Serum and ileocecal valve proteomic profiles associated with the multifocal pathological form of bovine paratuberculosis

Abstract Bovine paratuberculosis (PTB) lesions progress from focal to multifocal and diffuse pathological forms as infection advances. Whether multifocal lesions represent an intermediate stage in disease progression or a distinct disease outcome remains unclear. This study compares the serum and ileocecal valve (ICV) proteomes of cattle showing multifocal forms of PTB with diffuse forms and no-lesion controls using label-free quantitative proteomics. Compared with no-lesion controls, multifocal forms showed serum differentially expressed proteins (DEPs) involved in anti-inflammatory and oxidative stress responses, including phosphoglycerate kinase 1 (PGK1) and glutathione synthetase (GSS), while ICV DEPs included MHC class II-related proteins, linked to adaptive immunity. In the multifocal versus diffuse comparison, serum DEPs included ATP-binding cassette transporter C4 (ABCC4), associated with metabolite transport and PTB resistance. In contrast, the diffuse versus no-lesion comparison identified serum and ICV DEPs mainly related to immune and RNA-processing pathways. STRING analysis revealed enrichment of extracellular matrix and collagen organisation. ELISA pre-validation of eight serum DEPs followed proteomic trends but did not reach statistical significance. Overall, this study provides insight into the host-pathogen interaction associated with the multifocal form of PTB, compatible with a distinct host response to Mycobacterium avium subspecies paratuberculosis infection and potentially associated with resilience-related host responses.