Gene expression profiling of monocyte-derived macrophages following infection with Mycobacterium avium subspecies avium and Mycobacterium avium subspecies paratuberculosis

Varying conjunctival immune response adaptations of house finch populations to a rapidly evolving bacterial pathogen

Pathogen adaptations during host-pathogen co-evolution can cause the host balance between immunity and immunopathology to rapidly shift. However, little is known in natural disease systems about the immunological pathways optimised through the trade-off between immunity and self-damage. The evolutionary interaction between the conjunctival bacterial infection Mycoplasma gallisepticum (MG) and its avian host, the house finch (Haemorhous mexicanus), can provide insights into such adaptations in immune regulation. Here we use experimental infections to reveal immune variation in conjunctival tissue for house finches captured from four distinct populations differing in the length of their co-evolutionary histories with MG and their disease tolerance (defined as disease severity per pathogen load) in controlled infection studies. To differentiate contributions of host versus pathogen evolution, we compared house finch responses to one of two MG isolates: the original VA1994 isolate and a more evolutionarily derived one, VA2013. To identify differential gene expression involved in initiation of the immune response to MG, we performed 3'-end transcriptomic sequencing (QuantSeq) of samples from the infection site, conjunctiva, collected 3-days post-infection. In response to MG, we observed an increase in general pro-inflammatory signalling, as well as T-cell activation and IL17 pathway differentiation, associated with a decrease in the IL12/IL23 pathway signalling. The immune response was stronger in response to the evolutionarily derived MG isolate compared to the original one, consistent with known increases in MG virulence over time. The host populations differed namely in pre-activation immune gene expression, suggesting population-specific adaptations. Compared to other populations, finches from Virginia, which have the longest co-evolutionary history with MG, showed significantly higher expression of anti-inflammatory genes and Th1 mediators. This may explain the evolution of disease tolerance to MG infection in VA birds. We also show a potential modulating role of BCL10, a positive B- and T-cell regulator activating the NFKB signalling. Our results illuminate potential mechanisms of house finch adaptation to MG-induced immunopathology, contributing to understanding of the host evolutionary responses to pathogen-driven shifts in immunity-immunopathology trade-offs.

Bacteria and macrophages in the tumor microenvironment

Cancer and microbial infections are significant worldwide health challenges. Numerous studies have demonstrated that bacteria may contribute to the emergence of cancer. In this review, we assemble bacterial species discovered in various cancers to describe their variety and specificity. The relationship between bacteria and macrophages in cancer is also highlighted, and we look for ample proof to establish a biological basis for bacterial-induced macrophage polarization. Finally, we quickly go over the potential roles of metabolites, cytokines, and microRNAs in the regulation of the tumor microenvironment by bacterially activated macrophages. The complexity of bacteria and macrophages in cancer will be revealed as we gain a better understanding of their pathogenic mechanisms, which will lead to new therapeutic approaches for both inflammatory illnesses and cancer.

Exogenous Vitamin D3 Modulates Response of Bovine Macrophages to Mycobacterium avium subsp. paratuberculosis Infection and Is Dependent Upon Stage of Johne’s Disease

Mycobacterium avium subspecies paratuberculosis (MAP), the causative agent of ruminant enteritis, targets intestinal macrophages. During infection, macrophages contribute to mucosal inflammation and development of granulomas in the small intestine which worsens as disease progression occurs. Vitamin D₃ is an immunomodulatory steroid hormone with beneficial roles in host-pathogen interactions. Few studies have investigated immunologic roles of 25-hydroxyvitamin D₃ (25(OH)D₃) and 1,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃) in cattle, particularly cattle infected with MAP. This study examined the effects of exogenous vitamin D₃ on immune responses of monocyte derived macrophages (MDMs) isolated from dairy cattle naturally infected with MAP. MDMs were pre-treated with ± 100 ng/ml 25(OH)D₃ or ± 4 ng/ml 1,25(OH)₂D₃, then incubated 24 hrs with live MAP in the presence of their respective pre-treatment concentrations. Following treatment with either vitamin D₃ analog, phagocytosis of MAP by MDMs was significantly greater in clinically infected animals, with a greater amount of live and dead bacteria. Clinical cows had significantly less CD40 surface expression on MDMs compared to subclinical cows and noninfected controls. 1,25(OH)₂D₃ also significantly increased nitrite production in MAP infected cows. 1,25(OH)₂D₃ treatment played a key role in upregulating secretion of pro-inflammatory cytokines IL-1β and IL-12 while downregulating IL-10, IL-6, and IFN-γ. 1,25(OH)₂D₃ also negatively regulated transcripts of CYP24A1, CYP27B1, DEFB7, NOS2, and IL10. Results from this study demonstrate that vitamin D₃ compounds, but mainly 1,25(OH)₂D₃, modulate both pro- and anti-inflammatory immune responses in dairy cattle infected with MAP, impacting the bacterial viability within the macrophage.

Early response of monocyte-derived macrophages from vaccinated and non-vaccinated goats against in vitro infection with Mycobacterium avium subsp. paratuberculosis

Paratuberculosis is a disease of ruminants caused by Mycobacterium avium subsp. paratuberculosis (Map). Vaccination is the most cost-effective control method. However, despite the fact that macrophages are the main target cells for this pathogen, the precise mechanisms behind the response of the macrophage to Map infection and how it is modified by vaccination are yet poorly understood. The aim of this study was to investigate the effect of Silirum® vaccination in the early immune response of caprine monocyte-derived macrophages (CaMØs). Peripheral blood mononuclear cells (PBMCs) were obtained from vaccinated and non-vaccinated goats, cultured in vitro until differentiation to macrophages and infected with Map. After a 24 h incubation, Map viability and DNA were assessed in culture by viable colony count and real time quantitative polymerase chain reaction (qPCR). In addition, Map phagocytosis and expression of IL-10, IL-12, IFN-γ, TNF-α, IL-17A, IL-1β, iNOS, IL-6 and MIP-1β were also evaluated through immunofluorescence labelling and reverse transcriptase qPCR (RT-qPCR), respectively. A significant reduction of Map viability was observed in both supernatants (P < 0.05) and CaMØs (P < 0.001) from the vaccinated group. Similarly, the percentage of infected CaMØs and the number of internalized Map by CaMØs (P < 0.0001) was higher in the vaccinated group. Finally, iNOS (P < 0.01) and IL-10 were significantly up-regulated in CaMØs from vaccinated goats, whereas only MIP-1β was up-regulated in non-vaccinated animals (P < 0.05). These results show that vaccination modifies the immune response of CaMØs, suggesting that the phagocytosis and microbiocidal activity of macrophages against Map is enhanced after vaccination.

