Historically, plague is one of the most devastating epidemic diseases known to mankind (second only to smallpox), resulting overall in more than 200 million deaths related to three recorded plague pandemics. Since Y. pestis has the potential to cause large-scale outbreaks, the WHO has categorized plague as a re-emerging infectious disease, and there is a concern for a possible fourth pandemic because of global warming, resulting in an increased prevalence of plague in rodent hosts. The current relevance of Y. pestis as a bioweapon is due to its high virulence and the development of multi-antibiotic-resistant strains. Although immunization of humans with plague vaccine will discourage the use of Y. pestis as a bioweapon, currently there is no vaccine against plague. During the current funding of the grant, we identified a new antigen (Braun lipoprotein) of Y. pestis that contributed to the development of bubonic and pneumonic plague. Our studies indicated that mice immunized with the mutant strain of Y. pestis deleted for the lpp and pigmentation locus (pgm) genes were protected against developing pneumonic plague caused by the highly virulent Y. pestis CO92 strain. We have now delineated the signaling pathways initiated by Lpp to cause host damage. Most importantly, our data indicated that the lpp mutant was unable to survive within macrophages, which was linked to the down-regulation of a stress response gene (htrA) in this mutant. We inferred from these data that other stress-associated genes (e.g., exoribonucleases) could also be involved in lpp-mediated, attenuated virulence of the bacterium. Indeed, deletion of the gene encoding polynucleotide phosphorylase (PNPase) also attenuated Y. pestis in a mouse model of systemic infection and provided protection against plague. We have proposed 3 specific aims for this grant.
Aim 1 is to generate double mutants of Y. pestis CO92 in which genes encoding plasminogen-activating protease (pla), pnp, and two other predominant exoribonucleases (e.g., rnb [RNase II] and rnr [RNAse R]) will be deleted from the lpp gene minus background strain of Y. pestis CO92. These mutants will be tested for their attenuation in bubonic and pneumonic plague models (mice and rats).
In aim 2, we will characterize protective immune responses of the most highly attenuated mutant in an animal model and the protection afforded by such a mutant against challenge with the parental CO92 strain. We have identified several immunogenic proteins in the WT CO92 strain that reacted with the immune sera of rats infected with CO92 strain. These antigens may represent excellent candidates for addition in the recombinant plague vaccine. Therefore in aim 3, we will first delete these genes from the WT bacterium to demonstrate their effects on bacterial virulence. Second, we will purify such immunogenic proteins and evaluate their protective effects after immunization of mice and rats followed by subsequent infection with the virulent Y. pestis. Overall, our studies are focused on identifying new live-attenuated vaccine strains of Y. pestis and to characterize the new immuno-protective CO92 antigens that could be important for the recombinant plague vaccine.

Public Health Relevance

Y. pestis is a category A select agent and its potential to be used as a biothreat agent has caused significant concerns. In addition, plague represents a re-emerging infectious disease because of an increased number of cases worldwide. Currently, there is no vaccine available against this deadly disease, and hence our efforts are to develop new and novel countermeasures against plague, as well as to study new mechanisms of pathogenesis in Y. pestis.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
Research Project (R01)
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Vaccines Against Microbial Diseases (VMD)
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Mukhopadhyay, Suman
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University of Texas Medical Br Galveston
Schools of Medicine
United States
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van Lier, Christina J; Sha, Jian; Kirtley, Michelle L et al. (2014) Deletion of Braun lipoprotein and plasminogen-activating protease-encoding genes attenuates Yersinia pestis in mouse models of bubonic and pneumonic plague. Infect Immun 82:2485-503
Rosenzweig, Jason A; Ahmed, Sandeel; Eunson Jr, John et al. (2014) Low-shear force associated with modeled microgravity and spaceflight does not similarly impact the virulence of notable bacterial pathogens. Appl Microbiol Biotechnol 98:8797-807
Rosenzweig, Jason A; Chopra, Ashok K (2013) Modulation of host immune defenses by Aeromonas and Yersinia species: convergence on toxins secreted by various secretion systems. Front Cell Infect Microbiol 3:70
Tao, Pan; Mahalingam, Marthandan; Kirtley, Michelle L et al. (2013) Mutated and bacteriophage T4 nanoparticle arrayed F1-V immunogens from Yersinia pestis as next generation plague vaccines. PLoS Pathog 9:e1003495
Erova, Tatiana E; Rosenzweig, Jason A; Sha, Jian et al. (2013) Evaluation of protective potential of Yersinia pestis outer membrane protein antigens as possible candidates for a new-generation recombinant plague vaccine. Clin Vaccine Immunol 20:227-38
Sha, Jian; Rosenzweig, Jason A; Kirtley, Michelle L et al. (2013) A non-invasive in vivo imaging system to study dissemination of bioluminescent Yersinia pestis CO92 in a mouse model of pneumonic plague. Microb Pathog 55:39-50
Sha, Jian; Kirtley, Michelle L; van Lier, Christina J et al. (2013) Deletion of the Braun lipoprotein-encoding gene and altering the function of lipopolysaccharide attenuate the plague bacterium. Infect Immun 81:815-28
Tao, Pan; Mahalingam, Marthandan; Marasa, Bernard S et al. (2013) In vitro and in vivo delivery of genes and proteins using the bacteriophage T4 DNA packaging machine. Proc Natl Acad Sci U S A 110:5846-51
Lawal, Abidat; Kirtley, Michelle L; van Lier, Christina J et al. (2013) The effects of modeled microgravity on growth kinetics, antibiotic susceptibility, cold growth, and the virulence potential of a Yersinia pestis ymoA-deficient mutant and its isogenic parental strain. Astrobiology 13:821-32
Sha, Jian; Endsley, Janice J; Kirtley, Michelle L et al. (2011) Characterization of an F1 deletion mutant of Yersinia pestis CO92, pathogenic role of F1 antigen in bubonic and pneumonic plague, and evaluation of sensitivity and specificity of F1 antigen capture-based dipsticks. J Clin Microbiol 49:1708-15

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