Human Novel Coronavirus Nucleoprotein IgG antibody (2019-nCoV-Ab-IgG) ELISA Kit

The microtiter plate provided in this kit has been pre-coated with 2019-nCoV (N) protein. Samples are then added to the appropriate microtiter plate wells with a Horseradish Peroxidase (HRP)-conjugated anti-human IgG antibody and incubated. Then substrate solutions are added to each well. Only those wells that contain 2019-nCoV-Ab-IgG and enzyme-conjugated anti-human IgG antibody will exhibit a change in color. The enzyme-substrate reaction is terminated by the addition of a sulphuric acid solution and the color change is measured spectrophotometrically at a wavelength of 450 nm ± 2 nm. 

Coronaviruses are enveloped viruses with a positive-sense RNA genome and with a nucleocapsid of helical symmetry. Coronavirus nucleoproteins localize to the cytoplasm and the nucleolus, a subnuclear structure, in both virus-infected primary cells and in cells transfected with plasmids that express N protein. Coronavirus N protein is required for coronavirus RNA synthesis, and has RNA chaperone activity that may be involved in template switch. Nucleocapsid protein is a most abundant protein of coronavirus. During virion assembly, N protein binds to viral RNA and leads to formation of the helical nucleocapsid. Nucleocapsid protein is a highly immunogenic phosphoprotein also implicated in viral genome replication and in modulating cell signaling pathways. Because of the conservation of N protein sequence and its strong immunogenicity, the N protein of coronavirus is chosen as a diagnostic tool. 

This assay has high sensitivity and excellent specificity for detection of Human 2019-nCoV-Ab-IgG. No significant cross-reactivity or interference between Human 2019-nCoV-Ab-IgG and analogues was observed.

Intra-assay Precision (Precision within an assay) Three samples of known concentration were tested twenty times on one plate to assess intra-assay precision. Inter-assay Precision (Precision between assays) Three samples of known concentration were tested in forty separate assays to assess inter-assay precision. CV (%) = SD/meanX100 Intra-Assay: CV<8% Inter-Assay: CV<12%

The linearity of the kit was assayed by testing samples spiked with appropriate concentration of Human 2019-nCoV-Ab-IgG and their serial dilutions. The results were demonstrated by the percentage of calculated concentration to the expected.

The stability of ELISA kit is determined by the loss rate of activity. The loss rate of this kit is less than 5% within the expiration date under appropriate storage condition. The loss rate was determined by accelerated thermal degradation test. Keep the kit at 37°C for 4 and 7 days, and compare O.D.values of the kit kept at 37°C with that of at recommended temperature. (referring from China Biological Products Standard, which was calculated by the Arrhenius equation. For ELISA kit, 4 days storage at 37°C can be considered as 6 months at 2 - 8°C, which means 7 days at 37°C equaling 12 months at 2 - 8°C).

Serum: Use a serum separator tube (SST) and allow samples to clot for two hours at room temperature or overnight at 2 - 8°C before centrifugation for 15 minutes at 1000 × g. Remove serum and assay immediately or aliquot and store samples at ≤ -20°C. Avoid repeated freeze-thaw cycles.