A benign helminth alters the host immune system and the gut microbiota in a rat model system

PLoS One. 2017 Aug 3;12(8):e0182205. doi: 10.1371/journal.pone.0182205. eCollection 2017.

Abstract

Helminths and bacteria are major players in the mammalian gut ecosystem and each influences the host immune system and health. Declines in helminth prevalence and bacterial diversity appear to play a role in the dramatic rise of immune mediated inflammatory diseases (IMIDs) in western populations. Helminths are potent modulators of immune system and their reintroduction is a promising therapeutic avenue for IMIDs. However, the introduction of helminths represents a disturbance for the host and it is important to understand the impact of helminth reintroduction on the host, including the immune system and gut microbiome. We tested the impact of a benign tapeworm, Hymenolepis diminuta, in a rat model system. We find that H. diminuta infection results in increased interleukin 10 gene expression in the beginning of the prepatent period, consistent with induction of a type 2 immune response. We also find induction of humoral immunity during the patent period, shown here by increased IgA in feces. Further, we see an immuno-modulatory effect in the small intestine and spleen in patent period, as measured by reductions in tissue immune cells. We observed shifts in microbiota community composition during the patent period (beta-diversity) in response to H. diminuta infection. However, these compositional changes appear to be minor; they occur within families and genera common to both treatment groups. There was no change in alpha diversity. Hymenolepis diminuta is a promising model for helminth therapy because it establishes long-term, stable colonization in rats and modulates the immune system without causing bacterial dysbiosis. These results suggest that the goal of engineering a therapeutic helminth that can safely manipulate the mammalian immune system without disrupting the rest of the gut ecosystem is in reach.

MeSH terms

  • Animals
  • Bacteria / classification
  • Bacteria / isolation & purification
  • Biodiversity
  • Feces / chemistry
  • Female
  • Gastrointestinal Microbiome*
  • Gene Expression Regulation / immunology
  • Host-Parasite Interactions / immunology*
  • Hymenolepis diminuta / immunology*
  • Immune System*
  • Immunoglobulin A / analysis
  • Immunoglobulin A / immunology
  • Interleukin-10 / genetics
  • Interleukin-10 / metabolism
  • Intestines / microbiology*
  • Intestines / parasitology*
  • Models, Biological*
  • Phylogeny
  • Rats
  • Rats, Wistar
  • Spleen / immunology

Substances

  • Immunoglobulin A
  • Interleukin-10

Grant support

This work is financially supported by Young Investigators grant from the Human Science Frontiers Program (RGY0078/2015) to KJP and LWP, and by European projects (KJP): Modbiolin (7th Framework programme, no. 316304, Biology Centre CAS to KJP) and European project for the promotion and popularization of research, development and innovation (Operational Programme, Biology Centre CAS, CZ.1.05/3.1.00/10.0214 to KJP). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.