Adjuvant Templating Improves On-Target/Off-Target Antibody Ratio Better than Linker Addition for M2-Derived Peptide Amphiphile Micelle Vaccines

Abstract

Background: Peptide amphiphile micelles (PAMs) are a promising lipid-based nanotechnology currently in development for a variety of applications ranging from atherosclerosis to cancer therapy. Especially relevant for immune applications, PAMs improve trafficking through lymphatic vessels, enhance uptake by antigen-presenting cells, and inhibit the protease-mediated degradation of cargo. However, the creation of the peptide amphiphiles (PAs) necessary to induce micellization often requires modifying an immunotarget peptide with non-native moieties, which can induce the production of off-target antibodies. Methods: PAs containing different linkers between the antigen and non-native flanking regions were synthesized and physically characterized. BALB/c mice were then subcutaneously immunized on days 0 and 14 with these formulations and ELISAs were conducted on the sera collected from vaccinated mice on day 35 to evaluate antibody responses. Results: We determined that Palm2K-M22–16-(KE)4 PAMs elicited off-target antibody responses and sought to avoid these unintended responses by adding linkers in between the M22–16 antigen and the non-native flanking regions (i.e., Palm2K- and -(KE)4) of the PA. Most significantly, the addition of diproline linkers on either side of the M22–16 antigen conferred a loss of β-sheet structure, whereas changing the method of lipid attachment from Palm2K- to Pam2CS-induced the formation of primarily spherical micelles compared to a mixture of spherical and short cylindrical micelles. Despite these morphological changes, all linker-containing PAMs still induced the production of off-target antibodies. Excitingly, however, the formulation containing a Pam2CS moiety (intended to mimic the adjuvanticity of the TLR2 agonist adjuvant Pam2CSK4) elicited high on-target antibody titers similar to those induced by PAMs co-delivered with Pam2CSK4. Conclusions: While the linkers tested did not completely eliminate the production of off-target antibodies elicited by the PAMs, the inclusion of a Pam2CS moiety both increased the amount of on-target antibodies and improved the ratio of on-target to off-target antibodies in response to the M22–16 vaccine.

Keywords

• vaccine
• micelle
• influenza
• M2
• peptide amphiphile