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Analysis of the intestinal immune response to Giardia species in cattle and mice

Leentje Dreesen (UGent)
(2014)
Author
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(UGent)
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Abstract
The protozoan parasite Giardia duodenalis is a highly present pathogen around the globe in a vast array of hosts. Once ingested, Giardia can induce intestinal symptoms and could cause significant production losses in animals such as cattle. Although infections can pass by unnoticed and rapidly, a number of patients experience giardiosis as a persistent and chronic disease. Although we have already some knowledge on the immune response in natural hosts, the reason behind the observed chronicity is still unclear and Giardia induced host-pathogen interactions remain incompletely defined. The first step in the research presented in this thesis was to investigate the intestinal response in calves following a G. duodenalis infection using a bovine high-density oligo microarray to analyze global gene expression in the small intestine. The resulting data suggested a decrease in inflammation, immune response, and immune cell migration in infected animals. Quantitative real-time PCR revealed that he transcription levels of IL-6, IL-8, IL-13, IL-17, and IFN-γ showed a trend of being downregulated in the jejunum of infected animals compared to the negative controls. No immune cell recruitment could be seen after infection using histological stainings, and no intestinal pathologies, such as villus shortening or increased levels of apoptosis. Possible regulators of this intestinal response were the nuclear peroxisome proliferator-activated receptors alpha (PPARα), and gamma (PPARγ), all for which an upregulated expression was found in the microarray and qRT-PCR analyses. To gather further insights in the intestinal host response a murine giardiosis model was used where BALB/c and C57Bl/6 mice are infected with their natural parasite Giardia muris. In all mice, a strong up-regulation of Il17a could be observed starting around 1 week post infection. The significance of IL-17A in orchestrating a protective immune response was unequivocally demonstrated in an infection trial using IL-17 receptor A C57Bl/6 KO mice: whereas in wild type mice cyst excretion dropped significantly after 3 weeks of infection, the KO mice were unable to clear infection. No up-regulation could be seen for PPARγ in both mice strains, and in addition, no up-regulated expression was seen for PPARα in BALB/c animals. Analysis of the intestinal response in C57Bl/6 mice however revealed a PPARα induction soon after the initial contact with the parasite, as characterized by the transcriptional up-regulation of Ppara itself and several downstream target genes such as Pltp and Cpt1. This induction of PPARα did not seem to influence the immune response against G. muris since BALB/c mice administrated with a PPARα agonist and PPARα KO C7Bl/6 animals expressed Il17a and could clear the infection similar to WT controls. Overall, we concluded that IL-17A is likely to be a crucial cytokine in the response to Giardia infection and the elimination of the parasite. In cattle it seemed that the PPARs were responsible for the lack of immune response because of their anti-inflammatory and immune suppressing characteristics, but this could not be clarified in G. muris infected mice when looking at PPARα. This nuclear receptor showed an up-regulation early on in infection but did not seem to influence infection duration.
Keywords
Interleukin 17, Host-parasite interactions, Giardia, Intestinal immunity, Peroxisome proliferator-activated receptors

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Citation

Please use this url to cite or link to this publication:

Chicago
Dreesen, Leentje. 2014. “Analysis of the Intestinal Immune Response to Giardia Species in Cattle and Mice”. Merelbeke, Belgium: Ghent University. Faculty of Veterinary Medicine.
APA
Dreesen, L. (2014). Analysis of the intestinal immune response to Giardia species in cattle and mice. Ghent University. Faculty of Veterinary Medicine, Merelbeke, Belgium.
Vancouver
1.
Dreesen L. Analysis of the intestinal immune response to Giardia species in cattle and mice. [Merelbeke, Belgium]: Ghent University. Faculty of Veterinary Medicine; 2014.
MLA
Dreesen, Leentje. “Analysis of the Intestinal Immune Response to Giardia Species in Cattle and Mice.” 2014 : n. pag. Print.
@phdthesis{5714474,
  abstract     = {The protozoan parasite Giardia duodenalis is a highly present pathogen around the globe in a vast array of hosts. Once ingested, Giardia can induce intestinal symptoms and could cause significant production losses in animals such as cattle. Although infections can pass by unnoticed and rapidly, a number of patients experience giardiosis as a persistent and chronic disease. Although we have already some knowledge on the immune response in natural hosts, the reason behind the observed chronicity is still unclear and Giardia induced host-pathogen interactions remain incompletely defined. The first step in the research presented in this thesis was to investigate the intestinal response in calves following a G. duodenalis infection using a bovine high-density oligo microarray to analyze global gene expression in the small intestine. The resulting data suggested a decrease in inflammation, immune response, and immune cell migration in infected animals. Quantitative real-time PCR revealed that he transcription levels of IL-6, IL-8, IL-13, IL-17, and IFN-\ensuremath{\gamma} showed a trend of being downregulated in the jejunum of infected animals compared to the negative controls. No immune cell recruitment could be seen after infection using histological stainings, and no intestinal pathologies, such as villus shortening or increased levels of apoptosis. Possible regulators of this intestinal response were the nuclear peroxisome proliferator-activated receptors alpha (PPAR\ensuremath{\alpha}), and gamma (PPAR\ensuremath{\gamma}), all for which an upregulated expression was found in the microarray and qRT-PCR analyses. To gather further insights in the intestinal host response a murine giardiosis model was used where BALB/c and C57Bl/6 mice are infected with their natural parasite Giardia muris. In all mice, a strong up-regulation of Il17a could be observed starting around 1 week post infection. The significance of IL-17A in orchestrating a protective immune response was unequivocally demonstrated in an infection trial using IL-17 receptor A C57Bl/6 KO mice: whereas in wild type mice cyst excretion dropped significantly after 3 weeks of infection, the KO mice were unable to clear infection. No up-regulation could be seen for PPAR\ensuremath{\gamma} in both mice strains, and in addition, no up-regulated expression was seen for PPAR\ensuremath{\alpha} in BALB/c animals. Analysis of the intestinal response in C57Bl/6 mice however revealed a PPAR\ensuremath{\alpha} induction soon after the initial contact with the parasite, as characterized by the transcriptional up-regulation of Ppara itself and several downstream target genes such as Pltp and Cpt1. This induction of PPAR\ensuremath{\alpha} did not seem to influence the immune response against G. muris since BALB/c mice administrated with a PPAR\ensuremath{\alpha} agonist and PPAR\ensuremath{\alpha} KO C7Bl/6 animals expressed Il17a and could clear the infection similar to WT controls. Overall, we concluded that IL-17A is likely to be a crucial cytokine in the response to Giardia infection and the elimination of the parasite. In cattle it seemed that the PPARs were responsible for the lack of immune response because of their anti-inflammatory and immune suppressing characteristics, but this could not be clarified in G. muris infected mice when looking at PPAR\ensuremath{\alpha}. This nuclear receptor showed an up-regulation early on in infection but did not seem to influence infection duration.},
  author       = {Dreesen, Leentje},
  isbn         = {9789058643933},
  language     = {eng},
  pages        = {134},
  publisher    = {Ghent University. Faculty of Veterinary Medicine},
  school       = {Ghent University},
  title        = {Analysis of the intestinal immune response to Giardia species in cattle and mice},
  year         = {2014},
}