Researchers have developed a new antibody test for the virus that causes Covid-19 that can handle a much larger number of donor samples at lower overall cost than standard antibody tests currently in use.
In the near term, the test can be used to accurately identify the best donors for convalescent plasma therapy and measure how well candidate vaccines and other therapies elicit an immune response, said the study published in the The Journal of Clinical Investigation.
Additional uses coming later are to assess relative immunity in those previously infected by the SARS-CoV-2 virus and identify asymptomatic individuals with high levels of neutralising antibodies against the virus, said the researchers.
“This is potentially game-changing when it comes to serological testing for Covid-19 immunity,” said one of the study authors Jason Lavinder from the University of Texas at Austin in the US.
“We can now use highly scalable, automated testing to examine antibody-based immunity to Covid-19 for hundreds of donors in a single run. With increased levels of automation, limited capacity for serological testing can be rapidly addressed using this approach.”
The gold standard of Covid-19 antibody testing measures the amount of virus neutralising (VN) antibodies circulating in the blood, because this closely correlates with immunity.
However, this kind of antibody testing is not widely available because it is technically complex; requires days to set up, run and interpret; and needs to be performed in a biosafety level 3 laboratory.
The research team, therefore, looked to another type of test, called ELISA assays, that can be implemented and performed with relative ease in a high-throughput fashion and are widely available and extensively used in clinical labs across the world.
The ELISA tests, or enzyme-linked immunosorbent assays, look at whether antibodies against specific SARS-CoV-2 proteins are present and produce a quantitative measure of those antibodies.
The goal of the study was to test the hypothesis that levels of antibodies that target two regions of the virus’s spike protein – spike ectodomain (ECD) and receptor binding domain (RBD) – are correlated with virus neutralising antibody levels.
The researchers used the new test to evaluate 2,814 blood samples used in an ongoing study of convalescent plasma therapy.
They found that the ELISA tests had an 80 per cent probability or greater of comparable antibody level to virus neutralising levels at or above the US Food and Drug Administration (FDA)-recommended levels for Covid-19 convalescent plasma.