A52-75-2007E.pdf - AgroMedia International Inc

Health25Characterization of cytokine expression in milk somatic cells duringintramammary infections with Escherichia coli or Staphylococcusaureus by real-time PCRCorresponding AuthorZhao, X.McGill UniversityCollaboratorsLee, J.-W.McGill UniversityBannerman, D.D.USDA Beltsville AgriculturalResearch CenterPaape, M.J.USDA Beltsville AgriculturalResearch CenterHuang, M.-K.McGill UniversityVeterinary Research (2006) Vol. 37 p. 219-229.Escherichia coli (EC) and Staphylococcus aureus (SA) are the 2 most prevalentbacteria responsible for bovine mastitis. EC is an environmental gramnegativeorganism that causes acute mastitis which normally resolvesspontaneously. SA is a contagious gram-positive bacterium that inducesa chronic mastitis which may persist for the lifetime of the cow. Thesecontrasts in duration and severity of infection suggest that there are differencesin the way that the cow’s immune system responds to these 2pathogens. The objective of this study was to examine the patterns of immunesystem activation signals (cytokines) that are produced in responseto mammary gland challenges by EC or SA. One quarter in each of 8 cowswas injected with EC; quarters in a second group of 8 were challenged withSA. In each of the 16 cows, a second quarter was used as a control. At timeintervals after injection, somatic cells from each quarter were examined forthe expression of genes coding for various cytokines. With the exception ofinterferon-γ in SA-challenged quarters, the average level of expression ofall cytokine-coding genes increased in response to both pathogens. However,responses were higher and faster in cells from quarters challengedwith EC. The lower responses in SA cows and the absence of interferonγgene expression may partly explain why SA infections tend to becomechronic.26DNA immunization of dairy cows with the clumping factor A ofStaphylococcus aureusCorresponding AuthorLacasse, P.AAFC Dairy and Swine Researchand Development CentreCollaboratorsEl-Din, A.N.M.Alexandria UniversityShkreta, L.Université de SherbrookeTalbot, B.G.Université de SherbrookeDiarra, M.S.AAFC Dairy and Swine Researchand Development CentreVaccine (2006) Vol. 24 p. 1997-2006.Staphylococcus aureus (SA) is one of the most common and costly causesof chronic mastitis in dairy cattle. One of the first events in intramammaryinfection by SA is attachment to the cells lining the inside of the gland.Clumping factor A (ClfA) and fibronectin-binding protein (FBP) are SA surfaceproteins that facilitate attachment. In a previous study, the authors ofthis paper showed that a DNA vaccine targeting ClfA and FBP providedpartial protection to cows challenged with an intramammary dose of SA.The level of protection provided by the vaccine was directly proportionalto the level of antibody response it provoked. The objective of the currentstudy was to investigate ways to improve the effectiveness of thevaccine through the addition of agents designed to amplify the immuneresponse. Although most of the agents tested did not augment the antibodyresponse, they did decrease the number of cows that failed to respondto the vaccine. Administration of a dose (boost) of recombinant ClfA3 months after vaccination further reduced the ability of SA to adhere tomammary cells.76 Highlights in Canadian Dairy Cattle Research - 2007