This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Mueller, K. J. Articles by Freitag, N. E. Search for Related Content PubMed PubMed Citation Articles by Mueller, K. J. Articles by Freitag, N. E.

Pleiotropic Enhancement of Bacterial Pathogenesis Resulting from the Constitutive Activation of the Listeria monocytogenes Regulatory Factor PrfA

Seattle Biomedical Research Institute and,¹ Departments of Pathobiology and Microbiology, University of Washington, Seattle, Washington²

Received 14 June 2004/ Returned for modification 15 September 2004/ Accepted 6 December 2004

Listeria monocytogenes is a facultative intracellular bacterial pathogen that causes serious disease in immunocompromised individuals, pregnant women, and neonates. Bacterial virulence is mediated by the expression of specific gene products that facilitate entry into host cells and enable bacterial replication; the majority of these gene products are regulated by a transcriptional activator known as PrfA. L. monocytogenes strains containing prfA E77K or prfA G155S mutations exhibit increased expression of virulence genes in broth culture and are hypervirulent in mice. To define the scope of the influences of the prfA E77K and prfA G155S mutations on L. monocytogenes pathogenesis, multiple aspects of bacterial invasion and intracellular growth were examined. Enhanced bacterial invasion of host epithelial cells was dependent on the expression of a number of surface proteins previously associated with invasion, including InlA, InlB, and ActA. In addition to these surface proteins, increased production of the hly-encoded secreted hemolysin listeriolysin O (LLO) was also found to significantly enhance bacterial invasion into epithelial cell lines for both prfA mutant strains. Although prfA E77K and prfA G155S strains were similar in their invasive phenotypes, the infection of epithelial cells with prfA E77K strains resulted in host cell plasma membrane damage, whereas prfA G155S strains did not alter plasma membrane integrity. Bacterial infection of human epithelial cells, in which the production of LLO is not required for bacterial entry into the cytosol, indicated that prfA E77K cytotoxic effects were mediated via LLO. Both prfA E77K and prfA G155S strains were more efficient than wild-type bacteria in gaining access to the host cell cytosol and in initiating the polymerization of host cell actin, and both were capable of mediating LLO-independent lysis of host cell vacuoles in cell lines for which L. monocytogenes vacuole disruption normally requires LLO activity. These experiments illuminate the diverse facets of L. monocytogenes pathogenesis that are significantly enhanced by the constitutive activation of PrfA via prfA mutations and underscore the critical role of this protein in promoting L. monocytogenes virulence.

Editor: V. J. DiRita

This article has been cited by other articles:

• Yan, L., Qiu, J., Chen, J., Ryan-Payseur, B., Huang, D., Wang, Y., Rong, L., Melton-Witt, J. A., Freitag, N. E., Chen, Z. W. (2008). Selected prfA* Mutations in Recombinant Attenuated Listeria monocytogenes Strains Augment Expression of Foreign Immunogens and Enhance Vaccine-Elicited Humoral and Cellular Immune Responses. Infect. Immun. 76: 3439-3450 [Abstract] [Full Text]  
• Lauer, P., Hanson, B., Lemmens, E. E., Liu, W., Luckett, W. S., Leong, M. L., Allen, H. E., Skoble, J., Bahjat, K. S., Freitag, N. E., Brockstedt, D. G., Dubensky, T. W. Jr. (2008). Constitutive Activation of the PrfA Regulon Enhances the Potency of Vaccines Based on Live-Attenuated and Killed but Metabolically Active Listeria monocytogenes Strains. Infect. Immun. 76: 3742-3753 [Abstract] [Full Text]  
• Mertins, S., Joseph, B., Goetz, M., Ecke, R., Seidel, G., Sprehe, M., Hillen, W., Goebel, W., Muller-Altrock, S. (2007). Interference of Components of the Phosphoenolpyruvate Phosphotransferase System with the Central Virulence Gene Regulator PrfA of Listeria monocytogenes. J. Bacteriol. 189: 473-490 [Abstract] [Full Text]  
• Mauder, N., Ecke, R., Mertins, S., Loeffler, D. I. M., Seidel, G., Sprehe, M., Hillen, W., Goebel, W., Muller-Altrock, S. (2006). Species-Specific Differences in the Activity of PrfA, the Key Regulator of Listerial Virulence Genes. J. Bacteriol. 188: 7941-7956 [Abstract] [Full Text]