Rifabutin-Loaded Nanostructured Lipid Carriers as a Tool in Oral Anti-Mycobacterial Treatment of Crohn's Disease

Oral anti-mycobacterial treatment of Crohn's disease (CD) is limited by the low aqueous solubility of drugs, along with the altered gut conditions of patients, making uncommon their clinical use. Hence, the aim of the present work is focused on the in vitro evaluation of rifabutin (RFB)-loaded Nanostructured lipid carriers (NLC), in order to solve limitations associated to this therapeutic approach. RFB-loaded NLC were prepared by hot homogenization and characterized in terms of size, polydispersity, surface charge, morphology, thermal stability, and drug payload and release. Permeability across Caco-2 cell monolayers and cytotoxicity and uptake in human macrophages was also determined. NLC obtained were nano-sized, monodisperse, negatively charged, and spheroidal-shaped, showing a suitable drug payload and thermal stability. Furthermore, the permeability profile, macrophage uptake and selective intracellular release of RFB-loaded NLC, guarantee an effective drug dose administration to cells. Outcomes suggest that rifabutin-loaded NLC constitute a promising strategy to improve oral anti-mycobacterial therapy in Crohn's disease.

Immunoinformatic-Based Prediction of Candidate Epitopes for the Diagnosis and Control of Paratuberculosis (Johne's Disease)

Paratuberculosis is an infectious disease of ruminants caused by Mycobacterium avium subsp. paratuberculosis (MAP). MAP is an intracellular pathogen with a possible zoonotic potential since it has been successfully isolated from the intestine and blood of Crohn’s disease patients.Since no cure is available, after the detection of the disease, animal culling is the sole applicable containment strategy. However, the difficult detection of the disease in its subclinical form, facilitates its spread raising the need for the development of effective diagnosis and vaccination strategies. The prompt identification and isolation of the infected animals in the subclinical stage would prevent the spread of the infection.In the present study, an immunoinformatic approach has been used to investigate the immunogenic properties of 10 MAP proteins. These proteins were chosen according to a previously published immunoproteomics approach. For each previously-described immunoreactive protein, we predicted the epitopes capable of eliciting an immune response by binding both B-cells and/or class I MHC antigens. The retrieved peptide sequences were analyzed for their specificity and cross-reactivity. The final aim is to employ the discovered peptides sequences as a filtered library useful for early-stage diagnosis and/or to be used in novel multi-subunit or recombinant vaccine formulations.

Notch-1 Signaling Modulates Macrophage Polarization and Immune Defense against Mycobacterium avium paratuberculosis Infection in Inflammatory Diseases

Despite the extensive research on Notch signaling involvement in inflammation, its specific role in macrophage response in autoimmune disease and defense mechanisms against bacterial infection, such as Mycobacterium avium paratuberculosis (MAP), remains unknown. In this study, we investigated the molecular role of Notch-1 signaling in the macrophage response during MAP infection. In particular, we measured the in vitro effect of MAP on Notch-1 signaling and downstream influence on interleukin (IL)-6 and myeloid cell leukemia sequence-1 (MCL-1) and consequent cellular apoptosis, MAP viability, and macrophage polarization. Overall, the data show significant upregulation in Notch-1, IL-6, and MCL-1 in MAP-infected macrophages, parallel with a decrease in apoptosis and elevated pro-inflammatory response in these infected cells. On the contrary, blocking Notch signaling with γ-secretase inhibitor (DAPT) decreased MAP survival and burden, increased apoptosis, and diminished the pro-inflammatory response. In particular, the treatment of infected macrophages with DAPT shifted macrophage polarization toward M2 anti-inflammatory phenotypic response. The outcome of this study clearly demonstrates the critical role of Notch signaling in macrophage response during infection. We conclude that MAP infection in macrophages activates Notch-1 signaling and downstream influence on IL-6 which hijack MCL-1 dependent inhibition of apoptosis leading to its chronic persistence, and further inflammation. This study supports Notch-1 signaling as a therapeutic target to combat infection in autoimmune diseases such as Crohn’s disease and Rheumatoid Arthritis.

Mycobacterium avium Subspecies paratuberculosis Drives an Innate Th17-Like T Cell Response Regardless of the Presence of Antigen-Presenting Cells

The gastrointestinal disease of ruminants is clinically known as Johne's disease (JD) and is caused by Mycobacterium avium subspecies paratuberculosis (MAP). An accumulative effect by insensitive diagnostic tools, a long subclinical stage of infection, and lack of effective vaccines have made the control of JD difficult. Currently lacking in the model systems of JD are undefined correlates of protection and the sources of inflammation due to JD. As an alternative to commonly studied immune responses, such as the Th1/Th2 paradigm, a non-classical Th17 immune response to MAP has been suggested. Indeed MAP antigens induce mRNAs encoding the Th17-associated cytokines IL-17A, IL-17F, IL-22, IL-23, IL-27, and IFNγ in CD3+ T cell cultures as determined by RT-qPCR. Although not as robust as when cultured with monocyte-derived macrophages (MDMs), MAP is able to stimulate the upregulation of these cytokines from sorted CD3+ T cells in the absence of antigen-presenting cells (APCs). CD4+ and CD8+ T cells are the main contributors of IL-17A and IL-22 in the absence of APCs. However, MAP-stimulated MDMs are the main contributor of IL-23. In vivo, JD+ cows have more circulating IL-23 than JD– cows, suggesting that this proinflammatory cytokine may be important in the etiology of JD. Our data in this study continue to suggest that Th17-like cells and associated cytokines may indeed play an important role in the immune responses to MAP infection and the development or control of JD.

