The Veterinary Immunological Toolbox: Past, Present, and Future

Alternative treatment candidates to antibiotic therapy for bovine mastitis in the post-antibiotic era: a comprehensive review

Mastitis, an inflammation of mammary tissue frequently associated with infection, is a prevalent disease among dairy animals. Bacterial intra-mammary infection is identified as a primary cause of bovine mastitis (BM). In dairy cattle, antimicrobials are used for mastitis treatment during the lactating phase and for dry cow therapy. Although self-curing can occur, the success of mastitis treatment depends on several factors, including the type of bacteria responsible for the infection, the effectiveness of the administered antibiotics, and the host's overall immune response. Moreover, the growing resistance of microorganisms to antibiotics has restricted the available treatment options for managing intramammary infections. In addition, the utilization of critically essential antimicrobials in animals raised for food production may elevate the risk of human infections that are challenging to treat. Therefore, it is crucial to have alternative treatments with equivalent or superior effectiveness as part of any stewardship program. These may include the application of nanotechnology, stem cell technology, photodynamic and laser radiation or the use of traditional herbal medical plants, nutraceuticals, antibacterial peptides, bacteriocins, antibodies therapy, bacteriophages, phage lysins, and probiotics as alternatives to antibiotics. This review aims to discuss the potential of vaccination as an indirect strategy, along with nanotechnology, probiotics, stem cell therapy, antimicrobial peptides, photodynamic therapy, laser irradiation, and antibody treatments as direct approaches. These approaches are examined as possible alternative therapeutic options to antibiotic treatment for BM.

OMIP-113: Characterization of Cytokine Producing T Cells in Swine

T cells are essential for preventing diseases and providing long-term protective immunity. The functional capacity of T cells and the quality of their responses to antigens can be measured by the cytokines they produce. We developed a conventional flow cytometry panel utilizing commercially available antibodies to measure antigen-specific T cell mediated immune responses in swine. The panel can simultaneously detect Th1 and Th17 cytokines (IFN-γ, TNF, and IL-17A) to characterize multifunctional αβ and γδ T cells. We also included CD40L (CD154) to identify cells that are activated upon antigen recall and that may contribute to B-cell help or activate antigen presenting cells. The assay can be applied to study T cell mediated immune responses to vaccines and diseases and can be used with cryopreserved or freshly isolated peripheral blood mononuclear cells.

Generation and characterization of chicken monocyte-derived dendritic cells

Introduction

Dendritic cells (DCs) play a crucial role in orchestrating immune responses by bridging innate and adaptive immunity. In vitro generation of DCs from mouse and human tissues such as bone marrow and peripheral blood monocytes, has been widely used to study their immunological functions. In chicken, DCs have mainly been derived from bone marrow cell cultures, with limited characterization from blood monocytes.

Methods

The present study takes advantage of newly available chicken immunological tools to further characterize chicken monocyte-derived dendritic cells (MoDCs), focusing on their phenotype, and functions, including antigen capture and T-cell stimulation, and response to live Newcastle disease virus (NDV) stimulation.

Results

Adherent chicken PBMCs were cultured with recombinant chicken granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-4 (IL-4), for 5 days, leading to the upregulation of putative CD11c and MHCII, markers of DC differentiation. Subsequent stimulation with lipopolysaccharide (LPS) or 24 h triggered phenotypic maturation of MoDCs, characterized by the increased surface expression of MHCII and co-stimulatory molecules CD80 and CD40, and elevated IL-12p40 secretion. This maturation reduced endocytic capacity but enhanced the allogenic stimulatory activity of the chicken MoDCs. Upon NDV stimulation for 6 h, MoDCs upregulated antiviral pathways, including retinoic acid-inducible gene I (RIG-I)-like receptors (RLRs), melanoma differentiation-associated protein 5 (MDA5) and laboratory of genetics and physiology 2 (LGP2), alongside increased production of type I interferons (IFNs), and the pro-inflammatory cytokines tumor necrosis factor-α (TNF-α), IL-1β, and IL-6. However, these responses were downregulated after 24 hours.

Conclusion

These findings provide a comprehensive characterization of chicken MoDCs and suggest their potential as a model for studying host-pathogen interactions.

