The Outer membrane protein OmpA ofMannheimia haemolyticaA1 is involved in the binding of fibronectin

Abstract

An enzyme-linked immunosorbent assay using bovine fibronectin as the substrate was used to demonstrate that Mannheimia haemolytica A1 binds to fibronectin. This binding to fibronectin was specific as no binding was observed with bovine fibrinogen. The binding to fibronectin was not observed if the M. haemolytica A1 cells were pretreated with trypsin or proteinase K, suggesting that it involved a protein molecule on the cell surface. Interestingly, the fibronectin-binding activity was found to be higher in an acapsular mutant compared with its parent strain. The fibronectin-binding protein was shown to be present in the outer membrane fraction of M. haemolytica A1. A 45 kDa outer membrane protein that binds to fibronectin was identified by Far-Western immunoblot analysis. This protein was purified and subjected to MS matrix-assisted laser desorption ionization time-of-flight analysis. The results identified it to be outer membrane OmpA based on comparison with the M. haemolytica A1 genomic sequence.

Outer Membrane Protein A of Bovine and Ovine Isolates of Mannheimia haemolytica Is Surface Exposed and Contains Host Species-Specific Epitopes

“…Since a well-developed capsule was observed by Maneval staining in these isolates under different growth conditions, our findings strongly suggest that the capsule does not mask the OmpA protein since antibody binding seemed unaffected. However, in a previous study the OmpA protein of an acapsular mutant was shown to have higher fibronectin-binding activity than that of the capsular parental strain (48), suggesting that the capsule may partially mask the protein.…”

“…In particular, it has been shown that the OmpA protein of bovine serotype A1 isolates of M. haemolytica binds to fibronectin (48) and to bovine bronchial epithelial cells (41). However, a potential role of OmpA as an adhesin has yet to be investigated in ovine isolates of M. haemolytica.…”

“…Based on the distribution of the OmpA1 and OmpA2 proteins among bovine and ovine isolates, respectively, and the localization of the amino acid variation to the tips of the four loops, it was hypothesized that OmpA acts as a ligand, plays an important role in adherence, and is involved in host specificity (22). Subsequently, it was demonstrated that OmpA is involved in the binding of serotype A1 M. haemolytica to bovine bronchial epithelial cells (41) and that fibronectin is a potential host receptor molecule in cattle (48).…”

“…There is growing evidence to suggest that the OmpA protein of M. haemolytica functions as an adhesin (41,48). OmpA is a highly conserved, integral, outer membrane protein of Gramnegative bacteria that has been implicated in a diverse range of functions in different species (reviewed in reference 72).…”

Immunogenicity of Mannheimia haemolytica Recombinant Outer Membrane Proteins Serotype 1-Specific Antigen, OmpA, OmpP2, and OmpD15

“…E. coli OmpA has been shown to be an abundant protein and a predominant antigen, occurring at a copy number of approximately 100,000 copies per cell (27,45). With the demonstrated pathogenic functions of OmpA, such as epithelial adhesion and binding to fibronectin, and its immunogenicity, addition of rOmpA to M. haemolytica vaccines should be examined further (26,29,31).…”