Cytokine mRNA expression in cattle infected with different dosages of Mycobacterium bovis

Comparative proteome analysis revealed the differences in response to both Mycobacterium tuberculosis and Mycobacterium bovis infection of bovine alveolar macrophages

Tuberculosis (TB), attributed to the Mycobacterium tuberculosis complex, is one of the most serious zoonotic diseases worldwide. Nevertheless, the host mechanisms preferentially leveraged by Mycobacterium remain unclear. After infection, both Mycobacterium tuberculosis (MTB) and Mycobacterium bovis (MB) bacteria exhibit intimate interactions with host alveolar macrophages; however, the specific mechanisms underlying these macrophage responses remain ambiguous. In our study, we performed a comparative proteomic analysis of bovine alveolar macrophages (BAMs) infected with MTB or MB to elucidate the differential responses of BAMs to each pathogen at the protein level. Our findings revealed heightened TB infection susceptibility of BAMs that had been previously infected with MTB or MB. Moreover, we observed that both types of mycobacteria triggered significant changes in BAM energy metabolism. A variety of proteins and signalling pathways associated with autophagy and inflammation-related progression were highly activated in BAMs following MB infection. Additionally, proteins linked to energy metabolism were highly expressed in BAMs following MTB infection. In summary, we propose that BAMs may resist MTB and MB infections via different mechanisms. Our findings provide critical insights into TB pathogenesis, unveiling potential biomarkers to facilitate more effective TB treatment strategies. Additionally, our data lend support to the hypothesis that MTB may be transmitted via cross-species infection.

The Bovine Tuberculoid Granuloma

The bovine tuberculoid granuloma is the hallmark lesion of bovine tuberculosis (bTB) due to Mycobacterium bovis infection. The pathogenesis of bTB, and thereby the process of bovine tuberculoid granuloma development, involves the recruitment, activation, and maintenance of cells under the influence of antigen, cytokines and chemokines in affected lungs and regional lymph nodes. The granuloma is key to successful control of bTB by preventing pathogen dissemination through containment by cellular and fibrotic layers. Paradoxically, however, it may also provide a niche for bacterial replication. The morphologic and cellular characteristics of granulomas have been used to gauge disease severity in bTB pathogenesis and vaccine efficacy studies. As such, it is critical to understand the complex mechanisms behind granuloma initiation, development, and maintenance.

Evaluation of tumor necrosis factor-alpha (TNF-α); gamma interferon (IFN-γ) genes and oxidative stress in sheep: immunological responses induced by Oestrus ovis (Diptera: Oestridae) infestation

This study aimed to evaluate the cell mediated immune responses against Oestrus ovis (O. ovis) in sheep through measurement of the changes in mRNA expression of the tumor necrosis factor alpha (TNF-α) and gamma interferon (IFN-γ) cytokines using quantitative Real time-PCR (qRt-PCR). Also; to detect the role of Oestrus ovis infestation in the oxidative stress markers in sheep. Fifty sheep head were examined in Cairo abattoir from the period of May to August 2019. Sera were separated and collected for measurement of nitric oxide, zinc and malondialdehyde (MDA). While TNF-α and IFN-γ mRNA were extracted from nasal mucosa. Levels of IFN-γ and TNF-α were significantly higher in infested sheep than that in non-infested one. Also, oxidative stresses were indicated by high level of nitric oxide as one of reactive oxygen species (ROS) and serum MDA as oxidative stress marker and low antioxidant capacity (zinc concentration in serum) in infested sheep. The obtained results indicated that measurements of TNF-α and IFN-γ cytokines using qRT-PCR could be used as an association and reproducible quantitative method for the diagnosis of O. ovis infestation in sheep.

