SARS-CoV-2 Can Infect Neurons and Fuse Brain Cells

Researchers at The University of Queensland have uncovered how viruses, including SARS-CoV-2, can cause chronic neurological symptoms. Professor Massimo Hilliard and Dr. Ramon Martinez-Marmol from the Queensland Brain Institute have revealed that these viruses can initiate a fusion process in brain cells, leading to malfunctions that result in persistent neurological effects. Their findings were recently published in Science Advances.

The team found that SARS-CoV-2 can infect neurons and trigger a fusion of these cells. This fusion process, previously unseen, has a profound impact on neuronal function. Once fusion occurs, the affected neurons either become hyperactive, firing synchronously, or cease functioning altogether. Professor Hilliard compared neurons to wires connecting switches to lights in a kitchen and bathroom, stating that fusion disrupts the independent circuits, causing both lights to turn on simultaneously or not at all.

This discovery offers a potential explanation for the long-lasting neurological symptoms experienced by individuals with “long COVID.” While the conventional understanding of viral brain infections suggests two outcomes—cell death or inflammation—the researchers have now revealed a third possibility: neuronal fusion. 

It is important to note that this phenomenon may extend beyond SARS-CoV-2, as several other viruses, such as HIV, rabies, measles, and Zika virus, are known to cause cell fusion in other tissues and could potentially induce similar problems within the nervous system.

The research conducted by Dr. Martinez-Marmol and Professor Hilliard has unveiled a new mechanism behind the neurological events that occur during viral infections. Unlike previously thought, where neuronal death or inflammation were considered the primary causes, neuronal fusion emerges as a crucial contributor to neurological diseases and clinical symptoms. This aspect of viral infections in the brain opens up new avenues for understanding and combating chronic neurological conditions.

For their work, the researchers infected both mouse and human brain organoids with SARS-CoV-2 and observed fusion between neurons, as well as between neurons and glia. They also discovered that this progressive fusion process led to the formation of multicellular syncytia, which enabled the spread of large molecules and organelles. Through calcium imaging, they also determined that fusion severely compromised neuronal activity.

These findings provide an updated mechanistic understanding of how these viruses affect the nervous system and cause neuropathology, as well as facilitate further investigations into the development of therapies that specifically target viral fusogens.