experimental-infection-mice-with-parasitic-nematode-strongyloides

Experimental Infection of Mice with the Parasitic Nematode  <i>Strongyloides ratti </i>

Strongyloides ratti is a parasitic nematode that naturally infects wild rats. However, most laboratory rat and mouse strains are fully susceptible to ...

Bernhard Nocht Institute for Tropical Medicine

Parasitic helminths are sensed by the immune system via tissue-derived alarmins that promote the initiation of the appropriate type 2 immune responses. Here we establish the nuclear alarmin cytokine IL-33 as a non-redundant trigger of specifically IL-9-driven and mast cell-mediated immunity to the intestinal parasite Strongyloides ratti. Blockade of endogenous IL-33 using a helminth-derived IL-33 inhibitor elevated intestinal parasite burdens in the context of reduced mast cell activation while stabilization of endogenous IL-33 or application of recombinant IL-33 reciprocally reduced intestinal parasite burdens and increased mast cell activation. Using gene-deficient mice, we show that application of IL-33 triggered rapid mast cell-mediated expulsion of parasites directly in the intestine, independent of the adaptive immune system, basophils, eosinophils or Gr-1+ cells but dependent on functional IL-9 receptor and innate lymphoid cells (ILC). Thereby we connect the described axis of IL-33-mediated ILC2 expansion to the rapid initiation of IL-9-mediated and mast cell-driven intestinal anti-helminth immunity.

IL-33 facilitates rapid expulsion of the parasitic nematode Strongyloides ratti from the intestine via ILC2- and IL-9-driven mast cell activation.

Parasitic nematodes such as hookworms actively penetrate the skin of their hosts, encountering skin-resident innate immune cells that represent the host´s first line of defense. Here we use  as a model for an intestinal helminth parasite with tissue migrating stages. We show that interception and killing of migrating larvae in mice during a 1 infection occurred predominantly in skin and muscle tissue before larvae migrated  lung and head tissue to the intestine. Inhibition of larval migration was even more efficient in immune mice during a 2 infection where larvae barely left the site of entry i.e. the foot. Using cell-deficient mice we show that interception in the tissue was predominantly mediated by neutrophils and eosinophils while basophils and mast cells were dispensable . Likewise, neutrophils and eosinophils inhibited  L3 motility  in the context of ETosis. Thereby eosinophils were strictly dependent on the presence of anti- antibodies while neutrophils inhibited L3 motility as such. Also, MPO and MMP-9 were released by neutrophils in response to L3 alone, but immune plasma further stimulated MPO release in an antibody-dependent manner. In summary, our findings highlight the central role of the skin as first line of defense against helminth parasites in both, innate and adaptive immunity.

Eosinophils and Neutrophils Eliminate Migrating  Larvae at the Site of Infection in the Context of Extracellular DNA Trap Formation.

[This corrects the article DOI: 10.3389/fimmu.2021.715766.].

Corrigendum: Eosinophils and Neutrophils Eliminate Migrating  Larvae at the Site of Infection in the Context of Extracellular DNA Trap Formation.

Strongyloidiasis is a neglected tropical disease estimated to affect more than 600 million people worldwide. Recently, the World Health Organization road map on neglected tropical diseases 2021-2030 has put the focus on strongyloidiasis, including this disease within its mass drug administration campaigns. With the use of ivermectin in extensive treatment of all populations at-risk, identifying effective therapeutic alternatives is crucial in case ivermectin resistance arises. The objective of the present study was the development of a larval migration inhibition assay to evaluate the anthelmintic efficacy of commercial drugs and diamine and aminoalcohol derivatives against infective Strongyloides ratti third stage larvae. Through this technique, we successfully screened and estimated the in vitro anthelmintic efficacy of six commercial drugs, seven diamine derivatives and eight aminoalcohol derivatives. Unexpectedly, the half-maximal effective concentration of ivermectin and moxidectin (2.21 and 2.34 μM, respectively) were observed as the highest value obtained among all commercial drugs tested by this in vitro technique. Moreover, some diamine and aminoalcohol derivatives showed superior efficacy inhibiting S. ratti motility compared to ivermectin, with five compounds (AA23, AA34, AO2 AO7 and AO14b) also displaying selectivity indexes on HepG2 and Caco2 higher than 1. These findings underscore the potential of these derivatives as promising alternatives for strongyloidiasis treatment, warranting further investigation and in vivo efficacy assessment.

Evaluating alternative compounds for strongyloidiasis therapy: Novel insights from larval migration inhibition test.

Strongyloides ratti is a helminth parasite that displays tissue-migrating and intestinal life stages. Myeloid C-type lectin receptors (CLRs) are pattern recognition receptors that recognize pathogen-derived ligands and initiate immune responses. To date, the role of CLRs in S. ratti infection has not been investigated. Here, we show that S. ratti-derived ligands are recognized by the CLR Macrophage inducible Ca-dependent lectin receptor (MINCLE). While MINCLE-deficiency did not affect initiation of a protective anti-S. ratti type 2 immunity, MINCLE-deficient mice had a transient advantage in intestinal immunity. Unravelling the underlying mechanism, we show that next to macrophages, dendritic cells and neutrophils, a fraction of eosinophils express MINCLE and expand during S. ratti infection. MINCLE-deficient eosinophils exhibited a more active phenotype and prolonged expansion in vivo and displayed increased capacity to reduce S. ratti motility and produce reactive oxygen species in vitro, compared to wild-type (WT) eosinophils. Depletion of eosinophils in S. ratti-infected mice after the tissue-migration phase elevated intestinal worm burden in MINCLE-deficient mice to the WT level. Thus, our findings establish a central contribution of eosinophils to parasite ejection from the intestine and suggest that S. ratti-triggered signalling via MINCLE interferes with eosinophil mediated ejection of S. ratti from the intestine.

Article	Year
IL-33 facilitates rapid expulsion of the parasitic nematode Strongyloides ratti from the intestine via ILC2- and IL-9-driven mast cell activation. PLoS pathogens\| PubMed ID: 33351862	2020
Eosinophils and Neutrophils Eliminate Migrating Larvae at the Site of Infection in the Context of Extracellular DNA Trap Formation. Frontiers in immunology\| PubMed ID: 34475874	2021
Corrigendum: Eosinophils and Neutrophils Eliminate Migrating Larvae at the Site of Infection in the Context of Extracellular DNA Trap Formation. Frontiers in immunology\| PubMed ID: 35386718	2022
Evaluating alternative compounds for strongyloidiasis therapy: Novel insights from larval migration inhibition test. PLoS neglected tropical diseases\| PubMed ID: 39374184	2024
The C-type lectin receptor MINCLE interferes with eosinophil function and protective intestinal immunity in Strongyloides ratti-infected mice. Mucosal immunology\| PubMed ID: 39581231	2024

Lennart Heepmann

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