A strain of coronavirus that has affected swine for years was recently found to be contagious to humans. A new study led by the University of North Carolina at Chapel Hill reveals how human cells are susceptible to infection.
The recent paper was published in the journal Proceedings of the National Academy of Sciences. The researchers describe swine acute diarrhea syndrome coronavirus, or SADS-CoV, which may be an evolved strain of the HKU2 bat coronaviruses.
SADS-CoV, an alphacoronavirus, belongs to the same family as SARS-CoV-2, a beta coronavirus. The researchers "synthetically recovered recombinant wild-type and derivative" swine coronavirus with indicator genes.
SADS-CoV Infecting Human Cells
SADS-CoV was tested on human cells of the liver, gut, and airway, where the virus was efficiently replicated. The swine strain was observed to invade human cells not using the ACE-2 receptor protein, which has been associated with Covid-19. The team was able to treat SADS-CoV with remdesivir in the laboratory. They recommend that pigs and farm workers should "be continually monitored for indications of SADS-CoV infections to prevent outbreaks and massive economic losses."
The swine virus has affected China's pig farms since 2016. The virus can potentially cause large economic damages to the pork industry around the world.
Symptoms of SADS-CoV for pigs, especially piglets, include severe diarrhea and vomiting. This particular strain of coronavirus is also different from strains that cause the common cold in humans.
Professor Ralph Baric shared that researchers have focused largely on betacoronavirus outbreaks such as SARS and the Middle East respiratory syndrome (MERS). However, "alphacoronaviruses may prove equally prominent - if not greater - concerns to human health, given their potential to rapidly jump between species."
Thus far, there had been no reported cases of humans affected with SADS-CoV. But the current pandemic is a reminder that there are many coronavirus strains from animals that can potentially infect people as a result of a spillover.
Efficient replication of SADS-CoV in human lung and intestinal cells indicates the pathogen's potential to "negatively impact the global economy and human health," wrote the authors. In the 21st century, there had been three human and three swine coronavirus strains that suddenly became global outbreaks.
Preventing a Global Outbreak
Humans often resist infection from coronavirus strains found in animals due to cross-protective herd immunity. However, the range of human cells infected in the study shows that people do not have immunity to SADS-CoV yet.
Caitlin Edwards said, "it is impossible to predict if this virus, or a closely related HKU2 bat strain, could emerge and infect human populations." There may be a potential risk of future outbreaks in both animal and human populations
Baric shared that they are looking for partners to further investigate and develop SADS-CoV vaccine candidates for pigs. For now, early separation of infected pigs and continuous monitoring of swine farms may help prevent large outbreaks as well as spillover to human populations. Moreover, "vaccines may be key for limiting [the] global spread and human emergence events in the future."
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