Abstract
Paratuberculosis (PTB) or Johne’s disease is a contagious enteritis of ruminants caused by Mycobacterium avium subsp. paratuberculosis (MAP). Ovine PTB is less understood than bovine PTB, especially concerning paucibacillary infection and its evolution into clinical disease. We combined shotgun proteomics, histopathology and immunohistochemistry for the characterization of ileal tissues collected from seven asymptomatic sheep negative to serum ELISA, positive to feces and tissue MAP IS900 and F57 PCR, histologically classified as paucibacillary, actively infected, together with 3 MAP-free controls (K). Following shotgun proteomics with label-free quantitation and differential analysis, 96 proteins were significantly changed in PTB vs K, and were mostly involved in immune defense processes and in the macrophage-MAP interaction. Principal component analysis (PCA) of protein abundances highlighted two PTB sample clusters, PTB1 and PTB2, indicating a dichotomy in their proteomic profiles. This was in line with the PCA of histopathology data and was related to features of type 2 (PTB1) and type 3a (PTB2) lesions, respectively. PTB2 proteomes differed more than PTB1 proteomes from K: 43 proteins changed significantly only in PTB2 and 11 only in PTB1. The differential proteins cathelicidin, haptoglobin, S100A8 and S100A9 were evaluated by immunohistochemistry. K tissues were negative to cathelicidin and haptoglobin and sparsely positive to S100A8 and S100A9. PTB tissues were positive to all four proteins, with significantly more cells in PTB2 than in PTB1. In conclusion, we described several pathways altered in paucibacillary PTB, highlighted some proteomic differences among paucibacillary PTB cases, and identified potential markers for disease understanding, staging, and detection.
Highlights
Paratuberculosis (PTB) or Johne’s disease is a chronic, contagious enteritis of ruminants caused by Mycobacterium avium subspecies paratuberculosis (MAP)
Principal component analysis (PCA) and hierarchical clustering based on protein abundance values (NSAFs as reported in Additional file 3) generated three main clusters: one including all K samples, one including three PTB samples (P4, P6, and P7) and one including four PTB samples (P1, P2, P3, and P5) (Figures 1A and B)
K and PTB1 were separated from PTB2 by the first component (16.4%), while K was separated from PTB1 by the second component (11.5%)
Summary
Paratuberculosis (PTB) or Johne’s disease is a chronic, contagious enteritis of ruminants caused by Mycobacterium avium subspecies paratuberculosis (MAP). MAP and its role in PTB have been the subject of numerous studies on disease progression and evolution in cattle. Our knowledge in this respect has increased considerably, but some aspects remain unclear in this species, and more effective tools for disease diagnosis and control are still needed [10]. Infected sheep with the subclinical disease can either remain such for their whole life, acting as MAP reservoirs and shedders, or develop clinical disease by showing either paucibacillary (3c) or multibacillary (3b) lesions. Factors, pathways, stages and dynamics of disease progression are not completely understood [20], and the best diagnostic approach remains postmortem evaluation with histopathology image analysis, which represents the best indicator to confirm PTB and define its stage [1, 2, 23, 24]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
