Location: Infectious Bacterial Diseases Research
2019 Annual Report
Objectives
Objective 1: Define the immunopathogenesis of bovine tuberculosis at the lesion and cellular level by evaluating local cytokine and biomarker expression.
Subobjective 1.1. Characterize and compare known or implied relevant cytokine and biomarker expression in granulomas of different histopathologic stages (i.e. early vs. late) in lungs and lymph nodes from cattle experimentally inoculated with M. bovis.
Subobjective 1.2. Characterize cytokine and biomarker expression at the lesion level over time.
Subobjective 1.3. Characterize and compare lesion level cytokine and cellular responses between non-vaccinated cattle and cattle with vaccine-induced protective immune responses.
Objective 2: Using antigen mining and transcriptome analysis, develop novel diagnostic tests with improved sensitivity and specificity as compared to current methods.
Subjective 2.1. Improve specificity of diagnostic tests by developing diagnostic reagents from proteins found in M. bovis but not in non-tuberculous mycobacteria.
Subobjective 2.2: Identify proteins/genes expressed by M. bovis in vivo that may be considered as potential diagnostic test targets.
Subobjective 2.3: Use genomics/transcriptomics to characterize genes/gene profiles of M. bovis-infected vs non-infected cattle.
Objective 3: Develop novel vaccines, technologies and platforms (e.g. attenuated live vaccines and vectored vaccines) that can be used to reduce TB in cattle and white-tailed deer and interrupt disease transmission.
Subobjective 3.1. Examine duration of immunity to experimental infection provided by the vaccine M. bovis BCG in white-tailed deer.
Subobjective 3.2. Examine the effects of oral BCG vaccination of white-tailed deer on deer-to-deer transmission of virulent M. bovis.
Subjective 3.3. Determine the efficacy of simultaneous administration of parenteral BCG and a mucosally delivered bacterial-vectored subunit vaccine against aerosol M. bovis infection in neonatal calves.
Approach
Characterize and compare cytokine and biomarker expression (immune responses) at the cellular level in lungs and lymph nodes of Mycobacterium bovis-infected cattle. Comparing responses between tissues, as well as over time, will aid in understanding the host response to M. bovis within the environment where host and pathogen interact (granuloma). We aim to improve the specificity of diagnostic tests by developing diagnostic reagents from proteins found in M. bovis but not in non-tuberculous mycobacteria, thus avoiding cross-reactivity elicited by environmental mycobacteria that contributes to false positive results on cattle tuberculosis diagnostic tests. Similarly, we aim to identify proteins/genes expressed by M. bovis in vivo that may be considered as potential diagnostic test targets and to use genomics/transcriptomics to characterize genes/gene profiles of M. bovis-infected vs non-infected cattle. These data will aid diagnosis and provide insight into the immunopathogenesis of bovine tuberculosis. In terms of vaccine evaluation, we aim to examine duration of immunity to experimental infection provided by the vaccine M. bovis BCG in white-tailed deer and examine the effects of oral BCG vaccination on deer-to-deer transmission of virulent M. bovis. In cattle, we aim to determine the efficacy of simultaneous administration of parenteral M. bovis BCG and a mucosally delivered bacterial-vectored subunit vaccine against aerosol M. bovis infection in neonatal calves.
Progress Report
Over 100 years ago, in 1917, USDA initiated a bovine tuberculosis eradication program that is still in place today. Since that time, significant progress has been made, but eradication has proved elusive. Two significant obstacles include, 1) the lack of rapid and accurate diagnostic tests to detect animals infected with Mycobacterium bovis (the cause of tuberculosis in animals), and 2) wildlife acting as a source of infection for cattle. Research activities within the ARS Tuberculosis (TB) Project in Ames, Iowa, provide direct support for the USDA TB eradication program, specifically targeting development of more sensitive diagnostics, efficacious vaccines, and improved animal disease models to enhance the capability to detect, prevent and control tuberculosis in animal reservoirs.
