Specific antibody responses to SARS-CoV-2 peptide epitopes with
homology to endemic HCoVs and avian coronavirus infectious bronchitis
virus
After observing cross-reactivity between SARS-CoV-2 and IBVs, we
selected peptides with varying degrees of a homology between SARS-CoV-2
and endemic HCoVs and IBV. We investigated whether IgG levels against a
selection of 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), and S (aa. 1138-1161) with varying
degrees of homology with endemic HCoVs and IBV. As shown in Figure S8G,
the most homologous region is S (aa. 807-830) in the comparison between
IBV and SARS-CoV-2. Rhinovirus A (aa. 567-591) and a human herpesvirus 4
(aa. 398-422) peptides were included as positive controls and an HIV-1
(aa. 967-991) peptide was included as a negative control. IgG levels
against ORF3a (aa. 172-205) were higher in COVID-19 patients compared to
poultry farm personnel and pre-pandemic control samples (Figure 3A).
Similarly, IgG against the regions corresponding to residues 153 to 176,
221 to 244, 358 to 381, and 382 to 405 of the SARS-CoV-2 N protein was
higher in COVID-19 patients than in poultry farm personnel and
pre-pandemic control samples (Figure 3B-E). According to the S (aa.
547-570), S (aa. 782-805), S (aa. 807-830), and S (aa. 1138-1161)
regions, the IgG OD ratios in COVID-19 patients were significantly
higher compared to poultry farm personnel and pre-pandemic control
samples (Figure 3F-I and M; Table S7).
IgG OD ratios against all peptides, except ORF3a (aa. 172-205), were
significantly higher in COVID-19 patient samples than in poultry farm
personnel and pre-pandemic control samples. In pre-pandemic control
group, the IgG OD ratios against ORF3a (aa. 172-205) and N (aa. 221-244)
regions were statistically higher than poultry farm personnel.
IgG levels specific for the positive control rhinovirus A (aa. 567-591)
and human herpesvirus 4 (aa. 398-422) peptides were significantly higher
in pre-pandemic control samples and poultry farm personnel compared to
COVID-19 patients (Figure 3J,K). In contrast, HIV-1 (aa.
967-991)-specific IgG levels were significantly higher in COVID-19
patients compared to poultry farm personnel and pre-pandemic control
samples (Figure 3L).
IgG levels specific for the SARS-CoV-2 peptides N (aa 153-176), N (aa
221-244), N (aa 358-381), N (aa 382-405), S (aa 547-570), S (aa
782-805), and S (aa 1138-1161) were significantly higher in hospitalized
COVID-19 patients compared to non-hospitalized COVID-19 patients (Figure
S3A). In contrast, IgG specific for rhinovirus A (aa. 567-591) and human
herpesvirus 4 (aa. 398-422) peptides, was higher in non-hospitalized
than in hospitalized COVID-19 patients (Figure S3B). IgG specific for
the S (aa 1138-1161) peptide was significantly higher in vaccine
implementers than in poultry workers (Figure S4A). However, there were
no significant differences between vaccine implementers and poultry
workers in the evaluation of IgG levels specific to rhinovirus A (aa.
567-591), human herpesvirus 4 (aa. 398-422), and HIV-1 (aa. 967-991)
peptides (Figure S4B).
Long-term employment as poultry farm personnel is associated
with higher levels of SARS-CoV-2 S1-, RBD-, and avian coronavirus
infectious bronchitis virus -specific IgG
Next, we wanted to determine whether poultry farm personnel with more
work experience had higher levels of SARS-CoV-2- and IBV-specific IgG.
Vaccine implementers and poultry workers were categorized into three
groups (2-20 months, 21-100 months, >100 months). The
levels of IgG specific for a S1, RBD, 4/91, IS/1494/06, M41, and D274
were significantly higher in the vaccine implementers with
>100 months’ experience than in those with 2-20 months’
experience (Figure 4A). In the poultry workers, only anti-4/91 IgG
levels were higher in the group with >100 months’
experience compared to the group with 2-20 months’ experience (Figure
4B). The comparison between vaccine implementers and poultry workers did
not show a significant difference.