Immunoinformatics: A Veritable Toolbox for Livestock Omics and Veterinomics

Immunoinformatics, an integrative field consisting of bioinformatics and immunology, has showcased its potential in addressing zoonotic diseases, as evidenced during the Coronavirus disease 2019 (COVID-19) pandemic. However, its application in livestock health remains largely untapped. This opinion commentary explores how immunoinformatics, combined with advancements in genomics, multi-omics integration, and genome editing technologies, can revolutionize livestock management by enhancing disease resistance, vaccine development, and productivity. We examine the current and critical challenges, such as limited breed-specific data, computational barriers, and economic constraints, while highlighting the transformative potential of immunoinformatics in addressing these issues. We underscore the importance of leveraging immunoinformatics to bridge the phenotype-genotype gap, develop effective diagnostics and vaccines, and tackle emerging pathogens with zoonotic potential. By emphasizing interdisciplinary collaboration and the need for accessible veterinomics solutions, particularly in low- and middle-income countries, we outline herein the actionable steps to harness immunoinformatics for sustainable livestock management and global food security. In all, this opinion commentary aims to inspire a renewed focus on and veritable innovations in planetary health by unpacking and recognizing immunoinformatics' key role in shaping the future of veterinomics, the convergence of veterinary medicine with omics systems science, in the pursuit of agricultural sustainability.

In situ staining with antibodies cross-reactive in pigs, cattle, and white-tailed deer facilitates understanding of biological tissue status and immunopathology

Identifying cellular markers within archived formalin-fixed, paraffin-embedded (FFPE) tissues is critical for understanding tissue landscapes impacting animal health, but in situ detection methods are limited in veterinary species by a restricted toolbox of species-compatible immunoreagents. We identify antibodies with conserved in situ reactivity to IBA-1 (macrophages/dendritic cells), CD3ε (T cells), Pax5 (B cells), Ki-67 (cycling cells), and cytokeratin type I/II (epithelial cells) in FFPE tissues of pigs, cattle, and white-tailed deer. Multiplexed brightfield detection (IBA-1/CD3ε/Pax5) in lymph nodes of all three species demonstrated species-specific and species-conserved features of cellular architecture. Multiplexed fluorescent staining in pig lymph nodes for IBA-1/CD3ε/Pax5/Ki-67 allowed detection of colocalizing signals and identification of active germinal centers. Antibody compatibility with RNA in situ hybridization was confirmed for all antibodies in all species, allowing co-detection of RNA markers, which is a strategy highly useful in veterinary species where protein-reactive reagents are often lacking. Multiplexed protein and RNA staining was performed in tonsil tissue of a pig infected with Senecavirus A, enabling identification of virally-infected cell types via simultaneous detection of host cell type-specific proteins and virus-specific RNA. Findings have important applications for future in situ identification and comparative study of tissue landscapes and immunopathology in a diverse range of veterinary species.

OMIP-107: 8-color whole blood immunophenotyping panel for the characterization and quantification of lymphocyte subsets and monocytes in swine

We developed this whole blood immunophenotyping panel with the aim to monitor and quantify major lymphocyte subsets (CD4+, CD8+, CD4+CD8+ αβ T cells, γδ-T cells, B and NK cells) and monocytes in pigs. The panel involved the use of commercially available reagents, avoiding secondary antibody staining or in-house antibody conjugations, with the aim to make the assay accessible and reproducible across laboratories. The assay is accurate, robust and represents a useful tool for immune monitoring of swine in the pharmacology and toxicology fields, or to monitor the immune status in response to vaccination and diseases.

An update on the development of a bottlenose dolphin, Tursiops truncatus, immune reagent toolkit

There are extensive immunological reagents available for laboratory rodents and humans. However, for veterinary species there is a need for expansion of immunological toolkits, with this especially evident for marine mammals, such as cetaceans. In addition to their use in a research setting, immune assays could be employed to monitor the health status of cetaceans and serve as an adjunct to available diagnostic tests. Such development of specific and sensitive immune assays will enhance the proper care and stewardship of wild and managed cetacean populations. Our goal is to provide immune reagents and immune assays for the research community, clinicians, and others involved in care of bottlenose dolphins. This review will provide an update on our development of a bottlenose dolphin immunological toolkit. The future availability and continued development of these reagents is critical for improving wild and managed bottlenose dolphin population health through enhanced assessment of their responses to alterations in the marine environment, including pathogens, and improve our ability to monitor their status following vaccination.

