Prior infection with SARS-CoV-2 boosts and broadens Ad26.COV2.S immunogenicity in a variant-dependent manner

Abstract

The Johnson and Johnson Ad26.COV2.S single-dose vaccine represents an attractive option for coronavirus disease 2019 (COVID-19) vaccination in countries with limited resources. We examined the effect of prior infection with different SARS-CoV-2 variants on Ad26.COV2.S immunogenicity. We compared participants who were SARS-CoV-2 naive with those either infected with the ancestral D614G virus or infected in the second wave when Beta predominated. Prior infection significantly boosts spike-binding antibodies, antibody-dependent cellular cytotoxicity, and neutralizing antibodies against D614G, Beta, and Delta; however, neutralization cross-reactivity varied by wave. Robust CD4 and CD8 T cell responses are induced after vaccination, regardless of prior infection. T cell recognition of variants is largely preserved, apart from some reduction in CD8 recognition of Delta. Thus, Ad26.COV2.S vaccination after infection could result in enhanced protection against COVID-19. The impact of the infecting variant on neutralization breadth after vaccination has implications for the design of second-generation vaccines based on variants of concern.

Keywords: Ad26CoV2.S; Fc effector function; SARS-CoV-2; hybrid immunity; neutralization; vaccines; variants of concern.

Graphical abstract

Figure 1

Spike-specific antibody responses in Ad26.COV2.S-vaccinated healthcare workers (A) Study design showing three groups (left panel), either with no prior infection or infection in the first wave (May–August 2020) and infection in the second wave (November 2020–January 2021). Samples were taken pre-vaccination and one month after vaccination. SARS-CoV-2 epidemiological dynamics in the Western Cape (South Africa) are shown (top right panel). Prevalence of SARS-CoV-2 lineages is shown on the left y axis. The ancestral strain (D614G) is depicted in blue, and Beta is depicted in red. The number of COVID-19 cases is represented on the right y axis. The bars on top of the graph indicate the periods when participants were infected in the first and second waves. Vertical dotted lines indicate when vaccination occurred. Characteristics of participants in the three groups (bottom right panel). Sex, age (median and IQR), and days since PCR-confirmed infection. (B) Plasma samples from participants with no prior infection (green, n = 19), first-wave infection (blue, n = 20), or second-wave infection (red, n = 19) were tested for binding to D614G spike protein pre- and post-vaccination (OD_450nm). (C) Cross-reactivity of vaccine-induced antibody responses to D614G and Beta spike. The colored lines below the graph correspond with the key. The threshold for positivity is indicated by a dotted line. Horizontal bars indicate GMT, with values shown. Statistical analyses were performed with the Mann-Whitney test between groups, and the Wilcoxon test was performed for pre- and post-vaccine time points or D614G in comparison with Beta responses. ^∗∗∗p < 0.001.

Figure 2

Neutralizing antibody responses to Ad26.COV2.S vaccination (A) Neutralization of the SARS-CoV-2 D614G pseudovirus by plasma pre- and post-vaccination from participants with no prior infection (green, n = 19) and those infected in the first (blue, n = 20) and second waves (red, n = 19). Neutralization is reflected as an ID₅₀ titer. The threshold for positivity is indicated by a dotted line (B) Cross-reactive neutralization post-vaccination against D614G, Beta, and Delta. Pie charts show the proportion of vaccine non-responders (NR; gray), knockout of neutralization of Beta or Delta (KO; black), and the titer of 20–400 (orange), or >400 (red). The horizontal bars indicate GMT, with values indicated. Statistical analyses were performed with the Friedman test between groups and the Wilcoxon test for paired analyses. ^∗p < 0.05, ^∗∗∗p < 0.001. (C) Fold change of post-vaccination D614G neutralization titers relative to Beta or Delta. The vertical bars indicate median fold change with error bars for IQR.

Figure 3

ADCC responses to Ad26.COV2.S vaccination (A) ADCC activity represented as relative light units (RLU). (B) Cross-reactive ADCC activity 28 days post-vaccination against D614G, Beta, and Delta. Pie charts show the proportion of vaccine non-responders (NR; gray), knockout of Beta/Delta neutralization (KO; black), or detectable ADCC activity (41–150, orange; >150, red). Statistical analyses were performed with the Friedman test between groups and the Wilcoxon test for pre- and post-vaccine time points or D614G in comparison with Beta/Delta responses. ^∗p < 0.05, ^∗∗p < 0.01, ^∗∗∗p < 0.001. (C) Fold change of post-vaccination D614G ADCC levels relative to those of the Beta/Delta variants. The vertical bars indicate median fold difference and error bars the IQR.

Figure 4

T cell responses to Ad26.COV2.S vaccination (A and B) Frequency of total cytokine-producing spike-specific CD4 T cells (A) and CD8 T cells (B) in those with no prior infection (green, n = 19), infection in the first wave (blue, n = 20), and infection in the second wave (red, n = 19), in PBMCs stimulated with peptides based on Wuhan spike. (C) Median fold change of CD4 and CD8 T cell frequencies after vaccination in responders. Error bars indicate IQR. Pie charts show responders (black) and non-responders (gray), with the percentage of responders indicated. (D) Cross-reactivity of T cell responses post-vaccination (n = 24) after peptide stimulation with spike from the ancestral strain, Beta, or Delta is shown. Horizontal bars indicate medians. The dotted line indicates the threshold for positivity and values are background subtracted. Statistical analyses were performed with the Wilcoxon test. ^∗p < 0.05, ^∗∗p < 0.01.