Researchers develop new tools to rapidly test COVID-19 antibodies

Researchers have developed new tools to rapidly test the ability of antibodies to neutralise SARS-CoV-2, the novel coronavirus responsible for the COVID-19 pandemic.

The approach, published in the Journal of Experimental Medicine (JEM), will help researchers understand whether patients are susceptible to reinfection by COVID-19 and assess the effectiveness of experimental vaccines, as well as develop antibody-based therapies against the disease.

People infected with COVID-19 produce neutralising antibodies that prevent the virus from infecting cells by binding to the spike protein on the virus's surface.

Early studies have suggested that the strength of this antibody response varies greatly between patients, and it remains unknown how long any such neutralising antibodies persist in the blood to provide protection against reinfection.

"Whether elicited by natural infection or vaccination or administered as a convalescent plasma or in recombinant form, neutralising antibodies will likely be crucial for curtailing the global burden of COVID-19 disease," said study researcher Paul D Bieniasz from the Rockefeller University in the US.

"For this reason, the availability of rapid, convenient, and accurate assays that measure neutralising antibody activity is crucial for evaluating naturally acquired or artificially induced immunity against COVID-19," Bieniasz added.

According to the study, the research team developed a number of safer, surrogate viruses that can be used in place of COVID-19 to test the neutralising activity of antibodies targeting the coronavirus spike protein.

The surrogate viruses are versions of either the human immunodeficiency virus type-1 (HIV-1) or vesicular stomatitis virus (VSV) that produce the SARS-CoV-2 spike protein instead of their own surface proteins.

Some of these surrogate viruses are unable to replicate, making them even safer to use in the laboratory.

Moreover, the viruses are engineered to generate fluorescent or luminescent infected cells, making it easy for researchers to track infection and measure how well this process is blocked by potential neutralising antibodies.

The researchers tested the ability of convalescent patient plasma samples and purified antibodies to block the entry of the surrogate viruses into human cells grown in the laboratory.

"Each of the surrogate virus-based assays generated quantitative measurements of neutralising activity that correlated well with neutralisation measured using authentic SARS-CoV-2," said study author Theodora Hatziioannou.

"We think that these surrogate viruses and assays will be of significant use in curtailing the COVID-19 pandemic," the researchers concluded.