Interleukin 10 knock-down in bovine monocyte-derived macrophages has distinct effects during infection with two divergent strains of Mycobacterium bovis

Cytokines as potential biomarkers for the diagnosis of Mycobacterium bovis infection in Mediterranean buffaloes (Bubalus bubalis)

Mycobacterium bovis (M. bovis) is the primary agent of bovine tuberculosis (TB) in Mediterranean buffalo, which has a negative economic impact on buffalo herds. Improving TB diagnostic performance in this species represents a key step to eradicate efficiently this disease. We have recently shown the utility of the IFN-γ assay in the diagnosis of M. bovis infection in Mediterranean buffaloes (Bubalus bubalis), but other cytokines might be useful immunological biomarkers of this infection. We therefore investigated the utility of key immune cytokines as diagnostic biomarkers of M. bovis infection in this species. Thirty-six Italian Mediterranean buffaloes were used in this study: healthy animals (N = 11), infected (IFN-γ test positive, no post-mortem lesions, no M. bovis detection; N = 14), and affected (IFN-γ test positive, visible post-mortem lesions; N = 11). Heparin blood samples were stimulated with bovine purified protein derivative (PPD-B), alongside controls, and 18-24 h later plasma were collected. Levels of 14 key cytokines were measured: IFN-γ, IL-17, IL-4, IL-10, TNF, IL-1α, IL-1β, IL-6, IP-10, MIP-1α, MIP-1β, MCP-1, IL-36Ra, and VEGF-A. We observed that both infected and affected animals released higher levels of IFN-γ, IL-17, IL-10, TNF, IL-1α, IL-6, MIP-1β, in response to PPD-B compared to healthy subjects. Mycobacterium bovis infected animals released also higher levels of IL-1β and IP-10 in response to PPD-B compared to healthy subjects, whereas only tendencies were detected in affected animals. Affected animals only released MIP-1α in response to PPD-B compared to healthy subjects and in this group higher values of PPD-B specific TNF was also observed. Finally, canonical discriminant analysis (CDA) was used to generate predictive cytokine profiles by groups. Our data suggest that IL-10, TNF, IL-1α, IL-6, MIP-1β could be useful biomarkers of TB in Mediterranean Buffalo and can improve the TB diagnostic performance in this specie.

In-depth systems biological evaluation of bovine alveolar macrophages suggests novel insights into molecular mechanisms underlying Mycobacterium bovis infection

Objective

Bovine tuberculosis (bTB) is a chronic respiratory infectious disease of domestic livestock caused by intracellular Mycobacterium bovis infection, which causes ~$3 billion in annual losses to global agriculture. Providing novel tools for bTB managements requires a comprehensive understanding of the molecular regulatory mechanisms underlying the M. bovis infection. Nevertheless, a combination of different bioinformatics and systems biology methods was used in this study in order to clearly understand the molecular regulatory mechanisms of bTB, especially the immunomodulatory mechanisms of M. bovis infection.

Methods

RNA-seq data were retrieved and processed from 78 (39 non-infected control vs. 39 M. bovis-infected samples) bovine alveolar macrophages (bAMs). Next, weighted gene co-expression network analysis (WGCNA) was performed to identify the co-expression modules in non-infected control bAMs as reference set. The WGCNA module preservation approach was then used to identify non-preserved modules between non-infected controls and M. bovis-infected samples (test set). Additionally, functional enrichment analysis was used to investigate the biological behavior of the non-preserved modules and to identify bTB-specific non-preserved modules. Co-expressed hub genes were identified based on module membership (MM) criteria of WGCNA in the non-preserved modules and then integrated with protein-protein interaction (PPI) networks to identify co-expressed hub genes/transcription factors (TFs) with the highest maximal clique centrality (MCC) score (hub-central genes).