Differential Cytokine Gene Expression in Granulomas from Lungs and Lymph Nodes of Cattle Experimentally Infected with Aerosolized Mycobacterium bovis

The hallmark lesion of tuberculosis in humans and animals is the granuloma. The granuloma represents a distinct host cellular immune response composed of epithelioid macrophages, lymphocytes, and multinucleated giant cells, often surrounding a caseous necrotic core. Within the granuloma, host-pathogen interactions determine disease outcome. Factors within the granulomas such as cytokines and chemokines drive cell recruitment, activity, function and ultimately the success or failure of the host's ability to control infection. Hence, an understanding of the granuloma-level cytokine response is necessary to understand tuberculosis pathogenesis. In-situ cytokine expression patterns were measured using a novel in situ hybridization assay, known as RNAScope® in granulomas of the lungs, tracheobronchial lymph nodes and caudal mediastinal lymph nodes of cattle experimentally infected with Mycobacterium bovis via aerosol exposure. In spite of microscopic morphological similarities, significant differences were seen between late stage granulomas of the lung compared to those of the tracheobronchial lymph nodes for IL-17A, IFN-γ, TGF-β, IL10 and IL-22 but not for TNF-α. Additionally, significant differences were noted between granulomas from two different thoracic lymph nodes that both receive afferent lymphatics from the lungs (i.e., tracheobronchial and caudal mediastinal lymph nodes) for TNF-α, IL-17A, IFN-γ, TGF-β and IL-10 but not for IL-22. These findings show that granuloma morphology alone is not a reliable indicator of granuloma function as granulomas of similar morphologies can have disparate cytokine expression patterns. Moreover, anatomically distinct lymph nodes (tracheobronchial vs caudal mediastinal) differ in cytokine expression patterns even when both receive afferent lymphatics from a lung containing tuberculoid granulomas. These findings show that selection of tissue and anatomic location are critical factors in assessing host immune response to M. bovis and should be considered carefully.

Differential Cell Composition and Cytokine Expression Within Lymph Node Granulomas from BCG-Vaccinated and Non-vaccinated Cattle Experimentally Infected with Mycobacterium bovis

Cattle vaccination against bovine tuberculosis (bTB) has been proposed as a supplementary method to help control the incidences of this disease. Bacillus Calmette-Guérin (BCG) is currently the only viable candidate vaccine for immunization of cattle against bTB, caused by Mycobacterium bovis (M. bovis). In an attempt to characterize the differences in the immune response following M. bovis infection between BCG-vaccinated and non-vaccinated animals, a combination of gross pathology, histopathology and immunohistochemical (IHC) analyses was used. BCG vaccination was found to significantly reduce the number of gross and microscopic lesions present within the lungs and lymph nodes. Additionally, the microscopically visible bacterial load of stages III and IV granulomas was reduced. IHC using cell surface markers revealed the number of CD68+ (macrophages), CD3+ (T lymphocytes) and WC1+ cells (γδ T cells) to be significantly reduced in lymph node granulomas of BCG-vaccinated animals, when compared to non-vaccinated animals. B lymphocytes (CD79a+) were significantly increased in BCG-vaccinated cattle for granulomas at stages II, III and IV. IHC staining for iNOS showed a higher expression in granulomas from BCG-vaccinated animals compared to non-vaccinated animals for all stages, being statistically significant in stages I and IV. TGFβ expression decreased alongside the granuloma development in non-vaccinated animals, whereas BCG-vaccinated animals showed a slight increase alongside lesion progression. IHC analysis of the cytokines IFN-γ and TNF-α demonstrated significantly increased expression within the lymph node granulomas of BCG-vaccinated cattle. This is suggestive of a protective role for IFN-γ and TNF-α in response to M. bovis infection. Findings shown in this study suggest that the use of BCG vaccine can reduce the number and severity of lesions, induce a different phenotypic response and increase the local expression of key cytokines related to protection.

