The in-house ELISA results correlated strongly with neutralization assay, indicating that the assay was sensitive and specific for the detection of anti-SARS-CoV-2 IgG. challenges in containing the spread of Echinocystic acid SARS-CoV-2 is the diagnosis of a large number of infected individuals within a population. Majority of the asymptomatic cases may remain undetected due to the limited resources for diagnosis. As approved by the World Health Organization (WHO), molecular Echinocystic acid assays are currently the mainstay of diagnosis of COVID-199. Serological assays have also been used as a screening tool for the surveillance of the emerging and re-emerging diseases. However, serological assays are not currently recommended for case detection and are not included Echinocystic acid in the WHO laboratory testing guidelines for COVID-19. The actual burden of infection and its spread can be determined using detection of IgM and IgG antibodies against SARS-CoV-2 by serological assays such as ELISA10,11,12,13,14. Haveri 0.001 with r2 value 0.8387; Lab 2: 0.001 with r2 value of 0.9068) (Fig. 2). Open in a separate window Fig. 2 Inter-laboratory correlation analysis: A panel of 150 serum samples tested at two external laboratories and compared with the ICMR-National Institute of Virology reference laboratory indicated a positive correlation between the reference laboratory and the other laboratories. em Correlation between anti-SARS-CoV-2 human IgG ELISA and MNT /em : The correlation between the in-house IgG ELISA against the neutralization titres indicated a strong positive correlation ( em r /em =0.7836, em P /em 0.001) (Fig. 3). Open in a separate window Fig. 3 Correlation analysis of SARS-CoV-2 antibody titre of microneutralization test (MNT) compared with optical densities of the in-house SARS-CoV-2 IgG ELISA ( em r /em =0.7836, em P /em 0.001). Discussion The U.S. Food and Drug Administration (FDA) has granted 31 molecular diagnostic kits (real-time RT-PCR, RT-LAMP and point-of-care test) for emergency use authorization. For surveillance of the emerging and re-emerging viruses, serological assays have been widely recommended. Several IgM/IgG ELISA kits for COVID-19 are in the stage of development. However, validated and approved SARS-CoV-2 serological assays are lacking for case detection17 and are not included in laboratory testing guidelines for COVID-19 of the WHO9. Due to the nonavailability of an indigenous, approved and cost-effective kit, an in-house ELISA was developed and validated for the detection of anti-SARS-CoV-2 human being IgG antibodies. The disease neutralization is regarded as the gold standard method for a serological assay20. The in-house ELISA results correlated strongly with neutralization assay, indicating that the assay was sensitive and specific for the detection of anti-SARS-CoV-2 IgG. The assay Echinocystic acid overall performance was not different with the use of serum or plasma. No cross-reactivity with additional respiratory viruses was detected. This kit may be used to detect revealed immune-protected individuals. This ELISA will become useful in screening healthcare workers, industry workers, em etc /em . The use of whole-cell antigen CD180 instead of recombinant nucleocapsid antigen or spike protein antigen provided a broad sensitivity to the assay. However, the assay overall performance needs to become assessed in a large cohort of related human being/zoonotic coronaviruses. The development of a sensitive and specific assay based on whole-virus antigen that may be produced at lower Echinocystic acid developing cost will provide easy-to-use and affordable packages to resource-limited settings. In conclusion, our findings suggested that this indigenous anti-SARS-CoV-2 human being IgG-ELISA was sensitive and specific for the detection of IgG antibodies among individuals who have been exposed to SARS-CoV-2. The ELISA results correlated strongly with disease neutralizing antibodies. This assay may be used for ascertaining the seroprevalence against SARS-CoV-2 inside a population and for epidemiological studies. Footnotes em Financial support & sponsorship /em : None. em Conflicts of Interest /em : None..