Novel test can detect antibodies to SARS-CoV-2 in human blood

A new blood test may help identify individuals whose plasma contains antibodies to SARS-CoV-2 virus that causes COVID-19, and could potentially be used to treat other patients, scientists said on Tuesday.

Tests that detect the presence of SARS-CoV-2 RNA are widely used to diagnose COVID-19, according to the researchers from Icahn School of Medicine at Mount Sinai in the US.

However, assays that can measure the presence of antibodies to the virus may potentially help determine the rate of infection in a population.

According to the research published in the journal Nature Medicine, the new enzyme-linked immunosorbent assay, tested in 16 patients, can be used to detect the presence of antibodies to SARS-CoV-2.

The researchers, including corresponding author Florian Krammer, created two versions of the spike protein found on the surface of the virus.

The spike protein mediates entry into host cells, and is targeted by antibodies during other coronavirus infections, they said.

The first version encompassed the full spike protein, while the second was limited to the receptor-binding domain -- a smaller section of the spike protein.

Using 16 plasma and serum samples -- fluid components of the blood -- from patients with SARS-CoV-2 infections, the researchers observed that all of the samples produced a positive result to both versions of the spike protein in the assay.

They found that a stronger reaction was observed against the full-length spike protein, which may suggest a greater number of antibody-binding sites on the larger protein.

In tests involving 50 serum samples collected from participants prior to the outbreak of SARS-CoV-2, the researchers found very low or no reactivity to the proteins in the assay.

They noted that their assay is relatively quick and simple to carry out and does not involve handling the live virus.

However, the researchers cautioned that samples from patients with SARS-CoV-1 or Middle Eastern Respiratory Syndrome CoV were not included in the research, so it is not known whether antibodies to these viruses would also produce a positive result.

They said further research with larger sample sizes will also be needed.