A highly specific and very sensitive serological SARS-CoV-2 antibody assay with overall accuracy at 97.3% was developed using CHO-expressed SARS-CoV-2 S1 protein for screening medical staff and others for SARS-CoV-2 infection. AbstractBackground: Thousands of medical staff had been infected with SARS-CoV-2 virus with hundreds of deaths reported. Such loss could be prevented if there is a serologic assay for SARS-CoV-2-specific antibodies for serological surveillance of its infection at the early stage of disease.Methods: Using CHO cell expressed full length SARS-CoV-2 S1 protein as capturing antigen, a COVID-19/SARS-CoV-2 S1 serology ELISA kit was developed and validated with negative samples collected prior to the outbreaks or during the outbreak, and positive samples from patients confirmed with COVID-19. Results:The specificity of the ELISA kit was 97.5%, as examined against total 412 normal human samples. The sensitivity was 97.1% by testing against 69 samples from hospitalized and/or recovered COVID-19 patients. The overall accuracy rate reached 97.3%. The assay was able to detect SARS-CoV-2 antibody on day one after the onset of COVID-19 disease. The average antibody levels increased during the hospitalization and after been discharged for two weeks. SARS-CoV-2 antibodies were detected in 28 out of 276 asymptomatic medical staff and one out of five nucleic acid test-negative "Close contacts" of COVID-19 patient. Conclusion:With the assays developed here, we can screen medical staff, in-coming patients, passengers and people who are in close contact with the confirmed patients to identify the "innocent viral spreaders", protect the medical staff and stop the further spreading of the virus.

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The COVID-19 China coronavirus started in Dec 2019 was challenged by the lack of accurate serological diagnostic tool for this deadly disease to quickly identify and isolate the infected patients. The generation of COVID-19-specific antibodies is essential for such tasks. Here we report that polyclonal and monoclonal antibodies were generated by immunizing animals with synthetic peptides corresponding to different areas of Nucleoprotein (N) of COVID-19. The specificities of the COVID-19 antibodies were assessed by Western Blot analysis against NPs from COVID-19, MERS and SARS. Antibodies were used for immunohistochemistry staining of the tissue sections from COVID-19 infected patient, as a potential diagnostic tool. A Sandwich ELISA kit was quickly assembled for quantitation of the virus/NP of COVID-19 concentrations in the vaccine preparations. Development of POCT is also aggressively undergoing.

The COVID-19 outbreak has become a global pandemic responsible for over 2,000,000 confirmed cases and over 126,000 deaths worldwide. In this study, we examined the immunogenicity of CHO-expressed recombinant SARS-CoV-2 S1-Fc fusion protein in mice, rabbits, and monkeys as a potential candidate for a COVID-19 vaccine. We demonstrate that the S1-Fc fusion protein is extremely immunogenic, as evidenced by strong antibody titers observed by day 7. Strong virus neutralizing activity was Highlights:1. CHO-expressed S1-Fc protein is very immunogenic in various animals and can rapidly induce strong antibody production 2. S1-Fc protein solicits strong neutralizing activities against live virus 3. Stable CHO cell line expressing 50 mg/L of S1-Fc and a 3,000 L Bioreactor can produce 3 million doses of human COVID-19 vaccine every 10 days, making it an accessible and affordable option for worldwide vaccination

28expressed full-length SARS-CoV-2 S1 proteins 29 WHO has declared COVID-19 a pandemic with more than 300,000 confirmed 30 cases and more than 14,000 deaths. There is urgent need for accurate and rapid 31 diagnostic kits. Here we report the development and validation of a COVID-32 19/SARS-CoV-2 S1 serology ELISA kit for the detection of total anti-virus 33 antibody (IgG+IgM) titers in sera from either the general population or patients 34 suspected to be infected. For indirect ELISA, CHO-expressed recombinant full 35 length SARS-CoV-2-S1 protein with 6*His tag was used as the coating antigen to 36 capture the SARS-CoV-2-S1 antibodies specifically. The specificity of the 37 ELISA kit was determined to be 97.5%, as examined against total 412 normal 38 human sera including 257 samples collected prior to the outbreak and 155 39 collected during the outbreak. The sensitivity of the ELISA kit was determined to 40 be 97.5% by testing against 69 samples from hospitalized and/or recovered 41 COVID-19 patients. The overall accuracy rate reached 97.3%. Most importantly, 42 in one case study, the ELISA test kit was able to identify an infected person who 43 had previously been quarantined for 14 days after coming into contact with a 44 confirmed COVID-19 patient, and discharged after testing negative twice by 45 nucleic acid test. With the assays developed here, we can screen millions of 46 medical staffs in the hospitals and people in residential complex, schools, public 47 transportations, and business parks in the epidemic centers of the outbreaks to 48 fish out the "innocent viral spreaders", and help to stop the further spreading of 49 the virus.50