New study boosts hopes for a broad vaccine to combat COVID-19 variants and future coronavirus outbreaks

Among the coronavirus family, one sub-group relies on the ACE2 molecule to enter human cells. Both SARS-CoV-1 and SARS-CoV-2 belong to this group as well as a number of coronaviruses circulating in animals such as bats, pangolins and civets. While the exact route of transmission remains unknown, these viruses have the potential to jump from animals to humans and could start the next pandemic. Collectively, this group of viruses is called sarbecovirus.

"We explored the possibility of inducing pan-sarbecovirus neutralising antibodies that can block the common human ACE2-virus interaction, which will be protective not only against all known and unknown SARS-CoV-2 VOCs, but also future sarbecoviruses," said Dr Chee Wah Tan, Senior Research Fellow with Duke-NUS' Emerging Infectious Diseases (EID) Programme and co-first author of this study.

To test their hypothesis, researchers recruited eight people who recovered from SARS-CoV-1, which was responsible for the 2003 SARS epidemic, as well as ten healthy people and ten COVID-19 survivors. They then compared the immune response of the three groups before and after they were vaccinated with the SARS-CoV-2 vaccine. In particular, they wanted to understand whether the neutralising antibodies developed in SARS-Vaccinated group could wipe out both SARS-CoV-1 and SARS-CoV-2 viruses as well as other sarbecoviruses, including potentially zoonotic sarbecoviruses that have been identified in bats and pangolins.

"Prior to vaccination, SARS-CoV-1 survivors had detectable neutralising antibodies against SARS-CoV-1 but no or low-level anti-SARS-CoV-2 neutralising antibodies. After receiving two doses of the mRNA vaccine, all displayed high levels of neutralising antibodies against both SARS-CoV-1 and SARS-CoV-2," said Dr Wanni Chia, Research Fellow at the Duke-NUS EID' programme and co-first author of this study. "Most importantly, they are the only group with a broad spectrum of neutralising antibodies against ten sarbecoviruses that were chosen to be examined."

"Our study points to a novel strategy for the development of next-generation vaccines, which will not only help us control the current COVID-19 pandemic, but may also prevent or reduce the risk of future pandemics caused by related viruses," said Professor Wang Linfa from Duke-NUS EID programme, who is the senior corresponding author of this study.

"Professor Wang's team made an astute serendipitous observation in an ongoing national multicentre immune monitoring study of COVID-19 vaccination called the Singapore COVID-19 Vaccine Immune Response and Protection Study (SCOPE), which is coordinated by NCID. As emerging variants of concern have already demonstrated some degree of immune evasion against the first-generation vaccines, this discovery has the potential to address that problem as the world continues COVID-19 vaccination to exit the pandemic. In addition, this can potentially act as a highly promising preventive vaccine against future coronavirus pandemics," said Associate Professor David Lye, Director, Infectious Disease Research and Training Office, NCID and joint corresponding author of the study.

The team conducted their investigation using an improved version of the surrogate virus neutralisation test (sVNT) developed by Duke-NUS in early 2020. Prof Wang and his team invented the sVNT assay, trade named cPass^TM, which has been granted Emergency Use Authorisation by the US FDA to determine SARS-CoV-2-specific neutralising antibodies in human sera following infection or vaccination. Dr Tan and Dr Chia are part of Prof Wang's team and co-inventors of the sVNT. The improved multiplex sVNT allows simultaneous detection of neutralising antibodies against different sarbecoviruses in a single tube, thus playing a pivotal role in studies like this that require accurate side-by-side comparison of neutralising antibody levels against different viruses.

The team is currently conducting a proof-of-concept study to develop a third-generation vaccine against different coronaviruses (3GCoVax) as well as broad neutralising antibodies for therapy and is looking to recruit individuals who recovered from SARS infection in 2003.