A Yale study found that two bat coronaviruses related to SARS-CoV-2, discovered in Laos, might not spread well in people despite their genetic similarities to the COVID-19 virus. Published in Nature Microbiology, the study helps explain why some viruses have more pandemic potential than others and how to identify these threats early.
For a virus to cause a pandemic, it must spread between people, enter human cells, evade immune defenses, and cause illness. SARS-CoV-2 can do all this, but its efficiency must be fully understood.
Mario Peña-Hernández, lead author of the Yale study, said that bat coronaviruses are 97% identical to SARS-CoV-2 but don’t spread or cause diseases like SARS-CoV-2.
These bat viruses can enter human cells and evade immune defenses better than SARS-CoV-2 but spread poorly between hamsters and cause milder disease in mice. The study shows that genetic similarity alone doesn’t predict a virus’s pandemic potential.
The study’s authors included Akiko Iwasaki and Craig Wilen from Yale. Using high-level biosafety precautions, they tested two bat coronaviruses on lab-cultured human respiratory cells and rodents. They found that the bat viruses could infect cells from the human bronchus but didn’t replicate well in cells from the nose.
The body has two immune defenses: innate immunity, a general first line of defense, and adaptive immunity, which develops over time. Innate immunity is crucial for fighting new viruses. The study found that two bat coronaviruses could evade some innate immunity molecules but didn’t spread between animals.
SARS-CoV-2 can evade innate immunity and spread, suggesting these bat viruses lack something SARS-CoV-2 has. The missing part is a “furin cleavage site,” a molecular feature that efficiently helps SARS-CoV-2 enter human cells. Without this site, SARS-CoV-2 and the bat viruses didn’t replicate well in nasal cells and were less effective at spreading.
Researchers suggest that a “furin cleavage site” in viruses might be a key feature to watch for in identifying potential threats. Other viral traits could also affect transmission and disease, so studying these viruses in the lab is crucial.
The two bat coronaviruses studied pose a lower threat to humans but could become more dangerous with small genetic changes. If these viruses did infect humans, existing vaccines and immunity against SARS-CoV-2 would likely offer protection. Understanding which viruses can spread between humans helps prepare for future threats, allowing for early vaccine development and other strategies.
Journal reference :
- Peña-Hernández, M.A., Alfajaro, M.M., Filler, R.B. et al. SARS-CoV-2-related bat viruses evade human intrinsic immunity but lack efficient transmission capacity. Nature Microbiology. DOI: 10.1038/s41564-024-01765-z.