Solid-phase synthesis and immunological evaluation of peptide conjugates containing stereochemically defined UPam-based TLR2 ligands and epitopes from SARS-CoV-2 virus

Castello, G.; Isendoorn, M.M.E.; Camps, M.; Meeuwenoord, N.J.; Verhoeks, V.F.H.; Ende T.C. van den; Codée, J.D.C.; Ossendorp, F.; Filippov D.V

doi:doi:10.1021/acs.bioconjchem.5c00345

The design of effective vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) relies on eliciting robust cellular and humoral immune responses. In this study, we report the synthesis and immunological evaluation of synthetic long peptide (SLP) vaccines incorporating immunodominant CD4+ and CD8+ T cell and B cell epitopes from the SARS-CoV-2 proteome, covalently conjugated to stereochemically defined UPam ligands, which serve as synthetic Toll-like receptor 2 (TLR2) agonists. Using solid-phase peptide synthesis, we generated a panel of R- and S-glycerol-based UPam conjugates with varied amino acids adjacent to the palmitoylated cysteine. These conjugates were evaluated for their ability to induce dendritic cell maturation, TLR2 activation, and antigen-specific immune responses. In vitro assays demonstrated that R-UPam ligands, particularly those containing Dab and Abu residues, were superior in stimulating IL-12p40 production and TLR2 activation compared with...Show moreThe design of effective vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) relies on eliciting robust cellular and humoral immune responses. In this study, we report the synthesis and immunological evaluation of synthetic long peptide (SLP) vaccines incorporating immunodominant CD4+ and CD8+ T cell and B cell epitopes from the SARS-CoV-2 proteome, covalently conjugated to stereochemically defined UPam ligands, which serve as synthetic Toll-like receptor 2 (TLR2) agonists. Using solid-phase peptide synthesis, we generated a panel of R- and S-glycerol-based UPam conjugates with varied amino acids adjacent to the palmitoylated cysteine. These conjugates were evaluated for their ability to induce dendritic cell maturation, TLR2 activation, and antigen-specific immune responses. In vitro assays demonstrated that R-UPam ligands, particularly those containing Dab and Abu residues, were superior in stimulating IL-12p40 production and TLR2 activation compared with their S-epimer counterparts. In vivo immunization studies in mice revealed that covalent conjugation of UPam to CD8+ T cell epitopes (VNF and REL) significantly enhanced antigen-specific T cell responses compared to unconjugated mixtures. Furthermore, a UPam-conjugated B cell epitope fused to a universal helper T cell peptide (PADRE) induced strong dendritic cell activation and enhanced PADRE-specific CD4+ T and B cell responses, as evidenced by elevated IgG production. These findings underscore the potential of chirally pure UPam-conjugated peptide vaccines to induce balanced, durable immunity against SARS-CoV-2 by combining TLR2-mediated adjuvanticity with precise epitope targeting.Show less

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Solid-phase synthesis and immunological evaluation of peptide conjugates containing stereochemically defined UPam-based TLR2 ligands and epitopes from SARS-CoV-2 virus