title: Cytokine expression by pulmonary leukocytes from calves challenged with wild-type and leukotoxin-deficient Mannheimia haemolytica.
abstract: The objective of this study was to assess the role of leukotoxin (LKT) in modulating the pulmonary cytokine response of calves challenged with Mannheimia haemolytica. Thirty-six calves, seronegative to LKT and M. haemolytica whole cell antigen were divided into three groups (I, II and III). Calves in groups I and II were challenged by the intra-bronchial route with 25 mL of phosphate buffered saline (PBS) containing 0.44×10(9) cfu/mL of LKT deficient (lkt(-)) and 25 mL of PBS containing 0.31×10(9) cfu/mL of wild-type (wt) M. haemolytica serotype 1, respectively. Group III calves were challenged intra-bronchially with 25 mL of sterile PBS. Leukocytes were collected from broncho-alveolar lavage fluid (BALF) 4 days before and at 1, 3, and 6 days post-inoculation (p.i.). Expression of the following cytokines in the recovered leukocytes was measured using real-time PCR: interleukin (IL)-1β, -8, -10, -12 (p40) and TNF-α. The amount of TNF-α produced was also quantified by ELISA. Although a statistically significant difference in the expression of these cytokines was not observed between groups challenged with the wt and lkt(-) strains, the wt infected group (II) did exhibit higher mean clinical scores. Overall, there was considerable variation in the composition of the BALF between the groups and by day 7 p.i., both lkt(-)- and wt-challenged calves had seroconverted to M. haemolytica.
authors.affiliation: Department of Veterinary Pathobiology, Center for Veterinary Health Sciences, Oklahoma State University, Stillwater, OK 74078, USA. ksingh08@illinois.edu
authors.forename: Kuldeep
authors.initials: K
authors.lastname: Singh
authors.forename: Anthony W
authors.initials: AW
authors.lastname: Confer
authors.forename: Douglas L
authors.initials: DL
authors.lastname: Step
authors.forename: Theresa
authors.initials: T
authors.lastname: Rizzi
authors.forename: John H
authors.initials: JH
authors.lastname: Wyckoff
authors.forename: Hsin-Yi
authors.initials: HY
authors.lastname: Weng
authors.forename: Jerry W
authors.initials: JW
authors.lastname: Ritchey
mesh_terms: D000818:Animals; D002417:Cattle / Q000276:immunology*; D016207:Cytokines / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay / Q000662:veterinary; D005098:Exotoxins / Q000172:deficiency / Q000378:metabolism*; D007962:Leukocytes / Q000166:cytology / Q000276:immunology / Q000378:metabolism*; D008168:Lung / Q000166:cytology / Q000276:immunology / Q000378:metabolism*; D016978:Mannheimia haemolytica / Q000276:immunology / Q000378:metabolism* / Q000472:pathogenicity; D011897:Random Allocation; D060888:Real-Time Polymerase Chain Reaction / Q000662:veterinary; D037521:Virulence Factors
chemical_list: D016207:Cytokines; D005098:Exotoxins; D037521:Virulence Factors; C018579:leukotoxin