Location: Infectious Bacterial Diseases Research
2023 Annual Report
Objectives
Objective 1: Develop vaccines that prevent disease or mitigate disease spread with an emphasis on platforms that allow for extended antigen release and remote delivery for livestock and wildlife species.
Subobjective 1.A: Assess the potential of a polyanhydride delivery platform to enhance BCG availability and immunogenicity in order to promote protective anti-mycobacterial responses.
Subobjective 1.B: Evaluate the immune response of WTD to encapsulated lyophilized BCG delivered in oral vaccine delivery units (VDUs).
Objective 2: Improve current diagnostic tests for bovine TB and develop novel, next generation diagnostics which are amenable to remote or continuous disease surveillance and can be incorporated into precision livestock management.
Sub-objective 2.A: Assess the sensitivity and specificity of a fluorescence polarization assay (FPA) to detect serum antibodies against synthetic M. bovis antigens.
Subobjective 2.B: Develop a battery-free, self-contained sensor for the detection of biological IFN-' in vivo that could be used as a diagnostic platform.
Objective 3: To enable the rational-design of intervention strategies, using transcriptomic approaches,define the immunopathogenesis of bovine tuberculosis at the tissue and cellular level by analyzing gene expression of peripheral immune responses and those responses involved in granuloma formation and maintenance.
Subobjective 3.A: Characterize the presence of key T cell subsets and transcription factors in granulomas from BCG-vaccinated vs. non-vaccinated animals following experimental infection with M. bovis.
Subobjective 3.B: Characterize the gene transcription profiles of Mycobacterium bovis-specific T cells in the periphery following M. bovis infection or vaccination.
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 (bTB) eradication program that is still in place today. Although significant progress has been made, eradication has proved elusive. Obstacles to eradication include, 1) lack of rapid and accurate diagnostic tests to detect animals infected with Mycobacterium bovis (M. bovis; the cause of tuberculosis in animals), and 2) wildlife acting as a source of infection for cattle. Research activities within the ARS bTB project in Ames, IA, provide direct support for the USDA bTB eradication program, specifically, through development of more sensitive diagnostics, efficacious vaccines, and improved animal disease models to enhance the capability to detect, prevent and control bTB.
In support of Objective 1, and in collaboration with other USDA scientists at Ft. Collins, Colorado, we developed an edible alginate sphere that contained a liquid form of the human TB vaccine, BCG. The spheres were delivered orally to white-tailed deer and their immune responses to BCG evaluated. Our previous work using free liquid forms of BCG demonstrated immune responses suggestive of acceptable levels of protection to tuberculosis. Evaluation of immune cell proliferation indicated that deer responded equally well to liquid BCG within alginate spheres as to free liquid BCG. In support of Objective 3, we compared granulomas from BCG-vaccinated and non-vaccinated cattle using microscopy and molecular methods. This data demonstrated significant differences in form and function of granulomas, including variable expression of key immune mediators, and provides novel basic knowledge on the pathogenesis of bovine tuberculosis.
Accomplishments
1. Identified a novel tuberculosis vaccine oral delivery system for use in white-tailed deer. Tuberculosis is a chronic zoonotic disease that can be transmitted from animal reservoirs. Wildlife reservoirs of tuberculosis are a challenging obstacle to eradication of this disease in the United States. In Michigan, prevalence of disease in wild deer populations has not changed for 2 decades and approximately 2-3 cattle herds are infected annually. Depopulation of infected cattle herds causes significant economic costs for producers. New intervention strategies, such as efficacious vaccination platforms, are needed to prevent tuberculosis transmission from infected wild deer. Using the Mycobacterium bovis strain BCG tuberculosis vaccine. ARS scientists in Ames, Iowa, demonstrated the efficacy of oral delivery of liquid BCG to white-tailed deer. To address issues associated with delivery of liquid vaccines to wild deer, the ARS scientists collaborated with USDA-APHIS scientists to develop small edible alginate spheres containing liquid BCG. Immune responses in deer eating alginate sphere vaccines were equal to those of deer receiving orally delivered liquid BCG. This data demonstrates this oral platform can be used to develop edible baits for vaccination of wild deer and is effective in decreasing tuberculosis transmission between deer and from deer to cattle. A tuberculosis vaccine for deer would be of interest to regulatory personnel, livestock producers, and wildlife health officials.
Review Publications
Kanipe, C.R., Boggiatto, P.M., Putz, E.J., Palmer, M.V. 2022. Histopathologic differences in granulomas of BCG vaccinated and non-vaccinated cattle with bovine tuberculosis. Frontiers in Microbiology. 13, Article 1048648. https://doi.org/10.3389/fmicb.2022.1048648.
Boggiatto, P.M., Olsen, S.C., Palmer, M.V. 2022. Pulmonary hamartoma in an elk calf (Cervus elaphus canadensis). Journal of Veterinary Diagnostic Investigation. 35(2). https://doi.org/10.1177/10406387221141091.
