New Diagnostic System Quickly and Accurately Measures Antibodies Against the COVID-19 Virus

The researchers developed a chip on which key SARS-CoV-2 is fixed. A small drop of blood from the fingertip is required and the sensitivity of the system is 500 times higher than that of the conventional method. Credit: RIKEN

A research team from the RIKEN Center for Emergent Matter Science (CEMS) in Japan has developed a diagnostic system that can quickly and sensitively measure the amount of antibodies in the blood that can protect us against SARS-CoV-2, the virus that causes COVID-19 . This achievement was published in the scientific journal Bulletin of the Chemical Society of Japan and is expected to enable efficient and accurate testing of the efficacy of SARS-CoV-2 vaccines in medical settings.

Currently, several vaccines against SARS-CoV-2 have been developed and are vaccinated worldwide. In the medical field, antibody testing is done using a technique called immunochromatography to determine if antibodies have been produced as a result of a viral infection or vaccination. However, because the results of this test are determined by looking at colored stripes on paper with the naked eye, it is not precise and not very sensitive. To make matters worse, blood samples must be sent to a third-party testing center for more accurate, quantitative results, with the turnaround taking a few days to a week.

The new research was led by Yoshihiro Ito of RIKEN CEMS, who several years ago developed a technology that immobilizes any organic compound, including substances of biological origin. Since then, Ito and his colleagues have continued to improve the system, focusing on immobilizing various allergens to measure the history of immune infections. They have already succeeded in developing a test kit with a microchip on which more than 40 different allergens are immobilized. Now they have expanded their diagnostic tools for use in a system that immobilizes several key SARS-CoV-2 proteins, allowing automatic detection of the presence of antibodies to SARS-CoV-2.

The technique is based on the use of light. A substance that reacts to light is first coated on a plastic microchip and a sample liquid containing the protein in question is dripped onto the microchip in the form of a spot. The chip is then exposed to ultraviolet light, which immobilizes the proteins. Using this method, the researchers developed a chip called a microarray onto which the main SARS-CoV-2 is fixed. When antibodies in blood serum bind to the viral proteins on the chip, they emit light and the amount of light emitted can be accurately measured with a CCD camera. Thus, this value can be used to quantify the number of antibodies in a manner not possible with immunochromatography.

“Standard quantitative analysis of antibodies usually requires half a milliliter of blood taken from one of your arms, which is a lot!” says Ito. “But in our system, all it takes is a small drop of blood from the fingertip, and the sensitivity of the system is 500 times higher than conventional immunochromatography, meaning detection is possible even if the antibody count is very low. .” In addition, the operation is quite simple: just drop human blood serum on the chip, press the start button and wait. The reaction process, washing and antibody detection are performed automatically in about 30 minutes.

“In the past, our team has been able to develop antibody detection systems for measles, rubella and chickenpox. Now we can also detect antibodies for the COVID-19 virus. This system is practical to use and enables precision testing in any medical facility, making it easier to quickly determine whether or not vaccination is required on site. It can also be used to conduct epidemiological research in preparation for future pandemics,” said Ito.

Reference: “SARS-CoV-2 proteins microarray by photoimmobilization for serodiagnosis of the antibodies” by Hiroharu Kashiwagi, Nobuhiro Morishima, Sei Obuse, Takashi Isoshima, Jun Akimoto, and Yoshihiro Ito, September 3, 2021, Bulletin of the Chemical Society of Japan.
DOI: 10.1246/bcsj.20210215