Bacterial adhesion to mucosal surfaces.

Abstract

Bacteria utilize one or more of several mechanisms to adhere to mucosal surfaces. Members of the enterobacteriaceae and related bacteria typically elaborate adhesive filamentous appendages from their surfaces termed fimbriae (or pili). Vibrio cholerae expresses at least three types of these structures that are likely involved in various stages of colonizing the intestine. So far one of these, termed TCP for toxin coregulated pilus, has been shown to be essential for colonization and virulence in humans and in an infant mouse model. The major pilin subunit, TcpA, is a member of the type 4 pilin class, common to a number of diverse pathogenic bacteria. To understand how these pili function at the molecular level, a transposon mutagenesis was undertaken which identified at least a dozen genes involved in TCP biogenesis, function, and regulation. Despite this complexity, passive immunization of infant mice using polyclonal and monoclonal antibodies directed against TCP suggests that the adhesive moiety lies within the major pilin subunit itself, rather than as a minor pilus adhesin protein as in the case of the PAP and type 1 fimbriae of Escherichia coli. Pilin or peptides corresponding to the epitopes recognized by the monoclonal antibodies represent possible immunogens for improved cholera vaccines.