Detection of SARS-CoV-2 Reinfections Using Nucleocapsid Antibody Boosting

Area of Science:

• Immunology
• Infectious Diseases
• Epidemiology

Background:

• Over 85% of US adults were infected with SARS-CoV-2 by end of 2023.
• Accurate detection of SARS-CoV-2 reinfections is crucial for transmission surveillance and immunity assessment.
• Existing methods may not fully capture the dynamics of reinfection.

Purpose of the Study:

• To develop and validate a serologic assay for identifying SARS-CoV-2 reinfections.
• To assess the performance of nucleocapsid (N) antibody boosting as a marker for reinfection.
• To estimate total infection incidence in a longitudinal blood donor cohort.

Main Methods:

• Developed a total immunoglobulin assay to detect nucleocapsid (N) antibody boosting.
• Utilized longitudinal blood donor data.
• Employed receiver operating characteristic (ROC) curve analysis to determine optimal detection thresholds.
• Investigated the impact of pre-existing anti-N antibody levels on assay sensitivity.
• Explored dilutional testing to improve assay performance in high-reactivity individuals.

Main Results:

• An optimal N antibody ratio >1.43 achieved 87.1% sensitivity and 96.0% specificity.
• Prioritizing specificity, a ratio >2.33 yielded 75.3% sensitivity and 99.3% specificity.
• Assay sensitivity was reduced in individuals with higher pre-reinfection anti-N antibody levels.
• Dilutional testing improved sensitivity from 38.8% to 66.7% in the highest reactivity group (signal-to-cutoff ratio >150).

Conclusions:

• Longitudinal testing for N antibodies is a viable method for identifying SARS-CoV-2 reinfections.
• The developed serologic assay can aid in estimating total infection incidence.
• Further assay optimization, including dynamic range expansion, can enhance reinfection detection capabilities.