Designing pathogen-like particles to augment vaccine potency through the induction of broadened and synergistic innate immune responses

Abstract Vaccines have protected against many deadly diseases, but they are less effective at defending against pathogens with weakly immunogenic or rapidly mutating antigen epitopes. Adjuvants that specifically trigger Toll-like and cytosolic receptors have been developed to enhance vaccine potency against antigens with poor immunogenicity. We hypothesized that adjuvant combinations delivered on pathogen-like particles (PLPs) could further improve the breadth and potency of the innate immune response. PLPs were synthesized by encapsulating hydrophobic adjuvants inside PLGA microparticles and nanoparticles, which were functionalized with polyethylenimine to facilitate surface loading of charged RNA or ssDNA adjuvants. The immune response of a virus PLP (TLR7/RIG-I adjuvants) and a Gram-negative bacteria PLP (TLR4/TLR9 adjuvants) was evaluated in bone marrow-derived dendritic cells (BMDCs). The viral PLP induced a broadened immune response by simultaneously inducing cytokine profiles representative of the individual adjuvants. The Gram-negative bacteria PLP induced synergistic upregulation of IFN-b and IL12-p70 at both the gene and protein level. Studies in BMDCs from knockout mice revealed that TRIF signaling cooperates with MyD88 signaling and IRF5, not IRF3 or IRF7, is the primary interferon regulatory factor driving synergistic cytokine responses. Moreover, the Gram-negative bacteria PLP could induce upregulation of pro-inflammatory genes and synergistic DC activation in vivoafter IM injection. Ongoing work will evaluate the molecular mechanisms governing adjuvant synergy with PLPs and assess if PLPs can enhance flu vaccine potency in challenge studies