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Using engineered bacteria to fight intestinal parasites

Over a decade ago, researchers at the University of California, San Diego, found that a common organic insecticide - a crystal protein made by bacteria found in dirt - could also be used to safely treat roundworm infections in rodents. The crystal protein, called Cry5B, showed promise as a possible way to treat intestinal parasites in humans. But patients would have to eat the soil bacteria live to receive the benefits of the Cry5B protein, and it wasn’t known if the bacteria were safe to ingest.

Now, the UCSD research team, led by Raffi Aroian, PhD, has found a way to make a bacteria that humans can safely ingest produce the same crystal protein that kills roundworms and other intestinal parasites. The findings of their study are published online in the journal Applied and Environmental Microbiology. From a press release:

Hookworms, and other intestinal parasites known as helminths infect more than 1 billion people in poverty-stricken, tropical nations, sucking the vitality from the body, and leaving hundreds of millions of children physically and mentally stunted. Current drugs are insufficiently effective, and resistance is rising, but little effort has been made to develop better drugs because the relevant populations do not represent a profitable market for drug companies.

"The challenge is that any cure must be very cheap, it must have the ability to be mass produced in tremendous quantities, safe, and able to withstand rough conditions, including lack of refrigeration, extreme heat, and remote locations," says [Aroian].

This study had two parts. First the research team engineered the bacteria (called Bacillus subtilis PY79) to produce the crystal protein that kills intestinal parasites. Then the team fed the engineered bacteria to animal models infected with a roundworm known to also infect humans. The crystal protein works by poking tiny holes in the cell membranes of nematodes and insects. The protein cannot bind to the cell membranes of vertebrates, so it is safe for vertebrates to ingest.

The study showed that "a small dose of Cry5B, expressed in this bacterium can achieve a 93 percent elimination of hookworm parasites from infected hamsters. That, says Aroian, is substantially better than current drugs."

At this point, only animals have been treated with the new Cry5B producing bacterium. But this new finding could someday help people with intestinal parasite infections -  a problem that affects more than 1 billion people worldwide.

Holly MacCormick is a writing intern in the medical school’s Office of Communication & Public Affairs. She is a graduate student in ecology and evolutionary biology at University of California-Santa Cruz. 

Previously: Could worms be the answer to treating autoimmune disease?


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