Human coronavirus (HCoV) has received more and more attention since the COVID-19 pandemic, it is a critical respiratory pathogen. In addition to 2019-nCoV, the remaining six known coronaviruses that can infect humans including HCoV-229E, HCoV-OC43, HCoV-NL63, HCoV-HKU1, SARS-CoV (causing Severe Acute Respiratory Syndrome) and MERS-CoV (causing Middle East Respiratory Syndrome).

N protein is a phosphorylated protein, it’s modified by a certain amount of serine and threonine, and the primary function of the N protein is to combine the viral RNA and forming a nucleocapsid. Among all structural proteins, N protein is strongest immune response protein after inducing In the process of viral infection. Due to its features of small size and lack of glycosylation sites, N protein is easy to be expressed and purified. Its mediated antibodies are produced early, with high titer and long duration. Therefore, N protein is often the most suitable antigen for serological detection of the virus.

Novel Coronavirus Protein (N Protein) Monoclonal Antibody

The newest N antibody pairs, launched by CUSAg, is systematically evaluated by using our Immune Colloidal Gold platform. The detection sensitivity is less than 10 pg/mL.The low-concentration inactivated virus culture can be sensitively detected. It can efficiently detected  the UK (B.1.1.7) mutant strain, South Africa (B.1.351) mutant strain and Brazil (P.1) mutant strains.This indicates our N antibody can recognize the mutant protein.

1. Detection of virus cultures

In the immunocolloidal gold rapid diagnosis platform, CSB-DA701BMN ⑧ was used as the capture antibody and crossed onto the nitocellulose thin film (NC). CSB-DA701BMN ⑦ was used as the labeled antibody and labeled colloidal gold. It enables to establish an immune colloidal gold chromatographic detection system for SARS-CoV-2. Then the virus culture samples (sample gradient dilution) were subjected to semi-quantitative detection. The detection results were as follows: with the increase of virus concentration, the T/C signal gradient was enhanced.

•Virus cultures were detected with SARS-CoV-2 N antibody pairs on the immune colloidal gold platform

2. The SARS-CoV-2 N protein and SARS-CoV-2 Mutant N protein detected

Sincethe COVID-19 pandemic, the virus has been constantly mutating. In order to verify that the antibody can recognize the mutated protein, we chose to test the spot focused mutants like British (B.1.1.7), South African (B.1.351) and Brazilian (P.1) mutants. We prepare the Serum N proteins(concentrations of 0-25 ng/mL ) as the calibration by diluting SARS-CoV-2 .SARS-CoV-2 Mutant N proteins with protein dilution solution. It showed that the N proteins of different mutants could be efficiently detected by our N antibody paris.

3、Verify coronavirus N protein cross - reaction

We prepare 0-1000 ng/mL of N proteins as calibrators by diluting six coronavirus recombinant N proteins with protein dilution solution. Except that SARS-CoV and SARS-CoV-2 have cross reactions to N proteins.  There was no cross-reaction between SARS-CoV and the other four coronaviruses.It is mainly due to the high N protein homology of SARS-CoV-2 and SARS-CoV (90.5% homology).

•The SARS-CoV N protein was detected by the self-produced SARS-CoV-2 N antibodies on the gold immunocolloid platform

•The SARS-CoV-2 N protein was detected by the self-produced SARS-CoV-2 N antibodies on the gold immunocolloid platform

•The HCoV-229E N protein was detected by the self-produced SARS-CoV-2 N antibodies on the gold immunocolloid platform

•TheHCoV-HKU1 N protein was detected by the self-produced SARS-CoV-2 N antibodies on the gold immunocolloid platform

•TheHCoV-NL63 N protein was detected by the self-produced SARS-CoV-2 N antibodies on the gold immunocolloid platform

•TheHCoV-OC43 N protein was detected by the self-produced SARS-CoV-2 N antibodies on the gold immunocolloid platform

SARS-CoV-2 N protein

CUSAg canalso provides high quality SARS-CoV-2 N protein (Catalog Number : CSB-DP701B) used for calibration of immunotest, western blot, etc