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

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.

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.

We determined that Palm₂K-M2_2-16-(KE)₄ PAMs elicited off-target antibody responses and sought to avoid these unintended responses by adding linkers in between the M2_2-16 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 M2_2-16 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.

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 M2_2-16 vaccine.