Photo: Martin Harvey via Getty Images
Recent research has found that toxoplasma is capable of attacking immune cells to spread to all organs in the body with a very worrying rate of infection. This dangerous parasite reproduces within its main host, the cat, and is estimated to have infected a third of the world’s population.
However, cats aren’t the only ones who can transmit Toxoplasma. All warm-blooded animals can become infected and carry the parasite to humans who eat contaminated food. Although it is of high risk to pregnant women and fetuses, this pathogen does not cause harmful symptoms in most people. Toxoplasma is a public health problem due to its dire nature. For example, rodents whose brains are infected with this parasite become less attentive to the presence of cats, so they are more likely to be eaten by cats and may allow parasites to multiply in the cat’s body. That’s why Toxoplasma is often advertised as turning rodents into “zombies”.
The results of the research led by Arne ten Hoeve and Antonio Barragan, molecular bioscientists at the University of Stockholm, have identified the main mechanism that distinguishes Toxoplasma as an effective parasite on the human body. By observing the parasite in cell culture, the research team found that Toxoplasma spread the GRA28 protein onto immune cells until the cells forgot their original function. Their findings are further elaborated in a study published in the journal Cell host and microbes.
“Toxoplasma infects so many species of animals, including humans,” Barragan explained via email to VICE’s technology section, Motherboard. “Parasites spread very efficiently in infected hosts and reach areas generally inaccessible to microbes, such as the developing fetus or brain.”
So far, the effect of Toxoplasma exposure in humans is still a matter of debate. Some studies show that this parasite can cause inflammation of the brain, while other studies suggest potential behavior change. However, I’m not sure yet whether these effects are true or not.
“We already know that Toxoplasma can manipulate immune cells, but it’s still a conundrum as to what the exact mechanism is,” Barragan continued. “Toxoplasma is very subtle in manipulating immune cells. The parasite spreads a protein which makes immune cells unable to fight it. The hijacked cells therefore serve as a means of spreading the parasite throughout the body ”.
Previous research has shown that GRA28 can be used by parasites to take control of macrophages, a type of white blood cell in the immune system that can digest parasites. To understand how it works, Barragan and his colleagues examined parasite interactions during the hijacking process using advanced microscopic imaging techniques.
The results showed that GRA28 helps parasites enter the macrophage nucleus so that they can suppress and activate cellular gene expression. In other words, previously immobile macrophages in the immune system act as if they were active dendritic cells. It is like a parasite capable of “igniting” the immune cells in a kind of small vehicle to transport them to all the organs of the body.
In addition to explaining the process of Toxoplasma attacking the body, this research also adds to our understanding of the process of spreading other infectious diseases in the human and animal body. “This research, which sheds light on the disease process, can help find a cure and prevent it,” Barragan concludes. “We hope this research will not only improve our understanding of Toxoplasma infection, but also how other infections (such as viruses and bacteria) spread in the body to make us sick.”
