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. 2022 May 13;119(20):e2118312119. doi: 10.1073/pnas.2118312119

Fig. 5.

Fig. 5.

Vaccine-induced virus-neutralizing antibodies and protective immunity to homologous WA Strain of SARS-CoV-2. Six- to 8-wk-old K18-ACE2tg mice were vaccinated twice IN or SQ with SARS-Co-V-2 S protein formulated in ADJ+GLA or ADJ+CpG. At 44 d after booster vaccination, BAL (undiluted to 1:80 dilution) and serum samples (starting at 1:20 dilution) were tested for SARS-COV-2–neutralizing capacity by a microneutralization assay. Virus neutralization was tested against two SARS-CoV-2 variants: USA-WA1/2020 (WA strain) and B.1.351 (SA variant). (A) Endpoint neutralization titer is shown against the indicated SARS-CoV-2 viruses. (B) Mice were vaccinated by the IN route as above, at 50 d after boost, when mice were ∼17 wk of age, they were challenged with the WA strain of SARS-CoV-2 virus; unvaccinated mice were challenged as controls. On day 5 after viral challenge, viral titers and S525-specific CD8 T cells were quantified in the lungs. (B) Viral titers in lungs and recall S525-specific CD8 T cell responses. Graphs show numbers and percentages of tetramer-binding cells gated on total CD8 T cells in lungs. (C) Mice were vaccinated with ADJ+GLA by the IN route as above and were treated with isotype control antibodies, anti-CD4 antibodies (during primary and booster vaccination) or anti-CD8 antibodies (prior to viral challenge). At 55 d postbooster vaccination when mice were ∼18 wk of age, they were challenged with the WA strain of SARS-CoV-2 virus. (C) Figures show viral titers and recall S525-specific CD8 T cell responses in lungs. Graphs show numbers of tetramer-binding cells gated on total CD8 T cells in lungs. (D) Frequencies and total numbers of IFN-γ–producing CD4 T cells in lungs were quantified by intracellular cytokine staining after stimulation with S protein peptide pool as above. (E) Graph showing weight loss as a percent of initial starting weight over days following infection. Asterisks indicate significance at *P < 0.05, **P < 0.005, ***P < 0.0005, and ****P < 0.00005; ns, not significant . Data in each graph indicate mean ± SEM.