Montmorillonite nanosheets as an adjuvant eliciting potent cellular immunity

The experience of fighting COVID-19 shows the growing importance of vaccine-induced cellular immunity, whereas aluminum adjuvants fail to meet this medical requirement. Herein, with very simple processing, we prepared a narrow lateral size of monolayer clay nanosheets from montmorillonite, a FDA-approved generally recognized as safe (GARS) material. The nanosheets adsorbed antigen ovalbumin (OVA) through hydrophilic and electrostatic interactions, while utilizing nanosheets to expose more octahedral Al-OH and tetrahedral Si-OH residues to complete the adsorption of mannose (Man) targeting antigen presentation cells, leading to the production of nanosheet vaccines. In additional, the lyophilization process did not significantly affect the loading of OVA and Man on the nanosheets. The obtained nanosheet vaccines induced a strong cellular immune response in addition to a potent humoral immune response. Inspired by the results, the prophylactic nanosheet adjuvant vaccine against Epstein-Barr virus (EBV) was developed, which induced a 13-fold increase in EBV-neutralizing antibody titers compared to aluminum adjuvant vaccine, and efficiently blocked EBV infection of target cells. Based on the simple formulation process, remarkable immune response effect and excellent safety profile, montmorillonite nanosheets have the potential to replace aluminum adjuvant as a vaccine platform for inducing effective immune responses.