Antibody response
Eight days after immunization with PTX-COVID19-B there were no detectable antibodies against Spike or RBD either determined by enzyme-linked immunosorbent assay (ELISA) or Mesoscale Discovery (MSD) platform. By day 28 after the first immunization anti-S and anti-RBD immunoglobulin G (IgG) antibodies were detected across the three cohorts indicating seroconversion of all participants (Fig. PTX-COVID19-B induction of anti-S and anti-RBD antibodies. Anti-S IgG antibody levels measured by ELISA are shown in Panel A. Anti-S antibody levels in sera from 29 subjects infected with COVID-19 were also determined by ELISA. The geometric mean and 95% confidence intervals are presented (The two assays for determination of anti-Spike antibodies, ELISA, and MSD, showed a strong positive correlation (correlation, 0.96 [95% confidence interval [CI] 0.95–0.98], 