Building on prior work, Moynihan et al. explored their highly immunogenic “albumin-hitchhiking” amphiphilic peptide vaccine and found that alternative albumin-binding moieties were nearly as effective as the original lipid tail. Various linkage strategies and molecular adjuvants also showed equivalent functionality. Conjugated PEG improved the stability of peptides in serum, and conjugated peptides reached distal lymph nodes and were presented for longer in vivo. Cross-presenting (Batf3+) DCs were critical for enhanced immunogenicity, and human DC presentation of conjugated peptides was comparable to that of free peptides.
Antitumor T-cell responses have the potential to be curative in cancer patients, but the induction of potent T-cell immunity through vaccination remains a largely unmet goal of immunotherapy. We previously reported that the immunogenicity of peptide vaccines could be increased by maximizing delivery to lymph nodes (LNs), where T-cell responses are generated. This was achieved by conjugating the peptide to 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-PEG (DSPE-PEG) to promote albumin binding, which resulted in enhanced lymphatic drainage and improved T-cell responses. Here, we expanded upon these findings and mechanistically dissected the properties that contribute to the potency of this amphiphile-vaccine (amph-vaccine). We found that multiple linkage chemistries could be used to link peptides with DSPE-PEG, and further, that multiple albumin-binding moieties conjugated to peptide antigens enhanced LN accumulation and subsequent T-cell priming. In addition to enhancing lymphatic trafficking, DSPE-PEG conjugation increased the stability of peptides in serum. DSPE-PEG-peptides trafficked beyond immediate draining LNs to reach distal nodes, with antigen presented for at least a week in vivo, whereas soluble peptide presentation quickly decayed. Responses to amph-vaccines were not altered in mice deficient in the albumin-binding neonatal Fc receptor (FcRn), but required Batf3-dependent dendritic cells (DCs). Amph-peptides were processed by human DCs equivalently to unmodified peptides. These data define design criteria for enhancing the immunogenicity of molecular vaccines to guide the design of next-generation peptide vaccines.