Figure 2.
SARS-CoV-2–specific humoral responses of one- and two-dose Ad26.COV2.S vaccine regimens in aged rhesus macaques. (A) SARS-CoV-2 spike protein–binding antibody concentrations were measured over time in 120 NHP serum samples (20 NHPs and six time points) with an ELISA qualified for human samples using a trimeric, soluble, stabilized spike protein produced in mammalian cells as coating antigen. Antibody levels in the individual animals are depicted with gray points, and paired measurements are connected with gray lines. The geometric mean titer (GMT) of binding antibody responses per group is indicated with the red line. The dotted lines indicate the LLOD and LLOQ. (B) SARS-CoV-2 spike protein neutralizing antibody titers were measured over time in 116 NHP serum samples (20 NHPs and six time points; four data points not available) with a psVNA qualified for human samples using pseudotyped virus particles made from a modified VSVΔG backbone and bearing the S glycoprotein of SARS-CoV-2 Wuhan-Hu-1. Neutralizing antibody responses were expressed as the reciprocal of the sample dilution where 50% neutralization is achieved (IC50). Antibody levels in the individual animals are depicted with gray points, and paired measurements are connected with gray lines. The GMT of neutralizing antibody responses per group is indicated with the red line. The dotted lines indicate the LLOD and LLOQ. For binding and psVNA neutralizing antibody data, comparisons between specific vaccine groups were made with the two-sample t test in an ANOVA. Successive time points were compared using the paired t test per vaccine group. (C) Correlation between spike-specific–binding antibody concentrations and neutralizing antibody titers per animal for all groups at each time point of analysis. The sham control group and week 0 (baseline) data were excluded. The dashed lines indicate the LLOD for each assay. Correlation coefficients between binding antibody concentrations and neutralizing antibody titers were calculated using two-sided Spearman rank correlation.

SARS-CoV-2–specific humoral responses of one- and two-dose Ad26.COV2.S vaccine regimens in aged rhesus macaques. (A) SARS-CoV-2 spike protein–binding antibody concentrations were measured over time in 120 NHP serum samples (20 NHPs and six time points) with an ELISA qualified for human samples using a trimeric, soluble, stabilized spike protein produced in mammalian cells as coating antigen. Antibody levels in the individual animals are depicted with gray points, and paired measurements are connected with gray lines. The geometric mean titer (GMT) of binding antibody responses per group is indicated with the red line. The dotted lines indicate the LLOD and LLOQ. (B) SARS-CoV-2 spike protein neutralizing antibody titers were measured over time in 116 NHP serum samples (20 NHPs and six time points; four data points not available) with a psVNA qualified for human samples using pseudotyped virus particles made from a modified VSVΔG backbone and bearing the S glycoprotein of SARS-CoV-2 Wuhan-Hu-1. Neutralizing antibody responses were expressed as the reciprocal of the sample dilution where 50% neutralization is achieved (IC50). Antibody levels in the individual animals are depicted with gray points, and paired measurements are connected with gray lines. The GMT of neutralizing antibody responses per group is indicated with the red line. The dotted lines indicate the LLOD and LLOQ. For binding and psVNA neutralizing antibody data, comparisons between specific vaccine groups were made with the two-sample t test in an ANOVA. Successive time points were compared using the paired t test per vaccine group. (C) Correlation between spike-specific–binding antibody concentrations and neutralizing antibody titers per animal for all groups at each time point of analysis. The sham control group and week 0 (baseline) data were excluded. The dashed lines indicate the LLOD for each assay. Correlation coefficients between binding antibody concentrations and neutralizing antibody titers were calculated using two-sided Spearman rank correlation.

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