The test is designed to be interchangeable with different viral mutant proteins, allowing it to be modified to detect immunity against any existing or future variants of SARS-CoV- 2.
Currently, the gold standard approach to measuring immunity involves mixing a blood sample with a live virus and measuring how many cells in the sample are killed by the virus.
That procedure is too dangerous to perform in most laboratories, so the more commonly used approaches involve modified “pseudovirus” particles that are not infectious, or they based on a test called an ELISA (enzyme-linked immunosorbent assay), which can detect antibodies that neutralize a segment of viral protein.
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However, these approaches still require trained personnel to work in laboratories with specialized equipment, so they are impractical to use in a doctor’s office to get immediate results. .
The researchers wanted to come up with something that could easily be used by a healthcare provider or even by people at home. They were inspired by home pregnancy tests, which are based on a type of test known as a lateral flow test.
Lateral flow testing typically involves strips of paper embedded with test lines that bind to a specific target molecule if it is present in the sample. This technology is also the basis of most rapid at-home tests for COVID-19.
They then developed a device that could detect the presence of antibodies that block the SARS-CoV-2 receptor-binding region (RBD) from binding to ACE2, the human receptor that the virus uses to infect. cell infection.
Predict COVID-19 immunity in easy steps
The first step of the test is to mix a human blood sample with the viral RBD protein that has been labeled with tiny gold particles that are visible when glued to a strip of paper.
After allowing time for the antibodies in the sample to interact with the viral protein, a few drops of the sample are applied to a test strip impregnated with the two test lines.
One of these pathways attracts viral free RBD proteins, while the other attracts any RBD that has been captured by neutralizing antibodies. A strong signal from the second line indicates high levels of neutralizing antibodies in the sample. There is also a control line that detects free gold particles, confirming that the solution has flowed over the entire range.
Along with the test box containing the paper test strips, this test kit also includes a finger prick that can be used to collect a small blood sample, less than 10 microliters.
This sample is then mixed with the reagents required for the test. After about 10 minutes, the sample is exposed to the test cartridge and the results are displayed after 10 minutes.
The output can be read in two different ways: One, just look at the lines indicating whether neutralizing antibodies are present. Or, the device can be used to measure antibody levels more precisely, using a smartphone app that can measure the strength of each line and calculate the ratio between neutralizing RBD protein and infectious RBD protein. infected.
When this rate is low, it may be suggested that another booster shot is needed, or that the individual should take additional precautions to prevent infection.
The researchers now hope to work with a diagnostics company that can mass-produce the tests and get FDA approval for their use.
Source: Medindia
