Scientists identify protein causing Covid-related inflammation

Scientists have identified a protein in the blood that could be responsible for an aggressive inflammatory response, known as a cytokine storm, which is also the leading cause of death in Covid-19 patients.

The team, from the University of Alberta in Canada, analysed the blood plasma of 120 patients with Covid-19. They found that Covid-19 patients have significantly elevated levels of a protein called galectin-9 in their blood plasma.

They also found a positive correlation between the levels of galectin-9 and pro-inflammatory cytokines released in the blood, which can lead to a cytokine storm.

"We have reported in the past that galectin-9 levels go up in HIV infection and with some cancers," said Shokrollah Elahi, Associate Professor in the School of Dentistry's Division of Foundational Sciences.

"However, when we compared the levels of galectin-9 in the Covid-19 patients to HIV and cancer patients, we could easily distinguish the Covid patients based on the galectin-9 levels," Elahi added. The findings have been published in the journal mBio.

The discovery of elevated galectin-9 levels in Covid-19 patients is important because of the positive correlation between the protein and a wide range of pro-inflammatory cytokines.

"Cytokines as small cell-signalling proteins are involved in checks and balances in the immune system; they can turn on or turn off some cells to regulate the immune system," said Elahi.

"In the context of Covid, the problem is that there is a dysregulation of cytokine production - they are released very quickly in elevated levels. That's what we call a 'cytokine storm.'"

Elahi found that galectin-9 is responsible for instructing immune cells to release the pro-inflammatory cytokines quickly in response to Covid-19 infection by binding to immune cells and forcing them to produce the cytokines.

Further, as tissues are damaged as a result of inflammation, more galectin-9 is released from the cells, which activates more immune cells and releases more cytokines in a vicious cycle. The resulting cytokine storm damages tissue and organs, causes severe inflammation and can lead to death, Elahi said.

Even if patients survive the storm, the dysregulation of the immune system can have ongoing consequences and could be associated with the condition known as post-Covid-19 syndrome or long Covid.