Microarray analysis of the intestinal host response in Giardia duodenalis assemblage E infected calves

Despite Giardia duodenalis being one of the most commonly found intestinal pathogens in humans and animals, little is known about the host-parasite interactions in its natural hosts. Therefore, the objective of this study 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 microarray data suggested a decrease in inflammation, immune response, and immune cell migration in infected animals. These findings were examined in more detail by histological analyses combined with quantitative real-time PCR on a panel of cytokines. The 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, and no intestinal pathologies, such as villus shortening or increased levels of apoptosis. Possible regulators of this intestinal response are the nuclear peroxisome proliferator-activated receptors alpha (PPARα), and gamma (PPARγ) and the enzyme adenosine deaminase (ADA), all for which an upregulated expression was found in the microarray and qRT-PCR analyses. Eight male Holstein calves aged two to four weeks old were used for the trial. Prior to arrival, all animals were screened for the presence of Giardia cysts in their faecal samples. After confirming their negative status for all these pathogens, four of the animals were randomly chosen and placed in a G. duodenalis contaminated environment, whereas the four remaining animals were kept as negative controls in separate G. duodenalis-free stables. All calves in the study received the same commercial milk replacer. After three weeks, the presence or absence of a G. duodenalis infection was confirmed by IFA on faecal samples after which the animals were euthanized. Changes in gene expression profiles induced by Giardia duodenalis infection were compared using a high-density 60mer bovine oligo microarray.