0
There is no goods in the shopping cart !
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z 0-9
Your Position: Home > COVID-19 R&D > How does the COVID-19 antibody ELISA test function?
How does the COVID-19 antibody ELISA test function?
Release time: 2020-05-20 Source: ACRO Read: 614

Antibody test, also known as the serology test, is an important supplementary diagnosis of COVID-19. In addition to the nucleic acid test, the antibody test can help with not only the accuracy of diagnosis but also the characterization of the prevalence and spread of the disease. Antibody test will identify if a person has been exposed to SARS-CoV-2 and developed immunity against SARS-CoV-2 infection, which is better suited for public health surveillance and vaccine development.


So far, the FDA has issued the Emergency Authorization Use to 12 antibody tests, including 3 colloidal gold assays, 4 chemiluminescent assays, and 5 ELISA assays (Table 1). Due to urgency and demand, a lot of antibody tests are rapidly developed and made available on the market with limited validation. To address the problem, some scientists are evaluating these assays using clinical samples. In this article, we will take a close look at the performance of the ELISA assays.  (Find more about the performance of colloidal gold and chemiluminescence methods.)

 

图片6.png

Table 1. Emergency Use Authorizations for COVID-19 by FDA 


Beijing Wantai Biological Pharmacy Enterprise Co., Ltd developed 3 enzyme-linked immunosorbent assay (ELISA) kits against the total antibodies (Ab), IgM, and IgG of SARS-CoV-2 respectively. Briefly, the ELISA for Ab was developed based on double-antigens sandwich ELISA, using the mammalian cell-expressed recombinant receptor binding domain (RBD) of the spike protein of SARS-CoV-2 and HRP-conjugated antigen. The IgM μ-chain capture ELISA was used to detect the IgM antibodies using the same HRP-conjugated antigen. The IgG antibodies were measured using an indirect ELISA kit based on a recombinant nucleocapsid protein.


173 patients were enrolled in this study. The seroconversion rate for Ab, IgM, and IgG was 93.1% (161/173), 82.7% (143/173), and 64.7% (112/173), respectively. Twelve patients who remained seronegative for Ab testing possibly due to that their samples involved were all collected at the early stage of illness. The specificity of the assays for Ab, IgM, and IgG was determined as 99.1% (211/213), 98.6% (210/213), and 99.0% (195/197) by using the samples collected from healthy individuals.


The performances of the different ELISA tests and the nucleic acid test in samples with different duration of illness were also analyzed. As the duration of illness increased, the sensitivity of ELISA tests kept increasing and surpassed that of the nucleic acid test after day 8.


Above all, combined use of the nucleic acid test and ELISA test is believed to improve markedly the sensitivities of COVID-19 diagnosis in different stages.

Another group from Denmark also investigated the performance of 3 commercially available ELISA kits, including a Wantai Ab ELISA kit we just mentioned and two ELISA kits from Euroimmun (IgG and IgA respectively), which gained EUA from FDA in May (Table 1). The IgA or IgG antibodies against SARS-CoV-2 spike protein subunit 1 (S1) are detected by using an indirect ELISA format.


As shown in the ELISA data distribution figure (Figure 1), the positive and negative data points were distinct for the Wantai total Ab assay, with a cut-off value above all the control serum samples, which allowed for unequivocal interpretation. Conversely, the Euroimmun IgA and IgG assays data had a less distinct separation.

 图片7.png

Figure 1. SARS-CoV-2 antibody ELISA assay performance

 

Overall, the Wantai total Ab ELISA had superior sensitivity and specificity compared to both Euroimmun IgA and IgG ELISAs (Table 2). This notably lower sensitivity for SARS-CoV-2-specific IgG detection is in agreement to that observed in the previous study we talked about (Wantai IgG ELISA kit). The possibility that overall lower sensitivity of SARS-CoV-2 IgG ELISAs may be a more universal occurrence rather than manufacturer dependent warrants further investigation.

图片1.png

Table 2. Analytical sensitivities and specificities for ELISA kits

 

In addition to lower sensitivities, the Euroimmun IgA and IgG ELISAs are also more prone to cross-react with negative serum samples. The difference performances between the assays may be partially explained by the ELISA format and the antigens they used. The nucleocapsid and spike proteins are critical reagents for the antibody detection kits, which could greatly affect the performance of the assay.


ACROBiosystems has developed S1, N, wild type RBD as well as mutant RBD proteins with various tags including His, Fc, mFc and His & Avi, which are suitable for COVID-19 serological test development. These proteins can be applied to a colloidal gold method, chemiluminescence method, and ELISA method. ACRO is gaining lots of positive feedback for the high-quality SARS-CoV-2 antigen proteins.


