Evaluation of Host Response in Calves Challenged with Mannheimia haemolytica using Expression Proteomics

Bovine Respiratory disease complex (BRD) is a multifactorial disease-affecting cattle and frequently characterized by the clinical onset of bronchopneumonia associated with Mannheimia haemolytica. Pathology of BRD is complex and requires the understanding of protein pathways altered during disease manifestation. However, mass spectrometry based expression proteomics to identify protein biomarkers for disease stratification or diagnosis remains underutilized in BRD. In order to identify a baseline protein expression associated with BRD, we chose to focus on lung tissue, which is the terminal site of infection. Utilizing lung biopsy samples from a challenge trial to identify proteins associated with BRD would rely only on clinical signs and could have confounding affects, as clinical signs do not correspond with lung pathophysiology. To address this our study design included collection of post-mortem samples from calves challenged with M. haemolytica from regions of the lung that showed lesions as well as non-lesion regions based on pathophysiology. We describe the first comprehensive and comparative proteomic analysis of lung tissue samples collected seven days post-challenge with M. haemolytica from affected and unaffected lobes within the same bovine lung, using 1D LC ESI MS/MS. This comparative expression analysis identified proteins in lung tissue that are differentially expressed following M. haemolytica challenge irrespective of the area of sampling, and can be be potential diagnostic markers.