USF Study Uncovers New Insights into Toxoplasma gondii Growth

A recent study led by the University of South Florida (USF) has advanced the understanding of Toxoplasma gondii, a parasite that infects nearly one-third of the global population. Published in Bio-Protocol, the research describes an adapted fluorescent imaging system capable of observing the parasite's growth in real-time.

Unlocking the Parasite's Secrets

Researchers at the USF Health Morsani College of Medicine modified a fluorescent imaging system typically used for human cells. This adaptation enables real-time observation of the parasite's growth, which was previously challenging due to its microscopic size and unusual cell cycle.

Understanding Toxoplasmosis

Toxoplasma gondii spreads through sources like uncooked meat and contaminated produce, causing toxoplasmosis. While often mild, the infection can be severe for pregnant women and individuals with weakened immune systems. Acute-stage infections can be treated, but long-term drugs can be toxic.

If not caught early, the parasite enters a chronic stage, forming cysts in the brain for which no current cures exist.

Mapping the Unusual Cell Cycle

The parasite's cell cycle differs from a typical cell, which grows, copies DNA, and then splits into two identical parts. Toxoplasma does not follow this standard pattern, making its growth and spread difficult to understand. The research aimed to map this unusual cell cycle to identify potential targets for preventing parasite multiplication.

To tailor the imaging model, researchers identified a protein called PCNA1 within the parasite's nucleus. This protein naturally shifts during the organism's growth cycle. By attaching bright neon green tags to PCNA1, the team developed a strong, clear signal. This allowed them to determine the parasite's stage by observing the fluorescent protein's behavior.

A "Fork-Like" Growth Revealed

The study revealed that Toxoplasma's cell cycle begins normally but its subsequent growth stages overlap, rather than occurring sequentially.

This "fork-like" structure allows as many as three cell cycle phases to occur simultaneously, contributing to the parasite's rapid multiplication and ability to evade the immune system before forming brain cysts.

Future Directions

With the cell cycle now mapped, researchers plan to identify weak points in the parasite to prevent its reproduction. They are also testing various drugs to observe their effects on specific stages of the cycle, with the goal of developing safer and more effective treatments for toxoplasmosis.