A study was completed comparing the human vaccine M. bovis BCG (BCG) to a bacterial-vectored, mucosally-delivered subunit vaccine to prevent tuberculosis in cattle. Data show BCG provided protection similar to our previous studies; however, the mucosally-delivered subunit vaccine provided no protection and the resulting disease was similar to that seen in non-vaccinated calves. Immune responses of cattle in all vaccine groups is being completed to identify correlates of protective immunity. In addition, ARS scientists in Ames, Iowa, have collaborated with Animal and Plant Health Inspection Service (APHIS) colleagues and international partners on studies to develop an international standard for bovine tuberculin. Development of an international standard for tuberculin will harmonize and improve diagnosis of bovine tuberculosis around the world. This work is of interest to livestock producers (beef, dairy and deer producer groups) state and federal regulatory officials, and Natural Resources personnel in states with tuberculosis in wildlife reservoirs. Research findings continue to be used to create or modify state and federal regulations regarding tuberculosis in domestic livestock and deer.
Accomplishments
1. Characterized early lesions of bovine tuberculosis. Historically, many studies on bovine tuberculosis examined changes in peripheral blood, attempting to associate changes in blood components with disease progression. Only recently has it become clear that it is at the tissue level, within the granuloma (the stereotypical lesion of tuberculosis in both animals and man) that key interactions between host and pathogen determine disease outcome. Scientists in Ames, Iowa, studied the earliest phases of granuloma formation in experimentally infected cattle, characterizing which immune cell types are present and which inflammatory mediators are being produced. Pathogenesis of early lesions provides key information on host immune responses that benefit development of diagnostic tests for bovine tuberculosis, especially in the early phases of infection. This work is of interest to livestock producers, state and federal regulatory officials, and scientists working in the field of tuberculosis.
Review Publications
Thacker, T.C., Palmer, M.V., Waters, W.R. 2017. Evaluation of tissue fixation methods to inactivate Mycobacterium bovis under routine laboratory conditions. Applied Biosafety. 22(4):152-155. https://doi.org/10.1177%2F1535676017737315.
Palmer, M.V., Thacker, T.C. 2018. Use of the human vaccine, Mycobacterium bovis Bacillus Calmette Guerin in deer. Frontiers in Veterinary Science. 5:244. https://doi.org/10.3389/fvets.2018.00244.
Palmer, M.V. 2018. Emerging understanding of tuberculosis and the granuloma by comparative analysis in humans, cattle, zebrafish and non-human primates. Veterinary Pathology. 55(1):8-10. https://doi.org/10.1177/0300985817712795.
Ellis, C.K., Rice, S., Maurer, D., Stahl, R., Waters, W.R., Palmer, M.V., Nol, P., Rhyan, J.C., Vercauteren, K.C., Koziel, J. 2017. Use of fecal volatile organic compound analysis to discriminate between non-vaccinated and BCG – vaccinated cattle prior to and after Mycobacterium bovis challenge. PLoS One. 12(7):e0179914. https://doi.org/10.1371/journal.pone.0179914.
Rusk, R.A., Palmer, M.V., Waters, W.R., McGill, J.L. 2017. Measuring bovine gamma delta T cell function at the site of Mycobacterium bovis infection. Veterinary Immunology and Immunopathology. 193-194:38-49. https://doi.org/10.1016/j.vetimm.2017.10.004.
Palmer, M.V., Wiarda, J.E., Kanipe, C., Thacker, T.C. 2019. Early pulmonary lesions in cattle infected via aerosolized Mycobacterium bovis. Veterinary Pathology. 56(4). https://doi.org/10.1177%2F0300985819833454.
Cox, R.J., Nol, P., Ellis, C.K., Palmer, M.V. 2019. Research with agricultural animals and wildlife. ILAR Journal. https://doi.org/10.1093/ilar/ilz006.
