Design of Fully Synthetic, Self-Adjuvanting Vaccine Incorporating the Tumor-Associated Carbohydrate Tn Antigen and Lipoamino Acid-Based Toll-like Receptor 2 Ligand

Overexpression of certain tumor-associated carbohydrate antigens (TACA) caused by malignant transformation offers promising targets to develop novel antitumor vaccines, provided the ability to break their inherent low immunogenicity and overcome the tolerance of the immune system. We designed, synthesized, and immunologically evaluated a number of fully synthetic new chimeric constructs incorporating a cluster of the most common TACA (known as Tn antigen) covalently attached to T-cell peptide epitopes derived from polio virus and ovalbumin and included a synthetic built-in adjuvant consisting of two 16-carbon lipoamino acids. Vaccine candidates were able to induce significantly strong antibody responses in mice without the need for any additional adjuvant, carrier protein, or special pharmaceutical preparation (e.g., liposomes). Vaccine constructs were assembled either in a linear or in a branched architecture, which demonstrated the intervening effects of the incorporation and arrangement of T-cell epitopes on antibody recognition

The structure of lipoamino acid (Laa).

<p>Lipoamino acids are described according to the total number of carbon atoms in the molecule. C12 Laa; n = 9. C14 Laa; n = 11. C16 Laa; n = 13.</p

J14-specific serum IgG titers (log10) at the final bleed (day 60) after primary immunization for each individual mouse.

<p>Mean J14-specific IgG antibody titers are represented as a bar. Statistical analysis was performed using a one-way ANOVA followed by the Tukey post hoc test (ns, <i>p</i>>0.05; *, <i>p</i><0.05; **, <i>p</i><0.01; ***, <i>p</i><0.001).</p

Structure of the lipopeptide vaccine candidates grouped according to the orientation of epitopes and Laa in the current study.

<p>* Lipopeptide 1 (C16 Laa), Lipopeptide 2 (C14 Laa), Lipopeptide 3 (C12 Laa).</p

Isotypes of J14-specific serum IgG titers (log10) present in the final bleed (day 60) after primary immunization.

<p>Bars represent the titer for pooled sera obtained from each group. Error bars represent standard error of mean.</p

The ability of the lipopeptides to signal through TLR2 was tested by using HEK293 cells stably expressing TLR2 transfected with an NFκB-luciferase reporter gene.

<p>The several fold increase in NFκB levels in treated cells are shown relative to that of the TLR2-expressing cells treated with media, which was set to a value of 1. Bars are means ± SD of indicated number of experiments (ns, <i>p</i>>0.05; *, <i>p</i><0.05; ** <i>p</i><0.01; ***, <i>p</i><0.001).</p

Polyacrylate-Based Delivery System for Self-adjuvanting Anticancer Peptide Vaccine

Vaccination can provide a safe alternative to chemotherapy by using the body’s natural defense mechanisms to create a potent immune response against tumor cells. Peptide-based therapeutic vaccines against human papillomavirus (HPV)-related cancers are usually designed to elicit cytotoxic T cell responses by targeting the HPV-16 E7 oncoprotein. However, peptides alone lack immunogenicity, and an additional adjuvant or external delivery system is required. In this study, we developed new polymer–peptide conjugates to create an efficient self-adjuvanting system for peptide-based therapeutic vaccines. These conjugates reduced tumor growth and eradicated E7-positive TC-1 tumors in mice after a “single shot” immunization, without the help from an external adjuvant. The new conjugates had a significantly higher anticancer efficacy than the antigen formulated with a commercial adjuvant. Furthermore, the polymer–peptide conjugates were promptly taken up by antigen presenting cells, including dendritic cells and macrophages, and efficiently activated CD4⁺ T-helper cells and CD8⁺ cytotoxic T lymphocyte cells