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An over-the-counter COVID test can quickly show if you have SARS-CoV-2. But if your test result is positive, there is no similar at-home test to assess how long you can avoid reinfection. In a new study, researchers from Johns Hopkins University and the Lagan Institute in the United States report a simple, accurate glucose meter-based test method that involves a novel fusion protein. Consumers may one day be able to use the test to monitor their own levels of SARS-CoV-2 antibodies, they say. The findings were published online June 8, 2022 in the Journal of the American Chemical Society under the title "Antibody–Invertase Fusion Protein Enables Quantitative Detection of SARS-CoV-2 Antibodies Using Widely." Available Glucometers”。

A vaccine against SARS-CoV-2 and infection with the virus itself can prevent future infections for some time, but it's unclear exactly how long this protection lasts. A good indicator of immune protection is a person's level of SARS-CoV-2 antibodies, but enzyme-linked immunosorbent assay (ELISA), a gold-standard measure, requires expensive equipment and specialized technicians.

Blood glucose meters are off-the-shelf, easy to use, and can be combined with remote clinical services. Scientists have been modifying these devices to combine detection with glucose production for the detection of other target molecules. For example, if the test antibody used in this test binds to an antibody in the patient's blood, a reaction occurs to produce glucose--- which is well detected by a blood glucose meter.

Invertase is an attractive enzyme for this type of analysis because it converts sucrose to glucose, but it is difficult to chemically attach the enzyme to detection antibodies.

Based on this, Netzahualcóyotl Arroyo-Currás, Jamie B. Spangler of Johns Hopkins University and colleagues wanted to see if the production of a fusion protein consisting of invertase and detection antibodies could work so that SARS-CoV-2 antibody levels could be read with a blood glucose meter.

Through this response, the blood glucose meter can detect SARS-CoV-2 antibodies in patient samples, image from Journal of the American Chemical Society, 2022, doi:10.1021/jacs.2c02537.

The authors designed and produced a novel fusion protein containing invertase and a mouse antibody that binds to human immunoglobulin (IgG) antibodies (i.e., mouse anti-human IgG antibodies). They found that the fusion protein binds to anti-human IgG and successfully allows sucrose to produce glucose.

Next, they made test strips with the SARS-CoV-2 spike protein. When immersed in samples from COVID-19 patients, the patients' SARS-CoV-2 antibodies bind to the SARS-CoV-2 spike protein. The addition of this invertase/anti-human IgG fusion protein followed by the addition of sucrose produces glucose, which can be detected with a blood glucose meter.

They validated the test by analyzing samples from multiple patients with a blood glucose meter and found that the new assay worked as well as four different ELISAs. The method could also only be improved to test for SARS-CoV-2 variants and other infectious diseases, they said.

Article source: Biovalley