Swine coronavirus shows potential to spread to humans

Research from the University of North Carolina at Chapel Hill suggests that swine acute diarrhea syndrome coronavirus (SADS-CoV) has the potential to spread to humans. The researchers report in PNAS that the virus efficiently replicated in human airway and intestinal cells.

SADS-CoV emerged from bats and has infected pigs throughout China since it was first discovered in 2016. Although it is in the same family of viruses as the betacoronavirus SARS-CoV-2, which causes the respiratory illness COVID-19 in humans, SADS-CoV is an alphacoronavirus that causes gastrointestinal illness in pigs. The virus causes severe diarrhoea and vomiting and has been especially deadly to young piglets.

SADS-COV is also distinct from two circulating common cold alphacoronaviruses in humans, HCoV-229E and HCoV-NL63.

“While many investigators focus on the emergent potential of the betacoronaviruses like SARS and MERS, actually the alphacoronaviruses may prove equally prominent — if not greater — concerns to human health, given their potential to rapidly jump between species,” said Ralph Baric, professor of epidemiology at UNC-Chapel Hill Gillings School of Global Public Health.

The Baric lab worked with Caitlin Edwards, a research specialist and master of public health student at UNC-Chapel Hill, on the study which suggests humans may be susceptible to spillover of SADS-CoV.

Edwards, the study’s first author, tested several types of cells by infecting them with a synthetic form of SADS-CoV to understand just how high the risk of cross-species contamination could be.

Evidence from the study indicates that a wide range of mammalian cells, including primary human lung and intestinal cells, are susceptible to infection. According to Edwards, SADS-CoV shows a higher rate of growth in intestinal cells found in the human gut, unlike SARS-CoV-2, which primarily infects lung cells.

Cross-protective herd immunity often prevents humans from contracting many coronaviruses found in animals. However, results from the testing done by Edwards and her team suggest that humans have not yet developed such immunity to SADS-CoV.

“SADS-CoV is derived from bat coronaviruses called HKU2, which is a heterogenous group of viruses with a worldwide distribution,” Edwards said. “It is impossible to predict if this virus, or a closely related HKU2 bat strain, could emerge and infect human populations. However, the broad host range of SADS-CoV, coupled with an ability to replicate in primary human lung and enteric cells, demonstrates potential risk for future emergence events in human and animal populations.”

The researchers found that remdesivir, a broad-spectrum antiviral that is effective against other group 1 and 2 coronaviruses, efficiently blocked SADS-CoV replication in vitro.

They also found that SADS-CoV demonstrated little, if any, replicative capacity in either immune-competent or immunodeficient mice, indicating a need for improved animal models.

The team is currently looking for partners to investigate the potential of SADS-CoV vaccine candidates to protect pigs.

Article: Edwards, C. E., Yount, B. L., Graham, R. L., Leist, S. R., Hou, Y. J., Dinnon, K. H., 3rd, Sims, A. C., Swanstrom, J., Gully, K., Scobey, T. D., Cooley, M. R., Currie, C. G., Randell, S. H., Baric, R. S. (2020). Swine acute diarrhea syndrome coronavirus replication in primary human cells reveals potential susceptibility to infection. Proceedings of the National Academy of Sciences of the United States of America, 202001046 (advance online publication), doi: 10.1073/pnas.2001046117

[SOURCE: University of North Carolina at Chapel Hill]