Adaptive glycemic monitor may reveal SARS-CoV-2 antibody

This reaction allows the glucose meter to detect the SARS-CoV-2 antibody in the patient sample. (Ab = antibody; Inv = invertase).Credits: Quoted from Journal of the American Chemical Society 2022, DOI: 10.1021 / jacs.2c02537

If you were vaccinated against SARS-CoV-2 in late 2020 or early 2021, you may not have any antibodies left to fight the virus, especially given the variants that emerged after that. But if you were infected with SARS-CoV-2 4 months ago (even with vaccines and booster immunity), are you protected from reinfection?

Despite the enormous amount of research and development done on COVID-19 at this time, the answer to that question is still unknown. Researchers have been unable to identify variables that contribute to the longevity of immune protection, or their lack. The latest data suggests that the factors may be highly individualized and may further complicate the problem.

At the population-wide level, this data is important because it helps to deepen the epidemiological understanding of COVID-19 and to develop public health and vaccination recommendations, both short-term and long-term. However, there is no home-based testing of SARS-CoV-2 antibodies, and the gold standard enzyme-linked immunosorbent assay (ELISA) requires expensive equipment and specialized technicians.

Researchers at Johns Hopkins University have developed innovative solutions using common devices with a new twist. This is a simple glucose meter-based test that incorporates a new fusion protein that consumers say can one day be used to monitor their SARS-CoV-2 antibody levels.

For years, scientists have adapted glucos meters to detect other target molecules, linking detection with glucose production. For example, when the detection antibody in the test binds to an antibody in the patient’s blood, a reaction that produces glucose occurs. This is what the device detects very well. On paper, invertase is the best enzyme for this type of analysis because it converts sucrose to glucose, but scientists have problems with it. When they try to bind invertase to the detection molecule using a chemical approach, the enzyme becomes inefficient and inconsistent.

Therefore, lead author Elissa Leonard and her team designed and manufactured a new fusion protein containing both invertase and mouse antibodies that bind to human immunoglobulin (IgG) antibodies. In their dissertation Journal of the American Chemical SocietyThe team showed that the fusion protein successfully bound to human IgG and produced glucose from sucrose.

To demonstrate the diagnostic potential of the protein, researchers devised a test strip with the SARS-CoV-2 spike protein attached. When immersed in a COVID-19 sample, the patient’s SARS-CoV-2 antibody bound to the peplomer. The addition of sucrose following the invertase / IgG fusion protein produced glucose, which was easily detected by the meter. The team validated the test by performing an analysis using a glucose meter on a variety of patient samples and found that the new assay was performed as well as four different ELISAs.

“This study represents one of the first examples of a full-length antibody being genetically fused to an enzyme for detection purposes,” the researchers wrote in the paper. However, the system links the enzyme to immunoglobulin M (IgM). Immunoglobulin M (IgM) has a naturally lower affinity than IgG and is more difficult to produce.

Researchers test their simple blood glucose meter-based method for SARS-CoV-2 variants and other infectious diseases, as well as other antigens, including those associated with cancer diagnosis and autoimmune diseases. Say you can adapt for.

On the other hand, the low technical requirements and low manufacturing costs of the new system mean that more people can test for antibodies than ever before, including those who do not have access to medical facilities with advanced testing capabilities.

“We also enhance continuous testing and combine the number and variety of people tested to provide the high-quality data needed to clearly and in detail understand the lifespan of immune protection from vaccination and natural infections. We provide it as protection against new concerns, “concludes the authors of the study.

The Massachusetts-based team said further efforts in device development will focus on simplifying detection schemes so that fusion proteins and other reagents can be integrated into a portable, user-friendly, point-of-the-point detection platform. increase.