March 15, 2016
A study led by researchers at the University of North Carolina at Chapel Hill found that a SARS-like virus known as WIV1-CoV, which is found in horseshoe bats, could bind to the same receptors as SARS-CoV and replicate in human cells without the need for adaptation. Thought to be a critical barrier, the results indicate that bat populations maintain SARS-like viruses poised to reemerge in humans.
The study, titled “SARS-like WIV1-CoV poised for human emergence,” was published in the latest issue of the Proceedings of the National Academy of Science (PNAS). The study’s primary investigator is Ralph Baric, PhD, professor of epidemiology at UNC’s Gillings School of Global Public Health.
“This study goes beyond sequence analysis, which clearly has its limits,” Baric said. “We focused on SARS-like corona viruses isolated from Chinese horseshoe bats, where SARS originated. One that we identified, WIV1-CoV, was a very likely candidate for transmission to humans.”
The research team worked with both full length and chimeric versions of WIV1-CoV. The virus readily and efficiently replicated in cultured human airway tissues, suggesting and ability to potentially jump directly to humans.
The research team also found that monoclonal antibodies developed to treat SARS were effective in both human and animal tissue sample against WIV1-CoV. However, existing vaccines against SARS would not provide protection for this new virus.
SARS (Severe Acute Respiratory Syndrome) was first seen in an outbreak in 2002 and resulted in 8000 cases and nearly 800 deaths. Spread through airborne contact, its onset presents symptoms similar to the flu with a dry cough but can accelerate rapidly to pneumonia, filling the lungs with fluid and putting extreme stress on the body’s immune system. According to the Centers for Disease Control and Prevention (CDC) SARS’ mortality rate can range from less than one percent in patients below age 24 years to more than 50 percent in patients aged 60 and older. The researchers involved with the UNC-led study theorized that WIV1-CoV has the potential to induce similar results with proper adaptation to humans.
“There is a subset of coronaviruses currently circulating in bats have the ability to bind and enter human cells,” said Vineet Menachery, PhD, a post-doctoral fellow in the Baric Lab at UNC Gillings who is also the study’s first author. “Instead of being the result of a rare mutation, the capacity of this group of viruses to jump into humans is greater than we originally thought.” While other adaptations may be required to produce an epidemic, several viral strains circulating in bat populations have already overcome the barrier of replication in human cells and suggest reemergence as a distinct possibility.
Baric and Menachery say other researchers can build on their findings with other viral families and that studies with full length and chimeric versions SARS-like viruses are the key to developing better therapeutics including both vaccine and antibody approaches.
“This type of work generates information about novel viruses circulating in animal populations and develops resources to help define the threat these pathogens may pose to human populations,” Baric said. “It’s important to note that it’s not an approach that’s limited to SARS or SARS-like viruses. It can be applied to other emerging pathogens to helping us prepare for the next emergent virus, whether it be MERS, the Zika virus or something we haven’t even heard of yet.”