Enhanced immune effect of CpG 7909/alum adjuvant to the inactivated vaccine of SARS-CoV-2

ABSTRACT

Objective: To evaluate the immunogenicity effect of CpG 7909 and Alum adjuvant to inactivated SARS-CoV-2 vaccine. Method(s) Mice were immunized with inactivated SARS-CoV-2 vaccines prepared with CpG 7909 and/or Alum adjuvant by intramuscular injection for 0 and 21 days. To evaluate the immunogenicity of inactivated SARS-CoV-2 vaccines with different adjuvants, serum samples were collected on Day 14, 28, 35 and 42 after immunization to detect the neutralizing antibody titers by microneutralization assay. Spleen samples were collected on Day 42 after immunization to detect the cellular immunity by flow cytometry and ELISPOT. Result(s) Compared with the inactivated SARS-CoV-2 vaccines adjuvanted with CpG 7909 or Alum only, the combination of CpG 7909 and Alum adjuvant significantly increased neutralizing antibody titers in mice and showed great cross-neutralization activity against the Delta variant. It also significantly induced the activation of specific IL-4, IFN-gamma and GCB cells. Conclusion(s) The combination of CpG 7909 and Alum adjuvant synergistically enhanced the humoral and cellular immune responses induced by inactivated SARS-CoV-2 vaccine and showed great cross-neutralization activity against the Delta variant. Copyright © 2022, Chinese Journal of New Drugs Co. Ltd. All right reserved.