title: Transcriptomic analysis of milk somatic cells in mastitis resistant and susceptible sheep upon challenge with Staphylococcus epidermidis and Staphylococcus aureus.
abstract: BACKGROUND
  The existence of a genetic basis for host responses to bacterial intramammary infections has been widely documented, but the underlying mechanisms and the genes are still largely unknown. Previously, two divergent lines of sheep selected for high/low milk somatic cell scores have been shown to be respectively susceptible and resistant to intramammary infections by Staphylococcus spp. Transcriptional profiling with an 15K ovine-specific microarray of the milk somatic cells of susceptible and resistant sheep infected successively by S. epidermidis and S. aureus was performed in order to enhance our understanding of the molecular and cellular events associated with mastitis resistance.
  
  
  RESULTS
  The bacteriological titre was lower in the resistant than in the susceptible animals in the 48 hours following inoculation, although milk somatic cell concentration was similar. Gene expression was analysed in milk somatic cells, mainly represented by neutrophils, collected 12 hours post-challenge. A high number of differentially expressed genes between the two challenges indicated that more T cells are recruited upon inoculation by S. aureus than S. epidermidis. A total of 52 genes were significantly differentially expressed between the resistant and susceptible animals. Further Gene Ontology analysis indicated that differentially expressed genes were associated with immune and inflammatory responses, leukocyte adhesion, cell migration, and signal transduction. Close biological relationships could be established between most genes using gene network analysis. Furthermore, gene expression suggests that the cell turn-over, as a consequence of apoptosis/granulopoiesis, may be enhanced in the resistant line when compared to the susceptible line.
  
  
  CONCLUSIONS
  Gene profiling in resistant and susceptible lines has provided good candidates for mapping the biological pathways and genes underlying genetically determined resistance and susceptibility towards Staphylococcus infections, and opens new fields for further investigation.
authors.affiliation: INRA, UR631, SAGA, F-31326 Castanet-Tolosan, France.
authors.forename: Cécile M D
authors.initials: CM
authors.lastname: Bonnefont
authors.forename: Mehdi
authors.initials: M
authors.lastname: Toufeer
authors.forename: Cécile
authors.initials: C
authors.lastname: Caubet
authors.forename: Eliane
authors.initials: E
authors.lastname: Foulon
authors.forename: Christian
authors.initials: C
authors.lastname: Tasca
authors.forename: Marie-Rose
authors.initials: MR
authors.lastname: Aurel
authors.forename: Dominique
authors.initials: D
authors.lastname: Bergonier
authors.forename: Séverine
authors.initials: S
authors.lastname: Boullier
authors.forename: Christèle
authors.initials: C
authors.lastname: Robert-Granié
authors.forename: Gilles
authors.initials: G
authors.lastname: Foucras
authors.forename: Rachel
authors.initials: R
authors.lastname: Rupp
mesh_terms: D000818:Animals; D058491:Bacterial Load; D002452:Cell Count; D016000:Cluster Analysis; D005260:Female; D020869:Gene Expression Profiling; D053263:Gene Regulatory Networks; D007113:Immunity, Innate; D007962:Leukocytes / Q000473:pathology; D008413:Mastitis / Q000235:genetics / Q000276:immunology / Q000382:microbiology / Q000662:veterinary*; D053858:Metabolic Networks and Pathways; D008892:Milk / Q000166:cytology* / Q000276:immunology / Q000382:microbiology; D020411:Oligonucleotide Array Sequence Analysis; D025341:Principal Component Analysis; D012756:Sheep; D012757:Sheep Diseases / Q000235:genetics* / Q000276:immunology / Q000382:microbiology; D013203:Staphylococcal Infections / Q000235:genetics / Q000276:immunology / Q000662:veterinary*; D013211:Staphylococcus aureus; D013212:Staphylococcus epidermidis