Polymorphisms in TNF Receptor Superfamily 1B (TNFRSF1B:rs3397) are Linked to Mycobacterium avium paratuberculosis Infection and Osteoporosis in Rheumatoid Arthritis

We previously discovered that single nucleotide polymorphisms (SNPs) in PTPN2/22 (T-cell negative-regulators) occur in 78% of rheumatoid arthritis (RA), along with Mycobacterium avium paratuberculosis (MAP) infection in 33% of patients. In Crohn's disease, we reported that SNPs in TNFα and receptors (TNFRSF1A/TNFRSF1B) benefited intracellular MAP-survival, increased infection, and elevated inflammatory response mimicking the poor response to anti-TNFα treatment in some patients. Here, we studied the frequency and effects of SNPs in TNFα/TNFRSF1A/TNFRSF1B in RA including gene expression, MAP infection, and osteoporosis marker levels in blood (54 RA and 48 healthy controls). TNFα:rs1800629 (GA) was detected in 19/48 (40%) RA and 8/54 (15%) controls (p-value < 0.05, odds ratio (OR) = 3.6, 95% CI: 1.37-9.54). TNFRS1B:rs3397 (CT) was detected in 21/48 (44%) RA and 10/54 (19%) controls (p-value < 0.05, OR = 4.43, 95% CI: 1.73-11.33). In RA, rs3397 downregulated TNFRSF1B expression (CC > CT (0.34 ± 0.14) and CC > TT (0.27 ± 0.12)), compared to wildtype CC (0.51 ± 0.17), p-value < 0.05. MAP DNA was detected significantly in 17/48 (35.4%) RA compared to 11/54 (20.4%) controls (p-value < 0.05, OR = 2.14, 95% CI: 1.12-5.20). The average osteocalcin level was significantly lower (p-value < 0.05) in RA (2.70 ± 0.87 ng/mL), RA + MAP (0.60 ± 0.31 ng/mL), RA + TNFRSF1B:rs3397 (TT) (0.67 ± 0.35 ng/mL), compared to the healthy control (5.31 ± 1.39 ng/mL), and MAP-free RA (3.85 ± 1.31 ng/mL). Overall, rs3397 appears to downregulate TNFRSF1B, increase MAP infection, worsen inflammation, and cause osteocalcin deficiency and possibly osteoporosis in RA.

Modelling Bovine Granuloma Formation In Vitro upon Infection with Mycobacterium Avium Subspecies Paratuberculosis

Mycobacterium avium subspecies paratuberculosis (Map) causes chronic granulomatous disease in cattle and ruminant livestock, causing substantial economic losses. Current vaccines delay clinical signs but cannot train the immune system to fully eradicate latent Map. During latency, Map uses host defenses, cage-like macrophage clusters called granuloma, as incubators for months or years. We used an in vitro model to investigate the early coordination of macrophages into granuloma upon Map infection over ten days. We found that at multiplicities of infection (MOI; Map:macrophages) of 1:2 and below, the macrophages readily form clusters and evolve pro-inflammatory cytokines in keeping with a cell-mediated immune response. At higher MOIs, viability of host macrophages is negatively impacted. At 1:4 MOI, we quantified viable Map in our model and confirmed that intracellular Map reproduced over the first five days of infection. Host cells expressed Type 1-specific cytokines, and Map-infected macrophages displayed reduced motility compared to Map-exposed, uninfected macrophages, suggesting an important role for uninfected macrophages in the early aggregative response. Reported is the first in vitro JD granuloma model capturing Map and macrophage viability, size distribution of resulting clusters, motility of monocyte-derived macrophages, and cytokine response during clustering, allowing quantitative analysis of multiple parameters of the Map-specific granulomatous response.

Inflammatory Th17 responses to infection with Mycobacterium avium subspecies paratuberculosis (MAP) in cattle and their potential role in development of Johne's disease

Chronic intestinal inflammation typically associated with late stage Johne's disease (JD) in cattle occurs despite a lack of significant expression of the typical proinflammatory cytokines IFNγ and TNFα derived from Th1- like T cells. In contrast, these cytokines appear to be relatively abundant during early infections with Mycobacterium avium subspecies paratuberculosis (MAP), the causative agent of JD in cattle. The roles of non-classical immune responses, such as those associated with Th17 cells, in response to MAP infection and development of clinical JD are less clear. In this review, we examine literature suggesting that Mycobacterial infections, including Mycobacterium tuberculosis, Mycobacterium bovis, and MAP, are all associated with expression of Th17 promoting cytokines (IL-23, IL-22, IL-17a). We discuss the possibility that Th17 associated cytokines, particularly IL-23, may act as contributing factors in development and maintenance of inflammation characteristic of clinical JD. An as yet relatively unexplored source of chronic inflammation due to over expression of IL-1α and IL-1β is also presented. We further discuss the fact that, as with the typical Th1-like cytokines IFNγ and TNFα , IL-17a is not significantly expressed in CD4+ T cells from cows with clinical JD, possibly due to T cell exhaustion. Finally, we present the notion that the Th17 driving cytokine IL-23 expressed by infected macrophages and associated epithelial cells may contribute to chronic inflammation during later stages of JD.

Mycobacterium avium sp. paratuberculosis (MAP) induces IL-17a production in bovine peripheral blood mononuclear cells (PBMCs) and enhances IL-23R expression in-vivo and in-vitro

Johne's disease (JD) is a chronic inflammatory gastrointestinal disease of ruminants caused by Mycobacterium avium subspecies paratuberculosis (MAP). Control of JD is difficult largely due to insensitive diagnostic tools, a long subclinical stage of infection, and lack of effective vaccines. Correlates of protection are lacking in model systems of JD and the sources of inflammation due to JD are not well characterized. Commonly studied immune responses, such as the Th1/Th2 paradigm, do not adequately explain host responses to MAP. A potential role for non-classical immune responses to MAP, such as that mediated by Th17 cells, has been suggested. Indeed, MAP antigens induce mRNAs encoding the cytokines IL-23 and IL-17a in bovine peripheral blood mononuclear cells (PBMCs). IL-23 and IL-17a production have both been associated with Th17-like immune responses. Th17 cells are also defined by surface expression of the IL-23 receptor (IL-23R). To determine the relative prevalence of potential Th17 cells in PBMCs from MAP test positive and MAP test negative cows, PBMCs were isolated and analyzed by immunostaining and flow cytometry. Fresh PBMCs from MAP test positive cows (n = 12) contained a significantly higher proportion of IL-23R positive cells in populations of CD4+, CD8+, and Yδ + T cells than in cells from MAP test negative cows (n = 12; p < 0.05). Treatment with MAP antigens increased the percentage of all T cell subsets with surface expression of IL-23R when compared to untreated (n = 12; p < 0.05) cells. ELISA results for IL-17a secretion revealed a higher concentration of IL-17a secreted from PBMCs treated with MAP antigen (n = 20) than from PBMCs not treated with MAP antigens (n = 20) (p < 0.001), regardless of the JD test status of source cows. Also, we observed a moderate negative correlation between JD diagnostic scores for JD + cows and plasma IL-17a concentration (n = 42; r = -0.437; p-value < 0.004). Plasma with low and mid JD- scores (n = 31; n = 9; 0.1 ≤ X < 0.3) had significantly more IL-17a when compared to plasma with high JD- scores (n = 10; 0.3 ≤ X < 0.46; p-values < 0.05). Similarly, plasma with low JD + score values (0.55 ≤ X < 1.0; n = 9) had significantly more IL-17a when compared to plasma with high JD + score values (X ≥ 2.0; n = 21; p < 0.05). Overall, plasma from JD + cows (0.55 < X ≤ 2.86; n = 41) had significantly less IL-17a than plasma from JD- cows (0 < X ≤ 0.46; n = 70). Our data suggests that Th17-like cells may indeed play a role in early immune responses to MAP infection and development or control of JD.

