Enantioselective Effect of Chiral Small Molecules in SARS-CoV-2 Vaccine-Induced Immune Response

Although numerous chiral small molecules have been discovered and synthesized, the investigation on their enantioselective immunological effects remains limited. In this study, we designed and synthesized a pair of small molecule enantiomers (R/S-ResP) by covalently bonding two immunostimulators (resiquimod/Res) onto a planar chiral framework (paracyclophane/P). Notably, we found that S-ResP exhibits a 4.05-fold higher affinity for toll-like receptor 7 (TLR7) than R-ResP, thereby more effectively enhancing the functions of dendritic cells and macrophages in cytokine secretion and antigen internalization. Furthermore, we observed that S-ResP significantly enhances RBD antigen-induced cross-neutralization against various SARS-CoV-2 strains compared to R-ResP. These findings demonstrate the enantioselective effects of small molecules on regulating vaccine-induced immune responses and emphasize the significance of chirality in designing small molecular adjuvants.