SARS-CoV-2 IgG ELISA Kit

Sample

Serum, plasma

Species Reactivity

Human

Detection Method

iELISA

Intended Use

The Bethyl SARS-CoV-2 IgG ELISA is an Enzyme-Linked Immunosorbent Assay (ELISA) intended for semi-quantitative detection of IgG antibodies to SARS-CoV-2 in human serum or plasma collected in Potassium EDTA, Sodium Citrate or Lithium Heparin.

Contents of Kit

1. 96 well Precoated SARS-CoV-2 S1-RBD plate, 1 plate
2. Positive Control: Recombinant Human anti-RBD IgG (ready to use). 1 vial -0.3 ml
3. Calibrator: Recombinant Human anti-RBD IgG antibody (ready to use), 1 vial - 0.3 ml
4. Negative Control: Dilute normal human serum (ready to use) 1 vial - 0.3 ml
5. Detection Antibody: Goat Anti-Human IgG-Fc antibody – HRP conjugated (ready to use), 1 vial - 11 ml
6. Assay Dilution Buffer (ready to use), 1 vial – 60 ml
7. TNT Wash Buffer packet for reconstitution 1 packet.
8. One Component TMB substrate: TMB (ready to use), 1 vial – 12 ml
9. Stop solution (0.18 M Sulfuric Acid; ready to use), 1 vial - 12 ml
10. Sealing Tape, 3 Sheets
11. SDS
12. Instructions for use

Storage

This kit should be refrigerated upon receipt and stored at 2-8°C. Do not freeze. Expiration date is 2 months post receipt of the kit.

Performance Characteristics

Class Specificity:
Human serum samples previously identified as either Negative, Equivocal, or Positive in the SARS-CoV-2 IgG ELISA were incubated with either diluent alone (Untreated), diluent + goat polyclonal anti-human IgG to deplete IgG, or diluent + goat polyclonal anti-human IgM to deplete IgM, and then RBD-specific IgG binding was measured in the SARS-CoV-2 IgG assay. All samples were also evaluated in an assay for anti-SARS-CoV-2 IgM binding.

The results demonstrate that depletion of IgG (>99% reduction in IgG assay ratio) from Positive samples converts them to Negatives and that depletion of IgM (>97% reduction in IgM assay ratio, data not shown) from Positive samples has no effect on their disposition in the assay. Similarly, the Negative and Equivocal samples saw no change in assay disposition with IgM depletion, while the Equivocal sample was converted to Negative with depletion of IgG.

These data show that signal in the SARS-CoV-2 IgG ELISA is due specifically to the IgG component of a patient's immune response to SARS-CoV-2 without significant interference from SARS-CoV-2-specific IgM.
Analytical Sensitivity:
Samples procured from a commercial source from 34 distinct patients that had tested positive by molecular test and tested as reactive by the Siemens ADVIA Centaur Sars-CoV-2 Total assay performed by an independent clinical laboratory were evaluated with the SARS-CoV-2 IgG ELISA.

Serum samples collected prior to December 2019 from 161 distinct donors, from two commercial sources were evaluated. One hundred fifty-eight samples (98.1%) were negative and three (1.9%) were not negative for IgG to SARS-CoV-2.

Matrix Equivalency:
Serum, citrate plasma, EDTA plasma, and heparin plasma were each collected from five individuals testing negative in both SARS-CoV-2 IgG ELISA and SARS-CoV-2 IgM ELISA. Convalescent serum from an individual who tested positive in SARS-CoV-2 IgG ELISA was spiked into a 1:100 dilution of each negative matrix at four different concentrations intended to yield negative, low positive (two different concentrations), and moderate positive IgG ELISA outcomes. 1:100 negative matrices were also tested without any spike. Each combination of negative matrix and spike was tested in duplicate.
Deming regression (α = 0.05) was performed for the comparison of plasma to serum and showed the following results:

For each spike amount, there was 100 % agreement of assay outcome across all matrices, all individuals, and all replicates, thus demonstrating robust matrix equivalency.

General Description

Coronavirus Disease 2019 (COVID-19) is a systemic disease caused by the novel Coronavirus designated SARS-CoV-2. The initial disease outbreak was first reported in Wuhan, Hubei province, China in December 2019. Within months the World Health Organization declared a global pandemic. COVID-19 can be a serious and life-threatening disease. "Understanding the number of individuals who are exposed and whether they then develop immunity is absolutely key to managing the epidemic."
The SARS-CoV-2 IgG ELISA is an Enzyme-Linked Immunosorbent Assay (ELISA) intended for semi-quantitative detection of IgG antibodies to SARS-CoV-2 in human serum or plasma collected in Potassium EDTA, Sodium Citrate or Lithium Heparin. The SARS-CoV-2 IgG ELISA is intended for use as an aid in identifying individuals with an adaptive immune response to SARS-CoV-2, indicating recent or prior infection. Understanding the timing, duration and effectiveness of humoral immune responses in individuals
previously infected with SARS-CoV-2 will be important for conducting vaccine and epidemiological research. At this time, it is unknown for how long antibodies persist following infection and if the presence of antibodies confers protective immunity.
Results are for the detection of SARS-CoV-2 antibodies. IgG antibodies to SARS-CoV-2 are generally detectable in blood several days after initial infection, although the duration of time antibodies are present post-infection is not well characterized. Individuals may have detectable virus present for several weeks following seroconversion.
The sensitivity of SARS-CoV-2 IgG ELISA early after infection is unknown. Negative results do not preclude acute SARS-CoV-2 infection.
False positive results for SARS-CoV-2 IgG ELISA may occur due to cross-reactivity from pre-existing antibodies to SARS-CoV-1 or other possible causes.