The receptor-binding domain of the viral spike protein is an immunodominant and highly specific target of antibodies in SARS-CoV-2 patients

Abstract

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that first emerged in late 2019 is responsible for a pandemic of severe respiratory illness. People infected with this highly contagious virus can present with clinically inapparent, mild, or severe disease. Currently, the virus infection in individuals and at the population level is being monitored by PCR testing of symptomatic patients for the presence of viral RNA. There is an urgent need for SARS-CoV-2 serologic tests to identify all infected individuals, irrespective of clinical symptoms, to conduct surveillance and implement strategies to contain spread. As the receptor binding domain (RBD) of the spike protein is poorly conserved between SARS-CoVs and other pathogenic human coronaviruses, the RBD represents a promising antigen for detecting CoV-specific antibodies in people. Here we use a large panel of human sera (63 SARS-CoV-2 patients and 71 control subjects) and hyperimmune sera from animals exposed to zoonotic CoVs to evaluate RBD's performance as an antigen for reliable detection of SARS-CoV-2-specific antibodies. By day 9 after the onset of symptoms, the recombinant SARS-CoV-2 RBD antigen was highly sensitive (98%) and specific (100%) for antibodies induced by SARS-CoVs. We observed a strong correlation between levels of RBD binding antibodies and SARS-CoV-2 neutralizing antibodies in patients. Our results, which reveal the early kinetics of SARS-CoV-2 antibody responses, support using the RBD antigen in serological diagnostic assays and RBD-specific antibody levels as a correlate of SARS-CoV-2 neutralizing antibodies in people.

SARS-CoV-2 infection induces robust germinal center CD4 T follicular helper cell responses in rhesus macaques

“…4A & B). This is consistent with reports that S-or RBD-speci c IgG and IgM antibodies often appear simultaneously in blood of most humans infected with 2002 SARS or CoV-2 [26][27][28] . Antibody responses to the N protein in humans are reported to increase 10 days following disease onset 29,30 , and interestingly, N-speci c IgG was evident in all macaques by day 7 but N-speci c IgM was not increased signi cantly (3-fold over baseline values) until day 10 in most animals.…”

COVID‐19 Clinical Diagnostics and Testing Technology

“…57 Another study found that asymptomatic patients have significantly longer duration of viral shedding, lower IgG, and neutralizing serum antibody levels compared with the symptomatic group, suggesting that asymptomatic patients may mount a weaker antibody response and immunity may diminish within months of infection. 58 Although these studies demonstrate variable antibody response, IgA/IgM antibodies seem to develop during the earlier stages (indicative of recent exposure) 59 whereas IgG antibodies show up later in the course of SARS-CoV-2 infection. The association between antibody response and clinical course remains to be determined, and recent studies have proposed that antibody detection may be used as an indicator of the stage of COVID-19 progression to aid in management of the disease.…”

“…63 A recent study found high sensitivity and specificity of the RBD for antibody detection and its strong association with SARS-CoV-2 neutralizing antibodies. 59 Studies are ongoing to determine the clinical performance characteristics of various antibody tests across different platforms. 64,65 The prevalence of SARS-CoV-2 antibody positive individuals in the US population remains to be determined and is based on the different rates of infection across various locations and populations.…”

Development of a Multi-Antigenic SARS-CoV-2 Vaccine Using a Synthetic Poxvirus Platform

“…While the single recombinant vectors induced binding antibodies only against the S or N antigen, the double recombinant vectors induced binding antibodies against both the S and N antigens. In addition, all sMVA-CoV2 vectors encoding the S antigen (sMVA-S, sMVA-S/N, sMVA-N/S) stimulated high-titer binding antibodies against the S receptor binding domain (RBD), which is considered the primary target of NAb 22,24 . Antigen-speci c binding antibody titers between the single and double recombinant vaccine groups were comparable.…”

“…To characterize the viral DNA of the sMVA vectors by PCR, CEF were seeded in 6-well plate tissue culture format and at 70-90% con uency infected at 5 MOI with sMVA or wtMVA. DNA was extracted at [16][17][18][19][20][21][22][23][24] hours post infection by the DNA Easy Blood and Tissue Kit (Qiagen) according to the manufacturer's instructions. All PCR reactions were performed with Phusion polymerase (ThermoFischer Scienti c).…”