Fig. 1: Immunogenicity of the different CoroVax vaccine variants.

a Schematic representation of the Spike variant expressed by each vaccine. S1 and S2 correspond to the Spike subunits. SS: Signal Sequence, NTD: N-Terminal Domain, RBD: Receptor Binding Domain, RBM: Receptor Binding Motif, SD1: Subdomain 1, SD2: Subdomain 2, FP: Fusion Peptide, HR1: Heptad Repeat 1, CH: Central Helix, CD: Connector Domain, HR2: Heptad Repeat 2, TD: Transmembrane Domain, CT: Cytoplasmic Tail. Solid black arrow: S1/S2 furin cleavage site; Clear arrow: S2’ cleavage site. Mutations in the scheme refer to the A.1 variant. Red letters denote aminoacid changes to stabilize Spike in the prefusion conformation. Blue letters denote aminoacid changes that mutate the furin cleavage motif. b Spike expression following in vitro transduction of Hs 729 T cells with the conformation-based vaccines. The arrow shows the absence of the band in Spike constructs expressing a mutated furin cleavage motif. Ad.C corresponds to control Adenovirus. c Surface expression of Spike protein in Hs 729 T cells transduced with conformation-based vaccines or vaccine candidates and analyzed by monoclonal antibodies directed to NTD (E7M5X) or RBD domains (40592-R0004). d BALB/c mice (n = 5) were vaccinated with a single 10⁸ vp dose of each CoroVaxG.3-D conformation-based constructs: Open Enriched (OE), Furin Resistant (FR), 5 (V) proline, Flexibly-Linked, Inter-Protomer bonded (VF) and Closed Locked (CL); sera were collected at 4 weeks postimmunization and assessed for SARS-CoV-2 B.1.617.2 Spike-specific IgG titer. e Spike expression of Hs 729 T cells transduced with the candidate vaccines. The arrow shows the furin cleavage motif and the absence of it in furin-resistant Spikes. (f, g, h) BALB/c mice (n = 5) were vaccinated with a single dose of each CoroVax variant; sera were collected at 4 weeks postimmunization and assessed for (f) SARS-CoV-2 B.1 Spike-specific IgG titers (g) neutralization titer against matched-PsV and (h) cellular immune response. SFU: mean of Spot Forming Units. Ad.C: control adenovirus with no transgene. Differences between experimental groups of animals in f and g were analyzed by Kruskal–Wallis test followed by Dunn’s multiple comparisons; statistical differences in h were analyzed using Brown-Forsythe and Welch ANOVA test with Dunnett T3 a posteriori; *p < 0.05, **p < 0.01, ***p < 0.001. The box plots show the median, 25th and 75th percentiles, and the whiskers show the range.