Characterization of paucibacillary ileal lesions in sheep with subclinical active infection by Mycobacterium avium subsp. paratuberculosis

Paratuberculosis (PTB) or Johne's disease is a contagious enteritis of ruminants caused by Mycobacterium avium subsp. paratuberculosis (MAP). Ovine PTB is less understood than bovine PTB, especially concerning paucibacillary infection and its evolution into clinical disease. We combined shotgun proteomics, histopathology and immunohistochemistry for the characterization of ileal tissues collected from seven asymptomatic sheep negative to serum ELISA, positive to feces and tissue MAP IS900 and F57 PCR, histologically classified as paucibacillary, actively infected, together with 3 MAP-free controls (K). Following shotgun proteomics with label-free quantitation and differential analysis, 96 proteins were significantly changed in PTB vs K, and were mostly involved in immune defense processes and in the macrophage-MAP interaction. Principal component analysis (PCA) of protein abundances highlighted two PTB sample clusters, PTB1 and PTB2, indicating a dichotomy in their proteomic profiles. This was in line with the PCA of histopathology data and was related to features of type 2 (PTB1) and type 3a (PTB2) lesions, respectively. PTB2 proteomes differed more than PTB1 proteomes from K: 43 proteins changed significantly only in PTB2 and 11 only in PTB1. The differential proteins cathelicidin, haptoglobin, S100A8 and S100A9 were evaluated by immunohistochemistry. K tissues were negative to cathelicidin and haptoglobin and sparsely positive to S100A8 and S100A9. PTB tissues were positive to all four proteins, with significantly more cells in PTB2 than in PTB1. In conclusion, we described several pathways altered in paucibacillary PTB, highlighted some proteomic differences among paucibacillary PTB cases, and identified potential markers for disease understanding, staging, and detection.

Another Look at the "Dismal Science" and Jenner's Experiment

The follow-up to Jenner's experiment, routine vaccination, has reduced more disease and saved more vertebrate lives than any other iatrogenic procedure by orders of magnitude. The unassailability of that potentially provocative cliché has been ciphered in human medicine, even if it is more difficult in our profession. Most public relations headaches concerning vaccines are a failure to communicate, often resulting in overly great expectations. Even in the throes of a tight appointment schedule remembering and synopsizing (for clients), some details of the dismal science can make practice great again.

Johne's disease in cattle: an in vitro model to study early response to infection of Mycobacterium avium subsp. paratuberculosis using RNA-seq

Johne's disease is a chronic granulomatous enteritis caused by Mycobacterium avium subsp. paratubercolosis (MAP) which affects ruminants worldwide and has a significant economic impact. MAP has also been associated with human Crohn's disease, although this connection is not well established. MAP is highly adapted for survival within host macrophages and prevents macrophage activation, blocks phagosome acidification and maturation, and attenuates presentation of antigens to the immune system. The consequence is a very long silent infection before clinical signs are observed. The present work examined the transcriptome of bovine monocyte-derived macrophages (MDM) infected with the L1 strain of MAP at 2h, 6h and 24h post infection using RNA-seq. Pathway over-representation analysis of genes differentially expressed between infected vs. control MDM identified that immune related pathways were affected. Genes belonging to the cytokine-cytokine receptor interaction pathway and members of the JAK-STAT pathway, which is involved in the regulation of immune response, were up-regulated. However, in parallel inhibitors of immune functions were activated, including suppressor of cytokine signaling (SOCS) and cytokine-inducible SH2-containing protein (CISH), which most likely suppresses IFNγ and the JAK/STAT signaling cascade in infected MDM, which may favour MAP survival. After exposure, macrophages phagocytise pathogens, activate the complement cascade and the adaptive immune system through the antigen presentation process. However, data presented here suggest that genes related to phagocytosis and lysosome function are down regulated in MAP infected MDM. Genes of MHC class II and complement pathway were also down-regulated. This study therefore shows that MAP infection is associated with changes in expression of genes related to the host immune response that may affect its ability to survive and multiply inside the host cell.

Quantitative and qualitative profiles of circulating monocytes may help identifying tuberculosis infection and disease stages

Tuberculosis (TB) is one of the most important cause of morbidity and death among infectious diseases, and continuous efforts are needed to improve diagnostic tools and therapy. Previous published studies showed that the absolute cells number of monocytes or lymphocytes in peripheral blood or yet the ratio of monocytes to lymphocytes displayed the ability to predict the risk of active TB. In the present study we evaluated the ratio of monocytes to lymphocytes variation and we also analyzed the ex-vivo expression of CD64 on monocytes as tools to identify biomarkers for discriminating TB stages. Significant differences were found when the average ratio of monocytes to lymphocytes of active TB patients was compared with latent TB infection (LTBI) subjects, cured TB and healthy donors (HD). By the receiver operator characteristics (ROC) curve analysis the cut-off value of 0.285, allowed the discrimination of active TB from HD, with a sensitivity of 91.04% and a specificity of 93.55% (95% of confidence interval: 0.92-0.99). The ROC curve analysis comparing TB patients and LTBI groups, led to a sensitivity and the specificity of the assay of 85.07% and 85.71%, respectively (95% of confidence interval: 0.85 to 0.96). The upregulation of CD64 expression on circulating monocytes in active TB patients could represent an additional biomarker for diagnosis of active TB. In conclusion, we found that the ML ratio or monocyte absolute count or phenotypic measures show predictive value for active TB.

