Abstract
To better understand the immune responses to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in individuals with COVID-19, it is important to investigate the kinetics of the antibody responses and their associations with the clinical course in different populations, since there seem to be considerable differences between Western and Asian populations in the clinical features and spread of COVID-19. In this study, we serially measured the serum titers of IgM, IgG and IgA antibodies generated against the nucleocapsid protein (NCP), S1 subunit of the spike protein (S1), and receptor-binding domain in the S1 subunit (RBD) of SARS-CoV-2 in Japanese individuals with COVID-19. Among the IgM, IgG, and IgA antibodies, IgA antibodies against all of the aforementioned viral proteins were the first to appear after the infection, and IgG and/or IgA seroconversion often preceded IgM seroconversion. In regard to the timeline of the antibody responses to the different viral proteins (NCP, S1 and RBD), IgA against NCP appeared than IgA against S1 or RBD, while IgM and IgG against S1 appeared earlier than IgM/IgG against NCP or RBD. The IgG responses to all three viral proteins and responses of all three antibody classes to S1 and RBD were sustained for longer durations than the IgA/IgM responses to all three viral proteins and responses of all three antibody classes to NCP, respectively. The seroconversion of IgA against NCP occurred later and less frequently in patients with mild COVID-19. These results suggest possible differences in the antibody responses to SARS-CoV-2 antigens between the Japanese and Western populations.
Keywords: COVID-19; IgA; IgG; IgM; Japanese population; Kinetics of antibody responses; Nucleocapsid protein; Receptor-binding domain; Spike protein.
【저자키워드】 COVID-19, IgG, IgM, nucleocapsid protein, spike protein., Receptor-binding domain, IgA, Japanese population, Kinetics of antibody responses, 【초록키워드】 SARS-CoV-2, coronavirus, immune response, spike, antibody, Infection, Viral proteins, severe acute respiratory syndrome Coronavirus, Clinical features, Population, Spike protein, nucleocapsid protein, Protein, Kinetics, Antibody responses, Clinical course, Seroconversion, Receptor-binding domain, RBD, IgM/IgG, immune responses, response, Patient, Mild, Japanese, SARS-CoV-2 antigen, respiratory, timeline, clinical feature, SARS-CoV-2 antigens, association, S1 subunit, IgM and IgG, IgG responses, IgG response, Asian, acute respiratory syndrome, Viral protein, acute respiratory syndrome coronavirus, acute respiratory syndrome coronavirus 2, IgM responses, IgA antibodies, domain, serum titer, populations, IgM seroconversion, serum titers, spread of COVID-19, the S1 subunit, occurred, less, the spike protein, sustained, the antibody response, IgA antibody, individuals with COVID-19, 【제목키워드】 antibody, SARS-CoV2 infection, response, Japanese, IgG titer,