New coronavirus as adept at infecting human lung cells as common cold virus: study
TORONTO — A study has shown that the new coronavirus is adept at infecting the cells of the airways of the human lung and can do it as well as a virus that is one of the causes of the common cold.
A senior author of the research says the findings suggest this new virus is already well-adapted to being a human pathogen.
They compared the new EMC virus with the virus that caused SARS and one called 229E that causes colds in people.
All three are members of the coronavirus family.
The cells were as susceptible to the EMC virus as to the other two and in fact, the new virus multiplied at a faster rate than the SARS virus did in the human cells.
The study was published Tuesday in the journal mBio.
Thiel is with the Institute of Immunobiology is at the Kantonal Hospital in St. Gallen, Switzerland. He also teaches at the University of Zurich. Other scientists on this project are with the University of Bonn Medical Centre, the Helmholtz Center for Infection Research in Braunschweig, Germany and Erasmus Medical Centre in Rotterdam, the Netherlands.
Thiel says the team was not surprised that the new virus could infect the airway cells — called epithelial cells — because it has already infected people. To date there have been 12 confirmed infections, and more cases that the World Health Organization considers probable infections.
But Thiel says the degree of susceptibility of the cells to the new virus was not expected.
“We were a bit surprised that it can so easily infect those cells,” he said in a telephone interview.
“Usually you think that there is a so-called species barrier when an animal virus gets into a human population. But at least on the epithelium layer, we don’t see that.”
The new virus was first spotted last June, when a Saudi Arabian man died from an initially unidentified respiratory infection. Since then, cases have emerged sporadically — some singly, others in small groups. As well, testing on stored samples revealed two people who died in a mysterious respiratory outbreak in Jordan last April were infected with the EMC virus.
All of the infections appear to have a link to the Middle East, with Saudi Arabia, Jordan and Qatar being the three countries from which most cases have arisen.
But last week, Britain’s Health Protection Agency announced that two British residents who had not recently left the country were infected, probably through contact with a family member who came down with an infection after travelling to Pakistan and Saudi Arabia.
Of the 12 confirmed cases, five people have died and several more remain gravely ill in hospital.
The source of the new virus is still unknown. As such, there are many unanswered — and currently unanswerable — questions about how much of a risk the virus poses to people. No one can say at this point whether it will fade away, continue to trigger the occasional infection or start to spread easily from person to person.
But the question of whether the virus would need to evolve more to gain the power to infect human lungs does seem to have been answered.
“If an animal virus gets into the human population, one assumes that some adaptation is needed,” Thiel says.
“As we have seen for instance for SARS, there was a phase of adaptation to the human cells, to the receptor. And obviously that is not needed for this new coronavirus.”
Still, he cautions that just because the virus can easily infect human lung cells doesn’t mean it has all the tools it would need to take off and spread widely among people.
“We have shown that the airway cells can easily be infected. But this does not mean that the virus can easily be transmitted,” Thiel says. “I think this distinction is important.”
The study also found that all three coronaviruses seem to be able to slip past the immune system because they don’t trigger much of an innate immune response. The innate immune system is the so-called first line of defence.
The researchers found, though, that if they treated the cells with interferons — signalling proteins that cells release to warn surrounding cells of the presence of an attacker — the number of infected cells was significantly reduced.
That finding opens up the possibility that interferons, which are currently used in the treatment of some viral diseases, could be used to treat infection with the EMC virus, Thiel says.