Unknown,Transcriptomics,Genomics,Proteomics

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Innate immunity and the evolution of resistance to an emerging infectious disease in a wild bird

ABSTRACT: Innate immunity is expected to play a primary role in conferring resistance to novel infectious diseases, but few studies have attempted to examine its role in the evolution of resistance to emerging pathogens in wild vertebrate populations. Here we used experimental infections and cDNA microarrays to examine whether changes in the innate and/or acquired immune responses likely accompanied the emergence of resistance in house finches (Carpodacus mexicanus) in the eastern United States subject to a recent outbreak of conjunctivitis-causing bacterium (Mycoplasma gallisepticum- MG). Three days following experimental infection with MG, we observed differences in the splenic transcriptional responses between House Finches from eastern U.S. populations, with a 12-year history of MG exposure, versus western U.S. populations, with no history of exposure to MG. In particular, western birds down-regulated gene expression, while eastern finches showed no expression change relative to controls. Studies involving poultry have shown that MG can manipulate host immunity, and our observations suggest that pathogen manipulation occurred only in finches from the western populations, outside the range of MG. Fourteen days after infection, eastern finches, but not western finches, up-regulated genes associated with acquired immunity (cell-mediated immunity) relative to controls. These observations suggest population differences in the temporal course of the response to infection with MG, and imply that innate immune processes were targets of selection in response to MG in the eastern U.S. population. Birds were randomly selected to be kept either as controls or infected via ocular inoculation with 20 μl of culture containing 1 x 104 to 1 x 106 color changing units/ml of an early 2007 Auburn MG isolate. All infected birds were inoculated with precisely the same volume of the same culture. Control birds were sham infected using sterile SP4 medium (Whitcomb 1983). Infected birds were euthanized three days (N=6 from Arizona and N=11 from Alabama) and 14 days (N=11 from Arizona and N=12 from Alabama) after treatment. Control birds were euthanized 14 days after sham-inoculation; Control (N=11 birds from Arizona and 9 from Alabama) and infected birds were maintained under identical conditions, but in separate rooms of an aviary. Infected birds were euthanized three days (N=6 from Arizona and N=11 from Alabama) and 14 days (N=11 from Arizona and N=12 from Alabama) after treatment. Control birds were euthanized 14 days after sham-inoculation. We used a common reference design (Yang & Speed 2002), in which we pooled 2 to 6 spleens from birds from the same population in the same treatment to generate enough mRNA for microarray hybridizations and hybridized two pools for each treatment from each population.

ORGANISM(S): Carpodacus mexicanus

SUBMITTER: Camille Bonneaud

PROVIDER: E-GEOD-35931 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Background: CrohnM-bM-^@M-^Ys disease is presently an incurable inflammatory bowel disease. Fistulae are extensions of the intestinal tract that may form connections with other organs. These are a common complication of CrohnM-bM-^@M-^Ys disease affecting up to 50% of patients with the most common including perianal and rectovaginal fistulae. The dysregulated growth observed in fistulae shares several major characteristics seen in the development of tumours. These similarities include epithelial-to-mesenchymal transition (EMT), invasive cell growth, increased extracellular matrix production and remodelling, up-regulated local expression of growth factors such as IGF-1 and the down-regulation of apoptosis pathways. Although several susceptibility loci have been described within CrohnM-bM-^@M-^Ys disease there is no individual gene or mutation that identifies susceptibility or the subsequent formation of fistulae within all people. Copy-number variation (CNV) is one mechanism that may explain much of this genetic complexity. CNV may be caused by a variety of mechanisms such as cycles of chromosomal breakage/fusion/bridging that are typical within chronically inflamed tissue. Interestingly CNV shows locus-specific mutation rates between individuals higher than that of SNPs and has been associated with complex Mendelian traits including disease susceptibility. In this current study we performed array comparative genomic hybridisation (aCGH) analysis of active fistulae resected from patients as part of a previous surgical intervention. As the control for comparison we employed tissue taken from the same patient within the same surgery at an uninvolved site of the gastrointestinal tract. This matched control was employed to better investigate CNV specific to the fistula tissue of each individual avoiding complications associated with the large number of CNV present within the healthy population. Major question addressed by the work: What are the differences in genetic copy-number within localised intestinal fistula tissue of individuals with CrohnM-bM-^@M-^Ys disease compared to healthy intestinal tissue from the same individual? Samples were selected from patients presenting with CrohnM-bM-^@M-^Ys Disease fistulae at Eastern Health Department of Gastroenterology and Hepatology (Arnold Street, Box Hill, Victoria, Australia). The 8 samples used in this study were formalin-fixed paraffin-embedded (FFPE) specimens following a surgical intervention to remove fistula tissue. To focus on changes within the individual patient we used tissue taken from the same surgery at an uninvolved region of the intestine as the matched control for CNV analysis.

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Innate immunity and the evolution of resistance to an emerging infectious disease in a wild bird

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