Parasite communication and African sleeping sickness

Scientists have known that African trypanosomes cause sleeping sickness for years, but new research from UGA researchers now shows just how these single-celled organisms communicate. The research may one day impact treatment for African sleeping sickness. Stephen Hajduk, a professor of biochemistry and molecular biology in the UGA Franklin College of Arts and Sciences, was the senior author on the study, alongside lead author Tony Szempruch, a doctoral student.

The UGA researchers discovered that long filaments—that look like beads on a string—form by budding from the flagellum of African trypanosomes and then release pieces of the parasite into the host. This causes anemia and influences the outcome of infection leading to human African sleeping sickness and the cattle disease nagana.

The UGA researchers theorize that the extracellular vesicles, as the free-floating beads are scientifically known, are being used by the parasite to communicate with each other and with the host's body. Even before they pop off into vesicles, the nanotubes extending from the flagellum help the single-celled parasites talk to each other. The severe anemia caused by the parasites may be an accidental side effect of the extracellular vesicles fusing with host red blood cells.

 

In 2013 alone, there were 6,314 new cases of African sleeping sickness. If untreated, the disease is fatal, but current medications to treat the disease still include an old arsenic-based drug that kills between 5 and 10 percent of those receiving the treatment. The disease is a major threat in the 36 countries in sub-Saharan African where the parasite-transmitting tsetse fly lives. Additionally, the parasite infects and kills 5 to 7 million cattle each year through nagana. 

Investigating the communication of this parasite began as a side project initially, but as study lead author Tony Szempruch looked more at the organism under a microscope, he saw its cellular communication potential. The project has caused quite a bit of excitement among researchers, as single-celled organisms weren't typically thought to communicate with each other at all. 

"What you see here," he said, pointing at the flagellum, "is that you can get that synthesis of the nanotube, but then it will quickly break down into what appears to be free vesicles that float out of focus."

Szempruch, a doctoral student in the biochemistry and molecular biology department, developed a 3-D reconstruction of the nanotubes budding at the flagellum membrane. He was then able to look at the relationship of the flagellum, nanotubes and extracellular vesicles.

UGA study co-authors included Steven Sykes, Rudo Kieft, Lauren Dennison, Allison Becker, Anzio Gartrell and William Martin, with John Harrington as a co-corresponding author, as well as Ernesto Nakayasu at Pacific Northwest National Laboratory and Igor Almeida at the University of Texas. Congratulations to all of the authors on their great work. This research has the potential to impact millions of people and is another great example of UGA research's reach and influence around the world.