Worm expulsion is independent of alterations in composition of the colonic bacteria that occur during experimental Hymenolepis diminuta-infection in mice

ABSTRACT

The tapeworm Hymenolepis diminuta fails to establish in mice. Given the potential for helminth-bacteria interaction in the gut and the influence that commensal bacteria exert on host immunity, we tested if worm expulsion was related to alterations in the gut microbiota. Specific pathogen-free (SPF) mice, treated with broad-spectrum antibiotics, or germ-free wild-type mice were infected with H. diminuta, gut bacterial composition assessed by 16S rRNA gene sequencing, and worm counts, blood eosinophilia, goblet cells, splenic IL-4, -5 and -10, and colonic cytokines/chemokines mRNA were assessed. Effects of a PBS-soluble extract of adult H. diminuta on bacterial growth in vitro was tested. H. diminuta-infected mice displayed increased α and β diversity in colonic mucosa-associated and fecal bacterial communities, characterized by increased Lachnospiraceae and clostridium cluster XIVa. In vitro analysis revealed that the worm extract promoted the growth of anaerobic bacteria on M2GSC agar. H. diminuta-infection was accompanied by increased Th2 immune responses, and colon from infected mice had increased levels of IL-10, IL-25, Muc2, trefoil factor 3, and β2-defensin mRNA. SPF-mice treated with antibiotics, or germ-free mice, expelled H. diminuta with kinetics similar to control SPF mice. In both settings, measurements of Th2-immune responses were not significantly different across the groups. Thus, while infection with H. diminuta results in subtle but distinct changes to the colonic microbiota, we have no evidence to support an essential role for gut bacteria in the expulsion of the worm from the mouse host.

KEYWORDS:

• Helminth
• colonic bacteria
• germ-free
• antibiotics
• mucosal immunity
• helminth extract
• bio-diversity
• gut immunomodulator mRNA

Acknowledgments

This research was supported by a Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery Grant to DMM. AS was supported by graduate studentships from Beverly Phillips Rising Scholars Award, Snyder Institute, University, NSERC CREATE in Host-Parasite Interactions (HPI), and the Canadian Association of Gastroenterology (CAG). TSJ was supported in part by NSERC CREATE HPI. DMM is recipient of a Canada Research Chair (Tier 1) in Intestinal Immunophysiology in Health and Disease. Support from the International Microbiome Center (IMC) at the University of Calgary (Dr. McCoy) as well as the Canadian Foundation for Innovation to Dr. Strous is gratefully acknowledged (the IMC is supported by the Cumming School of Medicine, University of Calgary, Western Economic Diversification (WED) and Alberta Economic Development and Trade (AEDT), Canada). We thank Dr. M. Workentine (Faculty Veterinary Medicine, Univ. Calgary) for assistance with bioinformatic analyses and Dr. T. Arai for initial help with eosinophil counting.

Disclosures

The authors declare no conflict of interest.

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Additional information

Funding

This work was supported by the Natural Sciences and Engineering Research Council of Canada.