Sars cov 2 trimerics igg

A chemiluminescent immunoassay to analyze the SARS-CoV-2-specific antibodies IgG (IgG anti-spike TRIM) [16 (link)] against three main domains of SARS-CoV-2 protein (SARS-CoV-2 TrimericS IgG—Diasorin, Italy) was used. Precision of the method for IgG determinations was evaluated by measuring daily internal quality controls (IQCs). The first IQC was a negative sample with a level less than 1.85 AU/mL; it showed a negativity agreement of more than 98% (n = 50), and a positive control with an average of 36.41 AU/mL with a variability (CV%) of 9.2% (n = 50). Moreover, we prepared two human serum pools from our routine samples with average levels of IgG of 3.25 AU/mL (CV%= 8.9%, n = 50) and of 37.85 AU/mL (CV% = 9.8, n = 50).

Measurement of IgG antibodies against SARS-CoV-2 spike protein (anti-SARS-CoV-2-S IgG) in patients’ sera was performed with the chemiluminescence assays SARS-CoV-2 S1/S2 IgG or SARS-CoV-2 TrimericS IgG, DiaSorin, Saluggia, Italy. The chemiluminescence analyzer LIASION-XL (DiaSorin) was used following the manufacturer’s instructions. The first assay is semi-quantitative as at the start of the study no standardized fully quantitative assays were available. The second assay is quantitative and adjusted to the upcoming WHO standard. Values >15 AU/ml corresponding to 39 BAU/ml, and values ≥33.8 BAU/ml were considered positive after first or second vaccination, respectively. Sensitivity/specificity for each assay are 94.4%/98.6% and 96.9%/100%, respectively. For this study, only qualitative results were used to document seroconversion.

Two types of SARS-CoV-2 IgG antibodies were measured. The first assays released at the start of the pandemic were used. The first assay to measure the anti-N IgG antibodies was the SARS-CoV-2 nucleocapsid total antibodies, which we analyzed using the Roche Cobas 6000 platform (Roche Diagnostics International AG, Rotkreuz, Switzerland). This assay was CE marked/FDA EUA-approved. The second assay that quantified the anti-S IgG antibodies was the SARS-CoV-2 Trimeric S IgG using the DiaSorin LIAISON^® (Saluggia, Italy) SARS-CoV-2 Trimeric S IgG. This assay is an indirect CLIA technology for the detection of IgG antibodies to SARS-CoV-2 Spikes 1 and 2 (S1 and S2) and RBD and is calibrated against the World Health Organization standard.