Could glucose meters be used to assess immunity against COVID-19?

Could glucose meters be used to assess immunity against COVID-19? ...

Using widely-available glucose meters, scientists at Johns Hopkins University have developed a novel rapid assay that can detect SARS-CoV-2 antibodies. This novel glucose meter-based antibody assay is more easy to use and less costly than the current gold-standard tests.

According to one of the authors, Dr. Jamie Spangler, a professor at Johns Hopkins University, is looking at an innovative approach to democratizing the availability of immune protection information by employing commercial glucometers to quantitatively measure levels of disease-targeted antibodies.

While there are notable obstacles to the development of fieldable glucometers, research such as these highlight a possibility future where home diagnostic is as cheap and precise as glucose detection. At this point, we will have a transformation in global surveillance and personal disease detection.

The study appears in the Journal of the American Chemical Society.

Quantifying antibody levels

COVID-19 diagnostic tests confirm the presence of viral genetic material or proteins. Comparatively, assays measuring antibodies against SARS-CoV-2 may assist in evaluating previous exposure to the virus.

IgG antibodies are the predominant type of antibodies present in the blood. IgG antibodies play a vital role in establishing an immune response against bacteria and viruses, including SARS-CoV-2.

Notably, these IgG antibodies persist for months following a SARS-CoV-2 infection or after receiving a COVID-19 vaccination.

The IgG antibodies levels are indicative of the degree of protection against a symptomatic SARS-CoV-2 infection. So, assessing antibodies levels in the population can help determine how long immunity against COVID-19 persists following vaccination or a previous infection.

The development of new SARS-CoV-2 variants has also triggered worries about lowering immunity, implying that measures should be taken to ensure immunity levels in the population. Determining antibody levels against SARS-CoV-2 might thus help guide policy decisions.

Enzyme-linked immunosorbent assays (ELISAs) are the gold standard for measuring antibody levels. However, accurately quantifying antibody levels using ELISAs requires blood samples to be shipped to specialized laboratories because to the necessity for costly detection equipment. These assays are often labor-intensive, and require skilled technicians.

Although rapid ELISA testing have been developed for clinic use, these tests only provide qualitative information and remain costly. There is therefore a need for cost-effective and broadly accessible alternatives to ELISAs that may be used by clinicians or the general public.

How glucose meters help

Scientists have developed tests that are compatible with glucose meters. Using commercially available glucose meters for antibody detection can reduce the cost of detection and the need for skilled technicians.

These tests involve antibodies or other detection molecules coupled with the enzyme invertase which breaks down sucrose or sugar into glucose. The antibodies coupled with invertase bind to the protein of interest in a sample and produce glucose when a sucrose solution is introduced. The amount of glucose produced is proportional to the amount of interest protein and may be detected by a glucose meter.

However, it has proved difficult to combine antibodies with invertase. In some studies, scientists have indirectly coupled invertase with antibodies with the help of intermediate compounds such as nanoparticles. However, such an approach may result in variation in the amount of coupling and results.

Researchers at Johns Hopkins University have developed a novel assay involving antibodies that are directly linked with two invertase molecules. These experiments were then used in laboratory cultured cells to express these antibodies that were fused with invertase molecules.

The invertase enzyme''s genetic fusion ensures that a consistent number of invertase molecules are attached to the antibody. These antibodies coupled with invertase are capable of binding to all human IgG antibodies.

The novel assay employs a plastic strip with the SARS-CoV-2 spike protein. Upon incubation of the strip with blood samples from individuals with a history of COVID-19, the SARS-CoV-2-specific antibodies selectively lie to the spike proteins coating the strip''s surface.

The strip is then repurposed to a sucrose solution with antibodies from the antibody-invertase fusion protein.

The SARS-CoV-2-specific IgG antibodies linked to the spike protein on the strip can then be detected by the antibody-invertase fusion protein. The invertase enzyme breaks down sucrose into glucose, which can be detected using a glucose meter. The assay produces glucose in comparison to the SARS-CoV-2-specific IgG antibodies found in the blood sample.

In the present study, researchers found that the glucose meter-based antibody-invertase protein assay could correctly detect IgG antibodies against SARS-CoV-2, and its effectiveness was comparable to commercially available ELISAs.

Potential for other diseases

All IgG antibodies produced by the human body are recognized by the antibody-invertase fusion protein, making this assay flexible.

The immediate goal of this technology is to expand manufacturing so that wide deployments may be limited. According to Dr. Spangler, we hope to utilize emerging evidence from this platform to help improve disease protection and antibody levels across a wide spectrum of subjects.

By coating the strip with a protein other than the wild-type SARS-CoV-2 spike protein, a strip may be used to measure antibody levels against the mutant.

We believe that the testing we have developed might be used to detect antibodies against future variants of the SARS-CoV-2 virus, as well as other infectious diseases. This assay may also be used to detect antibodies in the context of other conditions, such as cancer, autoimmune disorders, allergy, or transplantation. Dr. Jamie Spangler

This technology may provide valuable scientific insights and assist in making decision on treatment plans and public health practices. Additional, the versatility of this platform allows it to be readily adapted to meet specific needs beyond infection, according to Dr. Spangler.

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