Neutralizing antibodies (NAbs) against SARS-CoV-2 have been shown to strongly correlate with protection against infection.

We assessed the performance of a semiquantitative lateral flow assay (LFA), for the prediction of serum neutralizing activity against SARS-CoV-2 variants.

The LFA inhibition rate was found to be correlated with IgG levels, and with NAb levels.

In the vaccine cohort, an inhibition rate of 77.2%, 90.8% and 99.6% predicted accurately neutralization against Alpha, Delta and Omicron variants respectively.

Neutralizing antibodies (NAbs) against SARS-CoV-2 have been shown to correlate with protection against infection. Simple tools such as lateral flow assays (LFA) that can accurately measure NAbs may be useful for monitoring anti-SARS-CoV-2 immunity in the future.

We assessed the performance of the ichroma™ COVID-19 nAb test, a rapid semiquantitative LFA, for the prediction of serum neutralizing activity against SARS-CoV-2 variants.

Serum samples were collected from COVID-19 recovered patients and vaccinated individuals. The result of the ichroma assay was provided as inhibition rate, and was compared to anti-SARS-CoV-2 IgG levels, and NAbs against Alpha, Delta and Omicron variants.

A total of 90 sera from recovered unvaccinated patients and 209 sera from the vaccine cohort were included in this study. In post-infection samples, the ichroma inhbition rate was found to be correlated with IgG levels (ρ = 0.83), and with anti-Alpha NAbs levels (ρ = 0.78). In the vaccine cohort, a good correlation was also observed between the ichroma inhibition rate and IgG levels (ρ = 0.84), as well as NAbs against Alpha (ρ = 0.62), Delta (ρ = 0.88) and Omicron (ρ = 0.74). An ichroma inhbition rate of 77.2%, 90.8% and 99.6% accurately predicted neutralization against Alpha, Delta and Omicron variants respectively.

The ichroma™ COVID-19 nAb assay, with appropriate variant cut-offs, can be useful for the monitoring of anti-SARS-CoV-2 immunization and may provide a rapid prediction of protection, especially in individuals with significant levels of NAbs.

SARS-CoV-2

Neutralizing antibodies

Variants

Lateral flow assay

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