaccines BNT162b2/Comirnaty and mRNA-1273/Spikevax.…”