Intestinal worm study highlights role of microbiota

by Anne Crawford

Monash Professor Nicola Harris has for 15 years investigated the intestinal activities of helminths (parasitic worms), making landmark discoveries about them as she did. Her latest paper, published recently in ‘Mucosal Immunology’, showed some surprising interactions between the intestinal microbiota and helminths that could offer a new approach to fighting the parasites and which reinforces the role of the microbiota.

Soil-transmitted helminths cause widespread disease, infecting more than 1.5 billion people in poverty-stricken regions of tropical and subtropical countries. The intestinal infection they cause results in morbidity rather than death making the disease a neglected area, Professor Harris said.

“These worms can cause a lot of problems in the cycle of poverty, particularly in babies and mothers including stunted growth, lower cognition, increased absenteeism for work and school,” she said. 

To date there are no vaccines and the the medications available need to be given every six to 12 months, and have varying degrees of efficacay against the different helminth species, she said. 

Adult worms inhabit the intestine alongside bacterial communities. Previous work by Professor Harris and colleagues has shown that helminths interact with the host’s immune system and with the microbiota. “We had one of the first publications that came out really showing that helminths changed microbiota,” she said.

Her latest study sought to “close the loop” by seeing if bacterial microbiota impacted host resistance against intestinal helminth infection, in this case hook worms (Heligmosomoides polygyrus bakeri) in animal models.  

The findings were unexpected.

The researchers knew from research by other laboratories into whipworms that the helminths needed bacteria to hatch; the worms don’t develop without bacteria. 

“But we saw that the worms were much happier without bacteria around, that the presence of bacteria changed the host’s ability to resist these parasites,” Professor Harris said. “An increased type 2 (allergic) response should have been able to kill and get rid of the parasite, but instead the parasite was much happier,” she said. “It just raised all these unknowns and didn’t fit what we expected to happen, which was really cool!

“Instead we worked out that the bacteria are needed to provide the host with resistance against intestinal helminths because they help the gut to have proper motility, for food to pass through the gut and to expel pathogens.”

Professor Harris said the findings were significant as they would “open eyes, especially to people in the parasite field.”

“We have to think about everything we study in the context of host physiology and gut function. What was really at play here were things like the microbiota impacting on neural activity and gut physiology, and that these things are perhaps even more important than the immune system in attacking certain pathogens.”

The paper should change the way scientists think about, and approach the problem of helminths, she said. “It also adds increasing evidence that the microbiota really finely tunes pretty much everything about our bodies.”

First author was Dr Mati Moyat. 

Moyat M, Lebon L, Perdijk O, Wickramasinghe LC, Zaiss MM, Mosconi I, Volpe B, Guenat N, Shah K, Coakley G, Bouchery T, Harris NL. Microbial regulation of intestinal motility provides resistance against helminth infection. Mucosal Immunol. 2022 Mar 14. doi: 10.1038/s41385-022-00498-8. Epub ahead of print. PMID: 35288644. 

https://pubmed.ncbi.nlm.nih.gov/35288644/