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

Abstract

For successful carbohydrate based anti-cancer vaccines, it is critical that B cells are activated to secret antibodies targeting the tumor associated carbohydrate antigens (TACAs). Despite the availability of many TACA based constructs, systematic understanding of the effects of structural features on anti-glycan antibody responses is lacking. In this study, a series of defined synthetic glyco-polymers bearing a representative TACA, i.e., the Thomsen-nouveau (Tn) antigen, have been prepared to probe the induction of early B cell activation and antibody production via a T cell independent mechanism. Valency and density of the antigen in the polymers turned out to be critical. An average of greater than 6 Tn per chain was needed to induce antibody production. Glycopolymers with 40 antigens per chain and backbone molecular weight of 450 kDa gave the strongest stimulation to B cells in vitro, which correlated well with its in vivo activity. Deviations from the desired valency and density led to decreased antibody production or even antigen specific B cell non-responsiveness. These findings provide important insights on how to modulate anti-TACA immune responses facilitating the development of TACA based anti-cancer vaccines using glycopolymers.

The challenges of glycan recognition with natural and artificial receptors

“…28,29 While promising for diagnosis, they are not effective in activating the immune system and eliminating malignant cells, limiting progress in generating new immunotherapies against cancer. [30][31][32] Typically, glycan-binding antibodies exhibit lower affinities (with equilibrium dissociation constant (K D ) values in the micromolar range for monovalent interactions) than protein-specific antibodies (with K D values in the nanomolar range). 33,34 However, affinities can be enhanced by generating antibodies containing two or more glycan binding sites, or through non-covalent assembly into oligomers with multiple binding sites.…”

Optimization of aPlasmodium falciparumcircumsporozoite protein repeat vaccine using the tobacco mosaic virus platform

“…Interestingly, there was no significant improvement of vaccine performance between NPNAx5 and NPNAx20 in mice or rhesus, and there was evidence to indicate that NPNAx20 antibodies had lower titer and avidity compared to NPNAx5 group in mice. It is possible that at NPNA copy number around 20, increases the proportion of B cells that undergo apoptosis due to hypercross-linking (59)(60)(61). Overall in the mouse model, the NPNAx5 antigen displayed on a loop consistently showed optimal immunogenicity and presumably represented a balance between flexibility and copy number.…”

Engineering a Rugged Nanoscaffold To Enhance Plug-and-Display Vaccination

“… 75 , 76 Thus, future work in synthetic nanobiology may establish the factors maximizing nanoparticle immunogenicity, such as the ideal antigen spacing, number, and orientation. 32 , 77 , 78…”