Essential Role for Cyclic AMP and Its Receptor Protein in Yersinia enterocolitica Virulence

Abstract

Insertion mutations were isolated in cya and crp of Yersinia enterocolitica, which encode adenylate cyclase and the cyclic AMP (cAMP) receptor protein (CRP). The cya and crp mutants were affected for the production of proteins exported by the Ysc, Ysa, and flagellar type III secretion systems (TTSS). Protein production by each TTSS was restored when the respective mutation was complemented by a plasmid-encoded copy of the wild-type gene. Both cya and crp mutants exhibited reduced virulence for orally infected BALB/c mice in a 50% lethal dose analysis. Examination of bacterial survival in host tissues showed that cya and crp mutants colonized Peyer's patches and, to a lesser extent, mesenteric lymph nodes. However, the mutants did not appear to disseminate to the liver and spleen of infected mice. An initial examination of the effectiveness of Y. enterocolitica cya and crp mutants to stimulate protective immunity against subsequent challenge with virulent bacteria in mice was promising. The results indicate that the cAMP-CRP regulatory system is required for Y. enterocolitica virulence.

Yersinia pestiswith Regulated Delayed Attenuation as a Vaccine Candidate To Induce Protective Immunity against Plague

“…Pla is also involved in the development of pneumonic plague (27), which may explain why we observed lower titers of the two mutants than of the wild type in lung tissue on day 3. Yop secretion is reduced in crp mutants (23,38). The Yop virulon comprises both the Yop effector proteins and the proteins necessary for injecting them into host cells.…”

“…In a recent report, yopJ, a secreted effector protein involved in immune suppression, was also shown to be negatively regulated by crp (55). Crp is required for expression of the Ysc type 3 secretion system and other virulence factors in Yersinia, and functional loss of crp diminishes Yop secretion by Y. enterocolitica and Y. pestis (38,54). The effect of a crp mutation on LcrV secretion has not been reported.…”

“…Strains of Salmonella and Y. enterocolitica with crp deletions are attenuated in mice and stimulate protective immunity against subsequent challenge with the wildtype parent (10,38). In Y. pestis, the crp gene directly regulates expression of some 37 genes, including ypkA and yopO, which encode a secreted virulence factor, and the laterally acquired plasmid genes pla, a known virulence factor, and pst, encoding the bacteriocin pesticin (38,54). In a recent report, yopJ, a secreted effector protein involved in immune suppression, was also shown to be negatively regulated by crp (55).…”

“…In addition, crp regulates expression of the spv genes, also required for invasion of mucosal tissues, and several fimbrial operons (14,33). Strains of Salmonella and Y. enterocolitica with crp deletions are attenuated in mice and stimulate protective immunity against subsequent challenge with the wildtype parent (10,38). In Y. pestis, the crp gene directly regulates expression of some 37 genes, including ypkA and yopO, which encode a secreted virulence factor, and the laterally acquired plasmid genes pla, a known virulence factor, and pst, encoding the bacteriocin pesticin (38,54).…”

“…Crp modulates expression of genes in many pathogenic bacteria, including Salmonella, Vibrio cholerae, Yersinia enterocolitica, and Y. pestis (10,38,44,54). Crp regulation occurs either directly, by binding to specific DNA sequences near the regulated gene, or indirectly, through the action of CyaR, a regulatory RNA (13).…”