Modulation of tumor microenvironment using a TLR-7/8 agonist-loaded nanoparticle system that exerts low-temperature hyperthermia and immunotherapy for in situ cancer vaccination.

Most cancer vaccines under development are associated with defined tumor antigens rather than with all antigens of whole tumor cells, limiting the anti-tumor immune responses that they elicit. This work proposes an immunomodulator (R848)-loaded nanoparticle system (R848@NPs) that can absorb near-infrared light (+NIR) to cause low-temperature hyperthermia that interacts synergistically with its loaded R848 to relieve the tumor-mediated immunosuppressive microenvironment, generating robust anti-tumor memory immunity. In vitro results reveal that the R848@NPs could be effectively internalized by dendritic cells, causing their maturation and the subsequent regulation of their anti-tumor immune responses. Post-treatment observations in mice in which tumors were heat-treated at high temperatures reveal that tumor growth was significantly inhibited initially but not in the longer term, while low-temperature hyperthermia or immunotherapy alone simply delayed tumor growth. In contrast, a combined therapy that involved low-temperature hyperthermia and immunotherapy using R848@NPs/+NIR induced a long-lasting immunologic memory and consequently inhibited tumor growth and prevented cancer recurrence and metastasis. These results suggest that the method that is proposed herein is promising for generating cancer vaccines in situ, by using the tumor itself as the antigen source and the introduced R848@NPs/+NIR to generate a long-term anti-tumor immunity, for personalized immunotherapy.

Single-injecting, bioinspired nanocomposite hydrogel that can recruit host immune cells in situ to elicit potent and long-lasting humoral immune responses.

Vaccination is an effective medical intervention for preventing disease. However, without an adjuvant, most subunit vaccines are poorly immunogenic. This work develops a bioinspired nanocomposite hyaluronic acid hydrogel system that incorporates N-trimethyl chitosan nanoparticles (TMC/NPs) that carry a model subunit vaccine ovalbumin (OVA) that can elicit a potent and prolonged antigen-specific humoral response. Experimental results indicate that the nanocomposite hydrogel system (NPs-Gel) can retain a large proportion of its TMC/NPs that are bonded by covalent/electrostatic interactions and extend the release of the encapsulated OVA, enabling their localization at the site of hydrogel injection. The positively charged TMC/NPs can be effectively internalized by dendritic cells, significantly augmenting their maturation, suggesting that TMC can function as an adjuvant-based OVA delivery system. Upon subcutaneous implantation in mice, the NPs-Gel acts as an in situ depot that recruits and concentrates immune cells. The TMC/NPs that do not have any specific interactions with the hydrogel network are released rapidly and internalized by the neighboring immune cells, providing a priming dose, while those retained inside the NPs-Gel are ingested by the recruited and concentrated immune cells over time, acting as a booster dose, eliciting high titers of OVA-specific antibody responses. These experimental results suggest particulate vaccines that are integrated in such a bioinspired hydrogel system may be used as single-injection prime-boost vaccines, enabling effective and persistent humoral immune responses.