A common brain parasite, Toxoplasma gondii, can infect the immune cells tasked with destroying it, but a newly discovered “self-destruct” mechanism within those cells offers a critical defense, according to research published today by the University of Virginia Health System.
The parasite, which infects an estimated one-third of the global population, can persist in the brain for life, often without causing noticeable symptoms. Although, in individuals with compromised immune systems, Toxoplasma gondii can lead to a severe illness known as toxoplasmosis. Researchers, led by Tajie Harris, PhD, investigated how the immune system responds when the parasite invades CD8+ T cells – specialized immune cells responsible for eliminating infected cells.
The UVA Health research team found that when Toxoplasma gondii infects CD8+ T cells, these cells can activate a self-destruct process triggered by an enzyme called caspase-8. This programmed cell death, or apoptosis, effectively eliminates both the infected immune cell and the parasite residing within it. Examination of brain tissue in mice lacking caspase-8 revealed a significantly higher rate of Toxoplasma gondii infection within the CD8+ T cells, demonstrating the enzyme’s crucial role in controlling the infection.
People are commonly exposed to Toxoplasma gondii through contact with cats, consumption of contaminated fruits or vegetables, or ingestion of undercooked meat. Once inside the body, the parasite can migrate to various organs, ultimately establishing a presence in the brain. Despite its widespread prevalence, the majority of infected individuals remain asymptomatic, prompting scientists to seek a deeper understanding of the body’s natural defenses.
The discovery of the caspase-8 mechanism provides new insights into the complex interplay between the parasite and the immune system. While the research was conducted on mice, the presence of caspase-8 in human CD8+ T cells suggests a similar defense mechanism may be at play in humans. Further research is needed to fully elucidate the implications of this finding for the prevention and treatment of toxoplasmosis.
