A temporal shift in regulatory networks and pathways in the bovine small intestine during Cooperia oncophora infection.

Cooperia oncophora is an important parasitic nematode of cattle with a wide distribution in temperate areas. Twenty Holstein nematode-naïve bull calves were experimentally infected with approximately 100,000 infective L3s and infection was allowed to progress for 7, 14, 28, 42 days, respectively. This experiment was conducted to identify putative recognition and inflammatory pathways in the host-parasite relationship. Gene expression profiles of the small intestine were compared using a high-density bovine 60 mer oligo microarray. A total of 310 genes were differentially expressed during the course of infection. The pathways and regulatory networks significantly impacted by the infection were analysed. A total of 22 canonical pathways and nine regulatory networks were significantly affected during infection. During the early phase of the infection (7 days p.i.), parasites suppressed the acute phase response and the complement system of the host. At 14 days p.i., three out of the six pathways impacted were related with retinoid X receptor (RXR) functions. At 28 days p.i., the effects on RXR were less evident. The host response shifted to lipid metabolism and signalling, especially eicosanoid production and signalling, suggesting that eicosanoid-mediated inflammation might be a major host defence mechanism. By 42 days p.i., the pathways impacted involved glycosphingolipid biosynthesis and transforming growth factor beta (TGFbeta signalling. The expression of cadherin-like 26 (CDH26) was strongly up-regulated starting at 14 days p.i. and peaked at 28 days p.i. The extent of its expression is positively correlated with the infiltration of eosinophils (R=0.82) and coincides with the number of adult parasites in the tissue. CDH26 demonstrated an expression profile similar to two other cell adhesion molecules involved in recognition of carbohydrates on foreign organisms, collectin and galectin, suggesting that it may serve as a pattern recognition molecule for C. oncophora. These results provide a potential molecular roadmap for future studies aimed at defining host immune responses and understanding protective immunity against gastrointestinal nematodes.