Antibody Levels From High-Throughput Variant-Specific SARS-CoV-2 Anti-Spike Immunoglobulin G and Angiotensin-Converting Enzyme 2 Neutralization Assays Correlate With COVID-19 Infection Risk in a Large Population.

BACKGROUND

SARS-CoV-2 antibody levels have been proposed as a correlate of protection from infection. Yet, large-scale prospective studies of cost-effective scalable antibody measures as predictors of infection under real-world conditions are limited. We examined whether antibody levels measured by high-throughput variant-specific SARS-CoV-2 anti-spike immunoglobulin G (IgG) and angiotensin-converting enzyme 2 (ACE2) neutralization assays correlate with cell-based neutralizing antibody measurements and whether they can serve as a reasonable correlate of protection from SARS-CoV-2 infection.

METHODS

We conducted a large institutional cohort study between January 2022 and March 2023. Participants (N = 2513) provided dried blood spot (DBS) samples for assessment of anti-spike IgG and ACE2 inhibition levels through high-throughput assays. Comparison with authentic cell-based SARS-CoV-2 neutralizing antibody assays was conducted with serum samples (n = 105). Associations between antibody levels and risk of infection were evaluated.

RESULTS

Correlation between serum and DBS sampling and between cell-based neutralizing and high-throughput antibody binding assays was high for anti-spike IgG and ACE2 neutralization, though the degree of correlation varied by variant. Longitudinal evaluation suggested that DBS-based IgG and ACE2 inhibition levels were anticorrelated with infection risk, with higher sensitivity noted for ACE2 inhibition and variant-matched measures. IgG and ACE2 inhibition levels decreased over time, with more durable responses observed in participants whose most recent priming event was infection vs vaccination.

CONCLUSIONS

Findings suggest that variant-specific SARS-CoV-2 antibody levels may be a useful correlate of protection for infection, which has important implications for vaccination recommendations and evaluating infection risk. High-throughput assays measured via DBS may have utility in timing of boosters at the population or individual level.