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Genetics, Bioinformatics & Computational Biology (GBCB) Seminar
(Seminar/Conference)
Title: Microarray Analysis of Abomasal and Lymph Node Tissues of Hair and Wool Sheep to Identify Genes Associated with Resistance to the Gastrointestinal Parasite, Haemonchus contortus”.
Presenter: Kathryn MacKinnon, GBCB PhD Candidate
Abstract: Gastrointestinal parasitism results in extensive economic loss to livestock producers worldwide. Among sheep producers, the parasitic nematode Haemonchus contortus causes the greatest impact, especially in hot, humid areas conducive to rapid larval development. Carribbean hair sheep are known to be highly resistant to these abomasal parasites. We believe that hair sheep possess the ability to produce a stronger, faster immune response to the invading larvae, resulting in parasite expulsion. The precise genes and mechanisms involved in parasite resistance are poorly understood. In an effort to elucidate these mechanisms, resistant hair and susceptible wool sheep infected with H. contortus were compared to determine immune response differences in circulation, abomasal tissue and abomasal lymph nodes.
Increases in circulating and local antibodies have been shown to be associated with greater resistance to H. contortus in certain breeds of sheep. We measured total IgE levels in serum and supernatants from homogenized tissues and found significantly (P < 0.01) higher total IgE in hair sheep lymph node samples at 27 days after infection. Other time points and breed differences were not found to be different. Parasite-specific IgE will be measured to further evaluate these samples. Breed differences in total IgA and parasite-specific IgA will also be determined. Immune cells, including eosinophils, mast cells, and globule leukocytes, infiltrating into the abomasum were assessed. Globule leukocytes, a degranulated mast cell, were not found to differ. Eosinophils, which have been shown to damage parasitic larvae, significantly (P < 0.05) increased in infected animals, with the highest cell counts being in infected hair versus wool sheep (P < 0.10).
To determine differential gene expression between hair and wool sheep, a bovine cDNA microarray was used for both abomasal and lymph node tissues. Within the genes found to be significantly different, a high percentage ( > 10% in abomasal samples) were immune genes. Particular cytokines and cytokine receptors having increased expression in lymph node or abomasal tissues of hair sheep include IL4R-alpha, IL12R-beta1 and IFN-gamma receptor beta. These genes and others on the array will be validated with real-time RT-PCR in addition to candidate genes selected from the literature. Results suggest humoral and cellular immune responses to the parasite may be initiated at higher levels in infected hair sheep.
Preliminary analysis indicates that upon parasitic infection, the immune response in hair sheep is initiated sooner and at increased levels. Understanding these genes and mechanisms involved in parasite expulsion will not only help in determining resistant animals, but also provide markers for animal selection. These markers could be used in crossbreeding programs to improve parasite resistance in susceptible breeds of sheep. Differences in immune effectors in circulation could be used as an indicator of resistance, providing an accessible measure to be used in current selection programs. The information obtained from this study will provide new opportunities for the development of more effective parasite control strategies.
Public welcome!! Refreshments from 3:15-3:50, seminar starts promptly at 4 pm.
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540-231-1928