Location: Virus and Prion Research
2024 Annual Report
Objectives
Objective 1: Investigate the role of virulence mechanisms and impact on the swine respiratory microbiota of priority, emerging or re-emerging pathogens such as Glaesserella parasuis and Streptococcus suis. This includes evaluating the presence and mechanisms of transfer of antimicrobial resistance (AMR) genes harbored by these bacterial pathogens.
Subobjective 1.1: Identify genetic determinants contributing to the virulence of G. parasuis and S. suis through the use of comparative genomics, functional genomics, and proteomics.
Subobjective 1.2: Evaluate the presence of AMR genes, determine the genomic location of identified AMR genes, and determine which specific type of MGEs most abundantly contain AMR genes harbored by priority, emerging or re-emerging swine bacterial pathogens.
Subobjective 1.3: Determine the impact of infection with priority swine pathogens on the respiratory microbiota and development of secondary bacterial infections.
Objective 2: Develop and evaluate novel non-antibiotic intervention and management strategies to control priority bacterial diseases in swine, including vaccine platforms and therapeutics.
Subobjective 2.1: Develop novel vaccines and therapeutics to prevent clinical disease or decrease colonization caused by priority, emerging or re-emerging swine bacterial pathogens.
Subobjective 2.2: Evaluate the host response to vaccination or infection with bacterial pathogens such as G. parasuis or S. suis to identify mechanisms of cross protective immunity.
Approach
The first goal for this research plan is to investigate the role of virulence mechanisms and impact on the swine respiratory microbiota of priority, emerging or re-emerging pathogens such as Glaesserella parasuis and Streptococcus suis. This includes evaluating the presence and mechanisms of transfer of antimicrobial resistance (AMR) genes harbored by these bacterial pathogens. First, we will use genome sequence data to identify genes encoding virulence factors and compare population structure of isolates, determine whether and how bacterial gene and protein expression responds to mammalian host signals, and determine which genes enable bacteria to colonize the swine respiratory tract and cause invasive disease. Next, we will compare the whole genome sequences of swine bacterial pathogens to identify AMR genes and determine whether or not identified AMR genes are located within mobile genetic elements (MGEs) such as plasmids, prophages, integrative and conjugative elements (ICEs), insertion sequences, and transposons. Finally, we will determine whether and how the microbiota changes following infection with swine respiratory pathogens and whether changes contribute to enhanced disease and evaluate the impact of pathogen-pathogen interactions occurring during infections with G. parasuis or S. suis. The second goal for this research plan is to develop and evaluate novel non-antibiotic intervention and management strategies to control priority bacterial diseases in swine, including vaccine platforms and therapeutics. First, we will develop novel vaccines that can prevent clinical disease with priority bacterial pathogens of swine, such as G. parasuis and S. suis. Examples of these novel vaccines include a G. parasuis capsule mutant bacterin, protein subunit vaccines for S. suis and G. parasuis, a S. suis capsule mutant, a conjugated capsule vaccine for G. parasuis, and a SEZ bacterin vaccine. We will additionally isolate bacteriophages active against swine LA-MRSA ST398 isolates and evaluate the use of bacteriophage treatment to reduce colonization. Finally, we will identify immunogenic, protective, and conserved outer membrane proteins of G. parasuis through immunoproteomics that will be cross protective against multiple serotypes.
Progress Report
Subobjective 1.1: The goal of this subobjective is to use genome sequence data to identify genes encoding virulence factors and compare population structure of isolates, determine whether and how bacterial gene and protein expression responds to mammalian host signals, and determine which genes enable bacteria to colonize the swine respiratory tract and cause invasive disease. During transcriptomic analysis of G. parasuis exposed to joint and serosal fluid, genes were upregulated in G. parasuis that are of interest to investigate for their role in virulence. Samples from in vivo infection were obtained for RNA isolation. Whole-genome sequencing, assembly, and annotation for B. bronchiseptica isolates obtained from swine production facilities within the U.S. have been completed. These genome assemblies have been screened for genes encoding any putative factors that could increase the capacity of these isolates to cause disease using both publicly available databases as well as published literature detailing experimentally verified virulence factors.
Subobjective 2.1: The goal of this subobjective is to develop novel vaccines that can prevent clinical disease with priority bacterial pathogens of swine, such as G. parasuis and S. suis. Swine experiments have been completed investigating immune stimulation with S. suis bacterin vaccines. Swine experiments have been completed investigating the role of the bacteriocin produced by strain 90-1330 in protection against virulent S. suis infection.
Subobjective 2.2: The goal of this subobjective is to identify immunogenic, protective, and conserved proteins of G. parasuis or S. suis through immunoproteomics that will be cross protective against multiple serotypes. Repeated vaccination of pigs against S. suis was completed to generate hyperimmune serum for protein probing.
