Synthetic Multivalent Tn Antigen Elicits Valency-Dependent IgG Antibody Production

The Tn antigen is an attractive target for cancer vaccine development. In this study, we report the efficacies of dendrimer-based multivalent Tn antigens to elicit profound antibody generation in mice, in a subtype-specific manner. Multivalency of the Tn antigen is achieved by utilizing poly(ether imine) (PETIM) dendrimers of first-, second-, and third-generations, leading to tetra-, octa-, and hexadecavalent Tn antigen moieties at their peripheries through squarate ester linkage. The in vivo toxicities of the multivalent Tn antigens on mice show that these antigens are well-tolerated, with no signs of toxicity. The efficacies of the multivalent Tn epitopes to generate antigen-specific antibodies are assessed by periodic immunization of mice and assessment of the antibody production through ELISA analysis. The studies show that all three multivalent Tn epitopes express significantly stronger IgG antibody responses compared to the conventional Tn-BSA conjugate. Among the epitopes, the third-generation glycoconjugate induces the highest antibody titers, as adjudged through quantitation of antibody titer which occurs at a 1:204800 dilution. Sera from mice immunized with the hexadecavalent Tn antigen are tested on MCF-7 and Jurkat cells using FITC-labeled secondary antibodies. The antibodies show strong and selective binding to MCF-7 and Jurkat cells, whereas noncancerous HEK293 cells lack the binding to the Tn antigen-specific antibody. These results provide direct evidence of the correlation of antigen valencies, the efficacies of the antibody production, and the specificities.