Identification of novel protein biomarkers associated with Johne's disease in Camelus dromedarius plasma using differential proteomics

Johne’s disease is a chronic infectious disease that affects ruminant and pseudoruminant mammals including Arabian camel worldwide causing severe diarrhea ending in death. Several diagnostic tests of varying specificity and sensitivity are currently available for determining the presence of Johne’s disease causative agent Mycobacterium avium subsp. paratuberculosis; however, none of these tests is sufficiently sensitive to diagnose infected animals during the subclinical phase of the disease. Therefore, there is an urgent need to develop robust and reliable diagnostic tests capable of distinguishing between infected and healthy animals. This study utilized proteomic methodologies (GeLC-MS/MS and 2-dimensional gel analysis) to perform comparative proteomic profiling of plasma from three sample groups (healthy, exposed and diseased) to identify and characterize novel protein biomarkers. Total protein quantitation of plasma showed gross level differences within the three sample groups used in the study. Substantial qualitative differences in at least 18 protein spots were observed by 2D electrophoresis and dMS analyses between diseased and control groups suggesting qualitative differences in plasma proteins reflecting the physiological state under normal and diseased conditions. In conclusion, the feature-level dMS data shows multiple ions that are potential biomarkers for Johne’s disease. Targeted analysis with de novo sequencing is required to elucidate the identifications of associated peptides. These proteins may provide suitable diagnostic or prognostic markers as well as drug targets. To the best of our knowledge, this is the first report of plasma proteomic biomarker of camels infected with Mycobacterium avium subsp. paratuberculosis. We expect that these biomarkers might be contributing in explaining interaction between the camel and mycobacterium.