Secretion of the virulence-associated Campylobacter invasion antigens fromCampylobacter jejuni requires a stimulatory signal

Campylobacter jejuni are a common cause of human diarrheal illness. Previou s work has demonstrated that C. jejuni synthesize a novel set of proteins u pon coculturing with epithelial cells, some of which are secreted. The secr eted proteins have been collectively referred to as Campylobacter invasion antigens (Cia proteins). Metabolic labeling experiments revealed that Cia p rotein synthesis and secretion are separable and that secretion is the rate -limiting step of these processes. Additional work indicated that Cia prote in synthesis is induced in response to bile salts and various eukaryotic ho st cell components. Host cell components also can induce Cia protein secret ion. Culturing C. jejuni on plates supplemented with the bile salt deoxycho late retarded the inhibitory effect of chloramphenicol on C. jejuni invasio n, as judged by the gentamicin-protection assay. These data suggest that th e coordinate expression of the genes encoding the Cia proteins is subject t o environmental regulation.