Cat.No.: NUN-C51H9

Product:SARS-CoV-2 (COVID-19) Nucleocapsid protein, His Tag

The sensitivity of N protein binding to Anti-N mAb is 0.02 ng/mL as verified by ELISA.

图片8.png

Immobilized SARS-CoV-2 Nucleocapsid protein, His Tag (Cat. No. NUN-C51H9) at 2 μg/mL (100 μL/well) can bind SARS-CoV-2 NP Antibody, Rabbit MAb (CLN27) with a linear range of 0.02-0.3 ng/mL.

Protocol


Cat.No.: S1N-C52H4

Product:SARS-CoV-2 (COVID-19) S1 protein, His Tag (MALS verified)

The sensitivity of S1 protein binding to ACE2 protein is 0.2 ng/mL as verified by ELISA.

图片9.png

Immobilized SARS-CoV-2 S1 protein, His Tag (Cat. No. S1N-C52H4) at 2 μg/mL (100 μL/well) can bind Human ACE2, Fc Tag (Cat. No. AC2-H5257) with a linear range of 0.2-6 ng/mL.

Protocol


Cat.No.: SPD-C52H3

Product:SARS-CoV-2 (COVID-19) S protein RBD, His Tag (MALS verified)

The sensitivity of RBD protein binding to ACE2 protein is 0.008 ng/mL as verified by ELISA.

图片10.png

Immobilized Human ACE2, Fc Tag (Cat. No. AC2-H5257) at 2 μg/mL (100 μL/well) can bind SARS-CoV-2 S protein RBD, His Tag (Cat. No. SPD-C52H3) with a linear range of 0.008-0.125 μg/mL.

Protocol



Product List


Kits  For research use only.
MoleculeCat. No.SpeciesProduct DescriptionOrder/Preorder
S protein RBDEP-105SARS-CoV-2SARS-CoV-2 Inhibitor Screening Kit

Order

S1 proteinMBS-K001SARS-CoV-2SARS-CoV-2 Spike S1 protein-coupled magnetic beads

Order

S protein RBDMBS-K002SARS-CoV-2SARS-CoV-2 Spike protein RBD-coupled magnetic beads

Order

S1 proteinTAS-K001SARS-CoV-2SARS-CoV-2 antibody titer assay kit (Spike protein S1)

Preorder

S protein RBDTAS-K002SARS-CoV-2SARS-CoV-2 antibody titer assay kit (Spike protein RBD)

Preorder

TAS-K003SARS-CoV-2Anti-SARS-CoV-2 neutralizing antibody titer serologic assay kit

Preorder

Antibody
MoleculeCat. No.SpeciesProduct DescriptionOrder/Preorder
S protein RBDSAD-S35HumanAnti-SARS-CoV-2 neutralizing antibody (Human IgG1)

Order

Proteins
MoleculeCat. No.SpeciesHostProduct DescriptionOrder/Preorder
ACE2AC2-H82E6HumanHEK293Biotinylated Human ACE2 / ACEH Protein, His,Avitag™ (MALS verified)

Order

AC2-H82F9HumanHEK293Biotinylated Human ACE2 / ACEH Protein, Fc,Avitag™

Order

AC2-H5257HumanHEK293Human ACE2 / ACEH Protein, Fc Tag (MALS verified)

Order

AC2-C52H7CynomolgusHEK293Cynomolgus ACE2 / ACEH Protein, His Tag

Order

AC2-H52H8HumanHEK293Human ACE2 / ACEH Protein, His Tag (MALS verified)

Order

AC2-R5246RatHEK293Rat ACE2 / ACEH Protein, His Tag (MALS verified)

Order

AC2-M5248MouseHEK293Mouse ACE2 / ACEH Protein, His Tag (MALS verified)

Order

AC2-P5248Paguma larvataHEK293Paguma larvata ACE2 / ACEH Protein, His Tag

Order

S proteinSPN-C52H4SARS-CoV-2HEK293SARS-CoV-2 (COVID-19)  S protein (R683A, R685A), His Tag

Order

SPN-C52H8SARS-CoV-2HEK293SARS-CoV-2 (COVID-19)  S protein (R683A, R685A) , His Tag, active trimer (MALS verified)

Order

SPN-S52H5SARSHEK293SARS S protein (R667A), His Tag

Order

S1 proteinS1N-C52H3SARS-CoV-2HEK293SARS-CoV-2 (COVID-19) S1 protein, His Tag

Order

S1N-C82E8SARS-CoV-2HEK293Biotinylated SARS-CoV-2 (COVID-19) S1 protein, His,Avitag™ (MALS verified)

Order

S1N-S52H5SARSHEK293SARS S1 protein, His Tag (MALS verified)

