ELISA and virus neutralization assay
The following experimental steps were applied in the analyses:
- The serological analysis of SARS-CoV-2-specific IgG was performed by
in-house ELISA. The following SARS-CoV-2 antigens were used: S1 (Acro
Biosystems, Newark, DE, USA), RBD (ATUM, Newark, California, USA), S2
(Acro Biosystems, Newark, DE, USA), and N (Acro Biosystems, Newark,
DE, USA). Detailed information about the selected antigens is shown in
Table S4.
- To determine the IBV-specific IgG response, the in-house ELISA
procedure was performed using 4/91, IS/1494/06, M41, and D274 strains
(Table S5).
- For the measurement of IgG specific for SARS-CoV-2 peptides, peptide
epitope ELISA were applied (As previously reported by Shrock et
al.26). SARS-CoV-2 peptides ORF3a (aa. 172-205), N
(aa. 153-176), N (aa. 221-244), N (aa. 358-381), N (aa. 382-405), S
(aa. 547-570), S (aa. 782-805), S (aa. 807-830), S (aa. 1138-1161), a
rhinovirus A peptide (aa. 567-591), a human herpesvirus 4 peptide (aa.
398-422) and an HIV-1 peptide (aa. 967-991) (Biomatik, Ontario,
Canada) were used. Detailed information about the selected peptides is
listed in Table S6.
- The amino acid sequence of each selected peptide of SARS-CoV-2 and the
alignment of corresponding sequences in the endemic HCoVs (NL63, 229E,
HKU1, and OC43) and IBV (4/91, M41, and D274), are shown in Figure
S8A-H. Sequences were aligned by MUSCLE in JalView
(http://www.jalview.org, version 2.11.1.4).
- The presence of neutralizing antibodies against SARS-CoV-2 was
assessed by live-virus neutralization assay.27
For further details, please refer to the Supplementary Materials and
Methods.