Combination of Recombinant Proteins S1/N and RBD/N as Potential Vaccine Candidates

Abstract

Despite all successful efforts to develop a COVID-19 vaccine, the need to evaluate alternative antigens to produce next-generation vaccines is imperative to target emerging variants. Thus, the second generation of COVID-19 vaccines employ more than one antigen from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) to induce an effective and lasting immune response. Here, we analyzed the combination of two SARS-CoV-2 viral antigens that could elicit a more durable immune response in both T- and B-cells. The nucleocapsid (N) protein, Spike protein S1 domain, and receptor binding domain (RBD) of the SARS-CoV-2 spike surface glycoproteins were expressed and purified in a mammalian expression system, taking into consideration the posttranscriptional modifications and structural characteristics. The immunogenicity of these combined proteins was evaluated in a murine model. Immunization combining S1 or RBD with the N protein induced higher levels of IgG antibodies, increased the percentage of neutralization, and elevated the production of cytokines TNF-α, IFN-γ, and IL-2 compared to the administration of a single antigen. Furthermore, sera from immunized mice recognized alpha and beta variants of SARS-CoV-2, which supports ongoing clinical results on partial protection in vaccinated populations, despite mutations. This study identifies potential antigens for second-generation COVID-19 vaccines.

Major role of S-glycoprotein in providing immunogenicity and protective immunity in mRNA lipid nanoparticle vaccines based on SARS-CoV-2 structural proteins

“…For this purpose several studies have tested SARS-CoV-2 candidate vaccines that include other structural proteins (mostly the N protein) in adenoviral vectors [19][29], modified vaccinia Ankara vectors [30][31], subunit protein vaccine candidate [32][33] and others [34]. These studies showed protective efficacy, T-cell and humoral response caused by vaccination.…”

Major Role of S-Glycoprotein in Providing Immunogenicity and Protective Immunity in mRNA Lipid Nanoparticle Vaccines Based on SARS-CoV-2 Structural Proteins

“…For this purpose, several studies have tested SARS-CoV-2 candidate vaccines that include other structural proteins (mostly the N protein) in the adenoviral vectors [20,36], modified vaccinia Ankara vectors [37,38], subunit protein vaccine candidates [39,40], and others [41]. These studies have demonstrated the protective efficacy of and the T-cell and humoral responses induced by vaccination.…”

The Key to Increase Immunogenicity of Next-Generation COVID-19 Vaccines Lies in the Inclusion of the SARS-CoV-2 Nucleocapsid Protein

“…Immunization with S1 + N or RBD + N induced IgG1, IgG2, and neutralizing activity, and production of IFN- γ , TNF- α , and IL-2 with higher responses was observed in combination with the N protein. Moreover, sera from the immunized mice showed cross-reactivity with RBD from Alpha and Beta VOCs [ 84 ]. A combination of spike and nucleocapsid proteins using a conventional formulation with aluminum hydroxide, lipids, or other adjuvants has shown induction of humoral and cellular response [ 85 , 86 , 87 , 88 , 89 ].…”