Systems Analysis of Early Host Gene Expression Provides Clues for Transient Mycobacterium avium ssp avium vs. Persistent Mycobacterium avium ssp paratuberculosis Intestinal Infections

It has long been a quest in ruminants to understand how two very similar mycobacterial species, Mycobacterium avium ssp. paratuberculosis (MAP) and Mycobacterium avium ssp. avium (MAA) lead to either a chronic persistent infection or a rapid-transient infection, respectively. Here, we hypothesized that when the host immune response is activated by MAP or MAA, the outcome of the infection depends on the early activation of signaling molecules and host temporal gene expression. To test our hypothesis, ligated jejuno-ileal loops including Peyer’s patches in neonatal calves were inoculated with PBS, MAP, or MAA. A temporal analysis of the host transcriptome profile was conducted at several times post-infection (0.5, 1, 2, 4, 8 and 12 hours). When comparing the transcriptional responses of calves infected with the MAA versus MAP, discordant patterns of mucosal expression were clearly evident, and the numbers of unique transcripts altered were moderately less for MAA-infected tissue than were mucosal tissues infected with the MAP. To interpret these complex data, changes in the gene expression were further analyzed by dynamic Bayesian analysis. Bayesian network modeling identified mechanistic genes, gene-to-gene relationships, pathways and Gene Ontologies (GO) biological processes that are involved in specific cell activation during infection. MAP and MAA had significant different pathway perturbation at 0.5 and 12 hours post inoculation. Inverse processes were observed between MAP and MAA response for epithelial cell proliferation, negative regulation of chemotaxis, cell-cell adhesion mediated by integrin and regulation of cytokine-mediated signaling. MAP inoculated tissue had significantly lower expression of phagocytosis receptors such as mannose receptor and complement receptors. This study reveals that perturbation of genes and cellular pathways during MAP infection resulted in host evasion by mucosal membrane barrier weakening to access entry in the ileum, inhibition of Ca signaling associated with decreased phagosome-lysosome fusion as well as phagocytosis inhibition, bias toward Th2 cell immune response accompanied by cell recruitment, cell proliferation and cell differentiation; leading to persistent infection. Contrarily, MAA infection was related to cellular responses associated with activation of molecular pathways that release chemicals and cytokines involved with containment of infection and a strong bias toward Th1 immune response, resulting in a transient infection.

Mice Deficient in Angiopoietin-like Protein 2 (Angptl2) Gene Show Increased Susceptibility to Bacterial Infection Due to Attenuated Macrophage Activity

Macrophages play crucial roles in combatting infectious disease by promoting inflammation and phagocytosis. Angiopoietin-like protein 2 (ANGPTL2) is a secreted factor that induces tissue inflammation by attracting and activating macrophages to produce inflammatory cytokines in chronic inflammation-associated diseases such as obesity-associated metabolic syndrome, atherosclerosis, and rheumatoid arthritis. Here, we asked whether and how ANGPTL2 activates macrophages in the innate immune response. ANGPTL2 was predominantly expressed in proinflammatory mouse bone marrow-derived differentiated macrophages (GM-BMMs) following GM-CSF treatment relative to anti-inflammatory cells (M-BMMs) established by M-CSF treatment. Expression of the proinflammatory markers IL-1β, IL-12p35, and IL-12p40 significantly decreased in GM-BMMs from Angptl2-deficient compared with wild-type (WT) mice, suggestive of attenuated proinflammatory activity. We also report that ANGPTL2 inflammatory signaling is transduced through integrin α5β1 rather than through paired immunoglobulin-like receptor B. Interestingly, Angptl2-deficient mice were more susceptible to infection with Salmonella enterica serovar Typhimurium than were WT mice. Moreover, nitric oxide (NO) production by Angptl2-deficient GM-BMMs was significantly lower than in WT GM-BMMs. Collectively, our findings suggest that macrophage-derived ANGPTL2 promotes an innate immune response in those cells by enhancing proinflammatory activity and NO production required to fight infection.

Comparative functional genomics and the bovine macrophage response to strains of the mycobacterium genus

Mycobacterial infections are major causes of morbidity and mortality in cattle and are also potential zoonotic agents with implications for human health. Despite the implementation of comprehensive animal surveillance programs, many mycobacterial diseases have remained recalcitrant to eradication in several industrialized countries. Two major mycobacterial pathogens of cattle are Mycobacterium bovis and Mycobacterium avium subspecies paratuberculosis (MAP), the causative agents of bovine tuberculosis (BTB) and Johne's disease (JD), respectively. BTB is a chronic, granulomatous disease of the respiratory tract that is spread via aerosol transmission, while JD is a chronic granulomatous disease of the intestines that is transmitted via the fecal-oral route. Although these diseases exhibit differential tissue tropism and distinct complex etiologies, both M. bovis and MAP infect, reside, and replicate in host macrophages - the key host innate immune cell that encounters mycobacterial pathogens after initial exposure and mediates the subsequent immune response. The persistence of M. bovis and MAP in macrophages relies on a diverse series of immunomodulatory mechanisms, including the inhibition of phagosome maturation and apoptosis, generation of cytokine-induced necrosis enabling dissemination of infection through the host, local pathology, and ultimately shedding of the pathogen. Here, we review the bovine macrophage response to infection with M. bovis and MAP. In particular, we describe how recent advances in functional genomics are shedding light on the host macrophage-pathogen interactions that underlie different mycobacterial diseases. To illustrate this, we present new analyses of previously published bovine macrophage transcriptomics data following in vitro infection with virulent M. bovis, the attenuated vaccine strain M. bovis BCG, and MAP, and discuss our findings with respect to the differing etiologies of BTB and JD.

