Effect of Chiral Purity on Adjuvanticity of Archaeol-Based Glycolipids

Archaeosomes composed of sulfated lactosyl archaeol (SLA) glycolipids from stereoisomerically pure archaeol (1) are vaccine adjuvants that can boost immunogenicity and vaccine efficacy in preclinical models. Herein, we report a new synthesis of 2,3-bis((3,7,11,15-tetramethylhexadecyl)oxy) propan-1-ol (3) by treating (+/-)-3-benzyloxy-1,2-propanediol with a mesylated phytol derivative through a double nucleophilic substitution reaction, followed by reductive debenzylation. Three SLA archaeosomes from archaeols of different chiral purities were prepared, and the effect of stereochemistry on their adjuvanticity toward ovalbumin was investigated. It was found that all SLA archaeosomes induced strong humoral and cell-mediated antigen-specific immune responses following immunization of C57BL/6NCrl mice, with no significant differences, irrespective of the chiral purities. The responses were comparable or better than those obtained using mimetics of approved adjuvants. The performance of SLA archaeosomes during immunization and their lack of dependence on the stereochemistry of archaeol points toward a promising, safe, scalable, and economically viable vaccine adjuvant system.