Brain parasite, new star of health professionals? Usually, we can’t really say that scientists appreciate these parasites that can cause damage. However, the intracellular parasite, Toxoplasma gondiicould well regain its stripes by becoming a real tool for delivering drugs directly into our heads. This is in any case what this new study, published in the journal Nature Microbiology.
Toxoplasma gondiia brain parasite that causes toxoplasmosis
Toxoplasma gondii is the brain parasite that causes toxoplasmosis. It is a intracellular parasite obligate that infects different mammals and birds. Its life cycle thus involves several animals.
It begins with asexual multiplication in various animals, however, sexual multiplication mainly takes place in the digestive system of cats. The eggs are then excreted in the feces of cats and can infect other animals if ingested. They then spread into the bloodstream and the parasites can encyst in different parts of the body, especially the muscles and brain.
These cysts can also be infective when infected tissues are eaten. This is the main mechanism through which humans contract the parasite. They can also become infected by eating fruits and vegetables contaminated with feces from contaminated cats.
This brain parasite can then cause toxoplasmosis. Most often asymptomatic, this disease can however be serious for the fetus and immuno-depressed people.
The pathology is not contagious in itself, since you have to contract the parasite to declare it. In addition, it is very often benign: 80% of individuals do not feel any symptoms. This is also true for pregnant women.
On the other hand, toxoplasmosis can become serious for people suffering from immunodeficiency or fetuses. Indeed, the parasite can cross the placental barrier and contaminate the fetus. The earlier this contamination occurs during pregnancy, the more serious the consequences can be. The brain parasite can thus cause neurological after-effects, premature delivery, or even death. in utero.
In view of these important consequences, the potential occurrence of toxoplasmosis is widely monitored throughout pregnancy.
A parasite capable of manipulating us
Toxoplasma gondii is a brain parasite. It will therefore be able to settle in this organ and even manipulate it, which could modify the behavior of its host.
Of previous studies have shown that the parasite is capable of modifying the functioning of neurons. Observations in mice illustrate that the parasite settles in the amygdala, the place of fear. It then modifies the mouse’s reaction to the cat’s urine. Instead of fleeing, the rodent will instead rush towards the smell and therefore increase the risk of being devoured.
This change in behavior could be an advantage for the parasite, as it increases its chances of infecting its preferred host: the cat.
The mechanisms leading to the changes in neurons are not yet well understood. However, infection with the brain parasite could increase dopamine levels in the brain. This would then induce greater risk-taking.
The same studies in humans and monkeys show similar results. People are more attracted to cat urine and take more risks.
The brain parasite Toxoplasma gondii is often transmitted via cat feces.
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Modifying this brain parasite to deliver treatments directly
Given its ability to colonize the brain, scientists are interested in Toxoplasma gondii as a vector to transport and deliver treatments directly into the brain. This would provide a new therapy option for diseases that are difficult to access.
Scientists have tested the tool on human tissue grown in the lab and on living mice. It shows promise, particularly because it can cross the blood-brain barrier. The blood-brain barrier is a membrane that separates blood vessels from brain tissue and the central nervous system. It thus prevents anything unwanted from infecting the brain. This is particularly problematic when trying to deliver therapeutic proteins that could help treat brain diseases.
When it crosses the blood-brain barrier, the brain parasite develops mainly in neurons. It then interacts with them using three specific organelles. The researchers targeted two of these organelles. They modified them so that they could secrete certain proteins that are effective in treating neurological disorders in humans.
In human tissues cultured in the laboratory, the protein delivered by the modified parasite was able to bind to the DNA of the tissues to modify gene expression and allow the excretion of therapeutic proteins. A process that did not take place in control tissues, receiving the unmodified parasite. The results were similar in living mice. This therefore confirms the interest of Toxoplasma gondii for the delivery of treatments.
In addition, the side effects are minimal. This demonstrates that this therapeutic option is plausible. In addition, it can also be used for other analyses, such as a more in-depth study of the brain.
Scientists say, thanks to this study, the brain parasite Toxoplasma gondii can help address many of the challenges associated with protein delivery for research and therapeutic applications. This tool can be used for several cells, such as differentiated neurons or fibroblasts, support cells that notably ensure collagen renewal.