Results

As result, WGCNA analysis led to the identification of 21 modules in the non-infected control bAMs (reference set), among which the topological properties of 14 modules were altered in the M. bovis-infected bAMs (test set). Interestingly, 7 of the 14 non-preserved modules were directly related to the molecular mechanisms underlying the host immune response, immunosuppressive mechanisms of M. bovis, and bTB development. Moreover, among the co-expressed hub genes and TFs of the bTB-specific non-preserved modules, 260 genes/TFs had double centrality in both co-expression and PPI networks and played a crucial role in bAMs-M. bovis interactions. Some of these hub-central genes/TFs, including PSMC4, SRC, BCL2L1, VPS11, MDM2, IRF1, CDKN1A, NLRP3, TLR2, MMP9, ZAP70, LCK, TNF, CCL4, MMP1, CTLA4, ITK, IL6, IL1A, IL1B, CCL20, CD3E, NFKB1, EDN1, STAT1, TIMP1, PTGS2, TNFAIP3, BIRC3, MAPK8, VEGFA, VPS18, ICAM1, TBK1, CTSS, IL10, ACAA1, VPS33B, and HIF1A, had potential targets for inducing immunomodulatory mechanisms by M. bovis to evade the host defense response.

Conclusion

The present study provides an in-depth insight into the molecular regulatory mechanisms behind M. bovis infection through biological investigation of the candidate non-preserved modules directly related to bTB development. Furthermore, several hub-central genes/TFs were identified that were significant in determining the fate of M. bovis infection and could be promising targets for developing novel anti-bTB therapies and diagnosis strategies.

The Development of 3D Bovine Intestinal Organoid Derived Models to Investigate Mycobacterium Avium ssp Paratuberculosis Pathogenesis

Mycobacterium avium subspecies paratuberculosis (MAP) is the etiological agent of Johne's Disease, a chronic enteritis of ruminants prevalent across the world. It is estimated that approximately 50% of UK dairy herds are infected with MAP, but this is likely an underestimate of the true prevalence. Infection can result in reduced milk yield, infertility and premature culling of the animal, leading to significant losses to the farming economy and negatively affecting animal welfare. Understanding the initial interaction between MAP and the host is critical to develop improved diagnostic tools and novel vaccines. Here we describe the characterisation of three different multicellular in vitro models derived from bovine intestinal tissue, and their use for the study of cellular interactions with MAP. In addition to the previously described basal-out 3D bovine enteroids, we have established viable 2D monolayers and 3D apical-out organoids. The apical-out enteroids differ from previously described bovine enteroids as the apical surface is exposed on the exterior surface of the 3D structure, enabling study of host-pathogen interactions at the epithelial surface without the need for microinjection. We have characterised the cell types present in each model system using RT-qPCR to detect predicted cell type-specific gene expression, and confocal microscopy for cell type-specific protein expression. Each model contained the cells present in the original bovine intestinal tissue, confirming they were representative of the bovine gut. Exposure of the three model systems to the K10 reference strain of MAP K10, and a recent Scottish isolate referred to as C49, led to the observation of intracellular bacteria by confocal microscopy. Enumeration of the bacteria by quantification of genome copy number, indicated that K10 was less invasive than C49 at early time points in infection in all model systems. This study shows that bovine enteroid-based models are permissive to infection with MAP and that these models may be useful in investigating early stages of MAP pathogenesis in a physiologically relevant in vitro system, whilst reducing the use of animals in scientific research.

Bos taurus: urn:lsid:zoobank.org:act:4C90C4FA-6296-4972-BE6A-5EF578677D64

Recent advances in non-specific immune memory against bovine tuberculosis

Bovine tuberculosis is an important worldwide disease mainly related to cattle, although it also affects other mammals, including humans. In recent years, there have been considerable advances in the knowledge of the immune response mechanisms underlying the interaction of Mycobacterium bovis, the main agent of bovine tuberculosis, with its hosts. In this review we describe the most recent findings on the cattle immune response to M. bovis, particularly regarding trained innate immune responses and γδ T cells, that could support the development of vaccines and diagnostic tools to control this disease.