Viruses can cause brain cells to fuse leading to a malfunctioning CNS

Researchers at The University of Queensland, Australia, have discovered viruses such as SARS-CoV-2 can cause brain cells to fuse, initiating malfunctions that lead to chronic neurological symptoms.

Professor Massimo Hilliard and Dr Ramon Martinez-Marmol from the Queensland Brain Institute, published in Sciences Advances, have explored how viruses alter the function of the nervous system.

SARS-CoV-2, the virus that causes COVID-19, has been detected in the brains of people with ‘long COVID’ months after their initial infection. “We discovered COVID-19 causes neurons to undergo a cell fusion process, which has not been seen before,” Hilliard said.

“After neuronal infection with SARS-CoV-2, the spike S protein becomes present in neurons, and once neurons fuse, they don not die.”

Image of fused neurons (yellow) expressing Spike S fusogen from the SARS-CoV-2 virus and the human receptor hACE2.
(Credit: Professor Massimo Hilliard and Dr Ramon Martinez-Marmol)

“They either start firing synchronously, or they stop functioning altogether. Once fusion takes place, each switch either turns on both the kitchen and bathroom lights at the same time, or neither of them,” he continued.

The discovery offers a potential explanation for persistent neurological effects after a viral infection.

“In the current understanding of what happens when a virus enters the brain, there are two outcomes – either cell death or inflammation,” Martinez-Marmol explained.

“But we have shown a third possible outcome, which is neuronal fusion.”

Martinez-Marmol described that numerous viruses cause cell fusion in other tissues, but also infect the nervous system and could be causing the same problem there. “These viruses include HIV, rabies, Japanese encephalitis, measles, herpes simplex virus and Zika virus,” he said.

“Our research reveals a new mechanism for the neurological events that happen during a viral infection. This is potentially a major cause of neurological diseases and clinical symptoms that is still unexplored.”