Sampling Site Effects on Bronchoalveolar Lavage Fluid Protein Expression in Bovine Respiratory Disease: A Proteomic Analysis

Bovine Respiratory disease complex (BRDC), is a multifactorial disease affecting cattle and is most frequently characterized by the clinical onset of bronchopneumonia. Bronchoalveolar lavage fluid (BALF) from the alveoli and epithelial airway is enriched in proteins indicative of pathogenesis. The use of BALF in the diagnosis of pulmonary diseases in humans is well established and is valuable in the diagnosis of BRD. In BRDC, since the manifestation of bronchopneumonia is punctate, the area of sampling could alter the diagnostic value of in vivo BALF. Therefore, it is important to establish a baseline of protein expression profiles of BALF from different anatomical locations of bovine lungs. Here, we describe the first preliminary comparative proteomic analysis of BALF collected from post mortem lungs in a single agent challenge model with M. haemolytica. From the challenged animals BALF was collected from areas of the lung that appeared normal and affected by visual examination, proteins were isolated from these samples and compared to the proteins isolated from the control animals by 1D LC ESI MS/MS. We found that the trends in protein expression changes were consistent between normal and affected BALF for shared proteins. Expression changes that were unique to each sample type represented proteins belonging to different functional categories. Our results clearly show that the inherent variation in protein expression from different anatomical locations of lung in BRD needs to be accounted for when using in vivo BALF for diagnostics.