Francisella tularensis is a facultative intracellular bacterium that causes tularemia (a.k.a. rabbit fever), which when inhaled causes severe morbidity and mortality in human beings. After inhalation, the bacterium causes a fulminant bacterial pneumonia but also disseminates to a number of other tissues and organs including the spleen, lymph nodes, intestines, liver, kidney, bone marrow, and brain. Although macrophages and dendritic cells are thought to be a primary target of F. tularensis, the pathological mechanisms by which F. tularensis causes disease and death are not understood.
Because of the potential to cause disease when inhaled, tularemia is a potential biological weapon for which there are no licensed vaccines or antibiotics. We have successfully re-established the rabbit as a model of pneumonic tularemia that is relevant to the human disease. Within 3 days of exposure, naïve rabbits develop fever and begin losing weight. Erythrocyte sedimentation rate rises dramatically, an indicator of a robust inflammatory response. CBC results show a marked decline in lymphocytes and platelets in the blood. Radiographs show the development of a severe bacterial pneumonia in the rabbits. Naïve rabbits exposed to aerosolized virulent F. tularensis die between 4-7 days of infection.
In collaboration with Eileen Barry at the University of Maryland-Baltimore, we have used the rabbit model to evaluate attenuated strains of F. tularensis as possible vaccines. Three of these strains provided better protection than the existing vaccine candidate, the Live Vaccine Strain (LVS). The level of protection seen depends on the attenuated strain, the route of vaccination, and the number of vaccinations. Using an aerosol prime-boost vaccine approach we have achieved 83% survival with our lead vaccine candidate while LVS can only extend time to death. Serum IgG and IgM titers against F. tularensis in vaccinated rabbits correspond with the level of protection elicited. We are working with Dr. Barry and Dr. Karsten Hazlett of Albany Medical College to determine the antigens important for protection as well as the role of antigen persistence and inflammation. Our long term goals are 1) to determine the immunological mechanisms of protection responsible for the protection seen with these vaccines in order to design a subunit-based vaccine and 2) to understand the role of the host immune response in the outcome of disease.
In addition to the work on F. tularensis, we work with other investigators to develop animal models for aerosol exposure to infectious agents and to use those models to either understand pathogenesis or evaluate candidate vaccines and therapeutics. This includes not only natural respiratory pathogens (influenza, tuberculosis) but also pathogens that are biodefense threats. This includes development of nonhuman primate models for aerosol exposure to a number of highly pathogenic viruses including Highly Pathogenic Avian Influenza (HPAI), Venezuelan equine encephalitis virus (VEEV), western equine encephalitis virus (WEEV), eastern equine encephalitis virus (EEEV), and Rift Valley Fever virus (RVFV). In addition to doing aerosol exposures, we use radiotelemetry in the nonhuman primates to study the physiological response infection. This response can be used as an early indicator of outcome or as a means for determining efficacy of potential vaccines or therapeutics.
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- Caroline, A.C., Kujawa, M.R, Oury, T., Reed, D.S., Hartman, A.L. 2016. Inflammatory biomarkers associated with lethal Rift Valley fever encephalitis in the Lewis rat model. Front Microbiol Immunol. 6:1509 doi:10.3389/fmicb.2015.01509
- Abdelbaqi, S., Deslouches, B., Steckbeck, J., Montelaro, R., Reed, D.S. 2015. Novel engineered cationic antimicrobial peptides have a broad-spectrum activity against Francisella tularensis, Yersinia pestis, and Burkholderia pseudomallei. J. Med Microbiol. doi: 10.1099/jmm.0.000209
- Reed, D.S.*, Glass, P.J.*, Bakken, R.R., Barth, J.F., Lind, C.M., Hart, M.K., Rayner, J., Alterson, K., Custer, M., Dudek, J., Owens, G., Kamrud, K.I., Parker, M.D., Smith, J. 2014. Combined alphavirus replicon particle vaccine induces durable and cross-protective immune responses against equine encephalitic viruses. J. Virol. 88(20):12077-86 PMID: 25122801 *- equal contribution
- Reed, D.S., Smith, L., Cole, K.S., Santiago, A.E., Mann, B.J., Barry, E.M. 2014. Live attenuated mutants of Francisella tularensis protect rabbits against aerosol challenge with a virulent type A strain. Infection & Immunity 82(5):2098-2105 PMID: 24614653
- Caroline, A.L., Powell, D.S., Bethel, L.M., Oury, T.D., Reed, D.S., Hartman, A.L. 2014. Broad spectrum antiviral activity of Favipiravir (T-705): Protection from highly lethal inhalational Rift Valley Fever in Wistar-Furth rats. PLoS Negl Trop Dis 8(4):32790 PMID: 24722586
- Hartman, A.L., Powell, D.S., Bethel, L.M., Caroline, A.L., Schmid, R.J., Oury, T., Reed, D.S. 2014. Aerosolized Rift Valley Fever virus causes fatal encephalitis in African green monkeys and common marmosets. J. Virol. 88(4):2235-2245. PMID: 24335307
- Faith, S.A., Smith, L.P., Swatland, A.S., Reed, D.S. 2012. Growth conditions and environmental factors impact aerosolization but not virulence of Francisella tularensis infection in mice. Front Cell Inf Microbio. 2(126):1-10. PMID: 23087911
- Bales, J.M., Powell, D.S., Bethel, L.M., Reed, D.S., Hartman, A.L. 2012. Choice of inbred rat strain impacts lethality and disease course after respiratory infection with Rift Valley Fever virus. Front Cell Inf Microbio 2(105):1-14. PMID: 22919694
- Dupuy, L.C., Reed, D.S. 2012. Nonhuman Primate Models of Encephalitic Alphavirus Infection: Historical Review and Future Perspectives. Curr Opin Virol. 2(3):363-7 PMID: 22709522
- Roy, C.J., Reed, D.S. 2012. Infectious disease aerobiology: miasma incarnate. Front Cell Inf Microbio. 2(163):1-2. PMID: 23267441
- Reed, D.S., Smith, L., Dunsmore, T., Trichel, A., Ortiz, L.A., Cole, K.S., Barry, E. 2011. Pneumonic tularemia in rabbits resembles the human disease as illustrated by radiographic and hematological changes after infection. PLoS One. 6(9):1-9. PMID: 21931798
- Roy, C.J., Reed, D.S., and Hutt, J.A. 2010. Pathological Considerations in the Inhalation Exposure to Biological Select Agents and Toxins. Vet Pathol. 47(5):779-89. PMID: 20682804
- Dupuy, L.C., Richards, M.J., Reed, D.S., Schmaljohn, C.S. 2010. Immunogenicity and protective efficacy of a DNA vaccine against Venezuelan equine encephalitis virus aerosol challenge in nonhuman primates. Vaccine 28(46):7345-50. PMID: 20851089
- respiratory infection
- immune correlates
- encephalitic viruses