Sensitivity in Detection of Antibodies to Nucleocapsid and Spike Proteins of Severe Acute Respiratory Syndrome Coronavirus 2 in Patients With Coronavirus Disease 2019.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the cause of coronavirus disease 2019 (COVID-19), is associated with respiratory-related disease and death. Assays to detect virus-specific antibodies are important to understand the prevalence of infection and the course of the immune response. Quantitative measurements of plasma or serum antibodies to the nucleocapsid and spike proteins were analyzed using luciferase immunoprecipitation system assays in 100 cross-sectional or longitudinal samples from patients with SARS-CoV-2 infection. A subset of samples was tested both with and without heat inactivation. At >14 days after symptom onset, antibodies against SARS-CoV-2 nucleocapsid protein showed 100% sensitivity and 100% specificity, whereas antibodies to spike protein were detected with 91% sensitivity and 100% specificity. Neither antibody levels nor the rate of seropositivity were significantly reduced by heat inactivation of samples. Analysis of daily samples from 6 patients with COVID-19 showed anti-nucleocapsid and spike protein antibodies appearing between days 8 and 14 after initial symptoms. Immunocompromised patients generally had a delayed antibody response to SARS-CoV-2, compared with immunocompetent patients. Antibody to the nucleocapsid protein of SARS-CoV-2 is more sensitive than spike protein antibody for detecting early infection. Analyzing heat-inactivated samples with a luciferase immunoprecipitation system assay is a safe and sensitive method for detecting SARS-CoV-2 antibodies.

Burbelo PD ，Riedo FX ，Morishima C ，Rawlings S ，Smith D ，Das S ，Strich JR ，Chertow DS ，Davey RT ，Cohen JI ... -  《-》

Antibody response against SARS-CoV-2 spike protein and nucleoprotein evaluated by four automated immunoassays and three ELISAs.

The aim was to determine the antibody response against SARS-CoV-2 spike protein and nucleoprotein using four automated immunoassays and three ELISAs for the detection of total Ig antibodies (Roche) or IgG (Abbott, Diasorin, Snibe, Euroimmun, Mikrogen) in COVID-19 patients. Sensitivity and dynamic trend to seropositivity were evaluated in 233 samples from 114 patients with moderate, severe or critical COVID-19 confirmed with PCR on nasopharyngeal swab. Specificity was evaluated in 113 samples collected before January 2020, including 24 samples from patients with non-SARS coronavirus infection. Sensitivity for all assays was 100% (95% confidence interval 83.7-100) 3 weeks after onset of symptoms. Specificity varied between 94.7% (88.7-97.8) and 100% (96.1-100). Calculated at the cut-offs that corresponded to a specificity of 95% and 97.5%, Roche had the highest sensitivity (85.0% (79.8-89.0) and 81.1% (76.6-85.7), p < 0.05 except vs. Abbott). Seroconversion occurred on average 2 days earlier for Roche total Ig anti-N and the three IgG anti-N assays (Abbott, Mikrogen, Euroimmun) than for the two IgG anti-S assays (Diasorin, Euroimmun) (≥50% seroconversion day 9-10 vs. day 11-12 and p < 0.05 for percent seropositive patients day 9-10 to 17-18). There was no significant difference in the IgG antibody time to seroconversion between critical and non-critical patients. Seroconversion occurred within 3 weeks after onset of symptoms with all assays and on average 2 days earlier for assays detecting IgG or total Ig anti-N than for IgG anti-S. The specificity of assays detecting anti-N was comparable to anti-S and excellent in a challenging control population.

Van Elslande J ，Decru B ，Jonckheere S ，Van Wijngaerden E ，Houben E ，Vandecandelaere P ，Indevuyst C ，Depypere M ，Desmet S ，André E ，Van Ranst M ，Lagrou K ，Vermeersch P ... -  《-》

Accurate serology for SARS-CoV-2 and common human coronaviruses using a multiplex approach.

van Tol S ，Mögling R ，Li W ，Godeke GJ ，Swart A ，Bergmans B ，Brandenburg A ，Kremer K ，Murk JL ，van Beek J ，Wintermans B ，Reimerink J ，Bosch BJ ，Reusken C ... -  《Emerging Microbes & Infections》

Evaluation of a novel multiplexed assay for determining IgG levels and functional activity to SARS-CoV-2.

The emergence of SARS-CoV-2 has led to the development of serological assays that could aid in an understanding of the burden of COVID-19 disease. Many available tests lack rigorous evaluation and therefore results may be misleading. The aim of this study was to assess the performance of a novel multiplexed immunoassay for the simultaneous detection of antibodies against SARS-CoV-2 trimeric spike (S), spike receptor binding domain (RBD), spike N terminal domain and nucleocapsid antigen and a novel pseudo-neutralisation assay. A multiplexed solid-phase chemiluminescence assay (Meso Scale Discovery) was evaluated for the simultaneous detection of IgG binding to four SARS-CoV-2 antigens and the quantification of antibody-induced ACE-2 binding inhibition (pseudo-neutralisation assay). Sensitivity was evaluated with a total of 196 COVID-19 serum samples (169 confirmed PCR positive and 27 anti-nucleocapsid IgG positive) from individuals with mild symptomatic or asymptomatic disease. Specificity was evaluated with 194 control serum samples collected from adults prior to December 2019. The specificity and sensitivity of the binding IgG assay was highest for S protein with a specificity of 97.4 % and sensitivity of 96.2 % for samples taken 14 days and 97.9 % for samples taken 21 days following the onset of symptoms. IgG concentration to S and RBD correlated strongly with percentage inhibition measured by the pseudo-neutralisation assay. Excellent sensitivity for IgG detection was obtained over 14 days since onset of symptoms for three SARS-CoV-2 antigens (S, RBD and N) in this multiplexed assay which can also measure antibody functionality.

Johnson M ，Wagstaffe HR ，Gilmour KC ，Mai AL ，Lewis J ，Hunt A ，Sirr J ，Bengt C ，Grandjean L ，Goldblatt D ... -  《-》

Kinetics of SARS-CoV-2 specific IgM and IgG responses in COVID-19 patients.

Sun B ，Feng Y ，Mo X ，Zheng P ，Wang Q ，Li P ，Peng P ，Liu X ，Chen Z ，Huang H ，Zhang F ，Luo W ，Niu X ，Hu P ，Wang L ，Peng H ，Huang Z ，Feng L ，Li F ，Zhang F ，Li F ，Zhong N ，Chen L ... -  《Emerging Microbes & Infections》