Vaccination is one of the most successful public health interventions. Peptide-based vaccines come up as the next generation of modern immunization. They are safe, easy to produce and well defined. However, due to the weak immunogenic effect, there is a requirement of adjuvants to improve the efficacy. Thus it is of importance to develop appropriate adjuvant in the construction of peptide-based vaccine.
In this work, a series of four adjuvanting moieties was synthesized as alkyne derivatives incorporating (1) dipalmitoyl serine (DPS), (2) 1,3-diglyceride lipid (DGL), (3) two C16 lipoamino acids (LCP), and (4) 2,3-dipalmitoyl-S-glycerylcysteine (Pam2Cys). The azide derivative of biotinylated J14 peptide (model B-cell epitope) was synthesized and attached to the above alkynes through copper-catalyzed alkyne-azide 1,3-dipolar cycloaddition (CuAAC) reaction.
Analysis of interaction of the final conjugates with cell-free expressed toll-like receptor (TLR) 2 or 8 using AlphaScreen proximity assay was performed. The AlphaScreen assay was achieved at fixed concentration of TLRs with varying concentrations (0.5 nM – 100 μM) of the four ligands. Among tested compounds, our newly designed self-adjuvanting moiety DPS showed binding efficacy similar to classical TLR2 agonist Pam2Cys.