Regulatory T Cell Activity and Signs of T Cell Unresponsiveness in Bovine Paratuberculosis

Johne's disease, caused by infection with Mycobacterium avium subspecies paratuberculosis (MAP), is a wasting disease of ruminants displaying a long subclinical stage of infection followed by clinical disease characterized by severe diarrhea, wasting, and premature death. Immunologically, subclinical disease is characterized by a Th1 response effective at controlling intracellular infections such as that caused by MAP. In late subclinical disease, the Th1 response subsides and a non-protective Th2 response becomes prominent. One hypothesis for this shift in immune paradigm is that a population of MAP-reactive regulatory T cells (Tregs) develops during subclinical infection, limiting Th1-type responses to MAP antigens. To investigate this, we sought to accomplish the following: (1) determine if CD4(+)CD25(-) T cells exposed to MAP-infected macrophages develop a Treg phenotype, (2) develop a method to expand the relative abundance of Tregs in bovine peripheral blood lymphocyte populations, and (3) identify functional activities of expanded Tregs when combined with autologous peripheral blood mononuclear cells (PBMCs) and live MAP. We found that CD4(+)CD25(-) T cells exposed to MAP-infected macrophages from cows with Johne's disease do not show signs of a Treg phenotype and appear unresponsive to MAP antigens. A method for Treg expansion was successfully developed; however, based on results obtained in the subsequent functional studies it appears that these Tregs are not MAP-specific. Overall, it seems that T cell unresponsiveness, rather than Treg activity, is driving the Th1-to-Th2 immune shift observed during Johne's disease. Further, we have successfully developed a method to enrich non-specific bovine Tregs that exert suppressive effects against Th1 cytokine production.

Mycobacterium Avium subsp. paratuberculosis isolates induce in vitro granuloma formation and show successful survival phenotype, common anti-inflammatory and antiapoptotic responses within ovine macrophages regardless of genotype or host of origin

The analysis of the early macrophage responses, including bacterial growth within macrophages, represents a powerful tool to characterize the virulence of clinical isolates of Mycobcaterium avium susbp. paratuberculosis (Map). The present study represents the first assessment of the intracellular behaviour in ovine monocyte-derived macrophages (MDMs) of Map isolates representing distinct genotypes (C, S and B), and isolated from cattle, sheep, goat, fallow deer, deer, and wild boar. Intracellular growth and survival of the selected isolates in ovine MDMs was assessed by quantification of CFUs inside of the host cells at 2 h p.i. (day 0) and 7 d p. i. using an automatic liquid culture system (Bactec MGIT 960). Variations in bacterial counts over 7 days from the baseline were small, in a range between 1.63 to 1.05-fold. After 7 d of infection, variations in the estimated log₁₀ CFUs between all the tested isolates were not statistically significant. In addition, ovine MDMs exhibited enhanced anti-inflammatory, antiapoptotic and antidestructive responses when infected with two ovine isolates of distinct genotype (C and S) or with two C-type isolates from distinct hosts (cattle and sheep); which correlated with the successful survival of these isolates within ovine MDMs. A second objective was to study, based on an in vitro granuloma model, latter stages of the infection by investigating the capacity of two Map isolates from cattle and sheep to trigger formation of microgranulomas. Upon 10 d p.i., both Map isolates were able to induce the formation of granulomas comparable to the granulomas observed in clinical specimens with respect to the cellular components involved. In summary, our results demonstrated that Map isolates from cattle, sheep, goats, deer, fallow-deer and wild boar were able not only to initiate but also to establish a successful infection in ovine macrophages regardless of genotype.

Screening of Mycobacterium avium subsp. paratuberculosis mutants for attenuation in a bovine monocyte-derived macrophage model

Vaccination remains a major tool for prevention and progression of Johne's disease, a chronic enteritis of ruminants worldwide. Currently there is only one licensed vaccine within the United States and two vaccines licensed internationally against Johne's disease. All licensed vaccines reduce fecal shedding of Mycobacterium avium subsp. paratuberculosis (MAP) and delay disease progression. However, there are no available vaccines that prevent disease onset. A joint effort by the Johne's Disease Integrated Program (JDIP), a USDA-funded consortium, and USDA—APHIS/VS sought to identify transposon insertion mutant strains as vaccine candidates in part of a three phase study. The focus of the Phase I study was to evaluate MAP mutant attenuation in a well-defined in vitro bovine monocyte-derived macrophage (MDM) model. Attenuation was determined by colony forming unit (CFUs) counts and slope estimates. Based on CFU counts alone, the MDM model did not identify any mutant that significantly differed from the wild-type control, MAP K-10. Slope estimates using mixed models approach identified six mutants as being attenuated. These were enrolled in protection studies involving murine and baby goat vaccination-challenge models. MDM based approach identified trends in attenuation but this did not correlate with protection in a natural host model. These results suggest the need for alternative strategies for Johne's disease vaccine candidate screening and evaluation.

From mouth to macrophage: mechanisms of innate immune subversion by Mycobacterium avium subsp. paratuberculosis

Johne’s disease (JD) is a chronic enteric infection of cattle caused by Mycobacterium avium subsp. paratuberculosis (MAP). The high economic cost and potential zoonotic threat of JD have driven efforts to develop tools and approaches to effectively manage this disease within livestock herds. Efforts to control JD through traditional animal management practices are complicated by MAP’s ability to cause long-term environmental contamination as well as difficulties associated with diagnosis of JD in the pre-clinical stages. As such, there is particular emphasis on the development of an effective vaccine. This is a daunting challenge, in large part due to MAP’s ability to subvert protective host immune responses. Accordingly, there is a priority to understand MAP’s interaction with the bovine host: this may inform rational targets and approaches for therapeutic intervention. Here we review the early host defenses encountered by MAP and the strategies employed by the pathogen to avert or subvert these responses, during the critical period between ingestion and the establishment of persistent infection in macrophages.

Expression of genes associated with cholesterol and lipid metabolism identified as a novel pathway in the early pathogenesis of Mycobacterium avium subspecies paratuberculosis-infection in cattle

Johne's disease (JD) is a chronic disease affecting ruminants and other species caused by the pathogenic mycobacterium, Mycobacterium avium subsp. paratuberculosis (MAP). MAP has developed a multitude of mechanisms to persist within the host, and these in turn are counteracted by the host through various immune pathways. Identifying and characterising the different strategies employed by MAP to alter the host immune system in its favour, and thereby persist intracellularly, could hold the key to developing strategies to fight this disease. In this study we analysed a subset of bovine microarray data derived from early time points after experimental infection with MAP. A specifically developed integrated approach was used to identify and validate host genes involved in cholesterol homeostasis (24DHCR, LDLR, SCD-1), calcium homeostasis and anti-bacterial defence mechanisms, (CD38, GIMAP6) which were downregulated in response to MAP exposure. A trend for upregulation of granulysin gene expression in MAP-exposed cattle in comparison to unexposed cattle was also observed. From these analyses, a model of potential pathogen-host interactions involving these novel pathways was developed which indicates an important role for host lipids in mycobacterial survival and persistence.

