How Toxoplasmosis, a lifelong infection alters common brain disorders?

Toxoplasmosis infection

One third of humans on earth have a lifelong infection with the brain-dwelling parasite Toxoplasma gondii. Almost 15 million people have congenital toxoplasmosis, a neurobehavioral disease is associated with seropositivity, causality is unproven.

Researchers describe efforts to learn how toxoplasmosis infection alters several brain disorders as well as some cancers.

When a woman infected with T. gondii during pregnancy and passes the parasite on to her unborn child. The consequences can be profound, including devastating damage to the brain, nervous system and eyes.

However, an evidence that acquiring this infection later in life may be far from harmless. So, the researchers began looking for connections between this chronic, but seemingly dormant infection and its potential to alter the course of common neurologic disorders.

“We wanted to understand how this parasite lives in the brain, might contribute to and shed light on pathogenesis of other brain diseases,” said, Rima McLeod, medical director of the Toxoplasmosis Center at the University of Chicago.

More than a decade, researchers noted subtle behavior manipulations associated with a latent T. gondii infection. Rats and mice that harbor this parasite to lose their aversion to the smell of cat urine. This is dangerous for a rodent, making it easier for cats to catch and eat them. An acutely infected cat can excrete up to 500 million oocysts in a few weeks’ time. Even one oocyst, which can remain in soil or water for up to a year, is infectious.

connection involving primates

A recent study found a similar connection involving primates. Infected chimpanzees lose their disinclination to the smell of urine of their natural predator, leopards.

The research team decided to search for similar effects in people. They focused on what they call the human “infectome” plausible links between the parasite secreted proteins, expressed human microRNAs.

Using a data collected from the infected patients and their families, researchers performed a comprehensive system analysis, looking at a range of parasite-generated biomarkers and assessing their probable impact.

However, they looked at the effect of infections of primary neuronal stem cells from the human brain in tissue culture, focusing on gene expression and proteins perturbed. Using a “reconstruction and deconvolution” approach, the researchers identified perturbed pathways associated with neurodegenerative diseases as well as connections between toxoplasmosis, human brain disorders and some cancers.

Researchers also found, the parasite manipulates 12 human olfactory receptors that mimicked the cat-mouse or the chimp-leopard exchange. T. gondii increases the risk of epilepsy, “possibly by altering GABAergic signaling. The parasite infection associate with a network of 1,178 human genes, many of which modified in various cancers.

However, the results provide insights into the mechanisms whereby this parasite could cause these associated diseases under some circumstances.

More information: [Scientific Reports]