SARS-CoV-2 replicates ten times more efficiently in upper airway temperatures than in lower airways. This is what virologists from the University of Bern found out in human cell cultures. This could explain why SARS-CoV-2 is more easily transmitted than the SARS pathogen from 2002.
The SARS pathogen from 2002 (SARS-CoV) and the new coronavirus SARS-CoV-2 are genetically very similar and use the same receptor to hijack human cells. Nevertheless, they differ significantly in terms of infectivity and the course of the disease.
A team led by virologist Ronald Dijkman from the University of Bern has now investigated how different temperatures affect an infection with the two respiratory viruses in human epithelial cells from the airways. They report on the results in the journal “PLOS Biology”.
There are different temperatures in the upper and lower airways of humans: In the upper airways, i.e. in the nasal cavity or the throat, it is 33 degrees. The lower airways, for example the bronchi, have temperatures of around 37 degrees.
The study with the cell experiments showed that SARS-CoV-2 multiplies very efficiently at temperatures of the upper respiratory tract. At 37 degrees, however, the innate immune response of the epithelial cells was more strongly stimulated and the virus was fought more effectively. In infected people, however, this can lead to an excessive immune reaction and severe disease.
SARS-CoV is different: the virus replicated to a similar extent at both 33 and 37 degrees over the entire course of the infection. The disease of this SARS pathogen is characterized in particular by severe illness and inflammation of the lower respiratory tract.
“The detailed analysis of the multiplication of SARS-CoV-2 and the temperature-related differences in the innate immune defense could explain why SARS-CoV-2 spreads so well in the upper respiratory tract and why it is more easily transmitted than SARS-CoV,” said Dijkman according to a statement from the University of Bern on Wednesday. Unlike SARS-CoV-2, the SARS pathogen from 2002 is only transmitted after the outbreak of the disease.
According to the University of Bern, a detailed picture of the key factors that influence the fight between virus and infected cells opens up new starting points for developing active ingredients against coronavirus infections.