Self-adjuvanted L-arginine-modified dextran-based nanogels for sustained local antigenic protein delivery to antigen-presenting cells and enhanced cellular and humoral immune responses.

In the development of cancer vaccines, antigens are delivered to elicit potent and specific T-cell responses to eradicate tumour cells. Nonetheless, successful vaccines are often hampered by the poor immunogenicity of tumour antigens, rapid clearance by the innate immunity, and limited cross-presentation on MHC-I to activate CD8 ⁺ T-cells arm. To address these issues, we developed dextran-based nanogels to promote antigen uptake, storage, and cross-presentation on MHC-I, while directing immunogenic maturation of the antigen-presenting cells (APCs). To promote the nanocarriers interaction with cells, we modified DX with L-arginine (Arg), whose immunomodulatory activities have been well documented. The ArgDX nanogel performance was compared with the nanogel modified with L-histidine (His) and L-glutamate (Glut). Moreover, we introduced pH-sensitive hydrazone crosslinking during the nanogel formation for the conjugation and controlled release of antigen ovalbumin (OVA). The OVA-laden nanogels have an average size of 325 nm. We demonstrated that the nanogels could rapidly release cargoes upon a pH change from 7 to 5 within 8 days, indicating the controlled release of antigens in the acidic cellular compartments upon internalization. Our results revealed that the ArgDX nanogel could promote greater antigen uptake and storage in DCs in vitro and promoted a stronger immunogenic maturation of DCs and M1 polarization of the macrophages. The OVA signals were co-localized with lysosomal compartments up till 96 hours post-treatment and washing, suggesting the nanogels could facilitate prolonged antigen storage and supply from endo-lysosomal compartments. Furthermore, all the tested nanogel formulations retained antigens at the skin injection sites until day 21. Such delayed clearance could be due to the formation of micron-sized aggregates of OVA-laden nanogels, extending the interactions with the resident DCs. Amongst the amino acid modifications, ArgDX nanogels promoted the highest level of lymph node homing signal CCR7 on DCs. The nanogels also showed higher antigen presentation on both MHC-I and II than DX in vitro . In the in vivo immune studies, ArgDX nanogels were more superior in inducing cellular and humoral immunity than the other treatment groups on day 21 post-treatment. These results suggested that ArgDX nanogel is a promising self-adjuvanted nanocarrier for vaccine delivery.