2006 merck/merial - School of Veterinary Medicine - Louisiana State ...

will decrease their contractile response to acetylcholine (ACh) in a muscle bath system. Since LPS initially exerts its effectson the intestinal mucosa, we felt it would be valuable to retain both mucosa and muscularis on the tissue strips. Muscle bathswill be incubated with different concentrations of endotoxin and the responses of the tissues to ACh will be noted.Secondly, Polymyxin B (PMB) will be tested to determine its effects on equine intestinal contractility in vitro. Thiswill verify whether it is an appropriate antagonist for our model of LPS-induced immotility. We hypothesize thatadministration of PMB will not result in recordable contractile responses by longitudinal strips of equine jejunum. Acumulative concentration response curve for PMB will be performed. The effect of the drug will be ascertained by noting thecontractile activity following cumulative addition of half-log increments in concentration at 5-minute intervals.Successful simulation of endotoxin exposure by our in vitro model will increase the pool of tissues available forfuture studies. Additionally, investigation of the effects of PMB on equine intestinal contractility may enhance ourunderstanding of its activity in patients treated for colic and endotoxemia.The Effect of Feline Immunodeficiency Virus on CD40 Ligand Response in Bone Marrow DerivedDendritic CellsLindsey M. Habermann, Kevin P. O'Halloran, Tracy L. Lehman, Paul R. AveryDepartment of Microbiology, Immunology, and Pathology, College of Veterinary Medicine and BiomedicalSciences, Colorado State University, Fort Collins COImpairment of Dendritic cell (DC) function contributes to the pathogenesis disease. Studies examining thesignificance of DC dysfunction in human immunodeficiency virus (HIV) infection are ongoing. We used the felineimmunodeficiency virus (FIV) model system to determine at which level DC dysfunction occurs. DCs are potent antigenpresentingcells, critical in pathogen recognition and the initiation of primary T cell response. DCs express toll like receptors(TLR) that activate the immune response via the production of cytokines in response to pathogens. We have previouslyshown that DCs from FIV-infected cats produce increased amounts of IL-10 relative to IL-12 in response to TLR2, TLR4 andTLR9 ligation. After initial pathogen recognition, dendritic cells amplify T cell responses through the expression of CD40, aco-stimulatory molecule that binds CD40L (CD154) on the surface of T cells. This binding results in the production ofcytokines determining the efficacy of the T cell response. Dendritic cell production of IL-12 after CD40 ligation results in theexpansion of CD8+ T lymphocytes, a cell-mediated response. To determine if a similar shift in the IL-12:IL-10 axis atpathogen recognition occurs at the CD40-CD40L binding, feline cytokine production was characterized after DCs werestimulated with 3T3 cells expressing CD40L. We have analyzed the cytokine response from 5 naïve and 4 FIV-infected catsand the same shift favoring IL10 production is not apparent. Instead, there is a trend to a ratio that favors IL-12 expression inthe infected animals. Our results suggest that, while the initial steps in pathogen recognition are altered in FIV-infected DCs,the ability of FIV-infected dendritic cells to amplify an appropriate cell-mediated T cell response remains intact. Futurestudies will be directed at determining which intracellular signaling pathways are involved. This information will be useful inthe design of therapies for lentiviral infections.Effects of genetic background and probiotic treatment on mucosal biofilm integrity in a mouse model ofbacterial-induced inflammatory bowel disease.Katherine Hodes* and Craig L. Franklin, DVM, PhDResearch Animal Diagnostic Laboratory, Department of Veterinary PathobiologyCollege of Veterinary Medicine, University of Missouri, Columbia, MOInflammatory bowel disease (IBD) is a chronic inflammatory disorder of the gastrointestinal tract. The two mostcommon forms of IBD, Crohn’s Disease and ulcerative colitis, have a prevalence of 175-400 cases per 100,000 persons inNorth America. Although the etiology of IBD remains unknown, most evidence suggests that it is the result of a dysregulatedmucosal immune response to microbial antigens in the intestine. Helicobacter hepaticus is a gram-negative bacterium thatcauses large intestinal inflammation in the A/J (A) mouse strain, but not in the C57BL/6 (B6) strain. The first aim of ourstudy is to determine if there is a difference in H. hepaticus biofilm colonization and/or mucus integrity in these two mousestrains that might explain their differing genetic susceptibility. The second aim is to investigate the effects of probiotictreatment on H. hepaticus colonization and mucus integrity prior to and during mucosal inflammation in susceptible A mice.Mucus integrity is assessed using Alcian Blue mucin stains, and biofilm colonization by H. hepaticus is assessed usingimmunohistochemistry. Mice are examined at 0, 30, 60 and 90 days following H. hepaticus inoculation. We hypothesize thatthe cecal mucus layer will be thicker and more continuous and H. hepaticus will be less intimately associated with themucosa in B6 mice as compared to A mice. Similarly, we predict that A mice given probiotic treatment will have thickercecal mucus and less H. hepaticus colonization when compared to mice given vehicle alone. Examination of the 30 daypreinflammatory time point showed decreased mucin staining and very mild inflammation in A mice as compared to B6mice. No differences in mucus staining were evident between probiotic and vehicle-treated A mice. Data generated in thecoming weeks will determine whether the two strains show differences in biofilm integrity as disease advances and ifprobiotics protect against advanced disease by maintaining this biofilm.99