Protein-polymer Bioconjugate Nanoparticles To Investigate Innate and Antigen-Specific CD4 T Cell Responses

Abstract Nanoparticles (NP) comprised of poly(lactic-co-glycolic acid) (PLGA) and poly(lactic acid) (PLA) have been shown to be effective delivery systems for peptide and protein antigens (Ags) capable of modulating Ag-specific T cell responses. Encapsulation and surface conjugation are common Ag association methods using NPs. However, these methods are associated with caveats such as imprecise Ag loading, high Ag burst release, and immune recognition. To improve the efficiency of Ag delivery and address these limitations, we prepared ovalbumin (OVA)-PLGA conjugates that were systematically combined with unmodified PLGA to produce NPs (acNP-OVA) with three precise Ag loadings, negligible immune recognition, and a reduced burst release. acNP-OVA was used to elucidate how NP formulation parameters, such as Ag content, influence innate and Ag-specific CD4 +T cell responses. We observed Ag loading-dependent innate immune cell activation (MHCII, CD80/86) and Ag-specific CD4 +T cell proliferation, cytokine secretions, and regulatory T cell induction in vitro. Ag-encapsulated NPs were employed as a control. CD25 expression and T cell expansion were achieved using both Ag delivery methods and observed at low Ag loading. However, high Ag loading was required to induce IFNg and IL-2 cytokine secretions. Notably, nanostring analysis identified inflammation-associated genes, such as S100a9, was significantly downregulated in dendritic cells due to NP treatment. We anticipate this study will aid in designing NP-based immunotherapies for Ag-specific immunomodulation.