Fig. 2.

Serological and cellular responses to the linear SARS-CoV-2 DNA vaccine candidate assessed by bead-based multiple, virus neutralization, and ELISpot assays. A Antibody responses following immunization were measured by bead-based multiplex assay to quantify IgG anti-SARS-CoV-2 spike receptor-binding domain (RBD) in serum samples collected on day 42 post-immunization (pi). Results are presented as fold change from day 0 (pre-immunization). B Neutralizing antibody (NA) responses to SARS-CoV-2 in serum samples collected on day 42 pi. Neutralizing antibody titers represent the reciprocal of the highest dilution of serum that completely inhibited infection with 100–200 TCID₅₀ of SARS-CoV-2. C The SARS-CoV-2 spike receptor-binding domain (RBD)-specific T cell response elicited by the linear DNA vaccine was assessed by ELISpot assay for IFN-γ. Proliferation of peripheral blood mononuclear cells (PBMCs) in samples from all of the ferrets was measured after stimulation with RBD pool peptides on day 42 post-immunization (pi). * = p < 0.05; ** = p < 0.01. Data are presented as the mean ± standard error.