Activation of the TLR2-MyD88 pathway is required for in-vivo efficacy of Lipid Nanoparticle based vaccine formulation

Emerging evidence suggests that bioengineered nanoparticles can be used as immunomodulatory agents. Using murine and non-human primate vaccination models, we have identified novel cationic lipid nanoparticles (LNPs) that significantly enhance antigen-specific B-cell, CD4+T cell, and most notably, CD8+ T-cell responses. Importantly, we found that LNP-containing vaccine formulations resulted in protective efficacy in a virus challenge model, as well as, in syngeneic murine tumor models. In-vivo imaging and immunophenotyping studies showed that LNPs prolong antigen retention at the injection site and enhance antigen migration to the lymph nodes. Unbiased screening of LNPs ability to activate innate immune sensors showed that LNPs selectively activate Toll-Like Receptor-2 (TLR2). Using genetic ablation, and antibody mediated blockade, we uncovered that TLR2-MyD88 pathway is required for LNPs ability to boost immune responses in-vivo . Ex-vivo and in-vitro studies using dendritic cells (DC) showed that neutralization of TLR2 does not impact the LNP mediated increase in antigen uptake. However, LNP dependent enhancement of DC maturation, antigen processing & presentation, and chemokine production, were significantly reduced when TLR2 was neutralized. Pharmacological inhibition TIRAP, and CD14-MD2, further confirmed the need for the activation of TLR2-MyD88 pathway in LNP’s functionality. Future studies are aimed at utilizing chosen Merck chemical inhibitors of innate immune kinases to further interrogate the TLR2-MyD88 pathway’s involvement in LNP functionality. Such detailed knowledge of LNP’s mode of action will significantly influence the future design of LNPs for vaccines and immune oncology applications.