Circling Disease: Basic Immunology to Vaccination

<p>NON-TECHNICAL SUMMARY:<br/> This project focuses on the basic mechanisms behind the development of encephalitis after Listeria monocytogenes infection, as well as whether vaccination with a novel, highly attenuated L. monocytogenes strains can protect against encephalitic listeriosis (also known as Circling disease in ruminants). A common risk factor for encephalitic listeriosis is the consumption of poor feed by ruminants, especially cattle. Within that poor feed there is likely a mixture of dead and live bacteria which could have a dramatic effect on the initial control of Listeria monocytogenes spread throughout the ruminant. Our hypothesis is that sensing of large quantities of killed bacteria by mast cells results in an aberrant immune response that enables the spread of live L. monocytogenes throughout the animal; thus resulting in the establishment of L.
monocytogenes infection in the brain and the subsequent development of encephalitis. In addition, we hypothesize that the induction of robust memory T cell populations using attenuated L. monocytogenes will protect against the development of encephalic listeriosis. Thus, this MAES project will address the basic biology behind the development of Circling disease, as well as whether vaccination could be a useful mechanism to protect animal against the development of Circling disease.
<p>APPROACH:<br/> Aim 1: Assess the prevalence of L. monocytogenes exposure in Montana cattle. To determine the prevalence of Listeria monocytogenes infections in Montana cattle we will do a survey for anti-Listeria antibodies. To do this plasma will be collected by centrifugation of heparinized venous blood from cattle from a range of Montana ranches. Aim 2: Are mast cells critical mediators in the detrimental outcome of the combined infection with HKL and live L. monocytogenes To determine the role mast cells play in the observed detrimental synergy between simultaneous infection with HKL and live L. monocytogenes, we will make use of the Wsh mouse. The Wsh mouse has an inversion mutation in an upstream regulatory element of the c-kit locus. As a result, Wsh mice lack mast cells after about 10 weeks of age. Importantly, bone marrow-cultured mast cells (BMCMC) can be
engrafted into Wsh mice in order to complement any observed phenotype. This cellular complementation system is extremely powerful as one can then determine which factor produced by the mast cells are necessary for the observed phenotype using BMCMC from knock-out mice. Through the use of this complementation system numerous studies have shown mast cells to be important in regulating the immune response to bacterial pathogens, such as TNFa. Since Khanna et al found that after HKL administration the marginal zone macrophages were destroyed in a TNFa-dependent manner within 9 hours, we hypothesize that mast cells will be the crucial source of the TNFa, similar to other bacterial infections. Thus, we hypothesis that mast cells are the primary source of early TNFa after treatment with HKL and their production of TNFa plays a central role in the death of the MZM and development of encephalitic
listeriosis. By understanding the role of mast cells during HKL + L. monocytogenes co-infection, we hope to uncover a potentially novel pathway that can be targeted to limit encephalitic listeriosis in ruminants. Aim 3: Does vaccination with the prs2A- htrA- L. monocytogenes strain induce a protective response in our Circling disease model system To determine if vaccination can provide protection against the development of Circling disease we will characterize the immune response and protective immunity induced using a novel attenuated L. monocytogenes strain. These studies will elucidate the basic mechanisms necessary for the induction of protective T cell response during L. monocytogenes, as well as address whether vaccination of large animals would be appropriate for protection against the development of Circling disease. We hypothesis that the prs2A- htrA- L. monocytogenes strain
will induce vigorous T cell responses after vaccination, which will provide robust protection against the development of Circling disease. The following experiments will characterize the T cell responses and protective immunity induced by the prs2A- htrA- L. monocytogenes strain. If these studies show promise, the prs2A- htrA- L. monocytogenes strain could be tested in a large animal system for its ability to protect against virulent L. monocytogenes infection.
<p>PROGRESS: 2013/01 TO 2013/09<br/>Target Audience: One hypothesis of this project is that the induction of robust memory T cell populations using attenuated Listeria monocytogenes will protect against the development of encephalic listeriosis. Thus, during this funding period we have testing whether novel, attenuated strains of L. monocytogenes can induced protective immunity against L. monocytogenes infection. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Nothing Reported How have the results been disseminated to communities of interest? Nothing Reported What do you plan to do during the next reporting period to accomplish the goals? We are currently writing a manuscript based on the finding of this chaperone deficient strain of L. monocytogenes is highly immunogenic and likely a good vaccine
candidate.
<p>PROGRESS: 2012/01/01 TO 2012/12/31<br/>OUTPUTS: No public presentation outputs to report. PARTICIPANTS: This project involved: 1) Joshua Obar, PI; experimental design and analysis; 2) Carly Grant, Undergraduate Research Assistant; conducted and analyzed the experiments; 3) Tyler Johnson, Master's Student; conducted experiments; 4) Julianne Zickovich, Research Associate; conducted and analyzed the experiments. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.