The adherence of bacteria to mucosal surfaces is the first step in the infectious process. It is now generally accepted that type 1 fimbriae mediate the adhesion of some pathogenic as well as non-pathogenic Escherichia coli and are characterized by their ability to bind specifically to D-mannose residues on mucosal cells. Very little fimbriae is known of the binding region of type 1 fimbriae. Recently, we observed that dissociated by guanidine hydrochloride retained binding activities suggesting that mannose binding adhesins resided either on the fimbrial subunit or on a minor component of the fimbriae. We have also observed that a deletion mutation remote from the structural gene encoding the 17 kDa subunit of type 1 fimbriae of E. coli results in loss of mannose binding activity of the fimbriae.
The aim of this project is to identify and characterize the mannose binding moiety(s) of type 1 fimbriae. Specifically, we plan to identify and isolate the adhesin(s) by affinity chromatography using a glycoprotein receptor recently isolated from guinea pig erythrocyte membranes. We plan to raise monoclonal antibodies against the purified adhesin that block the adhesion of the fimbriae. Finally, we plan to determine the minimum structure required for mannose binding; the adhesin will be cleaved by various proteolytic enzymes and the resulting fragments examined for mannose binding and ractivity with antiadhesive monoclonal antibodies. The proposed studies should provide valuable information on the biochemistry and immunology of the mannose binding adhesin. It may also prove useful in the development of a fimbrial vaccine to prevent against bacterial colonization of susceptible mucosal surfaces.
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