COVID-19 (SARS-CoV-2) has affected the daily lives of everyone around the world. To gain a better understanding of this virus and combat the pandemic, we need to be able to reliably identify who has been infected. When someone is infected by COVID-19, their immune system eventually produces antibodies, which recognize and bind to the virus to fight it. As a result, antibody tests can detect whether someone was infected with SARS-CoV-2. However, the fast and cheap antibody tests available cannot accurately measure the number of antibodies in a sample and only provide a positive or negative result. There are some quantitative antibody tests, but they require lab personnel, take a long time, and can be expensive. To address this issue, Riccardo Funari at the Okinawa Institute of Science and Technology Graduate University recently developed a fast, cheap, and quantitative test using light that has been shown to accurately measure antibodies in artificial human plasma. 

This antibody test is performed by delivering a blood plasma sample to a small chip coated with tiny gold spikes. Attached to these gold spikes are a part of the SARS-CoV-2 spike protein, a component that helps the virus find and infect human cells. Antibodies against SARS-CoV-2 in the plasma sample then recognize this spike protein and bind to it, which changes how the gold spike area reacts to light. When light is directed onto the chip over the gold area, the researchers can read the “color” of the light (measured by its wavelength) that comes from the area (Fig. 1). The researchers then compare this wavelength to what the wavelength would be with no antibodies present and determine the difference (or shift). As more antibodies bind to the spike protein attached to the gold spikes, the wavelength shifts more and more. By measuring the amount of shift, this test can quantitatively estimate the number of antibodies in a person’s plasma.

Because this antibody test can accurately measure the number of SARS-CoV-2 antibodies present, doctors and researchers can use this test to better understand how the immune system of an actual or vaccine trial patient is reacting to the virus, if at all. In addition, because this test is fast, cheap, and doesn’t have to be carried out by lab personnel, it can be employed more widely than previous quantitative tests. In particular, it could potentially be used on a global scale to provide information on how many people have been infected and how long they have immunity. So far, the researchers have only evaluated this test on artificial human plasma with SARS-CoV-2 antibodies from rabbits, but after further optimization and evaluations on real samples, this antibody test could become a widely used technology in the battle against COVID-19.