Host-Mycobacterium avium subsp. paratuberculosis interactome reveals a novel iron assimilation mechanism linked to nitric oxide stress during early infection

BACKGROUND

The initial interaction between host cell and pathogen sets the stage for the ensuing infection and ultimately determine the course of disease. However, there is limited knowledge of the transcripts utilized by host and pathogen and how they may impact one another during this critical step. The purpose of this study was to create a host-Mycobacterium avium subsp. paratuberculosis (MAP) interactome for early infection in an epithelium-macrophage co-culture system using RNA-seq.

RESULTS

Establishment of the host-MAP interactome revealed a novel iron assimilation system for carboxymycobactin. Iron assimilation is linked to nitric oxide synthase-2 production by the host and subsequent nitric oxide buildup. Iron limitation as well as nitric oxide is a prompt for MAP to enter into an iron sequestration program. This new iron sequestration program provides an explanation for mycobactin independence in some MAP strains grown in vitro as well as during infection within the host cell. Utilization of such a pathway is likely to aid MAP establishment and long-term survival within the host.

CONCLUSIONS

The host-MAP interactome identified a number of metabolic, DNA repair and virulence genes worthy for consideration as novel drug targets as well as future pathogenesis studies. Reported interactome data may also be utilized to conduct focused, hypothesis-driven research. Co-culture of uninfected bovine epithelial cells (MAC-T) and primary bovine macrophages creates a tolerant genotype as demonstrated by downregulation of inflammatory pathways. This co-culture system may serve as a model to investigate other bovine enteric pathogens.

Global gene expression profiling of monocyte-derived macrophages from red deer (Cervus elaphus) genotypically resistant or susceptible to Mycobacterium avium subspecies paratuberculosis infection

Mycobacterium avium subspecies paratuberculosis (MAP) can cause a chronic inflammatory bowel disease, Johne's disease (JD), in ruminant animals. This study has explored the molecular basis of resistance and susceptibility to this disease in red deer breeds previously confirmed to express polarised phenotypes by experimental infection trials and following natural infection. Monocyte-derived macrophage cultures were obtained from uninfected red deer selected for either a resistant or susceptible phenotype. Cells were infected with MAP in vitro and gene expression analysed by RNA-Seq. Transcriptome analysis revealed a more disrupted gene expression profile in macrophages from susceptible animals compared with cells from resistant animals in terms of the number of genes up- or downregulated. Highly upregulated genes were related to chemotaxis (CXCL10, CSF3, and CCL8) and type 1 interferon signalling (RSAD2, IFIT1, IFIT2, ISG12, ISG15, USP18, and HERC6). Upregulation of these genes was observed to be greater in macrophages from susceptible animals compared to cells from resistant animals in response to in vitro MAP infection. These data support the use of transcriptomic approaches to enable the identification of markers associated particularly with susceptibility to MAP infection.

Anti-inflammatory and antiapoptotic responses to infection: a common denominator of human and bovine macrophages infected with Mycobacterium avium subsp. paratuberculosis

Mycobacterium avium subsp. paratuberculosis (Map) is the causative agent of a chronic intestinal inflammation in ruminants named Johne's disease or paratuberculosis and a possible etiopathological agent of human Crohn's disease (CD). Analysis of macrophage transcriptomes in response to Map infection is expected to provide key missing information in the understanding of the role of this pathogen in establishing an inappropriate and persistent infection in a susceptible host and of the molecular mechanisms that might underlie the early phases of CD. In this paper we summarize transcriptomic studies of human and bovine peripheral blood mononuclear cells (PBMC), monocyte-derived macrophages (MDMs), and macrophages-like cell lines in vitro infected with Map. Most studies included in this paper consistently reported common gene expression signatures of bovine and human macrophages in response to Map such as enhanced expression of the anti-inflammatory cytokines IL-10 and IL-6, which promote bacterial survival. Overexpression of IL-10 could be responsible for the Map-associated reduction in the expression of the proapoptotic TNF-α gene observed in bovine and human macrophages.

Systems biology analysis of gene expression during in vivo Mycobacterium avium paratuberculosis enteric colonization reveals role for immune tolerance

Survival and persistence of Mycobacterium avium subsp. paratuberculosis (MAP) in the intestinal mucosa is associated with host immune tolerance. However, the initial events during MAP interaction with its host that lead to pathogen survival, granulomatous inflammation, and clinical disease progression are poorly defined. We hypothesize that immune tolerance is initiated upon initial contact of MAP with the intestinal Peyer's patch. To test our hypothesis, ligated ileal loops in neonatal calves were infected with MAP. Intestinal tissue RNAs were collected (0.5, 1, 2, 4, 8 and 12 hrs post-infection), processed, and hybridized to bovine gene expression microarrays. By comparing the gene transcription responses of calves infected with the MAP, informative complex patterns of expression were clearly visible. To interpret these complex data, changes in the gene expression were further analyzed by dynamic Bayesian analysis, and genes were grouped into the specific pathways and gene ontology categories to create a holistic model. This model revealed three different phases of responses: i) early (30 min and 1 hr post-infection), ii) intermediate (2, 4 and 8 hrs post-infection), and iii) late (12 hrs post-infection). We describe here the data that include expression profiles for perturbed pathways, as well as, mechanistic genes (genes predicted to have regulatory influence) that are associated with immune tolerance. In the Early Phase of MAP infection, multiple pathways were initiated in response to MAP invasion via receptor mediated endocytosis and changes in intestinal permeability. During the Intermediate Phase, perturbed pathways involved the inflammatory responses, cytokine-cytokine receptor interaction, and cell-cell signaling. During the Late Phase of infection, gene responses associated with immune tolerance were initiated at the level of T-cell signaling. Our study provides evidence that MAP infection resulted in differentially regulated genes, perturbed pathways and specifically modified mechanistic genes contributing to the colonization of Peyer's patch.

Gene expression profiling of Mycobacterium avium subsp. paratuberculosis in simulated multi-stress conditions and within THP-1 cells reveals a new kind of interactive intramacrophage behaviour

BACKGROUND

Recent studies have identified in Mycobacterium avium subsp. paratuberculosis (MAP), already known as a pathogen in ruminants, a potential zoonotic agent of some autoimmune diseases in humans. Therefore, considering the possible risk for public health, it is necessary a thorough understanding of MAP's gene expression during infection of human host as well as the identification of its immunogenic and/or virulence factors for the development of appropriate diagnostic and therapeutic tools.

