Know the Bodys Ability to Fight COVID-19 With New Test

That procedure is too hazardous to perform in most labs, so the more commonly used approaches involve non-infectious modified “pseudo viral” particles, or they are based on a test called ELISA (enzyme-linked immunosorbent assay), which can detect antibodies that neutralize a fragment of a viral protein.

Researchers wanted to come up with something that could be easily used by a health care provider or even by people at home. They drew inspiration from at-home pregnancy tests, which are based on a type of test called a lateral flow assay.

Lateral flow assays generally consist of paper strips embedded with test lines that bind to a particular target molecule if it is present in a sample. This technology is also the basis of most at-home rapid tests for COVID-19.

Later, they developed a device that can detect the presence of antibodies that block the SARS-CoV-2 receptor binding domain (RBD) from binding to ACE2, the human receptor that the virus uses to infect cells.

Predicting COVID-19 Immunity in Easy Steps

The first step in the test is to mix human blood samples with viral RBD protein that has been labeled with tiny gold particles that can be visualized when bound to a paper strip.

After allowing time for antibodies in the sample to interact with the viral protein, a few drops of the sample are placed on a test strip embedded with two test lines.

One of these lines attracts free viral RBD proteins, while the other attracts any RBD that has been captured by neutralizing antibodies. A strong signal from the second line indicates a high level of neutralizing antibodies in the sample. There is also a control line that detects free gold particles, confirming that the solution flowed across the entire strip.

Along with a testing cartridge, which contains the paper test strip, the testing kit also includes a finger prick lancet that can be used to obtain a small blood sample, less than 10 microliters.

This sample is then mixed with the reagents needed for the test. After about 10 minutes, the sample is exposed to the test cartridge, and the results are revealed in 10 minutes.

The output can be read in two different ways: One, by simply looking at the lines, which indicate whether neutralizing antibodies are present or not. Or, the device can be used to obtain a more precise measurement of antibody levels, using a smartphone app that can measure the intensity of each line and calculate the ratio of neutralized RBD protein to infectious RBD protein.

When this ratio is low, it might suggest that another booster shot is needed, or that the individual should take extra precautions to prevent infection.

Researchers now hope to partner with a diagnostics company that could manufacture large quantities of the tests and obtain FDA approval for their use.

Source: Medindia