Figure 4: Dose dependent antibody response to mRNA vaccine reveals correlate of protection in K18 mice.
(A) B6.Cg-Tg(K18-ACE2)2Prlmn/J (K18-hACE2) mice received a single intramuscular injection of Pfizer/BioNTech BNT162b2 mRNA vaccine at the indicated doses. (B) 28 days post injection serum samples were harvested and anti-SARS-CoV-2 anti S1 antibody concentration was measured by ELISA at indicated dilutions (LN-natural log transformed). At 30 days post vaccination mice were challenged with 4×105 PFU WA1 SARS-CoV-2. (C) Weight loss (please see raw data file for calculated p values) and (D) Kaplan-Meier survival curve of animals monitored for 15 DPI. P values were calculated by Log-rank (Mantel-Cox) test. *, P< 0.05; **, P < 0.01. Individual preinfection serum from (B) was used to calculate (E) S1 IgG area under the curve (AUC) or (G) IC50 with VSV pseudovirus neutralization assay and plotted against weight change at 6 DPI (Rs=Spearman correlation coefficient) and P values indicated. Differences in (F) preinfection S1 IgG AUC and (H) VSV pseudovirus neutralization IC50 between mice that survived and mice that died from infection. Logistic regression (Prism) was used to calculate 50% survival titers indicated by dotted line. N=5 mice per condition.