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.