Scientists from Lancaster University have discovered immune responses that are important in eliminating the causative agent of Trichinosis.
Researchers from the university in the United Kingdom found immune responses that prevent fungal infections also help eliminate Trichinella spiralis. The work has been published in the journal PLOS Pathogens.
They hope findings will help to design new treatments for people who suffer from intestinal parasitic infections and may inform other intestinal diseases involving altered muscle function.
People acquire trichinellosis by eating raw or undercooked meat infected with the Trichinella parasite such as wild game meat or pork. Trichinella spiralis infects pigs, horses, rats and other animals.
Contaminated meat contains “nurse cells” of the parasite. Once in the stomach these cells hatch, releasing infective larvae which then bury themselves within the lining of the small intestine.
Previously, immune responses to expel the parasite have been shown to rely on white blood cells called T-helper 2 cells, specialized for eliminating gastrointestinal parasites. However, scientists discovered that following this T-helper 2 reaction, a second T-helper 17 response, previously shown to be specialized for eliminating fungal infections and certain bacterial infections occurred.
One protein that can be key in controlling immune responses is transforming growth factor beta. With Professors Mark Travis and Richard Grencis from the University of Manchester, the team identified how the T-helper 17 cells arose and that they were key in maintaining intestinal muscle contractions needed to flush out the worms.
Mice were infected with 300 Trichinella spiralis larvae and followed throughout the course of infection. Findings showed mice lacking the ability to activate a key signaling molecule important in producing T-helper 17 cells have a reduced ability to expel the parasite.
Researchers saw a delayed transit time in the small intestine hinting at alterations in muscle contraction. In isolating the small intestine they demonstrated that a molecule produced from T-helper 17 cells, termed IL-17, could increase intestinal contraction and restoring levels of IL-17 in the mice rescued their ability to expel the parasite.
It is estimated there are 10,000 human trichinellosis infections per year worldwide. Symptoms depend on stage of the infection. Initially when larvae or adults are in the intestines there may be abdominal discomfort with nausea, diarrhea, vomiting, fatigue and fever, according to the World Organization for Animal Health (OIE).
As larvae migrate into the muscles they may cause severe pain, headaches, fevers, chills, cough, eye swelling, aching joints and muscle pains, itchy skin, rash, and diarrhea or constipation. Severity of the disease is related to the number of larvae ingested, and fatalities can occur with high doses.
John Worthington, from the department of biomedical and life science at Lancaster, said they were surprised by what was found.
“Normally, these immune responses are thought of as acting quite distinctly depending on what type of infection you may have. It’s well established that the T-helper 2 response is beneficial during gastrointestinal worm infections, so traditionally any other response would be thought of as hindering worm expulsion. So, it was quite surprising to see that this late acting T-helper 17 response was actually beneficial to the mouse’s ability to resolve an infection and get rid of the worm,” Worthington said.
He also said the study provides insights into how the immune system interacts with muscle contraction during intestinal inflammation.
“Although the occurrence of this infection is very rare in the developed world, we hope it will help us to design new treatments for the many millions of people who suffer from intestinal parasitic infections worldwide and may even inform other intestinal diseases involving altered muscle function.”
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