Duke-NUS has come up with a serology test (sVNT kit) called cPass™, which is capable of rapidly mass-detecting virus-neutralising antibodies in Covid-19 patients within one hour. They will be co-developing and manufacturing the kit along with global biotech group GenScript Biotech and Agency for Science, Technology and Research's Diagnostics Development Hub (DxD Hub).

Modelled after the 'gold standard' of serological tests, the test ensures no false positives, does not require the collection of live viruses or cells, and can test for Covid-19 in animals too.

The cost of the test kit has not been revealed.

What will the test be used for?

The test will not replace the PCR test kits, which uses nasal swabs to detect the presence of the virus in suspected Covid-19 cases.

However, cPass can be used to determine if a Covid-19 survivor has generated good immunity, through the detection of neutralising antibodies, against the virus.

The data can then be used to determine who can go back to work or to enjoy social life more safely. This would be the most practical way to determine the level of “herd immunity”.

“The cPass™ developed by our team can be used for contact tracing, reservoir or intermediate animal tracking, assessment of herd immunity, longevity of protective immunity and efficacy of different vaccine candidates,” said Professor Wang Linfa, the principal investigator of this collaboration and one of the most internationally recognised experts on COVID-19.

When/if a vaccine is available for Covid-19, the test can determine the effectiveness of the vaccine within a large community.

The test is also useful to test if an animal had been infected and developed immunity to the Covid-19 virus. Thus, cPass can test for the reservoir and intermediate animal hosts of Covid-19. To date, Covid-19 has been observed to be transmitted from humans to dogs, cats, tigers and minks.

A new form of Covid-19 therapy is to use the antibodies produced by virus survivors to treat seriously ill patients who require these antibodies to combat the virus. However, people have differing levels of immunity, and some survivors may not produce enough neutralising antibodies for donation. cPass can test if the levels of neutralising antibodies are sufficient for donation.

When will it be available?

As the kit has recently received provisional authorisation by the Health Sciences Authority, Dr Sidney Yee of DxD Hub said that production of the test will be ramped up and is currently available for clinical use in Singapore hospitals.

There are plans for this know-how to be transferred to local biotech companies for scaled-up production.

How does the test work?

cPass mimics the virus neutralisation process that happens naturally in our bodies as our immune system fights the Covid-19 virus, with the help of two engineered proteins. Our bodies would produce neutralising antibodies(NAbs) to stop the virus from entering and infecting our cells.

Generally, it takes 1 to 3 weeks after someone becomes infected with SARS-CoV-2 for their body to make antibodies; some people may take longer to develop antibodies.

A 1-millilitre blood sample will be required from a test subject. When there are neutralising antibodies(NAbs) detected in the patient's blood serum, the neutralisation process will occur and a colour change will occur.

Traditional serological tests require the use of live viruses, live cells, a biosafety containment facility to prevent infection of skilled lab technicians and up to four days to test for antibodies.

But with cPass, no live viruses or cells are required, it can be done in a regular lab, and testing time is reduced to a mere one hour, which dramatically cuts the cost of serological testing.

The test has also been validated with two COVID-19 patient cohorts in Singapore and China, achieving 100% specificity and 95-100% sensitivity.

Aiding the international community

Dr Zhu Li, the Chief Strategy Officer of GenScript said that cPass is immediately accessible to aid the global community, particularly developing nations, as the test does not require a biosafety containment facility.

He added that more than 1000 test kits can be produced within a week, and countries such as China and the U.S. would most likely have high demand for this test kit.

In addition, neighbouring countries such as Thailand, Malaysia, Philippines, Cambodia and Vietnam have also expressed interest in cPass, said Prof Wang.

"The test results will be of great help to governments in guiding the resumption of work since it is extremely useful for quick and reliable surveillance to determine how widely a population has gained immunity to SARS-CoV-2 virus.

Detection of neutralising antibodies determines who can more safely go back to work or to more social life. Our partnership with Duke-NUS and DxD Hub is one of several proactive steps we are taking to strengthen our R&D and manufacturing capacity to meet this urgent global need,” added Dr Zhu Li.

Top photo from GenScript.