Polyelectrolyte Multilayers Assembled Entirely from Immune Signals on Gold Nanoparticle Templates Promote Antigen-Specific T Cell Response

Materials that allow modular, defined assembly of immune signals could support a new generation of rationally designed vaccines that promote tunable immune responses. Toward this goal, we have developed the first polyelectrolyte multilayer (PEM) coatings built entirely from immune signals. These immune-PEMs (iPEMs) are self-assembled on gold nanoparticle templates through stepwise electrostatic interactions between peptide antigen and polyanionic toll-like receptor (TLR) agonists that serve as molecular adjuvants. iPEMs do not require solvents or mixing, offer direct control over the composition and loading of vaccine components, and can be coated on substrates at any scale. These films also do not require other structural components, eliminating the potentially confounding effects caused by the inherent immune-stimulatory characteristics of many synthetic polymers. iPEM loading on gold nanoparticle substrates is tunable, and cryoTEM reveals iPEM shells coated on gold cores. These nanoparticles are efficiently internalized by primary dendritic cells (DCs), resulting in activation, selective triggering of TLR signaling, and presentation of the antigens used to assemble iPEMs. In coculture, iPEMs drive antigenspecific T cell proliferation and effector cytokines but not cytokines associated with more generalized inflammation. Compared to mice treated with soluble antigen and adjuvant, iPEM immunization promotes high levels of antigen-specific CD8(+) T cells in peripheral blood after 1 week. These enhancements result from increased DC activation and antigen presentation in draining lymph nodes. iPEM-immunized mice also exhibit a potent recall response after boosting, supporting the potential of iPEMs for designing well-defined vaccine coatings that provide high cargo density and eliminate synthetic film components.