The Nucleocapsid protein triggers the main humoral immune response in COVID-19 patients

Abstract

made to identify infected patients and to detect patients with a positive immune response against the virus. Currently, attemprs ro generare a vaccine against the coronavirus are ongoing. To understand SARSCoV- 2 immunoreactivity, we compared the lgG antibody response against SARS-CoV-2 in infected versus control patients by dot blot using recombinant viral particle proteins: N (Nucleocapsid ). M (Membrane) and S (Spike). In addition, we used difTerent prorein fragments of the N and S protein to map immune epitopes. Most of the COVID-19 patients presented a speci fic immune response against the full length and fragments of the N protein and. to lesser exten t. against a fragment containing amino acids 300- 685 of the S protein. In contrast, immunoreacrivity against other S protein fragments or the M prorein was low. This response is speci fic for COVID-19 patien ts as very few of the control patients displayed immunoreactiviry, like ly reflecting an immune response against other coronaviruses. Altogether. our results may help develop method(s) for measuring COVID-19 antibody response, selectivity of methods detecting such SARS-CoV-2 antibodies and vaccine development.