Analysis of Cytokine Gene Expression using a Novel Chromogenic In-situ Hybridization Method in Pulmonary Granulomas of Cattle Infected Experimentally by Aerosolized Mycobacterium bovis

Mycobacterium bovis is the cause of tuberculosis in most animal species including cattle and is a serious zoonotic pathogen. In man, M. bovis infection can result in disease clinically indistinguishable from that caused by Mycobacterium tuberculosis, the cause of most human tuberculosis. Regardless of host, the typical lesion induced by M. bovis or M. tuberculosis is the tuberculoid granuloma. Tuberculoid granulomas are dynamic structures reflecting the interface between host and pathogen and, therefore, pass through various morphological stages (I to IV). Using a novel in-situ hybridization assay, transcription of various cytokine and chemokine genes was examined qualitatively and quantitatively using image analysis. In experimentally infected cattle, pulmonary granulomas of all stages were examined 150 days after aerosol exposure to M. bovis. Expression of mRNA encoding tumour necrosis factor (TNF)-α, transforming growth factor-β, interferon (IFN)-γ, interleukin (IL)-17A, IL-16, IL-10, CXCL9 and CXCL10 did not differ significantly between granulomas of different stages. However, relative expression of the various cytokines was characteristic of a Th1 response, with high TNF-α and IFN-γ expression and low IL-10 expression. Expression of IL-16 and the chemokines CXCL9 and CXCL10 was high, suggestive of granulomas actively involved in T-cell chemotaxis.

Design and evaluation of a unique SYBR Green real-time RT-PCR assay for quantification of five major cytokines in cattle, sheep and goats

Background

Today, when more than 60% of animal diseases are zoonotic, understanding their origin and development and identifying protective immune responses in ruminants are major challenges. Robust, efficient and cost-effective tools are preconditions to solve these challenges. Cytokines play a key role in the main mechanisms by which the immune system is balanced in response to infectious pathogens. The cytokine balance has thus become the focus of research to characterize immune response in ruminants. Currently, SYBR Green reverse transcriptase quantitative PCR (RT-qPCR) is the most widely method used to investigate cytokine gene expression in ruminants, but the conditions in which the many assays are carried out vary considerably and need to be properly evaluated. Accordingly, the quantification of gene expression by RT-qPCR requires normalization by multiple reference genes. The objective of the present study was thus to develop an RT-qPCR assay to simultaneously quantify the expression of several cytokines and reference genes in three ruminant species. In this paper, we detail each stage of the experimental protocol, check validation parameters and report assay performances, following MIQE guidelines.

Results

Ten novel primer sets were designed to quantify five cytokine genes (IL-4, IL-10, IL-12B, IFN-γ and TNF-α) and five reference genes (ACTB, GAPDH, H3F3A, PPIA and YWHAZ) in cattle, sheep, and goats. All the primer sets were designed to span exon-exon boundaries and use the same hybridization temperature. Each stage of the RT-qPCR method was detailed; their specificity and efficiency checked, proved and are reported here, demonstrating the reproducibility of our method, which is capable of detecting low levels of cytokine mRNA up to one copy whatever the species. Finally, we checked the stability of candidate reference gene expression, performed absolute quantification of cytokine and reference gene mRNA in whole blood samples and relative expression of cytokine mRNA in stimulated PBMC samples.

Conclusions

We have developed a novel RT-qPCR assay for the simultaneous relative quantification of five major cytokines in cattle, sheep and goats, and their accurate normalization by five reference genes. This accurate and easily reproducible tool can be used to investigate ruminant immune responses and is widely accessible to the veterinary research community.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-015-0382-0) contains supplementary material, which is available to authorized users.

