Parasite Found in Cat Feces May Offer Breakthrough Treatment for Neurological Disorders

The parasite infamous for its existence in cat feces can be effectively used as a delivery system to ferry therapeutic proteins to neurons in the brain, a new study published in Nature Microbiology shows, suggesting that a number of neurological disorders could be treated this way. 

Toxoplasma gondii, which notoriously is associated with a danger to pregnant women and people with compromised immune systems, infects about one-third of the global population. It can be contracted by eating undercooked meat, and it reproduces in the guts of cats. It can remain in a host’s brain for their entire life. 

Taking advantage of the parasite’s usual ability to secrete proteins, the researchers genetically engineered the parasite to be able to deliver therapeutic proteins once it had crossed the blood-brain barrier, which has generally been an obstacle for such treatments. 

In the current study, researchers injected genetically altered parasites into mice to deliver proteins into cell nuclei. They identified three basic methods that the parasite uses to secrete proteins and found that their engineered version could use two of those simultaneously.

T. gondii‘s ability to robustly deliver intracellular proteins to neurons emphasizes its potential as research too. Neurons are particularly difficult to target with existing methods, as they are less receptive to uptake of transfection reagents and to expression of exogenously delivered DNA.

Because T. gondii can latch itself to humans’ central nervous systems so effectively without significant damage to its hosts, researchers saw an opportunity to create specific targeting of certain proteins “with known utility in neurons,” the study says. 

The parasite’s three different organelles for protein secretion seemed to indicate a strong chance that such targeting could be successful. 

Dao told us that the study’s results highlight the great potential for targeting other neurological disorders. 

The human brain protects itself through a protective layer called the blood-brain barrier. This helps the brain hold onto things that are helpful and keeps harmful things out, such as toxins or infections. Because of the tight regulation of the blood-brain barrier, it can be very difficult to get drugs directly to the brain to combat neurologic disorders. 

Using T. gondii to inject therapeutic proteins into brain cells presents a novel potential approach to treating neurologic disorder conditions caused by specific protein deficiencies, such as Fragile X or Duchenne Muscular Dystrophy. Scientists have been using various microorganisms from viruses to bacteria for treatment of patients with various diseases in the past century. Only a few modified agents are approved by the FDA [Food and Drug Administration] — such as herpes virus for melanoma and adenovirus for bladder cancer — and many others are in clinical development.