Conventionally seen as harmful, parasites have recently emerged as unlikely heroes in medical research. Toxoplasma gondii, a single-celled organism notorious for causing severe foodborne illnesses and neurological disorders, has garnered attention for its potential to help deliver therapeutic drugs to the brain. This innovative approach can overcome the major issue of penetrating the blood-brain barrier, which has long impeded efficient treatment of neurological conditions like Parkinson’s disease and Rett syndrome.

Toxoplasma gondii and Neurological Diseases

The major problem with treating brain disorders is delivering high therapeutic proteins to the brain, as the blood-brain barrier functions as a nearly impenetrable shield. According to Shahar Bracha, a bio engineer at MIT, “Present methods of delivering therapies to the brain often produce unpredictable results” because they fail to cross this barrier efficiently. Researchers have sought alternatives, and T. gondii presents a potential solution because of its natural ability to penetrate the blood-brain barrier and inject proteins into brain cells without causing immediate harm. Once inside the brain, the parasite can live quietly, potentially acting as a vehicle to provide necessary proteins into damaged cells. Bracha’s team, in collaboration with T. gondii expert Lilach Sheiner, has explored whether T. gondii can be engineered to transport proteins into neurons, a concept that had previously seemed “crazy.” Using an approach called “kiss-and-spit,” T. gondii secretes proteins into host brain cells without fully invading them. By attaching therapeutic proteins to these secretions, researchers hope to utilize the parasite as a courier for drug delivery.

Challenges and Ethical Concerns

Despite the optimism surrounding this approach, many issues remain. As parasitologist Sebastian Lourido points out, T. gondii “hitches rides inside immune cells” and can destroy them in the process. Making the parasite safe while retaining its drug-delivery capabilities is complex. Also, brain cells injected by the parasite might eventually die, and the risks of infection remain high, especially for individuals with weakened immune systems. Critics, like Anita Koshy of the University of Arizona, initially believed that utilizing T. gondii as a therapeutic tool was a “terrible idea.” However, she later revised her opinion, recognizing the evolutionary benefits of utilizing the parasite’s ability to cross the blood-brain barrier. Over 40 million people in the US carry T. gondii, and while it can cause serious disease, especially in immunocompromised pregnant women and individuals, its relatively low effect on healthy people makes it an intriguing candidate for further research.

Future Directions

The idea of utilizing T. gondii as a drug delivery system is still in its infancy, and much more research is required to refine the technique. While only a fraction of engineered parasites reached the brains of mice in experimental trials, the initial results were promising enough for the formation of Epeius Pharma, a company assigned to creating T. gondii as a drug delivery tool. Bracha and her colleagues are cautiously optimistic but acknowledge that the road to clinical usage is long and uncertain. Researchers need to address safety concerns, including finding ways to neuter the parasite so that it can no longer cause harm while retaining its capability to deliver therapeutic proteins efficiently. As Bracha notes, the persistence needed to bring such a radical idea to fruition is immense, but the potential gains can revolutionize how neurological diseases are treated.

Reference

Saey, T. (2024). Getting drugs into the brain is hard. Maybe a parasite can do the job. ScienceNews. Available at- https://www.sciencenews.org/article/toxoplasma-drugs-brain-parasite

(Accessed: 10 September 2024)