Accomplishments
1. Exposure to a non-pathogenic, bacterioicin producing Streptococcus suis strain can protect pigs against disease caused by a pathogenic strain. Streptococcus suis causes large losses in the U.S. swine industry. Many producers use vaccines to reduce S. suis disease, but novel vaccines are needed due to the lack of commercially available vaccines. ARS researchers in Ames, Iowa, working with collaborators from the University of Montreal, investigated using a non-pathogen S. suis strain (strain 90-1330) as a vaccine. The 90-1330 strain inhibits the growth of pathogenic S. suis strains by producing an antimicrobial peptide (bacteriocin). Pigs given the 90-1330 strain were protected against disease after exposure to a pathogenic S. suis strain. Protection was not due to the bacteriocin but was likely due to the pigs’ immune response. The results of this study improve our understanding of the S. suis immune response. This work also provides a novel method for preventing S. suis disease using a single inoculation. Collectively this work will enhance vaccine development against S. suis and improve swine health by limiting S. suis disease addressing a high priority of producers and veterinarians.
2. Development of a novel vaccine and/or vaccine additive to prevent Glaesserella parasuis disease in pigs. Glaesserella parasuis causes severe disease in pigs with a high cost to swine producers. Producers use vaccines to prevent losses, but vaccines are not universally effective. ARS researchers in Ames, Iowa, developed a novel protein vaccine that reduces disease after exposure to G. parasuis. This vaccine is effective as the sole component and when used as an additive in vaccines containing killed bacteria. The vaccine also shows efficacy against multiple strains of G. parasuis. This groundbreaking work created a novel vaccine candidate that could be universally protective and reduce losses due to G. parasuis in pigs. This work addresses a high priority of producers and veterinarians, providing needed solutions to animal health concerns.
3. Glaesserella parasuis alters transcription when exposed to swine serosal fluid or joint fluid. Glaesserella parasuis is a pathogen of swine. It causes inflammation in the brain, joints, and serosal surfaces of pigs. How G. parasuis causes arthritis (joint inflammation) or polyserositis (inflammation of serosal surfaces) is not well understood. To better understand how G. parasuis initiates joint and serosal infection, ARS researchers in Ames, Iowa, investigated the transcriptional profile of G. parasuis in joint fluid and serosal fluid. G. parasuis altered its gene activity after exposure to host fluid. Some of the changes were in virulence genes and genes with unknown functions. This work provides important information on how G. parasuis responds when it is exposed to host fluids. This information contributes to our understanding of host infection and provides avenues for future research into virulence and possible targets for vaccine development helping to reducing losses due to G. parasuis infection. This work provides important information to G. parasuis researchers and contributes to novel interventions for G. parasuis needed by swine producers and veterinarians.
4. Bordetella bronchiseptica is pervasive in swine populations and plays multiple roles in respiratory disease. ARS researchers in Ames, Iowa, working with collaborators from the Federal Drug Administration (FDA), investigated three proteins known to regulate the productions of factors that allow this pathogen to transmit and cause disease. All the factors regulated by the three proteins were identified. Targeting these newly identified factors for future vaccines will not only decrease disease caused by Bordetella but also decrease host-to-host transmission as well, subsequently reducing infections and secondary bacterial infections in swine. Collectively this work will enhance vaccine development against B. bronchiseptica, reducing losses due to B. bronchiseptica infection and helping producers, veterinarians, and public health officials.
Review Publications
Hau, S.J., Nielsen, D.W., Brockmeier, S.L. 2023. Prior infection with Bordetella bronchiseptica enhanced colonization but not disease with Streptococcus suis. Veterinary Microbiology. 284:109841. https://doi.org/10.1016/j.vetmic.2023.109841.
Arruda, B.L., Kanefsky, R.A., Hau, S.J., Janzen, G.M., Anderson, T.K., Baker, A.L. 2023. Mucin 4 is a cellular biomarker of necrotizing bronchiolitis in influenza A virus infection. Microbes and Infection. e105169. https://doi.org/10.1016/j.micinf.2023.105169.
Nielsen, D.W., Hau, S.J., Mou, K.T., Alt, D.P., Brockmeier, S.L. 2023. Shifts in the swine nasal microbiota following Bordetella bronchiseptica challenge in a longitudinal study. Frontiers in Microbiology. 14. Article 1260465. https://doi.org/10.3389/fmicb.2023.1260465.
Nicholson, T.L., Kalalah, A.A., Eppinger, M. 2023. Population Structure and Genetic Diversity of Streptococcus suis Isolates Obtained from the United States. Frontiers in Immunology. https://doi.org/10.3389/fmicb.2023.1250265.
Nicholson, T.L., Waack, U., Fleming, D.S., Chen, Q., Miller, L.C., Merkel, T.J., Stibitz, S. 2024. The contribution of BvgR, RisA, and RisS to global gene regulation, intracellular cyclic-di-GMP levels, motility, and biofilm formation in bordetella bronchiseptica . Frontiers in Microbiology. https://doi.org/10.3389/fmicb.2024.1305097.