Pathogen-Mimicking Polyanhydride Nanovaccines Induce Both Humoral and Cell-Mediated Immunity

Targeting antigen presenting cells (APCs) is a well-studied strategy in the design of vaccine delivery vehicles. It has been shown that antigen can be delivered more efficiently to APCs by targeting pattern recognition receptors (PRRs) on those cells. In particular, C-type lectin receptors (CLRs) are a specific class of PRRs on APCs that have been frequently studied for their ability to internalize carbohydrate-based pathogen associated molecular patterns. As phagocytic receptors, CLRs are attractive targets for carbohydrate-based ligands. For example, the macrophage mannose receptor is known to have a strong affinity for mannose moieties. Previous in vitro work from our laboratories has demonstrated that polyanhydride nanoparticles, whose surface is chemically functionalized with di-mannose, target CLRs on APCs and activate these cells. In this work, we administered carbohydrate-functionalized nanoparticles in vivo to evaluate their ability to induce humoral and cell-mediated immune responses.

Nanoparticles based on 1,8-bis-(p-carboxyphenoxy)-3,6-dioxaoctane (CPTEG) and 1,6-bis-(p-carboxyphenoxy)hexane (CPH)  were synthesized using an anti-solvent nanoprecipitation method. The particles were loaded with 2% ovalbumin, which served as the model antigen. Surface functionalization with either di-mannose or glycolic acid (linker) was performed using a two-step amine-carboxylic acid coupling reaction. C57BL/6 mice were subcutaneously immunized with particles and antibody titers were analyzed at select time points over a 100-day period. The results indicate that both the non-functionalized and functionalized particles elicited strong titers, which were sustainable over time. Separately, mice were immunized subcutaneously with the same formulations and peripheral bleeds over a 10 day period were performed to characterize T cell expansion and contraction as well as intracellular cytokine production elicited by the various formulations. These results provide foundational information for the development of targeted vaccine formulations against viral pathogens.