Evaluation of Virus-Like Particle-Based Tumor-Associated Carbohydrate Immunogen in a Mouse Tumor Model

Tumor-associated carbohydrate antigens (TACAs) are attractive targets for anticancer vaccine development. Due to the low immunogenicity of TACAs, a powerful carrier system is needed to boost immune responses. Virus-like particles (VLPs) are an exciting platform for delivering TACAs to the immune system. The high symmetry of VLPs enables the display of TACAs in an organized manner, which in turn can potently activate antibody secreting B cells, eliciting high titers of antiglycan IgG antibodies. In this chapter, the protocol for conjugating a prototypical TACA, the Tn antigen to a VLP, bacteriophage Qβ, is presented. On an average around 370 copies of Tn can be attached to each Qβ capsid. Immunization of mice with Qβ-Tn conjugate leads to over two orders of magnitude higher IgG antibodies compared to control mice receiving Qβ only without the Tn antigen. Antibodies induced by Qβ-Tn recognize Tn-expressing tumor cells strongly and protect mice from tumor-induced death. The techniques for evaluating antibody titers by enzyme-linked immunosorbent assay, antibody binding to tumor cells by flow cytometry, and the protection efficacy of the vaccine in a therapeutic model of tumor are discussed in this chapter.