Harnessing self-assembly for modular control of toll-like receptor signaling

Abstract

While vaccines have been transformative in stopping – and even eradicating – some pathogens, key hurdles face vaccines for many existing and emerging pathogens. The initiation of immune response requires specialized cells to present pieces of foreign pathogens termed antigens, alongside stimulatory molecules – adjuvants, that amplify and tune immunity. Activation of pathogen sensing pathways called toll-like receptors (TLRs) helps initiate this cascade, motivating exploration of TLR agonists (TLRas) as molecular vaccine adjuvants. Activating multiple TLRs has increased efficacy in trials for infectious diseases and cancer immunotherapy. Delivering rationally-defined combinations of TLRas with antigen might thus enable robust, tunable antigen-specific immunity. Our lab has developed immune polyelectrolyte multilayers (iPEMs), a modular platform to create carrier-free capsules composed entirely of antigen and TLRa. iPEMs allow the juxtaposition of distinct immune signals at high densities, a crucial feature to drive efficient immune responses.

The research in this dissertation focuses on design of iPEMs containing rationally-selected combinations of TLRas to tune the magnitude and type of immune response in immune cells and pre-clinical models. In primary immune cells, iPEMs were discovered to increase the level and rate of uptake relative to soluble signals, and to co-deliver TLRas intracellularly. Importantly, the TLRas in iPEMs were shown to interface with their cognate TLR receptors, which are spatially-restricted within antigen presenting cells (APCs). Over similar times, iPEMs drove presentation of antigen on the surface of APCs. Gene expression analysis revealed iPEMs activated distinct TLR signaling pathways, depending on the TLRas in iPEMs. Strikingly, iPEMs could elicit different T cells responses against the same antigen during co-culture with antigen-specific T cells, tunable by the TLRas in iPEMs. In mice, iPEM vaccination induced reorganization of lymph nodes, including development of structural microdomains associated with potent immunity. Further, iPEMs containing two classes of TLRas significantly enhanced antigen-specific immunity relative to a single TLRa class, indicating synergy in activating multiple TLRs. These discoveries reveal that precision co-delivery of distinct combinations of TLRas in iPEMs allows control over the type and level of antigen-specific immunity. This research helps inform design of future vaccines for infectious diseases and cancer immunotherapies.