Toxoplasma study uses fluorescent imaging to track parasite growth
Elena Suvorova and Mrinalini Batra
Toxoplasma gondii, a widespread parasite found in humans and animals, infects nearly one-third of the global population, yet its microscopic size has made it difficult for scientists to study.
Toxoplasma gondii is commonly spread through undercooked meat and contaminated produce. Once inside the human body, it causes toxoplasmosis, an infection that is often mild but can become serious in pregnant women and people with weakened immune systems. If detected within the first two weeks of exposure, it can be treated.
To better understand how it functions, infectious disease researchers at the University of South Florida (USF) Health Morsani College of Medicine adapted a fluorescent imaging system usually used for human cells to track the parasite’s growth in real time. The method is being used to support future treatment development.
Photo by: USF
Tracking a stealthy cell cycle
The research aimed to go beyond basic observation and support efforts to stop the parasite from multiplying. To do that, the team needed to map its cell cycle in order.
To adapt the fluorescent system for Toxoplasma gondii, researchers first identified proteins that appear at specific growth stages. These proteins also had to be located in visible structures such as the nucleus and needed to produce signals strong enough to detect in a single-celled organism under a microscope.
Because the parasite lacks many proteins common in human cells, the process involved repeated testing. The team applied red and green, fluorescent tags, but many markers either failed to produce strong signals or were too scarce to be useful.
A key protein reveals the cycle
The team eventually identified a protein called PCNA1, located in the parasite’s nucleus. This protein changes position as the organism moves through its growth cycle.
Mrinalini Batra, a research scientist in the Suvorova Lab said that when two copies of a bright neon green tag were attached to this protein, the signal became strong and clear. She explained that this enabled researchers to determine the parasite’s stage by observing how the glowing protein behaved. She added that, for the first time, the full cell cycle of Toxoplasma gondii was mapped.
The findings show that the parasite progresses normally through the first part of its cell cycle, but later stages overlap instead of occurring in sequence.
Developing treatment for an evasive organism
USF Associate Professor Elena Suvorova said that while the parasite can be suppressed during the acute stage, treatment often relies on drugs that may be toxic if used long term. If infection is not treated early, it can become chronic. In this stage, the parasite hides in brain tissue and forms cysts, for which there are currently no cures.
Developing treatments has been difficult because of the parasite’s unusual cycle. A typical cell cycle involves growth, DNA replication and division into two identical cells.
Suvorova said these later stages resemble a fork, while the parasite begins with a single strand and then branches. She explained that up to three stages can occur at the same time. This pattern allows rapid multiplication and helps the parasite avoid the immune system before forming brain cysts.
However, with the cell cycle now mapped through fluorescence imaging, the team is identifying weak points that could disrupt parasite growth. They are also testing how different drugs affect specific stages, with the aim of developing safer and more effective treatments.
Category: Education
