New Rapid Test Determines Amount of Neutralizing Antibodies Against SARS-CoV-2 Within Short Period of Time

A Swiss-German team of researchers have developed a test that determines the amount of neutralizing antibodies against SARS-CoV-2 within a short period of time.

The test was developed at the Institute of Virology and Immunology (IVI) of the University of Bern (Bern, Switzerland) and the Swiss Federal Office for Food Safety and Animal Health (Köniz, Switzerland), and evaluated by the Ruhr-University Bochum (RUB Bochum, Germany) using serum samples from COVID-19 patients.

To determine immunity to SARS-CoV-2 and the effectiveness of potential vaccines, the amount of neutralizing antibodies in the blood of recovered or vaccinated individuals must be determined. A traditional neutralization test usually takes two to three days and must be carried out with infectious coronaviruses in a laboratory complying with biosafety level 3. The new test launched by the team of Swiss-German researchers takes only 18 hours and does not have high biosafety requirements.

In order to detect antibodies against SARS-CoV-2, the researchers used another virus that does not propagate and exchanged the envelope protein of this virus for the spike protein of the novel coronavirus, which mediates virus entry and infection. As a result, the viruses can be identified by antibodies against SARS-CoV-2 that bind to the viruses which have been altered in this way and neutralize them so that they can no longer penetrate the host cells. Since the virus pseudotyped in this way cannot propagate in host cells, no elaborate biosafety precautions are necessary for the test.

In order to determine the amount of antibodies, the researchers genetically modified the virus so that green fluorescent protein and luciferase, an enzyme from fireflies, will be produced by the infected cells. The green fluorescence is an indicator of infection with the pseudotyped virus. The less green cells found, the more neutralizing antibodies are present which block the virus. In addition, a luminometer can be used to read the luminescence signal produced by the luciferase enzyme – another way of evaluating the test.

In order to check the reliability and comparability with the conventional neutralization test, the researchers applied it to blood samples from COVID-19 patients. The direct comparison showed a good correlation between the two test systems. As compared to 56 hours for the conventional test, the new test is much faster, with only 18 hours to test results.

Related Links:
University of Bern
Swiss Federal Office for Food Safety and Animal Health
Ruhr-University Bochum