Significant Impact of Immunogen Design on the Diversity of Antibodies Generated by Carbohydrate-Based Anticancer Vaccine

Abstract

Development of an effective vaccine targeting tumor associated carbohydrate antigens (TACAs) is an appealing approach toward tumor immunotherapy. While much emphasis has been typically placed on generating high antibody titers against the immunizing antigen, the impact of immunogen design on the diversity of TACA-specific antibodies elicited has been overlooked. Herein, we report that the immunogen structure can significantly impact the breadth and the magnitude of humoral responses. Vaccine constructs that induced diverse TACA-binding antibodies provided much stronger recognition of a variety of Tn positive tumor cells. Optimization of the breadth of the antibody response led to a vaccine construct that demonstrated long lasting effcacy in a mouse tumor model. After challenged with the highly aggressive TA3Ha cells, mice immunized with the new construct exhibited a statistically significant improvement in survival relative to controls (0% vs 50% survival; p < 0.0001). Furthermore, the surviving mice developed long-term immunity against TA3Ha. Thus, both the magnitude and the breadth of antibody reactivity should be considered when designing TACA-based antitumor vaccines.

Valency and density matter: Deciphering impacts of immunogen structures on immune responses against a tumor associated carbohydrate antigen using synthetic glycopolymers

“…The increase in the number of Tn specific antibody-secreting B cells (ASC) could be detected through an enzyme-linked immunospot (ELISPOT) assay using ELISPOT plates coated with a BSA-Tn conjugate. 30 …”

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

“…The robustness of this chemistry for TACA conjugation has been tested with several carbohydrate antigens (Astronomo et al, 2010; Hovlid et al, 2014; Yin et al, 2013, 2016, 2015). In the following, the protocol for conjugating a Tn NHS ester (Yin et al, 2013, 2015) with Qβ capsid (Fig. 1A) is presented.…”

“…As antibodies can be elicited against both the TACA and the carrier moiety through vaccination, it is important to use TACA conjugated to a different multivalent platform for ELISA to avoid the potential interference from anticarrier antibodies for the analysis. For evaluation of anti-Tn antibody responses by Qβ-Tn, BSA conjugated with Tn (BSA-Tn) containing 30–35 copies of Tn per BSA is used, which is superior to the alternative Tn-biotin/streptavidin system (Yin et al, 2012, 2015). …”

“…This model has been used in investigations of Tn-based cancer vaccines in vivo (Lo-Man et al, 2001, 2004). TA3Ha cells are derived from A/J mouse strain (Thingstad & Hilkens, 2003), but can grow well in both C57BL/6 and BALB/c mice (Leyva, Littrell, Yin, Huang, & Haas, 2016; Lo-Man et al, 2001; Yin et al, 2015). To mimic clinical condition for tumor therapy, vaccination is performed after mice receive injection of tumor cells.…”

“…Additional potential advantages of VLPs include their stability in organic solvents and reagents for chemical modification, multiple functional groups available for bio-conjugation, and high thermal stability. Recently, VLPs have been applied as carriers for the development of carbohydrate-based anticancer vaccines (Kaltgrad et al, 2007; Miermont et al, 2008; Yin et al, 2013, 2016, 2012, 2015). In the following, we will discuss the protocols for conjugating the Tn antigen to a VLP, bacteriophage Qβ, and immunological evaluations of this conjugate.…”