The Nucleocapsid Protein Of SARS-CoV-2, Combined With ODN-39M, Is A Potential Component For An Intranasal Bivalent Pancorona Vaccine

Abstract

Despite the rapid development of vaccines and their reported efficacy for controlling the COVID-19 waves, two key challenges remain: the scope of the immunity against upcoming variants and zoonosis events, and the induction of mucosal immunity able to clear the virus in the upper respiratory tract for halting the transmission. The present study is aiming at assessing a potential component for a new generation of vaccines so as to overcome such limitations. The recombinant nucleocapsid (N) protein from SARS-CoV-2 Delta variant was combined with a phosphodiester backbone CpG ODN (ODN-39M), forming high molecular weight aggregates. The evaluation of its immunogenicity in Balb/C mice revealed that only administration by intranasal route induced a systemic cross-reactive Cell-Mediated-Immunity (CMI). In turn, this combination was able to induce anti-N IgA in lungs, which along with the specific IgG in sera and CMI in spleen, resulted cross-reactive against the nucleocapsid protein of SARS-CoV-1. Furthermore, the nasal administration of the N+ODN-39M preparation combined with the RBD Delta protein, as inductor of neutralizing Abs, enhanced the local and systemic immune response against RBD with a modulation toward a Th1 pattern. Taken together, these results make the N+ODN-39M preparation a suitable component for a future intranasal pancorona vaccine against Sarbecoviruses. Particularly, the bivalent vaccine formulation N+ODN-39M+RBD could be used as an effective nasal booster in previously vaccinated population.

Broad Humoral Immunity Generated in Mice by a Formulation Composed by Two Antigens From Delta Variant of SARS-CoV-2

“…Concerning the possible immuno-enhancing effect of the N protein alone on RBD in this formulation, in our previous report using a similar preparation (w/o Alum) by intranasal route, it was demonstrated that N protein alone did not contribute to the RBD immunity [10]. This in accordance with the results obtained with another bivalent formulation of N+RBD where the anti-RBD response was similar in the monovalent group (RBD alone)…”

“…Importantly, the overall immunity generated was cross-reactive against N protein from SARS-CoV-2 Omicron variant and 4 SARS-CoV-1. Furthermore, the nasal bivalent formulation, based on N+ODN-39M preparation and combined with RBD Delta protein, enhanced the local and systemic immune response against RBD with a modulation toward a Th1-like pattern [10].…”

The Key to Increase Immunogenicity of Next-Generation COVID-19 Vaccines Lies in the Inclusion of the SARS-CoV-2 Nucleocapsid 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]. Moreover, formulation of spike + nucleocapsid with cationic or anionic lipids showed that this combination of antigens induced IgG and IgA antibodies and production of IL-5 and IFN-γ [86].…”