Immune System Response, Not Virus, Blamed for Neurological Damage: McMaster Study

A new study from McMaster University challenges the long-held belief that acute viral infections directly cause neurological damage. Led by Elizabeth Balint and Ali Ashkar, the research, published in Nature Communications, suggests that it's the immune system's response, not the virus itself, that leads to neurological issues.

“We were interested in trying to understand why so many viral infections are associated with neurological diseases,” says Balint. “Our evidence suggests that it's not the virus itself that causes the damage, but a unique population of T cells, which are part of the immune system, that are actually responsible for the damage."

The study’s findings indicate that a specific population of T cells, termed NKG2D+CD8+ T cells, are inflicting the damage. These cells exhibit an abnormal behavior, killing uninfected cells alongside infected ones.

The study centered on Zika virus, but implications extend to other infections like COVID-19 and septic shock. The aggressive response of NKG2D+CD8+ T cells stems from an overproduction of inflammatory cytokines, signaling proteins that coordinate immune responses. This overreaction leads to collateral damage, particularly hazardous in the brain.

"If our body’s immune cells overreact and over produce inflammatory cytokines, this condition will lead to non-specific activation of our immune cells which in turn leads to collateral damage. This can have severe consequences if it happens in the brain,” Ashkar says.

Their findings open avenues for targeted therapies, offering hope for improved outcomes in treating neurological complications associated with acute viral infections.