- A novel coronavirus antibody test kit can provide faster results than existing ones, and it can measure the strength of the immune response to COVID-19 or coronavirus vaccination.
- The cPass test looks for neutralizing antibodies, which are the proteins that can bind to the spike protein of SARS-CoV-2 and render it useless. The virus won’t be able to infect cells and multiply inside them.
- The test is already undergoing review with the US Food and Drug Administration and has been approved for use in the European Union and Singapore.
How long does COVID-19 immunity last once you survive the illness or receive a vaccine? That’s the critical answer the world needs to better handle the ongoing novel coronavirus pandemic. What we know so far is that the immune system can repel the virus and that reinfection is unlikely in the first weeks and months following the primary infection. Researchers think the immunity to the novel coronavirus can’t be better than the resistance to the other human coronaviruses that cause common colds. If accurate, that means we might get COVID-19 again after up to a year after the first bout. Also, if immunity is short-lived, then we’ll need to be vaccinated regularly to keep staying protected.
Recent research also showed that the antibodies might disappear from the blood within two to three months of infection. We’d still be protected, as the immune response is more complicated than that. White blood cells, called T cells, would be able to engage the virus and help produce new antibodies in the future. But if tests can’t detect antibodies after three months, officials looking to track the disease and measure herd immunity will not get accurate results from current tests. This is where a breakthrough coronavirus test comes into play, as it’s been specifically designed to return quick results on a certain type of antibody that actually measures the strength of your immune response to COVID-19.
Neutralizing antibodies are proteins that can bind to the spike protein of the coronavirus, the protein that makes up its corona, or crown. As a result, the virus can’t connect to ACE2 receptors on human cells, and can’t enter them. Without this step, the virus can replicate, and it’s essentially neutralized from doing any harm. That’s why vaccine makers are looking to induce neutralizing antibodies with their experimental drugs. And why monoclonal antibodies are drugs based on neutralizing antibodies that can block the virus. Similarly, plasma therapies rely on the transfer of neutralizing antibodies from a COVID-19 survivor to a patient with a weaker immune response.
Researchers from GenScript Biotech came up with an assay that doesn’t look for antibodies in general, as it happens with the other antibody tests in use out there. Instead, the tries to detect only the neutralizing antibodies in a patient’s bloodstream. This test is much faster than traditional antibody tests, providing answers in as little as an hour compared to a few days. And the result doesn’t require the use of live virus and biosafety containment for the tests.
The company published a study in Nature that explains how the test works. Called cPass, the test was used in two cohorts of patients in Singapore and China measuring 375 and 250 subjects, respectively. The study compared traditional cell- and virus-based detection test (cVNT) with the new surrogate virus neutralization test (sVNT) and found that the latter (the cPass test) detected neutralizing antibodies from patients with 95%-100% sensitivity and 99.93% specificity.
The researchers also proved that even if patients had a low level of IgG and IgM antibodies, the cPass test still detected a significant level of neutralizing activity. If confirmed by future testing, this could be a massive deal for antibody testing. cPass assays could be used to see whether a COVID-19 is developing neutralizing antibodies, and could be used to measure the immunity of a community after an outbreak or after a vaccination campaign.
“As long as you have a small amount of neutralizing antibody, the patient may still be immune to the virus,” GenScript’s Eric Wang told Forbes.
The scientist explains the cPass uses a different testing principle. “We don’t detect the antibody itself, but instead, we check the blood for anything which blocks the binding of the virus [spike protein] to the hACE2 receptor on human cells,” Wang said. “It’s a functional assay that specifically looks for the neutralizing antibody.”
The announcement also says that results from two SARS serum panels showed that neutralizing antibodies were detectable 17 years after the initial infection, which is promising news. That’s not to say the SARS-CoV-2 neutralizing antibodies will last as long, but the cPass test works on other pathogens.
The cPass SARS-CoV-2 Neutralization Antibody Detection Kit is under review for Emergency Use Authorization (EUA) with the US Food and Drug Administration (FDA), the company said. The test kit is already allowed for use in the European Union and obtained provisional authorization in Singapore.