Direct comparison of canine and human immune responses using transcriptomic and functional analyses

The canine spontaneous cancer model is increasingly utilized to evaluate new combined cancer immunotherapy approaches. While the major leukocyte subsets and phenotypes are closely related in dogs and humans, the functionality of T cells and antigen presenting cells in the two species has not been previously compared in detail. Such information would be important in interpreting immune response data and evaluating the potential toxicities of new cancer immunotherapies in dogs. To address this question, we used in vitro assays to compare the transcriptomic, cytokine, and proliferative responses of activated canine and human T cells, and also compared responses in activated macrophages. Transcriptomic analysis following T cell activation revealed shared expression of 515 significantly upregulated genes and 360 significantly downregulated immune genes. Pathway analysis identified 33 immune pathways shared between canine and human activated T cells, along with 34 immune pathways that were unique to each species. Activated human T cells exhibited a marked Th1 bias, whereas canine T cells were transcriptionally less active overall. Despite similar proliferative responses to activation, canine T cells produced significantly less IFN-γ than human T cells. Moreover, canine macrophages were significantly more responsive to activation by IFN-γ than human macrophages, as reflected by co-stimulatory molecule expression and TNF-α production. Thus, these studies revealed overall broad similarity in responses to immune activation between dogs and humans, but also uncovered important key quantitative and qualitative differences, particularly with respect to T cell responses, that should be considered in designing and evaluating cancer immunotherapy studies in dogs.

Cattle killer immunoglobulin-like receptor expression on leukocyte subsets suggests functional divergence compared to humans

Cattle, sheep, and goats are the only species outside primates known to have an expanded and diversified family of killer immunoglobulin-like receptors (KIR). Primate KIR are expressed on the surface of NK and T cells and bind MHC-I to control activation. However, the surface expression, ligands and function of bovid KIR remain unknown. Cattle botaKIR2DL1 is the only functional KIR of the same DL-lineage as the expanded KIR in primates and we examined if leukocyte expression patterns were consistent with human. We raised a specific mouse anti-botaKIR2DL1 monoclonal antibody and assessed its utility in flow cytometry, ELISA, and western blot. Unlike primates, cattle DL-lineage KIR (botaKIR2DL1) is present on B cells and monocytes in addition to T cells and low-level expression on NK cells. Expression decreases after in vitro PBMC stimulation with IL-2. This suggests that botaKIR2DL1 has different functions, and potentially ligands, compared to primate KIR.

Intestinal single-cell atlas reveals novel lymphocytes in pigs with similarities to human cells

Lymphocytes can heavily influence intestinal health, but resolving intestinal lymphocyte function is challenging as the intestine contains a vastly heterogeneous mixture of cells. Pigs are an advantageous biomedical model, but deeper understanding of intestinal lymphocytes is warranted to improve model utility. Twenty-six cell types were identified in the porcine ileum by single-cell RNA sequencing and further compared with cells in human and murine ileum. Though general consensus of cell subsets across species was revealed, some porcine-specific lymphocyte subsets were identified. Differential tissue dissection and in situ analyses conferred spatial context, revealing similar locations of lymphocyte subsets in Peyer's patches and epithelium in pig-to-human comparisons. Like humans, activated and effector lymphocytes were abundant in the ileum but not periphery of pigs, suggesting tissue-specific and/or activation-associated gene expression. Gene signatures for peripheral and ileal innate lymphoid cells newly discovered in pigs were defined and highlighted similarities to human innate lymphoid cells. Overall, we reveal novel lymphocyte subsets in pigs and highlight utility of pigs for intestinal research applications.

