Submitted to: Animal Health Research Reviews
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 4, 2000
Publication Date: N/A
Interpretive Summary: Pathogenic members of the Brachyspira genus cause colitis in growing pigs. The organisms are attracted to the surface of the intestine, attach and frequently invade. These pathogenic mechanisms are poorly understood. Proteins that are expressed on the bacterial cell surface during infection may play an important role during infection but have not been well characterized. This paper reviews the current knowledge of the Brachyspira outer membrane including the characterization of unique proteins. It concludes with a summary of methods that we have used to isolate and characterize B. pilosicoli membrane proteins. This includes isolating membrane vesicles, producing a library of monoclonal antibodies to specific proteins that may be suitable for the development of diagnostic tests and the cloning and sequencing of a unique lipoprotein gene.
Technical Abstract: Little is known about the outer membrane structure of Brachyspira hyodysenteriae and Brachyspira pilosicoli or the role of outer membrane proteins (OMPs) in host colonization and the development of disease. The isolation of outer membrane vesicles from B. hyodysenteriae has confirmed that cholesterol is a significant outer membrane constituent and that it may impart unique characteristics to the lipid bilayer structure including a reduced density. Unique proteins that have been identified in the B. hyodysenteriae outer membrane include the variable surface (Vsp) proteins and lipoproteins such as SmpA and BmpB. While the function of these proteins remains to be determined, there is evidence to suggest that they may be involved in immune evasion. These data may explain the ability of the organism to initiate chronic infection. OMPs may be responsible for the unique attachment of B. pilosicoli to colonic epithelial cells; however, the only B. pilosicoli OMPs that have been identified to date are involved in metabolism. In order to identify further B. pilosicoli OMPs we have isolated membrane vesicle fractions from strain 95-1000 by osmotic lysis and isopycnic centrifugation. The fractions were free of cytoplasmic and flagella contamination and contained outer membrane. Inner membrane contamination was minimal but could not be completely excluded. An abundant 45 kDa heat modifiable protein was shown to have significant homology with B. hyodysenteriae Vsp, and monoclonal antibodies were produced that reacted with five B. pilosicoli-specific membrane protein epitopes.