Plague is a zoonosis that is present in wild rodent populations worldwide and is transmitted primarily by fleas. Yersinia pestis, the plague bacillus, is unique among the enteric group of gram-negative bacteria in having adopted an arthropod-borne route of transmission. Y. pestis has evolved in such a way as to be transmitted during the brief encounter between a feeding flea and a host. A transmissible infection depends on the ability of Y. pestis to grow in the flea as a biofilm that is embedded in a complex extracellular matrix. Bacteria in the biofilm phenotype are deposited into the dermis together with flea saliva, elements which cannot be satisfactorily mimicked by needle-injection of Y. pestis from laboratory cultures. The objective of this project is to identify and determine the function of Y. pestis genes that mediate flea-borne transmission and the initial encounter with the host innate immune system at the infection site in the skin. We study the interaction of Y. pestis with its insect vector by using an artificial feeding apparatus to infect fleas with uniform doses of wild type or specific Y. pestis mutants. We seek to identify Y. pestis genes that are required for the bacteria to infect the flea midgut and to produce a biofilm that blocks the flea foregut and that is required for efficient transmission. The strategy entails first identifying bacterial genes that are differentially expressed in the flea by gene expression analysis and other techniques. Specific mutations are then introduced into these genes, and the mutants tested for their ability to infect and block the flea vector. Identification of such transmission factors allows further studies into the molecular mechanisms of the bacterial infection of the flea vector. Detailed understanding of the interaction with the insect host may lead to novel strategies to interrupt the transmission cycle. During the last year, we have completed a characterization of the in vivo gene expression profile of Y. pestis during infection of the flea vector and identified new bacterial genes that are required to produce a transmissible infection in the flea. We have identified and characterized several examples of nonfunctional genes (pseudogenes) in Y. pestis that enhance biofilm formation in the flea, in a project to retrace the genetic changes that led to the evolutionarily recent transition of Y. pestis to arthropod-borne transmission. Restoration of these pseudogenes with the equivalent functional genes of Yersinia pseudotuberculosis, the recent ancestor of Y. pestis, reduces transmissibility in the flea;and conversely, mutation of these genes in Y. pseudotuberculosis results in the gain of biofilm-forming ability in the flea. Thus, gene loss appears to have played a significant role in Y. pestis evolution. We determined that the Y. pestis F1 capsule is important for flea-borne transmission of plague. We have also developed models to examine host-parasite interactions in the dermis after transmission by flea bite and the effects of flea saliva on this interaction.

Project Start
Project End
Budget Start
Budget End
Support Year
13
Fiscal Year
2009
Total Cost
$517,276
Indirect Cost
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State
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Bland, David M; Jarrett, Clayton O; Bosio, Christopher F et al. (2018) Infectious blood source alters early foregut infection and regurgitative transmission of Yersinia pestis by rodent fleas. PLoS Pathog 14:e1006859
Hinnebusch, B Joseph; Bland, David M; Bosio, Christopher F et al. (2017) Comparative Ability of Oropsylla montana and Xenopsylla cheopis Fleas to Transmit Yersinia pestis by Two Different Mechanisms. PLoS Negl Trop Dis 11:e0005276
Hinnebusch, B Joseph; Chouikha, Iman; Sun, Yi-Cheng (2016) Ecological Opportunity, Evolution, and the Emergence of Flea-Borne Plague. Infect Immun 84:1932-40
Bland, David M; Hinnebusch, B Joseph (2016) Feeding Behavior Modulates Biofilm-Mediated Transmission of Yersinia pestis by the Cat Flea, Ctenocephalides felis. PLoS Negl Trop Dis 10:e0004413
Vadyvaloo, Viveka; Viall, Austin K; Jarrett, Clayton O et al. (2015) Role of the PhoP-PhoQ gene regulatory system in adaptation of Yersinia pestis to environmental stress in the flea digestive tract. Microbiology 161:1198-1210
Johnson, Tammi L; Hinnebusch, B Joseph; Boegler, Karen A et al. (2014) Yersinia murine toxin is not required for early-phase transmission of Yersinia pestis by Oropsylla montana (Siphonaptera: Ceratophyllidae) or Xenopsylla cheopis (Siphonaptera: Pulicidae). Microbiology 160:2517-25
Sun, Yi-Cheng; Jarrett, Clayton O; Bosio, Christopher F et al. (2014) Retracing the evolutionary path that led to flea-borne transmission of Yersinia pestis. Cell Host Microbe 15:578-86
Uittenbogaard, Annette M; Myers-Morales, Tanya; Gorman, Amanda A et al. (2014) Temperature-dependence of yadBC phenotypes in Yersinia pestis. Microbiology 160:396-405
Chouikha, Iman; Hinnebusch, B Joseph (2014) Silencing urease: a key evolutionary step that facilitated the adaptation of Yersinia pestis to the flea-borne transmission route. Proc Natl Acad Sci U S A 111:18709-14
Rebeil, Roberto; Jarrett, Clayton O; Driver, James D et al. (2013) Induction of the Yersinia pestis PhoP-PhoQ regulatory system in the flea and its role in producing a transmissible infection. J Bacteriol 195:1920-30

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