Enhanced Immune Response Against the Thomsen-Friedenreich Tumor Antigen Using a Bivalent Entirely Carbohydrate Conjugate

• Main Authors: Kristopher A. Kleski, Kevin R. Trabbic, Mengchao Shi, Jean-Paul Bourgault, Peter R. Andreana
• Format: Article
• Language: English
• Published: MDPI AG 2020-03-01
• Series: Molecules
• Subjects: cancer vaccine; tumor associated carbohydrate antigen; zwitterionic polysaccharide; c-type lectin receptor; multivalent vaccine
• Online Access: https://www.mdpi.com/1420-3049/25/6/1319

The Thomsen-Friedenreich (TF) antigen is a key target for the development of anticancer vaccines, and this ongoing challenge remains relevant due to the poor immunogenicity of the TF antigen. To overcome this challenge, we adopted a bivalent conjugate design which introduced both the TF antigen and the Thomsen-nouveau (Tn) antigen onto the immunologically relevant polysaccharide A1 (PS A1). The immunological results in C57BL/6 mice revealed that the bivalent, Tn-TF-PS A1 conjugate increased the immune response towards the TF antigen as compared to the monovalent TF-PS A1. This phenomenon was first observed with enzyme-linked immunosorbent assay (ELISA) where the bivalent conjugate generated high titers of IgG antibodies where the monovalent conjugate generated an exclusive IgM response. Fluorescence-activated cell sorting (FACS) analysis also revealed increased binding events to the tumor cell lines MCF-7 and OVCAR-5, which are consistent with the enhanced tumor cell lysis observed in a complement dependent cytotoxicity (CDC) assay. The cytokine profile generated by the bivalent construct revealed increased pro-inflammatory cytokines IL-17 and IFN-&#947;. This increase in cytokine concentration was matched with an increase in cytokine producing cells as observed by ELISpot. We hypothesized the mechanisms for this phenomenon to involve the macrophage galactose <i>N</i>-acetylgalactosamine specific lectin 2 (MGL2). This hypothesis was supported by using biotinylated probes and recombinant MGL2 to measure carbohydrate-protein interactions.