Disease control tools to secure animal and public health in a densely populated world

Animal health is a prerequisite for global health, economic development, food security, food quality, and poverty reduction, while mitigating against climate change and biodiversity loss. We did a qualitative review of 53 infectious diseases in terrestrial animals with data from DISCONTOOLS, a specialist database and prioritisation model focusing on research gaps for improving infectious disease control in animals. Many diseases do not have any appropriate control tools, but the prioritisation model suggests that we should focus international efforts on Nipah virus infection, African swine fever, contagious bovine pleuropneumonia, peste des petits ruminants, sheeppox and goatpox, avian influenza, Rift Valley fever, foot and mouth disease, and bovine tuberculosis, for the greatest impact on the UN's Sustainable Development Goals. Easy to use and accurate diagnostics are available for many animal diseases. However, there is an urgent need for the development of stable and durable diagnostics that can differentiate infected animals from vaccinated animals, to exploit rapid technological advances, and to make diagnostics widely available and affordable. Veterinary vaccines are important for dealing with endemic, new, and emerging diseases. However, fundamental research is needed to improve the convenience of use and duration of immunity, and to establish performant marker vaccines. The largest gap in animal pharmaceuticals is the threat of pathogens developing resistance to available drugs, in particular for bacterial and parasitic (protozoal, helminth, and arthropod) pathogens. We propose and discuss five research priorities for animal health that will help to deliver a sustainable and healthy planet: vaccinology, antimicrobial resistance, climate mitigation and adaptation, digital health, and epidemic preparedness.

Adaptation and Diagnostic Potential of a Commercial Cat Interferon Gamma Release Assay for the Detection of Mycobacterium bovis Infection in African Lions (Panthera leo)

Mycobacterium bovis (M. bovis) infection in wildlife, including lions (Panthera leo), has implications for individual and population health. Tools for the detection of infected lions are needed for diagnosis and disease surveillance. This study aimed to evaluate the Mabtech Cat interferon gamma (IFN-γ) ELISA^Basic kit for detection of native lion IFN-γ in whole blood samples stimulated using the QuantiFERON^® TB Gold Plus (QFT) platform as a potential diagnostic assay. The ELISA was able to detect lion IFN-γ in mitogen-stimulated samples, with good parallelism, linearity, and a working range of 15.6–500 pg/mL. Minimal matrix interference was observed in the recovery of domestic cat rIFN-γ in lion plasma. Both intra- and inter-assay reproducibility had a coefficient of variation less than 10%, while the limit of detection and quantification were 7.8 pg/mL and 31.2 pg/mL, respectively. The diagnostic performance of the QFT Mabtech Cat interferon gamma release assay (IGRA) was determined using mycobacterial antigen-stimulated samples from M. bovis culture-confirmed infected (n = 8) and uninfected (n = 4) lions. A lion-specific cut-off value (33 pg/mL) was calculated, and the sensitivity and specificity were determined to be 87.5% and 100%, respectively. Although additional samples should be tested, the QFT Mabtech Cat IGRA could identify M. bovis-infected African lions.

Development and Characterization of New Monoclonal Antibodies Against Porcine Interleukin-17A and Interferon-Gamma

Current research efforts require a broad range of immune reagents, but those available for pigs are limited. The goal of this study was to generate priority immune reagents for pigs and pipeline them for marketing. Our efforts were aimed at the expression of soluble swine cytokines and the production of panels of monoclonal antibodies (mAbs) to these proteins. Swine interleukin-17A (IL-17A) and Interferon-gamma (IFNγ) recombinant proteins were produced using yeast expression and used for monoclonal antibody (mAb) production resulting in panels of mAbs. We screened each mAb for cross-species reactivity with orthologs of IL-17A or IFNγ and checked each mAb for inhibition by other related mAbs, to assign mAb antigenic determinants. For porcine IL-17A, the characterization of a panel of 10 mAbs identified eight different antigenic determinants; interestingly, most of the mAbs cross-reacted with the dolphin recombinant ortholog. Likewise, the characterization of a panel of nine anti-PoIFNγ mAbs identified four different determinants; most of the mAbs cross-reacted with dolphin, bovine, and caprine recombinant orthologs. There was a unique reaction of one anti-PoIFNγ mAb that cross-reacted with the zebrafish recombinant ortholog. The αIL-17A mAbs were used to develop a quantitative sandwich ELISA detecting the yeast expressed protein as well as native IL-17A in stimulated peripheral blood mononuclear cell (PBMC) supernatants. Our analyses showed that phorbol myristate acetate/ionomycin stimulation of PBMC induced significant expression of IL-17A by CD3+ T cells as detected by several of our mAbs. These new mAbs expand opportunities for immunology research in swine.