Differential responses of macrophages from bovines naturally resistant or susceptible to Mycobacterium bovis after classical and alternative activation

It is known that macrophages from naturally resistant animals possess a strong immune response against bovine tuberculosis to control mycobacterial infections. In the present study, the macrophage phagocytic activity, intracellular bacterial survival, and cytokine gene expression induced by classical and alternative activators against Mycobacterium bovis in naturally resistant or susceptible bovines, were evaluated. Animals were classified as naturally resistant or susceptible based on the capacity of their macrophages to allow M. bovis (BCG) growth. Peripheral blood macrophages from naturally resistant and susceptible animals were activated by classical and alternative stimuli and challenged with either non-pathogenic M. bovis BCG strain or pathogenic 9926 strain. Naturally resistant animals showed the highest phagocytosis index and microbial control after classical and alternative stimuli, being this response higher against the strain 9926 than the non-virulent strain. In addition, the response of macrophages activated by the classical pathway was higher than that under the alternative activation against both types of strains. Furthermore, classical pathway-activated macrophages derived from naturally resistant animals expressed higher levels of the pro-inflammatory markers iNOS, IL-1β, TNF-α, MIP-1 and MIP-3, and the anti-inflammatory markers ARGII and TGF-b, particularly to BCG. The results of this study showed that macrophages from naturally resistant animals produced stronger pro-inflammatory responses than those from susceptible ones to signals provided by classical pathway activators. Its role in innate immunity against M. bovis is yet to be determined.

Neonatal revaccination with Bacillus Calmette-Guérin elicits improved, early protection against Mycobacterium tuberculosis in mice

The protective effect of revaccination with Mycobacterium bovis Bacillus Calmette-Guérin (BCG) against Mycobacterium tuberculosis in animals is controversial. To investigate whether revaccination of neonates with BCG could improve the protection against M. tuberculosis, C57BL/6 neonates were vaccinated with BCG on day 1, or on days 1, 7, and 14, and the mice at eight weeks of age were challenged with M. tuberculosis and monitored for survival. The M. tuberculosis burden in their livers and lungs, the pathological changes in the lungs, their splenic T cell responses and serum cytokines were examined longitudinally post-challenge. BCG vaccination significantly prevented the M. tuberculosis-related mouse death and reduced the burden of M. tuberculosis in the liver and lungs, and lung damage in the mice, particularly at early stage of the pathogenic process in the BCG-revaccinated mice. However, the BCG revaccination-induced protection waned over time. BCG vaccination did not significantly modulate the levels of serum IFN-γ and the frequency of splenic PPD-reactive IFN-γ-secreting T cells, but significantly decreased the levels of serum TNF-α and PPD-specific IL-4 responses at 3 weeks post challenge. Taken together, these data suggest that revaccination of neonates with BCG elicits improved, early protection against M. tuberculosis by modulating cytokine responses in adult mice.

Time dependent expression of cytokines in Mycobacterium bovis infected cattle lymph nodes

Advancements in the current diagnostic and vaccination protocols employed against bovine tuberculosis rely heavily upon a sound knowledge of the bovine immunological response. Central to this is the importance of timing in the cellular immune profile and how this dynamic process evolves post-Mycobacterium bovis challenge. In the present study, we quantitatively analysed mRNA expression of interferon gamma (IFN-γ), tumour necrosis factor alpha (TNF-α) and interleukins (IL) 4 and 10 within select thoracic lymph nodes of cattle infected with M. bovis for 5, 12 and 19 weeks as compared to non-infected bovine tissues. The M. bovis infected lymph nodes displayed significantly higher expression levels of IFN-γ and TNF-α as compared to the non-infected lymph node tissues. This, in conjunction with undetectable levels of IL4, suggests a pro-inflammatory cytokine response. However a significant increase was also detected in IL10 mRNA which is consistent with a described aspect of T(H)1 type T cells in Leishmania infection, a 'self-limiting' process in which cells produced both IFN-γ and IL10 with the aim of controlling the heightened immunopathological responses. This was further reflected when comparing the cytokine profiles of the individual lymph node types, as those displaying a higher IFN-γ/IL10 ratio also had a greater level of gross pathology. This data highlights the important role of IL10 in the bovine response to M. bovis infection and supports its involvement as an immunological marker of disease progression.