Location: Infectious Bacterial Diseases Research
2020 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. Obstacles to eradication 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 bovine tuberculosis 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 animals.
Progress was made towards Objective 1 (Immunopathogenesis) by obtaining a unique set of samples (blood, saliva, nasal secretions) from a large number of calves during both early and late phases of infection. Analysis of these samples will give us valuable insight into bacterial shedding patterns and immune responses during the course of infection, allowing us to develop diagnostic tests that detect disease at both early and late stages of progression. Progress was made towards Objective 2 (diagnostic tests) by our participation with international labs in other countries to validate a new standard bovine tuberculin, a protein extract of M. bovis that is used for skin testing cattle. Further progress was made toward Objective 3 (Vaccines) by completing the analysis and formulating a manuscript for publication on the use of a bacterially-vectored, mucosally-delivered subunit vaccine for tuberculosis in cattle and parameters were identified for analysis if further testing of the vaccine is done.
Accomplishments
1. Validation of an international standard PPD for skin testing cattle. As bovine tuberculosis, which is caused by the bacterium Mycobacterium bovis, is a global problem impacting international and domestic trade, harmonization and acceptance of diagnostic tests for bovine tuberculosis are paramount. Working internationally with other bovine tuberculosis research labs and the World Organization for Animal Health (OIE), ARS scientists in Ames, Iowa, evaluated and validated a new international standard tuberculin, a sterile protein extract of M. bovis that is used for skin testing cattle for bovine tuberculosis. This new standard creates a global organized system to ensure uniform testing worldwide. As this project required the experimental infection with M. bovis of many calves, we took the opportunity to collect a wide variety of samples (nasal secretions, saliva, blood) at numerous time points. Although not directly related to tuberculin validation, analysis of these samples will give us a rare set of samples to characterize bacterial shedding patterns and immune responses at early and late stages of infection. These findings will benefit regulatory agencies, veterinarians and livestock producers involved with maintaining a tuberculosis-free status for the United States.
Review Publications
Palmer, M.V., Waters, W.R., Thacker, T.C. 2020. Vaccination of white-tailed deer (Odocoileus virginianus) with Mycobacterium bovis bacille Calmette-Guérin (BCG) results in positive tuberculin skin test results in a dose-dependent fashion. Research in Veterinary Science. 129:70-73. https://doi.org/10.1016/j.rvsc.2020.01.010.
Palmer, M.V., Kanipe, C., Cox, R.J., Robbe Austerman, S., Thacker, T.C. 2019. Characteristics of subclinical Mycobacterium avium ssp. paratuberculosis infection in a captive white-tailed deer herd. Journal of Veterinary Diagnostic Investigation. 31(6):844-851. https://doi.org/10.1177/1040638719873028.
Guerra-Maupome, M., Palmer, M.V., Waters, W.R., Mcgill, J.L. 2019. Characterization of gamma delta T cell effector/memory subsets based on CD27 and CD45R expression in response to Mycobacterium bovis infection. ImmunoHorizons. 3(6):208-218. https://doi.org/10.4049/immunohorizons.1900032.
Lyashchenko, K.P., Sridhara, A.A., Johnathan-Lee, A., Sikar-Gang, A., Lambotte, P., Esfandiari, J., Bernitz, N., Kerr, T.J., Miller, M.A., Waters, R.W. 2020. Differential antigen recognition by serum antibodies from three bovid hosts of Mycobacterium bovis infection. Comparative Immunology Microbiology and Infectious Diseases. 69(101424). https://doi.org/10.1016/j.cimid.2020.101424.
