Anti sars cov 2 spike elisa

A semi-quantitative in vitro determination of human IgG antibodies against the SARS-CoV-2 (S1) was performed on serum samples by using the anti-SARS-CoV-2 spike ELISA (EUROIMMUN, Lübeck, Germany), according to the manufacturer’s instructions. Values were then normalized by comparison with a calibrator. Results were obtained by calculating the ratio between the extinction of samples and the extinction of the calibrator. Results are reported as the ratio between the optical density (OD) from the sample and the OD from the calibrator. The ratio interpretation was as follows: negative, <0.8; borderline, ≥0.8 to <1.1; positive, ≥1.1.

A semi-quantitative in vitro determination of human IgG and IgA antibodies against the SARS-CoV-2 was performed on serum samples by using the Anti-SARS-CoV-2 Spike ELISA (EUROIMMUN), according to the manufacturer’s instructions. Values were then normalized for comparison with a calibrator. Results were evaluated by calculating the ratio between the extinction of samples and the extinction of the calibrator. Results are reported as the ratio between OD sample and OD calibrator. The ratio interpretation was as follows: < 0.8 = negative, ≥ 0.8 to < 1.1 = borderline, ≥ 1.1 = positive. To detect IgM anti-RBD we developed an in-house ELISA [17 (link)]. 96-well plates (Corning) were coated for 1 h at 37 °C with 1 μg/mL of purified SARS-CoV-2 RBD protein (Sino Biological). After washing with PBS 1 × /0.05% Tween and blocking with PBS 1 × /1% BSA, plates were incubated for 1 h at 37 °C with diluted sera (1:100). After washing again, plates were incubated for 1 h at 37 °C with peroxidase-conjugated goat anti-human IgM antibody (Jacksons ImmunoResearch Laboratories). The assay was developed with o-phenylenediamine tablets (Sigma-Aldrich) as a chromogen substrate. Absorbance at 450 nm was measured, and IgM concentrations were calculated by interpolation from the standard curve based on serial dilutions of monoclonal human IgM antibody against SARS-CoV-2 Spike-RBD (Invivogen).