Johne's disease or paratuberculosis is a chronic enteritis of ruminants caused by Mycobacterium avium subspecies paratuberculosis. It is endemic in Europe and the U.S.A and responsible for significant economic losses to the livestock industries through premature culling, lost productivity, infertility, susceptibility to disease, lost export markets and direct cost on diagnosis and control. Current control measures are generally inefficient because they depend on culling or removing animals that show positivity in sub-optimal diagnostic tests that lack specificity and have poor sensitivity.

In this study we investigated proteins expression changes associated to Johne's disease using a proteomic approach. 2D-PAGE coupled to mass spectrometry was used as a tool to investigate up or down regulated milk and serum proteins during natural infection.

Healthy and affected bovine sera and milk were harvested, quantitated and prepared for 2-DE by dilution in isoelectric focusing (IEF) rehydration solution on 18 cm pH 3-10 IPG strips and focused on the IPGphor III apparatus. Second dimension electrophoresis was performed on large format SDS - polyacrylamide gels. Silver stained and Coomassie stained proteins maps were analysed using ImageMaster 2D Platinum software.

Some different proteins expression were detected in both healthy and affected sera and milk. Image analysis of serum proteome from healthy and paratuberculosis infected bovine showed an increased expression of immunoglobulin IgG1, IgM ,IgG light chain, IgG heavy chain, and a transthyretin decrease. In both gels about 435 spot proteins were detected and only 35 did not matched each other. Image analysis of milk proteome have shown that caseins are most abundant in milk from infected bovines that in control milk. Their potential role in biomarker discovery and disease progression will be discussed.