(545b) Understanding Protein Nanoparticle Vaccine Adjuvancy through Dendritic Cell Antigen Presentation

Highly conserved pathogen proteins are essential for broadly cross-protective vaccines, but tend to be poorly immunogenic. We have previously demonstrated that protein nanoparticle vaccines made from conserved pathogen proteins trigger specific, adaptive immune responses that soluble protein vaccines cannot¹. Without excipients or adjuvants, protein nanoparticles eliminate the possibility of off-target immune responses, and their abiotic nature makes them amenable to cold chain-independent storage and use. The mechanisms by which protein nanoparticles enhance component protein immunogenicity are still not well understood. It is hypothesized that dendritic cells, the most potent antigen-presenting cells, and the bridge between innate and adaptive immunity, are responsible for mediating this effect. In this work, we investigate the role of size and surface properties of model ovalbumin (OVA) protein nanoparticles on particle uptake, maturation factor expression and antigen presentation in the JAWS II dendritic cell (DC) line.

Pure OVA nanoparticles of 250, 500 and 750 nm have been synthesized by a modified desolvation procedure. By incorporating Alexa Fluor 488-conjugated OVA into our particles, we demonstrate via flow cytometry that nanoparticles enhance DC protein delivery compared to soluble protein administration. However, enhanced delivery alone does not correlate to a greater inflammatory response. Ensuring that the proteins on the surface of the nanoparticles have retained their secondary structure is also critical and amplifies the DC TNF-α response. Optimal particle formulations are determined by a combination of uptake, TNF-α expression indicating an inflammatory response, and CD86 upregulation indicating dendritic cell maturation. Additional cytokine expression and surface marker upregulation is also investigated to determine the nature of the costimulatory signals induced by protein nanoparticles. Knowledge of critical particle properties identified here will be used for fabricating nanoparticles from recombinantly-expressed influenza proteins, and the relevant biomarkers identified in this study will have their downstream correlates assessed in an in vivo mouse vaccination model to further develop protein nanoparticles as an antigen-specific vaccination strategy.

1. Wang, L, Hess, A, Chang, TZ et al. “Nanoclusters self-assembled from conformation-stabilized influenza M2e as influenza vaccines.” Nanomedicine 2014 Feb;10(2):473-82.