Liaison sars cov 2 trimerics igg

All collected serum samples were analyzed using four different CLIA assays: LIAISON^® SARS-CoV-2 S1/S2 IgG (311450 – DiaSorin, Saluggia, Italy) to measure the antibodies against the SARS-CoV-2-native S1/S2 proteins, while iFlash-2019-nCoV Nab (C86109 – Shenzhen YHLO Biotech Co, Shenzhen, China), LIAISON^® SARS-CoV-2 TrimericS IgG (P/N311510 – DiaSorin, Saluggia, Italy), and Elecsys Anti-SARS-CoV-2 S (09 289 267 190 – Roche Diagnostics Rotkreuz, Switzerland) to quantify the specific RBD-binding antibodies. Moreover, samples collected at T0 and T5 were analyzed using iFlash SARS-CoV-2 IgG and IgM (C86095G – C86095M – Shenzhen YHLO Biotech Co, Shenzhen, China) to exclude a possible ongoing asymptomatic infection since that the assay targets nucleocapside and spike proteins (non-neutralizing antibodies). All the assay characteristics are summarized in Table 1.
NTA was used to quantify the titre of neutralizing antibody for all samples at each time point using the SARS-CoV-2 lineage B.1 (EU): results were considered positive if higher or equal to 1:10 serum titre [15 (link),16 (link)].
Furthermore, the serum samples collected at 1 month after dose II (T5) were used to evaluate the in vitro neutralizing response against the different isolated variants. Further details are reported in Supporting Information.

Serum samples were tested using LIAISON SARS-CoV-2 TrimericS IgG (DiaSorin), a quantitative CE-marked assay for the detection of IgG antibodies recognizing the native trimeric Spike glycoprotein of SARS-CoV-2 (Bonelli et al, 2021 (link)). According to the manufacturer’s instruction for use, the presence of an immune response in vaccine recipients was 100.0% (95% CI 96.3–100.0%) in 102 samples collected after ≥21 d from second dose. The levels of IgG antibodies were originally expressed in AU/ml. Following the definition of the WHO International Standard for anti-SARS-CoV-2 Immunoglobulin (NIBSC 20:136), the readout was updated and the assay currently calculates the levels of SARS-CoV-2 IgG antibodies in BAU/ml (Perkmann et al, 2021 (link)). Samples ≥33.8 BAU/ml were considered positive. In Fig S6, for the determination of IgG anti–SARS-CoV-2 in the serum of patients in hemodialysis the Liaison SARS-CoV-2 S1/S2 IgG assay (DiaSorin) was used (Bonelli et al, 2020 (link)).

IgG antibodies against the trimeric SARS-CoV-2 Spike protein were quantified in serum samples by chemiluminescence assay (LIAISON^® SARS-CoV-2 TrimericS IgG, Diasorin S.p.A, Saluggia, Italy) and run on a DiaSorin LIAISON XL platform (DiaSorin, Stillwater, USA). According to the manufacturer’s data, the sensitivity and specificity of this test were 98.7% and 99.5%, showing a good correlation with microneutralization test (PPA: 100%, NPA: 96.9%). Antibody concentration, expressed as BAU/mL, was automatically calculated by the analyzer from AU/mL by the following conversion formula: AU/mLx2.6=BAU/mL. A positive result was considered as ≥33.8 BAU/mL. The levels of IgG antibodies against the trimeric SARS-CoV-2 Spike protein were considered as a continuous variable, corresponding to the magnitude of the humoral response (titer values), but they were also transformed into a dichotomous variable, corresponding to the ability to response or seroconversion, defined as an antibody titter higher or equal to 33.8 BAU/mL (the established threshold for the used assay).

The humoral response was assessed qualitatively as the presence of IgG seroconversion (present/absent seroconversion) and quantitatively by measuring the concentration of anti-SARS-CoV-2 S protein IgG antibodies. Four-milliliter native blood samples were collected. After centrifugation, anti-SARS-CoV-2 IgG antibodies in the serum were determined using chemiluminescence technology. The LIAISON SARS-CoV2 Trimerics IgG (REF 311520) assay by DiaSorin Inc. (Northwestern Ave–Stillwater, MN, USA) was used for the evaluations. The lower quantification range was 3.8 AU/mL. The upper range was unlimited. In the event of a high titer, the sample was diluted according to the manufacturer’s recommendation.

IgG antibodies against the trimeric SARS-CoV-2 Spike protein were quantified in serum samples by using chemiluminescence assay (LIAISON® SARS-CoV-2 TrimericS IgG, Diasorin S.p.A, Saluggia, Italy) and run on a DiaSorin LIAISON XL platform (DiaSorin, Stillwater, USA). According to the manufacturer’s data, the sensitivity and specificity of this test were 98.7 and 99.5%, showing a good correlation with the microneutralization test (Positive percent agreement (PPA): 100%, Negative percent agreement (NPA): 96.9%) [22 (link)]. Antibody concentration, expressed as Binding Arbitrary Units (BAU)/mL, was automatically calculated by the analyzer from Arbitrary Units (AU/mL) by the following conversion formula: AU/mL*2.6 = BAU/mL, and a positive result was considered as ≥33.8 BAU/mL.