Pre-existing immunity modulates responses to mRNA boosters

Figures

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  Figure 1.. Pre-boost antibody levels are inversely correlated to fold-increase in antibody levels following mRNA vaccination in humans. (A) Experimental layout. Participants were determined to be unexposed prior to vaccination based on a negative serology test for SARS-CoV-2 spike and nucleocapsid proteins before vaccination. Participants were determined to be exposed to SARS-CoV-2 based on symptoms and confirmatory RT-PCR. (B) Summary of SARS-CoV-2 spike antibody responses in unexposed individuals. (C) Summary of SARS-CoV-2 spike antibody responses in exposed individuals. Since endpoint titers fall on discrete values (multiples of 25), several values overlapped on the same data point, so bubble plots were utilized to depict overlapping data points. Fold increase was calculated by dividing the post-boost antibody titer by the pre-boost antibody titer (SARS-CoV-2-spike specific IgG). Data are from 3 visits or time points (V0, V1, V2). Non-parametric Spearman correlation was used to calculate correlation between pre-boost antibody titer and fold-increase in antibody titers (twotailed test was used to calculate significance).

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  Figure 2.. Plasma from mRNA-1273 or BNT162b2 vaccinated humans abrogates de novo antibody responses following mRNA vaccination in mice. (A) Experimental layout. Donor-matched plasmas were harvested from 5 different human donors; pre-vaccination (V0) and post-vaccination (V2 corresponding to 2–3 weeks post 2nd dose). 100 μL of these donor-matched human plasmas were adoptively transferred via the intraperitoneal route into C57BL/6 mice. On the following day, all mice were immunized intramuscularly with 3 μg of an mRNA expressing SARS-CoV-2 spike; and immune responses were quantified every week. (B-C) SARS-CoV-2 spike–specific antibody responses in human donors who received mRNA-1273 or BNT162b2 vaccines; since endpoint titers fall on discrete values (multiples of 25), several values overlapped on the same data point, so data are shown as single replicates (B) or as donor-matched data points to visualize vaccine-elicited responses in each human donor (C). (D) Human-derived SARS-CoV-2 spike–specific antibody in mice that received plasma from mRNA-1273 or BNT162b2 vaccinated humans. (E-F) Mouse-derived SARS-CoV-2 spike–specific antibody in mice that received plasma from mRNA-1273 or BNT162b2…

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  Figure 3.. Plasma from vaccinated mice abrogates de novo antibody responses. (A) Experimental layout. Plasmas were harvested from C57BL/6 mice that were vaccinated with mRNA-spike (two doses). 400 μL of these plasmas were adoptively transferred via the intraperitoneal route into BALB/c mice. On the following day, all mice were immunized intramuscularly with 3 μg of an mRNA expressing SARS-CoV-2 spike; and immune responses were quantified every week. Naïve plasmas were used as control. (B) Donor-derived SARS-CoV-2 spike–specific antibody. (C-D) Recipient-derived SARS-CoV-2 spike–specific antibody; whole spike-specific (C) and RBD-specific (D). (E) Experimental layout for detection of antibody secreting cells. (F) Antibody secreting cells in bone marrow. Two-tailed Mann Whitney test was used. Data are from an experiment with 4 mice that received naïve plasma and 5 mice that received post-vaccine plasma (week 2 post-boost); experiment was repeated for a total of 2 times, with similar results; dashed lines represent the LOD. Error bars indicate the SEM.

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  Figure 4.. A homologous Omicron boost is not superior to a homologous ancestral vaccine boost. (A) Experimental layout. C57BL/6 mice were immunized intramuscularly with 3 μg of an mRNA expressing ancestral spike or Omicron spike. After 3 weeks, mice were boosted homologously and immune responses were quantified. (B) Summary of SARS-CoV-2 spike–specific CD8 T cells. These CD8 T cells were specific for a conserved CD8 T cell epitope present in both ancestral and Omicron viruses (KbVL8). (C-D) Summary of SARS-CoV-2 spike–specific CD8 and CD4 T cells after stimulation with ancestral spike peptide pools. (E-F) Summary of SARS-CoV-2 spike–specific CD8 and CD4 T cells after stimulation with Omicron spike peptide pools. (G) Polyfunctionality of CD8 T cells after stimulation with ancestral spike peptide pools. (H) Polyfunctionality of CD8 T cells after stimulation with Omicron spike peptide pools. (I) Ancestral spike–specific antibody responses. (J) Omicron spike–specific antibody responses. (K) Experimental layout for detection of antibody secreting cells specific for ancestral or Omicron spike. (L) Ancestral spike–specific antibody secreting cells. (M) Omicron spike–specific antibody secreting…

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  Figure 5.. A single prime with an Omicron vaccine results in superior protection against Omicron than a single prime with an ancestral vaccine. (A) Experimental layout. C57BL/6 mice were immunized intramuscularly with 3 μg of an mRNA expressing ancestral spike or Omicron spike. After 2 weeks, immune responses were quantified. (B) Representative FACS plots of SARS-CoV-2 spike–specific CD8 T cells. (C) Summary of SARS-CoV-2 spike–specific CD8 T cells. These CD8 T cells were specific for a conserved CD8 T cell epitope present in both ancestral and Omicron viruses (KbVL8). (D) Ancestral spike–specific antibody responses. (E) Omicron spike–specific antibody responses. (F) Ancestral spike–specific neutralizing antibody responses. (G) Omicron spike–specific neutralizing antibody responses. With only a single mRNA prime, there is substantial variability in antibody responses. (H) Viral loads after Omicron challenge. Data from panels A-G used wild type C57BL/6 mice, whereas data from panel H used K18-hACE2 mice (on C57BL/6 background). Two-tailed Mann Whitney test was used. Data from panels C-E are from 3 experiments; the first experiment with 9–10 mice per group, the second experiment with 3–5 mice…

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  Figure 6.. Humoral responses curtail antigen expression following mRNA immunization. (A) Experimental layout. C57BL/6 mice were immunized intramuscularly with 3 μg of an mRNA expressing Luciferase, and after 3 weeks, mice were boosted. We immunized another group of mice with a different vaccine platform expressing the same transgene (Ad5-Luciferase) or with an irrelevant mRNA vaccine expressing a different antigen (mRNA-spike). Two weeks after boost, mice were bled, and plasmas were collected. 400 μL of plasma was adoptively transferred into naïve BALB/c mice via the intraperitoneal route. On the following day, recipient mice received an intramuscular injection of mRNA-luciferase and luciferase expression was quantified by in vivo imaging (IVIS). (B) Bioluminescence images. (C) Summary of transgene expression by IVIS. BALB/c mice (with white coat) were used for improved visualization of luciferase. Data are from one experiment with 10 quadriceps per group (5 mice per group). Experiment was repeated for a total of 2 times, with similar results. Two-way ANOVA test (Dunnett’s multiple comparisons, with adjusted p-value) was used. P-values are indicated in blue (mRNA-control vs…