Premas Life Sciences partners with GenScript to launch a new antibody detection kit in India: What is this kit and how does it work
The test has got research-use authorisation and can detect the presence of neutralizing antibodies, which stop the spike protein of SARS-CoV-2 from binding to ACE2 receptors, in the blood or serum of a person.
Recently, an Okhla-based company Premas Life Sciences partnered with the American science research company Genscript to distribute a rapid SARS-CoV-2 surrogate virus neutralisation test (sVNT) kit called cPass in India.
The test was developed in collaboration by researchers at Genscript, Duke-NUS Medical School in Singapore and Diagnostics Development Hub (DxD) at Singapore’s Agency for Science, Technology and Research (A*STAR). It has got research-use authorisation and can detect the presence of neutralizing antibodies, which stop the spike protein of SARS-CoV-2 from binding to ACE2 receptors, in the blood or serum of a person.
The test does not need the level of biosafety that is required for live virus assays. It can differentiate between binding antibodies and neutralising antibodies and unlike other antibody tests that only look for IgG or IgM or a specific type of antibody, cPass can identify all antibody isotypes in a sample, theoretically making it a better test.
Neutralising antibodies are those antibodies that help eliminate the virus or pathogen from the body. Binding antibodies, on the other hand, may bind with the pathogen but may not neutralise it.
ELISA (enzyme-linked immunosorbent assay) is a serological test that is used to detect the presence of an antigen (disease-causing substance) or antibody in a given sample. This test can identify antibodies but it does not differentiate between binding and neutralizing antibodies. The cPass test uses an ELISA format to detect neutralising antibodies.
To detect antibodies through this test, a microtiter plate (a small plate with a lot of wells) is lined with ACE2. Then, the receptor-binding domain (RBD) of the spike protein of SARS-CoV-2 conjugated with an enzyme called horseradish peroxidase is added to the wells along with the sera (a yellowish liquid that remains after blood clots) of the patient. If the patient has neutralising antibodies against the RBD of the virus, it will compete with and prevent the binding of RBD with ACE2. The reaction is allowed to occur for a while, and all the unbound antibodies and RBDs are washed out of the plate. The binding can then be visualised by adding the substrate of the enzyme horseradish peroxidase. When the enzyme binds to its substrate, it produces a yellow shade. If a strong colour appears, it means less neutralising antibodies were present in the sera and vice versa.
The research proofs
Conventional research virus neutralising test and pseudovirus-based neutralization test need live virus, highly skilled technicians and a high safety level lab. Since cPass only uses the receptor-binding domain of the virus and ACE2 protein, it is much safer and does not need as much skill to use.
The test has been validated by researchers in Singapore and China in a group of 375 and 250 patients respectively. It has a 99-100 percent specificity and is 95-100 percent sensitive. Specificity refers to the ability of a test to correctly identify true negatives and sensitivity refers to a test’s ability to identify true positives accurately.
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