(Novavax, Inc

(Novavax, Inc., MD) for providing the SARS-CoV-2 full S protein and ACE-2 protein for the anti-S IgG and IgA ELISAs and the ACE-2 receptor blocking assay, Dr. curves and diagnostic test statistics were evaluated to define the optimal serum dilution and OD cutoff value for IgG anti-S and IgA anti-S ELISAs. The IgG and IgA anti-S, and three functional antibodies (ACE-2 receptor blocking antibody, lentipseudovirus-S neutralizing antibody, and SARS-CoV-2 neutralizing antibody) were measured using additional SARS-CoV-2 PCR positive sera (n=76) and surveillance sera (n=25). Lastly, the IgG and IgA anti-S levels were compared in different demographic groups. Results The optimal serum dilution for the qualitative IgG anti-S ELISA was at 1:1024 yielding a 99.6% specificity, 92.2% sensitivity, 92.9% positive predictive value (PPV), and 99.6% negative predictive value (NPV) at a SARS-CoV-2 seroprevalence of 5%. The optimal serum dilution for the qualitative IgA anti-S ELISA was at 1:128 yielding a 98.9% specificity, 76.5% sensitivity, 78.3% PPV, and Epipregnanolone 98.8% NPV at the same seroprevalence. Significant correlations were demonstrated between the IgG and IgA (r=0.833 for concentrations, r=0.840 for titers) as well as between IgG and three functional antibodies (r=0.811-0.924 for concentrations, r=0.795-0.917 for titers). The IgG and IgA anti-S levels were significantly higher in males than females (p<0.05), and in adults with moderate/severe symptoms than in adults with mild/moderate symptoms (p<0.001). Conclusion We developed a highly specific and sensitive IgG anti-S ELISA assay to SARS-CoV-2 using full length S protein. The IgG anti-S antibody level was strongly associated with IgA and functional antibody levels in adults with SARS-CoV-2 contamination. Gender and disease severity, rather than age, play an important role in antibody levels. Keywords: SARS-CoV-2, COVID-19, serology, human serum, binding antibody, functional antibody Introduction In December 2019, a novel coronavirus emerged in China that has subsequently proven to be the causative agent of an acute respiratory disease now known as coronavirus disease 2019 (COVID-19) (1), and has since sparked a pandemic. The computer virus was officially named severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (2). It is the seventh coronavirus species to cross the species barrier causing respiratory infections in humans (3, 4). Compared with the earlier SARS-CoV in 2003 and the Middle East Respiratory Syndrome Coronavirus (MERS-CoV) in 2012, SARS-CoV-2 has spread rapidly causing at least 201 million cases and 4.3 million deaths globally, as of August. 6th, 2021. Therefore, it is critical to develop mitigation strategies to control the spread of this emerging virus and use strong serological assays to determine the vulnerability of a populace, define immune correlates, and evaluate vaccines. SARS-CoV-2 is usually a positive-sense single-stranded RNA computer virus, measuring 50C200 nanometers in diameter. The virus has four structural proteins: S (spike), E (envelope), M (membrane), and N (nucleocapsid) proteins. The S protein is responsible for attaching to the host membrane-bound receptor, angiotensin-converting enzyme 2 (ACE-2), and fusing with the membrane of the host cell (5, 6). Specifically, the N-terminal S1 subunit catalyzes attachment to the host receptor, and the C-terminal S2 subunit mediates membrane fusion. The S1 subunit is usually further divided into the N terminal domain name (NTD) and the receptor binding domain name (RBD). In adults infected with SARS-CoV-2, neutralizing antibodies are generated to the S protein and its RBD, both of which are major targets for vaccine development (7). Antibodies are also generated to other structural proteins, particularly to the N protein, which is usually often included in commercial diagnostic antibody assessments (8). Antibody assays are useful tools that can be utilized for diagnosing an acute infection, determining seroprevalence in a populace, evaluating the immunogenicity Epipregnanolone of vaccines, studying antibody response induced by wild type contamination, and establishing immune correlates of protection. Data from seroprevalence Epipregnanolone studies can be used to determine the vulnerability of a populace and to identify those at risk for contamination and reinfection. Sensitive and Rabbit Polyclonal to FRS2 specific antibody assays that measure anti-SARS-CoV-2 antibodies are, therefore, crucial tools in the arsenal needed for gaining control of the SARS-CoV-2 pandemic. There are two major types of assays used to characterize serum antibody responses: assays that measure the presence, concentration, and isotype of antigen-specific binding antibodies; and those that measure the functional capabilities of serum antibodies based on their ability to block viral binding to cellular receptors, or neutralize viral contamination. The emergency use authorization (EUA) has allowed the United States Food and Drug Administration (FDA) to.