Encapsulating antigens with zeolitic imidazole framework-8 (ZIF-8) exhibits many advantages in vaccine development. However, most viral antigens with complex particulate structures are sensitive to pH or ionic strength, which cannot tolerate harsh synthesis conditions of ZIF-8. Balancing the viral integrity and the growth of ZIF-8 crystals is crucial for the successful encapsulation of these environment-sensitive antigens in ZIF-8. Here, we explored the synthesis of ZIF-8 on inactivated foot and mouth disease virus (known as 146S), which is easily disassociated into no immunogenic subunits under the existing ZIF-8 synthesis conditions. Our results showed that intact 146S could be encapsulated into ZIF-8 with high embedding efficiency by lowering the pH of the 2-MIM solution to 9.0. The size and morphology of 146S@ZIF-8 could be further optimized by increasing the amount of Zn2+ or adding cetyltrimethylammonium bromide (CTAB). 146S@ZIF-8 with a uniform diameter of about 49 nm could be synthesized by adding 0.01% CTAB, which was speculated to be composed of single 146S armored with nanometer-scale ZIF-8 crystal networks. Plenty of histidine on the 146S surface forms a unique His-Zn-MIM coordination in the near vicinity of 146S particles, which greatly increases the thermostability of 146S by about 5 °C, and the nano-scale ZIF-8 crystal coating exhibited extraordinary stability to resist EDTE-treatment. More importantly, the well-controlled size and morphology enabled 146S@ZIF-8(0.01% CTAB) to facilitate antigen uptake. The immunization of 146S@ZIF-8(4×Zn2+) or 146S@ZIF-8(0.01% CTAB) significantly enhanced the specific antibody titers and promoted the differentiation of memory T cells without adding another immunopotentiator. This study reported for the first time the strategy of the synthesis of crystalline ZIF-8 on an environment-sensitive antigen and demonstrated that the nano-size and appropriate morphology of ZIF-8 are crucial to exert adjuvant effects, thus expanding the application of MOFs in vaccine delivery.
Mengyue Pei,Rong Xu,Chuangnian Zhang,Xiaoli Wang,Chen Li,Yunzhang Hu
Cancer immunotherapy is an important tumor therapy option for prevention and treatment of tumors and has attracted tremendous interests. However, the therapeutic outcomes are limited by insufficient antigen uptake and presentation by antigen-presenting cells such as dendritic cells (DCs). In this study, mannose-functionalized antigen nanoparticles with endosome escape activity were designed for targeted DCs, accelerated endosomal escape and enhanced MHC-I antigen presentation for cancer immunotherapy. Mannose was selected as DCs targeting ligand to enhance antigen uptake. Model antigen ovalbumin (OVA) was directly conjugated with mannose to obtain DCs targeting antigen, which was then complexed with polyethylenimine (PEI) through electrostatic interaction to form mannose-functionalized antigen nanoparticles (MAN-OVA/PEI NPs). Flow cytometry analysis revealed that the MAN-OVA/PEI NPs greatly increased antigen uptake by DCs compared with OVA/PEI NPs. Confocal laser scanning microscopy further demonstrated that MAN-OVA/PEI NPs enhanced cytosolic antigen release. Moreover, MAN-OVA/PEI NPs significantly promoted cytokine production and DCs maturation in vitro . More importantly, MAN-OVA/PEI NPs treated DCs exhibited enhanced cross-presentation to B3Z T cell hybridoma in vitro . This work suggests that mannose-functionalized antigen nanoparticles provide a versatile delivery vehicle for targeted DCs, accelerated endosomal escape and enhanced MHC-I antigen presentation for cancer immunotherapy.
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