SARS-CoV-2 NP Ab ELISA kit is an enzyme-linked immunosorbent assay (ELISA) for the detection and qualitative measurement of total antibodies against the nucleocapsid protein (NP) of SARS-CoV-2 virus in human blood.

This product is intended for the diagnosis of coronavirus disease 2019 (COVID-19).

This product is intended for use by professional persons only.

In December 2019, a novel coronavirus, now officially named as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has been identified in Wuhan China, which caused the outbreak of a coronavirus-associated acute respiratory disease called coronavirus disease 19 (COVID-19), Signs and symptoms of COVID-19 may occur 2 to 14 days after infection, which include fever, cough, shortness of breath or difficulties in breathing, pain in the muscle and tiredness. In severe cases, the infection can further lead to pneumonia, severe acute respiratory syndrome (SARS), kidney failure and death.

Nucleocapsid protein (NP) is the most abundant protein on the helical nucleocapsid of coronaviruses, which envelopes the entire genomic RNA. NP also interacts with other viral structural proteins to play important roles during host cell entry and virus particle assembly and release. Anti-NP antibodies have been shown to be the earliest and the most predominant antibodies detectable in patient’s blood samples after coronavirus infection.

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ImmunoDiagnostics SARS-CoV-2 NP Ab ELISA kit is a two-step incubation immunoassay kit. Recombinant nucleocapsid protein (NP) of SARS-CoV-2 pre-coated onto the polystyrene microwell strips can specifically recognize anti-NP antibodies in human serum or plasma specimens. After a 1-hour incubation, anti-NP antibodies are captured by immobilized NP protein while the unbound components are washed away. Afterwards, a detection solution containing HRP-conjugated NP is added for another 1-hour incubation, wherein HRP-conjugated NP binds to the total antibodies previously bound to NP protein on the plate. After removal of nonspecific bindings, a HRP substrate solution containing 3,3′,5,5′-Tetramethylbenzidine (TMB) is added, resulting in the formation of a blue color. Color reaction is stopped by 2M H2SO4, transforming the blue color to yellow signals, which is quantified by an absorbance microplate reader at 450nm. The color intensity is proportional to the amount of anti-NP total antibodies captured inside the wells.

• Test samples are suggested to be assayed immediately after separation of serum or plasma, or preferably stored frozen (-200C or below) in aliquots. Multiple freeze-thaw cycles should be avoided. Duplicate test is recommended.
• Serum or plasma specimens with EDTA, sodium citrate or heparin can be tested. Highly lipaemic, icteric, or hemolytic specimens are not recommended. Specimens with visible microbial contamination should not be used.
• When required, vortex test serum or plasma samples at room temperature to ensure homogeneity. Then centrifuge samples at 10,000 to 15,000 rpm for 5 minutes prior to assay to remove particulates. Please do not omit this centrifugation step if samples are cloudy and containing particles.

• The kit is stable until the expiry date only when stored at 2-8°C in sealed foil pouches. The expiry date is the last day of the month stated on the foil pouch and kit container.
• The kit should be stored at 2-8°C upon receipt, and all reagents should be equilibrated to room temperature before use. Remove any unused antigen-coated strips from the microplate, return them to the foil pouch and re-seal.  Once opened, the strips may be stored at 2-8°C for up to one month. To assure maximum performance, protect the reagents from contamination with microorganism or chemicals during storage.

1. Coutant F, Pin JJ, Morfin-Sherpa F, Ferry T, Paul S, Pozzetto B, Normand M, Miossec P. Impact of Host Immune Status on Discordant Anti-SARS-CoV-2 Circulating B Cell Frequencies and Antibody Levels. International Journal of Molecular Sciences. 2021 Jan;22(20):11095.