Infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) initiates a cell-mediated and humoral immune response that produces antibodies against specific viral antigens such as the nucleocapsid (N) protein and spike (S) protein. These include anti-S protein antibodies that target the spike’s S1 protein subunit and receptor binding domain (RBD). Antibody tests can detect the presence of these antibodies in serum within days to weeks following acute infection.
SARS-CoV-2 antibodies are an excellent indicator of past COVID-19 infection and therefore helps determine the proportion of a population that has been previously exposed or infected. The Nucleocapsid Protein (N Protein) of severe acute respiratory syndrome Coronavirus 2 (SARS-CoV2) is located in the viral core. Immunoglobulin G (IgG) targeting N protein is detectable in the serum of infected or previously patients.
SARS-CoV-2 antibody tests are not used to diagnose current or active infection. Antibody tests can identify persons with resolving or past SARS-CoV-2 infection and thereby help scientists and public health experts better understand the epidemiology of SARS-CoV-2.
