One in Three People Carry Brain Parasite with Self-Destruct Switch

New research from UVA Health reveals how the immune system keeps this infection under control.

Published on Feb. 16, 2026

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A parasite that may already be living in the brains of one-third of the global population has the ability to infect the very immune cells designed to eliminate it. However, new research from the University of Virginia School of Medicine explains how the body still manages to keep this infection under control.

Why it matters

Understanding how the immune system fights the Toxoplasma gondii parasite is important, as people with compromised immune systems are vulnerable to this infection. The new findings provide insights that could help develop better treatments for those at risk.

The details

Toxoplasma gondii is a potentially dangerous parasite that infects warm-blooded animals and can spread to multiple organs, eventually settling in the brain. Researchers discovered that when the parasite invades CD8+ T cells - key defenders of the immune system - those cells can trigger a self-destruct mechanism powered by an enzyme called caspase-8. By sacrificing themselves, the infected cells also wipe out the parasite inside them.

  • The research findings were published in the journal Science Advances in February 2026.

The players

Toxoplasma gondii

A potentially dangerous parasite that infects warm-blooded animals, including humans, and can spread to multiple organs before settling in the brain.

Tajie Harris, PhD

The director of the Center for Brain Immunology and Glia (BIG Center) at the University of Virginia School of Medicine and the lead researcher on this study.

University of Virginia School of Medicine

The institution where the research was conducted.

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What they’re saying

“We know that T cells are really important for combatting Toxoplasma gondii, and we thought we knew all the reasons why. T cells can destroy infected cells or cue other cells to destroy the parasite. We found that these very T cells can get infected, and, if they do, they can opt to die. Toxoplasma parasites need to live inside cells, so the host cell dying is game over for the parasite.”

— Tajie Harris, Director, Center for Brain Immunology and Glia (BIG Center), University of Virginia School of Medicine (Science Advances)

What’s next

Researchers plan to further investigate how the caspase-8 enzyme helps the body control the Toxoplasma gondii parasite, with the goal of developing new treatments for those with compromised immune systems who are vulnerable to this infection.

The takeaway

This research provides important insights into how the immune system is able to keep the Toxoplasma gondii parasite, which infects an estimated one-third of the global population, under control in most people. The discovery of the key role played by the caspase-8 enzyme could lead to new therapeutic approaches for those at higher risk of developing serious illness from this infection.