Mycobacterium paratuberculosis and Escherichia coli share common antigenic determinants

Paratuberculosis (Johne's disease) is a chronic enteritis of ruminants, which is due to infection by Mycobacterium paratuberculosis. By comparative analysis of Western blots of M. paratuberculosis components incubated with sera from paratuberculous cows (either pre-absorbed or not on an Escherichia coli sonicate), we have shown the presence of cross-reactive antigens between M. paratuberculosis and E. coli. Components in the range of 22 to 75 kDa are recognized by sera from paratuberculous cows, but only some components in the range of 20 to 40 kDa are endowed with specific B-cell epitopes to M. paratuberculosis with respect to E. coli. Cross-reactions were further stressed by the fact that rabbit immunoglobulins to E. coli recognized some ten M. paratuberculosis components (in the range of 45 to 66 kDa). The importance of cross-reactivity between the two bacterial species was evaluated by enzyme-linked immunosorbent assay (ELISA) using soluble sonic-extract components from M. paratuberculosis as antigens. Pre-absorption of series of bovine sera with E. coli resulted in the diminution of ELISA mean optical density readings by 16.1% and 62.0% for paratuberculous or healthy animals, respectively.