Fig. 6: Relationship between anti-SP/RBD IgG titer (ELISA) and PRNT neutralization potency (ED99) among WT, Delta, and Omicron BA.1 variants.
Serum samples were obtained from 67 subjects on days 0, 28, 56, 90, 180, and 273 after receiving a 90 µg s.c. dose of AKS-452 ≥ 3 months after completing regimens of regulatory–approved vaccines. Anti-SP/RBD titers and the ED99 values were determined for WT (a), Delta (b), and Omicron BA.1 (c) variants and linear regression analyses were performed on log10 values. For each variant, a bivariate normal distribution fit to x and y variables was conducted with log10(IgG titer) vs. log10(ED99), respectively, in which correlations within each variant data set were significantly different from 0 (p values of slope) with correlation coefficients for WT, Delta, and Omicron of 0.730, 0.644, and 0.610, respectively. d The concentration of anti-SP/RBD IgG (ELISA) at which 99% neutralization occurred (PRNT ED99) was determined as the “specific potency of neutralization” ([IgG µg/mL]/ED99; note that decreasing values correlate with increasing potency). *, p < 0.05; ****, p < 0.0001; geometric mean values (± s.e.m.) were significantly different from the respective day-0 values (t test, equal variance, one-tailed).
