The quick antibody test determines whether someone has had the coronavirus at some point in the past.

A Drop of Blood is All it Takes

As Sars-CoV-2 often causes no symptoms whatsoever, many people don’t know whether they’ve already had the disease and are now potentially immune. In order to shed light on the number of unreported cases, a consortium of companies teamed up with researchers from the University of Jena to develop a quick antibody test that is now used around the world.
The quick antibody test determines whether someone has had the coronavirus at some point in the past.
Image: Jürgen Scheere (University of Jena)

Testing, testing, testing is one of the most important strategies in the fight against the novel coronavirus SARS-CoV-2. Medical professionals can check whether their patients are infected by taking a swab of their mouth, nose and throat. If these samples contain genetic material of the virus, it can be clearly identified in the laboratory using fluorescent dyes in a polymerase chain reaction (PCR). In the fight against the pandemic, however, it’s not just important to know whether someone is infected at the moment, but also whether they’ve already been infected and may be immune for the time being. This can be determined through antibody tests. As with most pathogens, the human immune system develops different types of antibodies to fight the coronavirus, and to remain in the body after fighting off the disease to prevent a repeated infection.

Test results in 10 minutes

In early spring 2020, researchers at the Leibniz Institute of Photonic Technology (Leibniz IPHT) in Jena developed an antibody test together with their Chinese colleagues and other business partners. The rapid test allows people to find out in just 10 minutes whether they’ve had the coronavirus at some point in the past. »By working with our international partners, we were able to react so quickly to the global developments and release a high quantity of the ready-to-use product in early April«, says Ralf Ehricht from the Leibniz IPHT, who also conducts research at the Institute of Physical Chemistry at the University of Jena. »Our colleagues trialled the quick test right at the source of the pandemic in China, where the effects of the pathogen were witnessed much sooner«. It works just like a simple pregnancy test; it was very quick to reach various markets and is now distributed and used throughout the world thanks to the production partners involved in the project (SENOVA GmbH in Weimar and SERVOPRAX in Wesel).

The quick test can even differentiate between two protein classes that the immune system produces and uses as antibodies: immunoglobulin M (IgM), which is formed around 5 to 7 days after infection; and immunoglobulin G (IgG), which only emerges after around 10 days. While the first antibody class indicates an acute infection, the second usually indicates recovery from infection and a longer-lasting acquired immunity and points to an illness that is getting better or has been overcome. The test can sometimes even provide approximate information about the time of infection.

»Our test is helpful, because it also sheds light on the number of people who have already overcome the disease. After all, many people don’t even notice they’ve caught SARS-CoV-2, because they don’t develop any of the serious COVID-19 symptoms«, explains Ehricht. »Those who are in close contact with other people as part of their job, such as nurses, will be particularly keen to know whether they’ve already had the disease«, especially in light of the current assumption that the virus cannot be transmitted by someone who has fought it off.

»The successful collaboration between Ralf Ehricht’s working group at the Leibniz Institute of Photonic Technology and the industrial partner in Weimar consolidates Jena’s reputation as a location for clinical diagnostics that is characterized by the interlinking of scientific theory and practice«, states Jürgen Popp, Chair of Physical Chemistry at the University of Jena and Scientific Director of the Leibniz Institute. »Researchers from the University of Jena have been working closely with partners from hospitals and businesses for many years within the ‘InfectoGnostics’ research campus. We’re using our scientific findings to improve diagnostic tools and quickly make them available to doctors and patients as marketable products«. When it comes to the fight against the coronavirus, various working groups at the Leibniz Institute of Photonic Technology are currently taking very different approaches to quickly produce further innovations with various optical and spectroscopic methods.

How does the test work?

A drop of blood is usually enough to check for Sars-CoV-2 antibodies. The blood is dripped onto a porous surface, allowing it to get inside the test strip. The test strip contains a nucleocapsid protein (N protein), one of the characteristic markers of the virus, that is marked with gold nanoparticles. The antibodies in the patient’s blood bind to the N protein. The resulting protein complexes concentrate in a certain area of the test strip, resulting in a visible reddish line.

Text: Sebastian Hollstein