Epitope Profiling Reveals the Antibody Immune Response Difference Between COVID‐19 Infected and Vaccinated

Antibodies play an important part in combating SARS‐CoV‐2 infection whether generated by the infection or vaccination. However, the many epitopes generated by infection have not been fully investigated with only a few epitopes known and these being mostly limited to the S protein’s receptor binding domain (RBD) and the N‐terminal domain which limits vaccine and drug design 1‐4. The difference between epitopes generated by infection and vaccination has also not been studied. To address this, we employed a SARS‐CoV‐2 proteome microarray to screen for linear epitopes recognized by antibodies present in COVID‐19 patients and individuals vaccinated with the Pfizer‐BioNTech mRNA COVID‐19 Vaccine. The proteome microarray consisted of S, N, and E proteins, as well as spotting peptides that were 15 amino acids in length with overlaps of 5‐amino acids, covering the entire SARS‐CoV‐2 proteome (MN908947.3) (Figure 1). Blood samples were incubated onto the arrays followed by an incubation of fluorescent secondary anti‐human antibodies. Fluorescent intensity data generated and normalized using the Z‐score method and then further analyzed for significance by parametric one‐way ANOVA with Dunnett's post hoc test (COVID‐19 cohort) and repeated measure ANOVAs with Dunnett's post hoc tests (vaccinated cohort). The full‐length S protein showed a significant increase in COVID‐19 patients at around 20‐23 days after symptom onset and vaccinated individuals over all time points in both IgM and IgG antibodies (Figure 2A). Linear mapping of the IgM epitopes revealed a degree of overlap between infected and vaccinated individuals (22.2%;6/27 total) with both having epitopes in the RBD and fusion peptide (FP) (Figure 2B). Structural mapping on 3D models of the S protein showed that all epitopes where on the surface of the protein and that COVID‐19 generated epitopes have a different pattern than those generated by vaccination (Figure 2C). An Epitope identified in this study with future prospects is epitope S481‐495 from COIVD‐19 patients that partially overlapped the binding site of two neutralizing antibodies previously isolated from COVID‐19 patients, S2H135 and F2B‐2F61, and contacted amino acids that interact with ACE2 receptor6,7. One epitope of note from the vaccinated individuals is epitope S811‐825 which mapped adjacent to the fusion‐peptide proximal region. These epitopes may be helpful in future vaccine and antibody therapy development. 1 Ju, B. et al. Nature 584, 115‐119. 2 Robbiani, D. F. et al. Nature 584, 437‐442. 3 Seydoux, E. et al. bioRxiv. 4 Wu, Y. et al. Science 368, 1274‐1278. 5 Piccoli, L. et al. Cell 183, 1024‐1042 e1021. 6 Casalino, L. et al. ACS Cent Sci 6, 1722‐1734. 7 Wang, Q. et al. Cell 181, 894‐904 e899.

SARS-CoV-2 Epitopes following Infection and Vaccination Overlap Known Neutralizing Antibody Sites.

Identification of epitopes targeted following virus infection or vaccination can guide vaccine design and development of therapeutic interventions targeting functional sites, but can be laborious. Herein, we employed peptide microarrays to map linear peptide epitopes (LPEs) recognized following SARS-CoV-2 infection and vaccination. LPEs detected by nonhuman primate (NHP) and patient IgMs after SARS-CoV-2 infection extensively overlapped, localized to functionally important virus regions, and aligned with reported neutralizing antibody binding sites. Similar LPE overlap occurred after infection and vaccination, with LPE clusters specific to each stimulus, where strong and conserved LPEs mapping to sites known or likely to inhibit spike protein function. Vaccine-specific LPEs tended to map to sites known or likely to be affected by structural changes induced by the proline substitutions in the mRNA vaccine's S protein. Mapping LPEs to regions of known functional importance in this manner may accelerate vaccine evaluation and discovery of targets for site-specific therapeutic interventions.