Abstract
Haemonchus contortus is one of the most pathogenic gastrointestinal nematodes in small ruminants. To understand molecular mechanisms underlying host resistance to this parasite, we used RNA-sequencing technology to compare the transcriptomic response of the abomasal tissue, the site of the host-parasite interaction, of Merino sheep bred to be either genetically resistant or susceptible to H. contortus infection. Two different selection flocks, the Haemonchus selection flock (HSF) and the Trichostrongylus selection flock (TSF), and each contains a resistant and susceptible line, were studied. The TSF flock was seemingly more responsive to both primary and repeated infections than HSF. A total of 127 and 726 genes displayed a significant difference in abundance between resistant and susceptible animals in response to a primary infection in HSF and TSF, respectively. Among them, 38 genes were significantly affected by infection in both flocks. Gene ontology (GO) enrichment of the differentially expressed genes identified in this study predicted the likely involvement of extracellular exosomes in the immune response to H. contortus infection. While the resistant lines in HSF and TSF relied on different mechanisms for the development of host resistance, adhesion and diapedesis of both agranulocytes and granulocytes, coagulation and complement cascades, and multiple pathways related to tissue repair likely played critical roles in the process. Our results offered a quantitative snapshot of changes in the host transcriptome induced by H. contortus infection and provided novel insights into molecular mechanisms of host resistance.
Highlights
Gastrointestinal nematodes (GIN) represent a major health issue for livestock production systems worldwide [1]
Principal component analysis (PCA) analysis shows that the separation between the two flocks, between the two lines (Additional file 2), or among the various experimental groups (Figure 1) was indistinguishable, suggesting that neither long-term selective breeding nor different experimental H. contortus infection protocols had a profound effect on the overall abomasal transcriptome structure and composition
We identified 127 and 726 Differentially expressed genes (DEG) in the innate infection groups between the R and S lines within the Haemonchus selection flock (HSF) and Trichostrongylus Selection Flock (TSF) flocks, respectively, while the number of DEG identified in the acquired groups was 19 and 378 between the R and S lines within
Summary
Gastrointestinal nematodes (GIN) represent a major health issue for livestock production systems worldwide [1]. GIN infection causes serious losses to farmers, both in impaired production and in control with anthelmintics. Current reliance on anthelmintics has resulted in public concerns for animal welfare and the contaminating residues in animal products [3]. Immunological protection against GIN infection is associated with T-helper (Th) responses as well as tissue repair systems. A hallmark of immunity to GIN is a strong Th2 immune response [8, 9], characterized by the production of cytokines interleukin 4 (IL4), IL5, and IL13 [10]. In sheep resistant to GIN, the characteristics of a Th2 host response include the production of elevated levels of parasite-specific immunoglobulin A (IgA), IgE and IgG1
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