Nanoadjuvants Produced by Advanced Nanochelating Technology in the Inactivated-Severe Acute Respiratory Syndrome Coronavirus-2 Vaccine Formulation: Preliminary Results on Cytokines and IgG Responses.

Despite the great success of vaccines in various infectious diseases, most current vaccines are not effective enough, and on the contrary, clinically approved alum adjuvants cannot induce sufficient immune responses, including a potent cellular immune response to confer protection. In this study, we used Nanochelating Technology to develop novel nanoadjuvants to boost the potency of the alum-adjuvanted inactivated severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) vaccine. BALB/c mice were immunized twice over 2 weeks with different doses of adjuvanted-vaccine formulations and immune responses were assessed. The analysis results of IFN- γ and IL-17 cytokines demonstrated the effectiveness of the nanoadjuvants produced by the Nanochelating Technology in shifting the alum-based vaccine toward a stronger Th1 pattern. In addition, these nanoadjuvants improved IL-2 cytokine response, which shows the efficacy of these novel formulations in inducing specific T lymphocyte proliferation. Using these nanoadjuvants increased IL-10 cytokine secretion that may be representative of a better immunoregulatory impact and may also potentially prevent immunopathology responses. Moreover, specific IgG titer analysis revealed the potency of these nanoadjuvants in improving humoral immune responses. The enzyme-linked immunosorbent assay of receptor-binding domain (RBD)-specific IgG response showed that the developed novel formulations induced strong IgG responses against this protein. This study shows that the nanostructures produced by the Advanced Nanochelating Technology have potent adjuvant effects on alum-based SARS-CoV-2 vaccines to not only compensate for alum weakness in inducing the cellular immune responses by smart regulation of the immune system but also significantly improve the humoral and cellular immune responses simultaneously.