Delta variant fuses cells to infect more efficiently

Compared to the spike protein on earlier versions of the coronavirus, the spike on the worrisome Delta variant is better able to break into lung cells and fuse them together, researchers have discovered.

“Spread by cell-to-cell fusion allows the virus to spread faster in infected people and partially hide from the immune system,” said Markus Hoffman of Georg-August-University Göttingen in Germany, coauthor of a report posted on Wednesday on bioRxiv ahead of peer review.

“For example, if a cell that is infected by the Delta variant is forced (by the spike protein) to fuse with a neighboring cell that is not yet infected, this allows the virus to enter the new cell much faster” than if the virus particles first needed to be released from a previously infected cell, he explained.

By spreading via cell-to-cell fusion, the virus reduces its risk of encountering immune system cells that might attack and inactivate it, Hoffman added.

These “skills” might make the Delta variant – first identified in India and now circulating widely in many countries – more transmissible, and the resulting illness more severe, the researchers said.

The researchers also found that although the Delta variant can evade antibodies, it is not completely resistant.

“It might be possible that the Delta variant can infect people who are vaccinated (especially if only one of two vaccine shots have been administered so far), but vaccination is highly effective in preventing severe disease,” Hoffman said.