Multifunctional Lipidated Protein Carrier with a Built-In Adjuvant as a Universal Vaccine Platform Potently Elevates Immunogenicity of Weak Antigens

Weak antigens represented by MUC1 are poorly immunogenic, which greatly constrains the development of relevant vaccines. Herein, we developed a multifunctional lipidated protein as a carrier, in which the TLR1/2 agonist Pam₃CSK₄ was conjugated to the N-terminus of MUC1-loaded carrier protein BSA through pyridoxal 5'-phosphate-mediated transamination reaction. The resulting Pam₃CSK₄-BSA-MUC1 conjugate was subsequently incorporated into liposomes, which biomimics the membrane structure of tumor cells. The results indicated that this lipidated protein carrier significantly enhanced antigen uptake by APCs and obviously augmented the retention of the vaccine at the injection site. Compared with the BSA-MUC1 and BSA-MUC1 + Pam₃CSK₄ groups, Pam₃CSK₄-BSA-MUC1 evoked 22- and 11-fold increases in MUC1-specific IgG titers. Importantly, Pam₃CSK₄-BSA-MUC1 elicited robust cellular immunity and significantly inhibited tumor growth. This is the first time that lipidated protein was constructed to enhance antigen immunogenicity, and this universal carrier platform exhibits promise for utilization in various vaccines, holding the potential for further clinical application.