A role in virulence for Campylobacter jejuni TlyA

Campylobacter jejuni is a leading cause of bacterial enteritis worldwide. Virulence factors in these organisms are mostly involved in adhesion, invasion, or toxicity. Although C. jejuni is known to be non-hemolytic under routine laboratory conditions, there are several reports that these bacteria may produce one or more hemolysins. TlyA proteins produced by Brachyspira, Mycobacterium, and Helicobacter have been described as hemolysins that are important in the pathogenesis of these organisms. The tlyA genes from these bacteria are homologous to the C. jejuni tlyA. In this study, the role of the tlyA gene in the virulence of C. jejuni was examined.;Significant hemolytic activity of C. jejuni cell-free supernatants was observed only when the growth medium was supplemented with 10% FBS, 10% rabbit serum, or 1% RNA-core, suggesting that the hemolytic activity produced by this bacterium depends on the presence of a molecule(s) in these materials capable of acting as a carrier, stabilizer, or inducer. The C. jejuni TlyA expressed in E. coli failed to show any hemolytic activity. Anti-TlyA antiserum prepared using the denatured TlyA protein did not neutralize the hemolytic activity of cell-free filtrates in C. jejuni and Western blot analysis failed to detect any protein band. However, TlyA does not appear to be directly responsible for the hemolytic activity of cell-free filtrates of C. jejuni, but its presence appeared to be necessary for full hemolytic activity. A tlyA insertion mutant incapable of expressing the TlyA protein demonstrated reduced hemolysis as well as significantly lower levels of attachment and invasion of INT-407 cells, though bacterial growth rates were not affected. Complementation of the tlyA mutant with the tlyA gene on a plasmid reconstituted these phenomena to the same level as wild type strain. The TlyA protein was identified as an inner-membrane protein in cell-fractionation experiments and immunoelectron microscopy, and showed significant homology with rRNA methyltransferase proteins. Since hemolytic activity, attachment ability, and internalization are considered virulence factors in pathogenic bacteria, the association of these three phenomena with the presence of the TlyA homolog supports the virulence role of this protein in the pathogenicity of C. jejuni.