Influence of Physicochemical Properties of Lipopeptide Adjuvants on the Immune Response: A Rationale for Engineering a Potent Vaccine

Adjuvant development and understanding the physicochemical properties of particles and interpreting the subsequent immunological responses is a challenge faced by many researchers in the vaccine field. We synthesized and investigated the physicochemical properties and immunogenicity of a library of multiple epitope self-adjuvant lipopeptides in a novel asymmetric arrangement. Vaccine candidates were synthesized using a combination of solid phase peptide synthesis and copper-mediated click chemistry. In-vivo studies showed that vaccine constructs containing a single OVA CD8+ T cell epitope and two N-terminally located C16 lipid moieties were more effective at generating robust cellular immune responses compared with the same molecule containing multiple copies of the OVA CD8+ T cell epitope with or without the C16 moieties. Furthermore, attachment of the two C16 lipids to the N-terminus provoked formation of long β-sheet fibrils and was shown to induce a higher CD8+ donor T cell frequency and IFN-ɣ secretion, compared to vaccine constructs with an internal lipid placement. A regression analysis indicated that particle secondary structure had a significant impact on CD8+ donor T cell frequency and cytolytic activity. In addition, IFN-ɣ production was influenced significantly by particle shape. The findings of this reaserch will impact the future deisgn of vaccine intended to elict cellular immune responses.