The infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) triggers both B-cell and T-cell responses directed against all viral antigens including the Nucleocapsid (N) and Spike (S) proteins. S protein is essential for viral entry into host cells and N protein is the most abundantly expressed immunodominant protein. Following the initial contact with the virus and fueled by pro-inflammatory cytokines an antibody response is mounted. Specific antibody tests can reliably detect the presence of these antibodies in biological fluids including serum, plasma, saliva [1], urine, human milk [2] and cerebrospinal fluid (CSF) [3].
