Impaired systemic nucleocapsid antigen clearance in severe COVID-19

Area of Science:

• Virology
• Immunology
• Clinical Medicine

Background:

• Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleocapsid antigen (NCP) is detectable in patients with coronavirus disease-2019 (COVID-19).
• Understanding NCP kinetics is crucial for elucidating COVID-19 disease severity.

Purpose of the Study:

• To investigate the clearance kinetics of serum NCP in hospitalized COVID-19 patients.
• To correlate NCP clearance with disease severity, inflammation, antibody response, and viral PCR results.

Main Methods:

• Serum NCP levels were quantified using an enzyme-linked immunoassay in 63 hospitalized COVID-19 patients.
• Data were analyzed in relation to clinical outcomes, inflammatory markers, and SARS-CoV-2 PCR status.

Main Results:

• Elevated NCP levels persisted beyond 8 days post-diagnosis in 46.7% of intensive care unit (ICU) patients.
• NCP clearance was significantly delayed in over 40% of severe COVID-19 cases, contrasting with non-ICU patients and PCR clearance.
• Delayed antigenemia correlated with intensive care needs and was associated with higher S1-specific IgG levels.

Conclusions:

• Delayed NCP antigenemia after 8 days post-COVID-19 diagnosis is characteristic of patients requiring intensive care.
• NCP antigen clearance kinetics may serve as a mechanistic biomarker for predicting COVID-19 severity.