Why COVID-19 caused a pandemic while other coronaviruses did not

Epithelial cells play a crucial role in the lungs. Ph.D. student Ying Wang researched the effects of cigarette smoke and viruses such as COVID-19 on these epithelial cells. "We hope to reduce the risk of pandemics in the future."

Epithelial cells line the inside of the lungs, making them the cells that have the first contact with the outside air. Wang investigated the effect on these cells of certain external influences, such as viruses and cigarette smoke. This involved exposing the epithelial cells to cigarette smoke and viruses that cause lung infections.

In her research, Wang mapped in detail the effects of viral infections on epithelial cells. She was able to determine which specific proteins we can target to fight viruses. For example, she found that treatment with interferons helps reduce viral infection. Interferons are proteins that play a role in the immune system. "By deploying interferons early in a virus outbreak, for example, we hope to reduce the risk of pandemics in the future," Wang explains.

The uniqueness of COVID-19

One of the viruses in Wang's study was the SARS-CoV-2 virus, which causes COVID-19. COVID-19 belongs to the coronaviruses, which usually just cause a cold. So what made the SARS-CoV-2 virus cause a major pandemic?

The structure of this virus is different from that of other coronaviruses, says Wang. As a result, the body's response to this virus is different. "A virus has a certain structure, which makes the body react when a virus infection occurs and causes all kinds of proteins to mobilize to fight the virus. In SARS-CoV-2 infection, part of this mobilization is missing, making it much more difficult for the body to fight the virus. Moreover, each body reacts differently to viral infections, and so too with SARS-CoV-2. This makes the virus incredibly difficult to predict."

Negative impact of cigarette smoke

Wang also looked at the precise effect of cigarette smoke on epithelial cells. Cigarette smoke negatively affects mitochondria in epithelial cells. Wang: "Mitochondria are the energy plants of the cell. Cigarette smoke makes them work less well. This makes you—as you might expect—tired much faster." Cigarette smoke was also found to make it even harder for the body to recover from a viral infection.

Wang is pleased with the results of her Ph.D. research. "We now have a much better understanding of the reactions that viruses cause in epithelial cells, which means we know, for instance, which types of proteins can help fight viral infections. This will enable us to make big strides in drug development, for example for COPD patients."

Wang will receive her Ph.D. on Thursday 26 January.

Provided by Leiden University