Double-layered N-S1 protein nanoparticle immunization elicits robust cellular immune and broad antibody responses against SARS-CoV-2

Abstract

BackgroundThe COVID-19 pandemic is a persistent global threat to public health. As for the emerging variants of SARS-CoV-2, it is necessary to develop vaccines that can induce broader immune responses, particularly vaccines with weak cellular immunity.MethodsIn this study, we generated a double-layered N-S1 protein nanoparticle (N-S1 PNp) that was formed by desolvating N protein into a protein nanoparticle as the core and crosslinking S1 protein onto the core surface against SARS-CoV-2.ResultsVaccination with N-S1 PNp elicited robust humoral and vigorous cellular immune responses specific to SARS-CoV-2 in mice. Compared to soluble protein groups, the N-S1 PNp induced a higher level of humoral response, as evidenced by the ability of S1-specific antibodies to block hACE2 receptor binding and neutralize pseudovirus. Critically, N-S1 PNp induced Th1-biased, long-lasting, and cross-neutralizing antibodies, which neutralized the variants of SARS-CoV-2 with minimal loss of activity. N-S1 PNp induced strong responses of CD4+ and CD8+ T cells, mDCs, Tfh cells, and GCs B cells in spleens.ConclusionsThese results demonstrate that N-S1 PNp vaccination is a practical approach for promoting protection, which has the potential to counteract the waning immune responses against SARS-CoV-2 variants and confer broad efficacy against future new variants. This study provides a new idea for the design of next-generation SARS-CoV-2 vaccines based on the B and T cells response coordination.Graphical Steps involved in the preparation of double-layered N-S1 protein nanoparticle vaccines and experimental design performed in combating virus infection. After intramuscular immunization of mice, the double-layered N-S1 protein nanovaccine could effectively promote the maturation of antigen-presenting and mature dendritic cells, robust broad-spectrum neutralizing antibody production, cytokines secretion, robust mDC, Tfh cell, and GCs B cell responses induction, T-cell memory formation and durable antibody responses, and unique global transcriptome characteristics, thus achieving a robust cellular immunity and broad antibody responses against SARS-CoV-2 based on the B and T cells response coordination