Abstract
SARS-CoV-2 has caused a global pandemic, infecting millions of people. An effective preventive vaccine against this virus is urgently needed. Here, we designed and developed a novel formulated recombinant receptor-binding domain (RBD) nucleocapsid (N) recombinant vaccine candidates. The RBD and N were separately expressed in E. coli and purified using column chromatography. The female Balb/c mice were immunized subcutaneously with the combination of purified RBD and N alone or formulated with saponin adjuvant in a two-week interval in three doses. Neutralization antibody (Nabs) titers against the SARS-CoV-2 were detected by a Surrogate Virus Neutralization (sVNT) Test. Also, total IgG and IgG1, and IgG2a isotypes and the balance of cytokines in the spleen (IFN-γ, Granzyme B, IL-4, and IL-12) were measured by ELISA. The percentages of CD4+ and CD8+ T cells were quantified by flow cytometry. The lymphoproliferative activity of restimulated spleen cells was also determined. The findings showed that the combination of RBD and N proteins formulated with saponin significantly promoted specific total IgG and neutralization antibodies, elicited robust specific lymphoproliferative and T cell response responses. Moreover, marked increase in CD4+ and CD8+ T cells were observed in the adjuvanted RBD and N vaccine group compared with other groups. The results suggest that the formulations are able to elicit a specific long-lasting mixed Th1/Th2 balanced immune response. Our data indicate the significance of the saponin-adjuvanted RBD/N vaccine in the design of SARS-CoV-2 vaccines and provide a rationale for the development of a protective long-lasting and strong vaccine.
Keywords: CD4+ and CD8+; RBD; SARS-CoV-2; neutralization antibody; nucleocapsid; recombinant protein; vaccine.
【저자키워드】 SARS-CoV-2, vaccine., nucleocapsid, RBD, Neutralization antibody, Recombinant protein, CD4+ and CD8+, 【초록키워드】 IgG, Vaccine, immune response, neutralization, Test, cytokine, virus, flow cytometry, ELISA, SARS-CoV-2 vaccine, global pandemic, mice, neutralization antibodies, female, N protein, T cell response, CD8+ T cell, spleen, IgG1, IFN-γ, Protective, IL-4, Combination, Saponin, E. coli, isotype, sVNT, domain, IgG2a, CD4+, vaccine candidates, doses, IL-12, lymphoproliferative, surrogate, granzyme, infecting, responses, effective, Cell, vaccine group, immunized, robust, caused, significantly, expressed, long-lasting, elicit, increase in, groups, elicited, purified, were measured, promoted, quantified, percentage, purified RBD, subcutaneously, the SARS-CoV-2, 【제목키워드】 COVID-19 vaccine, cellular immunity, recombinant, Saponin, induce, long-lasting neutralizing antibody,