The human pathogen Chlamydia trachomatis is a significant concern in the United States due to its prevalence and the combined health and socioeconomic impact of acute and chronic disease. Chlamydiae are obligate intracellular pathogens and possess the ability to modulate host-cell functions while sequestered within a membrane-bound vacuole. Expression of a virulence-associated type III secretion system (T3SS) represents one mechanism employed to modulate critical host cell pathways. During the past funding cycle, we identified multiple chlamydial T3S substrates capable of influencing these host cellular processes. The C. trachomatis locus containing the identified effector protein CT694 contains multiple substrates that are deployed by infectious particles during or subsequent to the invasion process. We propose to elucidate molecular mechanisms regarding the anti-host activities of these proteins and delineate the consequences of effector activity on the ability of Chlamydiae to establish and maintain a specialized intracellular niche. A combination of methods designed to identify interactions of chlamydial proteins with host targets will be employed to establish relevant functions. The consequences of these interactions will be investigated in both a tissue culture infection model and a murine model of acute chlamydial infection. We furthermore propose to evaluate whether differences in these effectors among chlamydial species account for any of the distinct, species-specific events related to early chlamydial development. The chlamydial type III secretion system represents an attractive, yet relatively unexplored, mechanism to achieve modulation of host cell activities. Given the comparative difficulty associated with study of obligate intracellular bacteria, investigation of host pathways specifically targeted by the type III secretion mechanism continues to represent a productive approach to elucidate novel pathogenic mechanisms. These studies will lead to an enhanced understanding of Chlamydia-mediated disease and have the potential to yield novel preventative and treatment therapies.

Public Health Relevance

Chlamydia trachomatis, an agent of sexually transmitted disease, relies on a specialized secretion mechanism to deploy proteins exerting anti-host activities essential to pathogenesis. This application contains work designed to identify these anti-host proteins and determine their specific contributions to chlamydial disease.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
Research Project (R01)
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Host Interactions with Bacterial Pathogens Study Section (HIBP)
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Hiltke, Thomas J
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University of Miami School of Medicine
Schools of Medicine
Coral Gables
United States
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Rahnama, Mostafa; Fields, Kenneth A (2018) Transformation of Chlamydia: current approaches and impact on our understanding of chlamydial infection biology. Microbes Infect 20:445-450
Keb, G; Hayman, R; Fields, K A (2018) Floxed-Cassette Allelic Exchange Mutagenesis Enables Markerless Gene Deletion in Chlamydia trachomatis and Can Reverse Cassette-Induced Polar Effects. J Bacteriol 200:
Mueller, Konrad E; Wolf, Katerina; Fields, Kenneth A (2017) Chlamydia trachomatis Transformation and Allelic Exchange Mutagenesis. Curr Protoc Microbiol 45:11A.3.1-11A.3.15
McKuen, M J; Mueller, K E; Bae, Y S et al. (2017) Fluorescence-Reported Allelic Exchange Mutagenesis Reveals a Role for Chlamydia trachomatis TmeA in Invasion That Is Independent of Host AHNAK. Infect Immun 85:
Ferrell, Joshua C; Fields, Kenneth A (2016) A working model for the type III secretion mechanism in Chlamydia. Microbes Infect 18:84-92
Mueller, Konrad E; Wolf, Katerina; Fields, Kenneth A (2016) Gene Deletion by Fluorescence-Reported Allelic Exchange Mutagenesis in Chlamydia trachomatis. MBio 7:e01817-15
Mueller, Konrad E; Fields, Kenneth A (2015) Application of ?-lactamase reporter fusions as an indicator of effector protein secretion during infections with the obligate intracellular pathogen Chlamydia trachomatis. PLoS One 10:e0135295
Mueller, K E; Plano, G V; Fields, K A (2014) New frontiers in type III secretion biology: the Chlamydia perspective. Infect Immun 82:2-9
McKuen, Mary J; Dahl, Gerhard; Fields, Kenneth A (2013) Assessing a potential role of host Pannexin 1 during Chlamydia trachomatis infection. PLoS One 8:e63732
Fields, K A; McCormack, R; de Armas, L R et al. (2013) Perforin-2 restricts growth of Chlamydia trachomatis in macrophages. Infect Immun 81:3045-54

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