Covid-19 tests can determine whether a person is infected with SARS-CoV-2, but cannot assess how long a person who has tested positive for the new coronavirus is protected from reinfection. A team of researchers recently reported a simple, accurate glucose meter-based test incorporating a novel fusion protein. The researchers have detailed in a new study that consumers could one day use this test to check their own SARS-CoV-2 antibody levels. The study entitled “Antibody-Invertase Fusion Protein Enables Quantitative Detection of SARS-CoV-2 Antibodies Using Widely Available Glucometers” was recently published in the Journal of the American Chemical Society†
Antibodies are a good indication of protection against SARS-CoV-2
Although vaccines against SARS-CoV-2 and infection with the virus may protect against future infections for a while, the exact duration of protection is not known. A person’s level of SARS-CoV-2 is a good indication of immune protection. The enzyme-linked immunosorbent assay (ELISA) is the gold standard measurement, but requires expensive equipment and specialized technicians.
Meanwhile, glucose meters are readily available, easy to use and integrate with remote clinical services. According to the statement, researchers have modified glucose meters to detect other target molecules so that they can perform the dual action of detection and glucose production.
How does the glucose meter work?
For example, if a detection antibody in the test binds to an antibody in a patient’s blood, a reaction occurs that produces glucose. This is something that the device detects very well.
Although invertase is an attractive enzyme for this type of analysis because it converts sucrose to glucose, it is difficult to attach the enzyme to detection antibodies by chemical approaches.
So researchers at the American Chemical Society set out to see whether producing a fusion protein consisting of both invertase and a detection antibody would work in a test that could read SARS-CoV-2 antibody levels with a glucose meter.
According to the study, the scientists designed and produced a new fusion protein that contains both invertase and a mouse antibody that binds to human immunoglobulin (IgG) antibodies. They found that the fusion protein bound to human IgGs and successfully produced glucose from sucrose.
The researchers then made test strips with the SARS-CoV-2 spike protein on them. When the strips were immersed in Covid-19 patient samples, the patients’ SARS-CoV-2 antibodies bound to the spike protein.
Since the invertase/IgG fusion protein and sucrose were added to the strips, this led to the production of glucose. This could be detected by the glucose meter. The scientists validated the test by performing the analysis with glucose meters on different patient samples. They found that the new test worked, along with four different ELISAs. According to the researchers, the method could also be adapted to test for SARS-CoV-2 variants and other infectious diseases.
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