Comparative Analysis of Nucleocapsid Antibody Levels, Neutralizing Antibodies, and Spike receptor-binding Domain in Severe Acute Respiratory Syndrome Coronavirus-2 Patients

ABSTRACT Serological testing for severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is crucial for detecting antibodies generated in response to infection. Neutralizing antibodies (NAbs) target the receptor-binding domain (RBD) of the spike protein (S-RBD) and can exist in the forms of immunoglobulin G (IgG), IgM, and IgA. This study aimed to assess specific antibody responses to the nucleocapsid protein (N), S-RBD, and NAbs and correlate them with the clinical spectrum of coronavirus disease 2019 (COVID-19). A cross-sectional design was conducted at the Dr. Soetomo General Academic Hospital, Indonesia. We examined 48 patients with confirmed COVID-19 of varying severity (mild, moderate, severe, and critical) on treatment days 0, 3, and 6. We measured nucleocapsid antibodies, S-RBD, and neutralization using the chemiluminescence immunoassay method. The comparative analysis of IgM, IgG, NAB, and S-RBD levels is adjudicated using the independent t-test. Specific antibody levels on treatment days 0, 3, and 6 showed significant differences (P < 0.05). Notably, significant differences were observed in comparisons such as severe recovery versus severe death groups on day 0 in IgG, mild versus severe recovery on day 3 in IgM, moderate versus severe recovery, severe recovery versus severe death, and mild versus severe recovery on day 3, as well as on day 6 in anti-S-RBD, and mild versus severe recovery on day 3 and day 6 in neutralization of SARS-CoV-2 (P < 0.05). These findings highlight the dynamic antibody responses during COVID-19 treatment and their relevance for clinical outcomes.