Fig. 1: Ad26.COV2.S vaccine elicits binding and neutralizing antibodies in plasma and purified IgG from human vaccine recipients.

a Schematic of the experimental design. Particpants in the COV1001 clinical trial were vaccinated with Ad26.COV2.S or placebo control. On day 71, plasma samples were collected and total IgG was purified. IgG was then transferred into naïve hamster recipients, followed by intra-nasal challenge with WA1/2020 SARS-CoV-2. b–d Binding and neutralizing activity was quantified in human plasma samples and corresponding IgG purified from plasma samples from either placebo recipients (N = 5) or recipients of the Ad26.COV2.S vaccine at the indicated dosing regimens (N = 20). Binding antibody responses were quantified via electrochemiluminescent assay (ECLA) specific for (b) WA1/2020 SARS-CoV-2 spike (S) protein and (c) WA1/2020 SARS-CoV-2 receptor binding domain (RBD) protein. d Similarly, neutralizing antibody titers were quantified using a pseudovirus neutralization assay. Data displated indicate the 50% neutralization titer (NT50) of a WA1/2020 SARS-CoV-2 S-expressing pseudovirus. In panels a-c, each data point displayed corresponds to one clinical trial study participant and red lines indicate the group medians. e–g Correlation of (e) S binding, (f) RBD binding, and (g) pseudovirus neutralizing antibody titers in pre-purification human plasma and corresponding purified IgG. Each data point displayed corresponds to one study participant. Statistics indicate the results of Spearman correlation analysis. h–j Purified IgG from vaccinees or placebo recipients was transferred to groups of naïve hamsters (n = 4–5 hamsters/study participant) via intraperitoneal injection. One day post-transfer, hamster serum was collected and analyzed for (h) S binding, (i) RBD binding, or (j) pseudovirus neutralizing antibody titers. Data points displayed in panels h–j correspond to the median titer of each group of n = 4–5 hamsters that corresponds to one clinical trial study participant. Horizontal red lines indicate medians of groups corresponding to vaccinees or placebo recipients. Statistics displayed are the results of two-sided Mann–Whitney tests. (****P ≤ 0.0001).