Location: Infectious Bacterial Diseases Research
2018 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 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. Consequently, research activities within the ARS Tuberculosis (TB) Project provide direct support for the USDA TB eradication program directed by the Animal and Plant Health Inspection Service (APHIS), specifically discovery and development of diagnostics, vaccines, and animal disease models to protect and ensure food safety through enhanced capabilities to detect, prevent and control animal diseases.
During FY18 in support of Subobjective 1.1, we used methods we developed for characterizing bovine immune response to M. bovis at the site of infection, where the overall outcome of infection (control vs dissemination) is determined. As part of this effort, we evaluated early lesions at 15 days after infection. Understanding host-pathogen interactions, especially at early time points, will identify new targets for vaccine development and new biomarkers for diagnostics. In support of Objective 2, ARS scientists in Ames, Iowa worked with APHIS regulatory staff to resolve diagnostic issues with an approved tuberculosis diagnostic test for cattle. Studies conducted by ARS scientists helped identify the cause for reductions in sensitivity and specificity of the test.
In support of Subobjective 3.3, cattle vaccine studies were completed comparing efficacy of a novel mucosal vaccine to protection induced by inoculation with the traditional M. bovis BCG vaccine. Development of a better cattle vaccine for TB would mitigate transmission of tuberculosis in cattle.
Research findings continue to be used to create or modify state and federal regulations regarding TB diagnostics including approval of novel tests for use in the USDA Uniform Methods and Rules (UM&R) for the eradication of bovine tuberculosis.
Accomplishments
1. Biomarkers for improved diagnostic tests. As bovine tuberculosis is a zoonotic disease, an eradication program was initiated over 100 years ago to protect public health. Complete eradication of bovine tuberculosis in the U.S. will require development of rapid and accurate diagnostic tests. A blood-based test measuring gamma interferon production has been used for years for diagnosis of bovine tuberculosis. Although it has reasonable accuracy (sensitivity and specificity), to maximize diagnostic sensitivity the blood-based test must be combined with other diagnostic tests (i.e. skin test) that are labor intensive and expensive. ARS scientists in Ames, Iowa, used whole blood from experimentally infected cattle to evaluate inflammatory mediators as alternatives to gamma interferon for use in tuberculosis diagnostic tests for cattle. Data suggested that several of the targets may be useful for diagnosis of tuberculosis using whole blood. Development of more accurate diagnostic tests will expedite eradication of bovine tuberculosis and decrease financial losses caused by reduced production and regulatory costs to protect public health.
2. New tuberculosis agent with novel means of transmission. In 2010 a new type of tuberculosis was discovered in Botswana in banded mongoose. The causative agent (Mycobacteria mungi) is closely related to other Mycobacteria species including those which cause tuberculosis in humans, cattle and other animals. Infection of mongoose with M. mungi is now common in some regions of Botswana, but infections in humans or other animals have not been detected at this time. The origin of this Mycobacteria spp is unknown in addition to a lack of knowledge on the disease pathogenesis. ARS scientists in Ames, Iowa, collaborated with wildlife biologists from Virginia Tech University on studying transmission of M. mungi in its natural host. Data suggests that M. mungi is spread through social marking of territory by anal gland and urinary secretions, thereby contaminating the environment and spreading disease to other social groups. This novel route of transmission of tuberculosis has not been previously described. Elucidating pathogenesis of disease associated with this Mycobacterium adds to our knowledge of tuberculosis in wildlife and suggests that transmission through secretions is a route that should be considered in other hosts of tuberculosis. This potential route of transmission has not been investigated thoroughly in all wildlife reservoirs of tuberculosis. Understanding routes of transmission is paramount in mitigating wildlife to livestock transmission.
Review Publications
Lyashchenko, K.P., Gortazar, C., Miller, M.A., Waters, W.R. 2017. Spectrum of antibody profiles in tuberculous elephants, cervids, and cattle. Veterinary Microbiology. 214:89-92. https://doi.org/10.1016/j.vetmic.2017.12.013.
Waters, W.R., Vordermeier, H.M., Rhodes, S., Khatri, B., Palmer, M.V., Maggioli, M.F., Thacker, T.C., Nelson, J.T., Thomsen, B.V., Robbe-Austerman, S., Bravo Garcia, D.M., Schoenbaum, M.A., Camacho, M.S., Ray, J.S., Esfandiari, J., Lambotte, P., Greenwald, R., Grandison, A., Sikar-Gang, A., Lyaschenko, K.P. 2017. Potential for rapid antibody detection to identify tuberculous cattle with non-reactive tuberculin skin test results. BMC Veterinary Research. 13(1):164. https://doi.org/10.1186/s12917-017-1085-5.
Lyashchenko, K.P., Grandison, A., Keskinen, K., Sikar-Gang, A., Lambotte, P., Esfandiari, J., Ireton, G.C., Vallur, A., Reed, S.G., Jones, G., Vordermeier, H.M., Stabel, J.R., Thacker, T.C., Palmer, M.V., Waters, W.R. 2017. Identification of novel antigens recognized by serum antibodies in bovine tuberculosis. Clinical and Vaccine Immunology. 24(12):e00259-17. https://doi.org/10.1128/CVI.00259-17.