Order

S1N-C52H4SARS-CoV-2HEK293SARS-CoV-2 (COVID-19) S1 protein, His Tag (MALS verified)

Order

S1N-C5255SARS-CoV-2HEK293SARS-CoV-2 (COVID-19) S1 protein, Fc Tag

Order

S1N-C5257SARS-CoV-2HEK293SARS-CoV-2 (COVID-19) S1 protein, Mouse IgG2a Fc Tag

Order

S protein RBDSPD-C82E9SARS-CoV-2HEK293Biotinylated SARS-CoV-2 (COVID-19) S protein RBD, His,Avitag™ (MALS verified)

Order

SPD-C5255SARS-CoV-2HEK293SARS-CoV-2 (COVID-19) S protein RBD, Fc Tag (MALS verified)

Order

SPD-S52H6SARSHEK293SARS S protein RBD, His Tag (MALS verified)

Order

SPD-C52H3SARS-CoV-2HEK293SARS-CoV-2 (COVID-19) S protein RBD, His Tag (MALS verified)

Order

SPD-C5259SARS-CoV-2HEK293SARS-CoV-2 (COVID-19) S protein RBD, Mouse IgG2a Fc Tag

Order

SPD-S52H4SARS-CoV-2HEK293SARS-CoV-2 (COVID-19) S protein RBD (V367F), His Tag

Order

SPD-S52H5SARS-CoV-2HEK293SARS-CoV-2 (COVID-19) S protein RBD (N354D), His Tag

Order

SPD-S52H7SARS-CoV-2HEK293SARS-CoV-2 (COVID-19) S protein RBD (W436R), His Tag

Order

SPD-S52H8SARS-CoV-2HEK293SARS-CoV-2 (COVID-19) S protein RBD (R408I), His Tag

Order

SPD-S52H3SARS-CoV-2HEK293SARS-CoV-2 (COVID-19) S protein RBD (N354D, D364Y), His Tag

Order

Nucleocapsid proteinNUN-C51H9SARS-CoV-2E.coliSARS-CoV-2 (COVID-19) Nucleocapsid protein, His Tag

Order

NUN-C5227SARS-CoV-2HEK293SARS-CoV-2 (COVID-19) Nucleocapsid protein, His Tag

Order

NUN-C81Q6SARS-CoV-2E.coliBiotinylated SARS-CoV-2 (COVID-19) Nucleocapsid protein, His,Avitag™

Order

Envelope proteinENN-C5128SARS-CoV-2E.coliSARS-CoV-2 (COVID-19) Envelope protein, His Tag

Order

Papain-like ProteasePAE-C5148SARS-CoV-2E.coliSARS-CoV-2 (COVID-19) Papain-like Protease Protein, His Tag

Order

NSP1NS1-C51H7SARS-CoV-2E.coliSARS-CoV-2 (COVID-19) NSP1 Protein, His Tag

Order

NSP7NS7-C51H6SARS-CoV-2E.coliSARS-CoV-2 (COVID-19) NSP7 Protein, His Tag

Order

NSP8NS8-C5149SARS-CoV-2E.coliSARS-CoV-2 (COVID-19) NSP8 Protein, His Tag

Order

NSP7 & NSP8NS8-C5125SARS-CoV-2E.coliSARS-CoV-2 (COVID-19) NSP7&NSP8 Protein, His Tag

Order

ACE2AC2-C5245CanisHEK293Canis ACE2 / ACEH Protein, His Tag

Preorder

S1 proteinS1N-C5256SARS-CoV-2HEK293SARS-CoV-2 (COVID-19) S1 protein (D614G), His Tag

Preorder

S2 proteinS2N-C5253SARS-CoV-2HEK293SARS-CoV-2 (COVID-19) S2 protein, Fc Tag

Preorder

S2N-C5254SARS-CoV-2HEK293SARS-CoV-2 (COVID-19) S2 protein, Mouse IgG2a Fc Tag

Preorder

Envelope proteinENN-C51P3SARS-CoV-2E.coliSARS-CoV-2 (COVID-19) Envelope protein, His,BBP Tag

Preorder

NSP15NS5-C5145SARS-CoV-2E.coliSARS-CoV-2 (COVID-19) NSP15 Protein, His Tag

Preorder

Expected launch date: May 24

NSP16 & NSP10NS0-C51W3SARS-CoV-2E.coliSARS-CoV-2 (COVID-19) NSP16&NSP10 Heterodimer Protein, His Tag&Twin Strep Tag

Preorder

Expected launch date: May 24


Reference:

1. Antibody responses to SARS-CoV-2 in patients of novel coronavirus disease 2019

2. Evaluation of nine commercial SARS-CoV-2 immunoassays


This web search service is supported by Google Inc.

totop