The SARS-CoV-2 surrogate virus neutralisation test (sVNT) was the fruit of collaborative efforts among Duke-NUS Medical School, NCID, A*STAR IMCB and GenScript Biotech. Its high specificity and sensitivity, and short time period needed to obtain results could make it a preferred alternative to current detection methods.
The global outbreak of COVID-19 has demonstrated the pressing need for a competent and potent method of infection and antibody detection. A research team in Singapore has developed a novel test, named the SARS-CoV-2 surrogate virus neutralisation test (sVNT) to complement the COVID-19 studies in ascertaining the infection rate, herd immunity, predicted humoral protection and vaccine effectiveness in clinical trials, which could be the answer to this need.
The sVNT was the result of a collaboration among researchers and medical professionals from Duke-NUS Medical School, National Centre for Infectious Diseases (NCID), Agency for Science, technology and Research (A*STAR)’s Institute for Molecular and Cell Biology (IMCB) Singapore and GenScript Biotech. The validity and effectiveness of the sVNT testing kit was evaluated with 375 samples from Singapore and 250 from China, in which it showed 99 to 100 percent specificity and 95 to 100 percent sensitivity. The sVNT also yields results in a very short time of under an hour.
sVNT is able to detect functional neutralising antibodies (Nabs), thus preventing the binding between the spike proteins of coronavirus and the angiotensin-converting enzyme 2 (ACE2) host receptor. This spike protein and ACE2 host receptor interaction simulated the actual virus-host interaction of SARS-CoV-2 in humans.
Professor Wang Linfa, Director of Duke-NUS’ Emerging Infectious Diseases programme is one of the most renowned specialists on emerging zoonotic viruses and serves on multiple COVID-19 committees in WHO shared that, “The sVNT kit can detect functional NAbs in an hour and differentiate them with binding antibodies (BAbs), without the need for live virus or a biocontainment facility. It also has the ability to detect total receptor binding domain (RBD)-targeting neutralising antibodies in patient samples, in contrast to most SARS-CoV-2 antibody tests published or marketed, which are isotype-specific. This makes the sVNT accessible to the broader community for both research and clinical applications.”
The presence of NAbs, which disrupt the interaction between RBD and ACE2 in the blood sample of a person forms the basis of diagnosis of prior infection or immunity to the SARS-CoV-2 virus. Given the exigent circumstances of the global COVID-19 pandemic, there is a pressing need for powerful and accurate serological tests for NAb detection. This will allow health authorities and governments to precisely evaluate the pervasiveness of the infection and the protective immunity in the community, both at the individual and population levels.
Currently, only the conventional virus neutralisation test (cVNT) and the pseudovirus-based virus neutralisation test (pVNT) are used for the detection of NAbs. However, in both tests, the handling of live viruses and cells demands specific competency and at least several days to obtain results. Alternatives like the enzyme-linked immunosorbent assay (ELISA) are available, but the ELISA is unable to distinguish Binding Antibodies (Babs) from NAbs. The sVNT, in contrast, can detect the NAbs accurately even in different species of animals. The sVNT can therefore help to shed light on the role of different relay animals as intermediate hosts in the transmission of COVID-19.
“It is an increasingly critical clinical question about what proportion of patients with COVID-19 develop antibodies to COVID-19, how long it lasts, and whether antibodies protect patients from reinfection. Neutralising antibody is the gold-standard serological platform to determine this. Unfortunately, the conventional virus neutralisation assay is laborious, time-consuming and requires Biosafety Level 3 for COVID-19. The sVNT developed by Prof Wang, in collaboration with the national COVID-19 PROTECT study, makes it accessible to all hospital laboratories, and is a great advance in COVID-19 serological assays,” remarked Associate Professor David Lye who is also the Director of Infectious Disease Research and Training Office (IDRTO), and Senior Consultant at NCID.
During the 2003 SARS outbreak, researchers in Singapore had first-hand experience of the SARS virus and learnt a great deal about it. The similarity between SARS and SARS-CoV-2 and the sharing of knowledge and expertise between A*STAR and Duke-NUS from prior studies on the SARS virus aided the development and testing of the novel sVNT, which could be an indispensable tool in the combat against COVID-19.
Mr David Martz, the Vice President of New Product Management, Life Sciences Group at GenScript said, “We are very pleased that Prof Wang’s work has come to fruition. This is great news for scientists researching herd immunity and vaccine efficacy as they will now have access to this innovative research tool to accurately determine the level of neutralising antibodies in a population. We believe the test will shed new light on the current plaguing mysteries of COVID-19.”
The sVNT is under the commercial management of GenScript and distributed globally under the cPass™ brand for scientific research purposes only. The sVNT has also been registered with the Emergency Use Authorisation and the U.S. Food and Drug Administration is pending this registration. Further applications of this sVNT test kit extends into vaccine development and therapeutics.