NET-inducing diamond nanoparticles with adsorbed hydrophobic SARS-CoV-2 antigens serving as vaccine candidate

This study addresses the current need for vaccine adjuvants able to induce an immune response to novel or mutated pathogens. It exploits the ability of nanodiamonds (ND) to induce the formation of neutrophil extracellular traps (NETs) triggering inflammation, accompanied by immune response to co-injected antigens. Hydrophobic nanodiamonds 10 nm in diameter were covered with 194 a.a. sequence of the receptor-binding domain of Spike protein of SARS-CoV-2 via passive adsorption. It was shown that antigen-covered ND induce activation of human neutrophils and stimulate NETs formation and ROS production. When used for immunization antigen-covered ND induced long-lasting immune response in mice with prevailing IgG1 among antibody subclasses. The injected nanoparticles were sequestered by NETs and safely covered with connective tissues when examined 1 year after injection. Keywords: adjuvants, IgG1, nanodiamonds, neutrophil extracellular traps, ROS, S-protein, SARS-COV-2, vaccine