RESULTS

In order to characterize MAP's transcriptome during macrophage infection, we analyzed for the first time the whole gene expression of a human derived strain of MAP in simulated intraphagosomal conditions and after intracellular infection of the human macrophage cell line THP-1 by using the DNA-microarray technology. Results showed that MAP shifts its transcriptome to an adaptive metabolism for an anoxic environment and nutrient starvation. It up-regulates several response factors to oxidative stress or intracellular conditions and allows, in terms of transcription, a passive surface peptidoglycan spoliation within the macrophage along with an intensification of the anabolic activity for lipidic membrane structures.

CONCLUSIONS

These results indicate a possible interactive system between MAP and its host cell based on the internal mimicry unlike other intracellular pathogens, bringing new hypothesis in the virulence and pathogenicity of MAP and its importance in human health.

Pan-genomic analysis of bovine monocyte-derived macrophage gene expression in response to in vitro infection with Mycobacterium avium subspecies paratuberculosis

Mycobacterium avium subspecies paratuberculosis is the causative agent of Johne's disease, an intestinal disease of ruminants with major economic consequences. Infectious bacilli are phagocytosed by host macrophages upon exposure where they persist, resulting in lengthy subclinical phases of infection that can lead to immunopathology and disease dissemination. Consequently, analysis of the macrophage transcriptome in response to M. avium subsp. paratuberculosis infection can provide valuable insights into the molecular mechanisms that underlie Johne's disease. Here, we investigate pan-genomic gene expression in bovine monocyte-derived macrophages (MDM) purified from seven age-matched females, in response to in vitro infection with M. avium subsp. paratuberculosis (multiplicity of infection 2:1) at intervals of 2 hours, 6 hours and 24 hours post-infection (hpi). Differentially expressed genes were identified by comparing the transcriptomes of the infected MDM to the non-infected control MDM at each time point (adjusted P-value threshold ≤ 0.10). 1050 differentially expressed unique genes were identified 2 hpi, with 974 and 78 differentially expressed unique genes detected 6 and 24 hpi, respectively. Furthermore, in the infected MDM the number of upregulated genes exceeded the number of downregulated genes at each time point, with the fold-change in expression for the upregulated genes markedly higher than that for the downregulated genes. Inspection and systems biology analysis of the differentially expressed genes revealed an enrichment of genes involved in the inflammatory response, cell signalling pathways and apoptosis. The transcriptional changes associated with cellular signalling and the inflammatory response may reflect different immuno-modulatory mechanisms that underlie host-pathogen interactions during infection.

Macrophage plasticity and polarization: in vivo veritas

Diversity and plasticity are hallmarks of cells of the monocyte-macrophage lineage. In response to IFNs, Toll-like receptor engagement, or IL-4/IL-13 signaling, macrophages undergo M1 (classical) or M2 (alternative) activation, which represent extremes of a continuum in a universe of activation states. Progress has now been made in defining the signaling pathways, transcriptional networks, and epigenetic mechanisms underlying M1-M2 or M2-like polarized activation. Functional skewing of mononuclear phagocytes occurs in vivo under physiological conditions (e.g., ontogenesis and pregnancy) and in pathology (allergic and chronic inflammation, tissue repair, infection, and cancer). However, in selected preclinical and clinical conditions, coexistence of cells in different activation states and unique or mixed phenotypes have been observed, a reflection of dynamic changes and complex tissue-derived signals. The identification of mechanisms and molecules associated with macrophage plasticity and polarized activation provides a basis for macrophage-centered diagnostic and therapeutic strategies.

Expression of genes associated with the antigen presentation and processing pathway are consistently regulated in early Mycobacterium avium subsp. paratuberculosis infection

The primary objective of this study was to evaluate early gene expression profiles associated with paratuberculosis in cattle exposed to known infectious doses of Mycobacterium avium sub-species paratuberculosis (MAP). A Johne's disease experimental infection field trial was conducted on a mixed population of Holstein and Holstein Red cattle. Blood samples from four MAP exposed and four unexposed cattle, selected based on IFNγ expressions were taken at 9, 13 and 21 weeks and RNA processed to Affymetrix GeneChip™ Bovine Genome arrays. Ontological analysis revealed consistent differences in gene expression between MAP exposed and control animals. A stark variation was observed in expression of a number of genes along antigen presentation pathways, suggesting that MAP exposure potentially results in the host immune response switching to a CD8(+) biased antigen presentation profile. This requires further in-depth analysis since it exposes a hitherto unconfirmed association between MAP exposure and in vivo MHC gene modulation.

Tuberculosis immunity: opportunities from studies with cattle

Mycobacterium tuberculosis and M. bovis share >99% genetic identity and induce similar host responses and disease profiles upon infection. There is a rich history of codiscovery in the development of control measures applicable to both human and bovine tuberculosis (TB) including skin-testing procedures, M. bovis BCG vaccination, and interferon-γ release assays. The calf TB infection model offers several opportunities to further our understanding of TB immunopathogenesis. Recent observations include correlation of central memory immune responses with TB vaccine efficacy, association of SIRPα⁺ cells in ESAT-6:CFP10-elicited multinucleate giant cell formation, early γδ T cell responses to TB, antimycobacterial activity of memory CD4⁺ T cells via granulysin production, association of specific antibody with antigen burden, and suppression of innate immune gene expression in infected animals. Partnerships teaming researchers with veterinary and medical perspectives will continue to provide mutual benefit to TB research in man and animals.

Genomic and transcriptomic studies in Mycobacterium avium subspecies paratuberculosis

Microarray technology is an important tool in functional genomic research. It has enabled a deeper analysis of genomic diversity among bacteria belonging to the Mycobacterium avium complex (MAC). In addition, the expression of thousands of genes can be studied simultaneously in a single experiment. With the complete genome sequence of a bovine isolate of M. avium subspecies paratuberculosis, and the independent construction of DNA microarrays in our laboratories, transcriptomic studies for this veterinary pathogen are now possible. Furthermore, the bovine genome sequence project is completed and bovine arrays have been developed to examine host responses to infection with M. avium subsp. paratuberculosis. Collectively, genomic and transcriptomic data has yielded novel insights surrounding the genetic regulation and biology of Johne's disease.

Expression profiling reveals differences in immuno-inflammatory gene expression between the two disease forms of sheep paratuberculosis

Paratuberculosis is a chronic enteropathy of ruminants caused by Mycobacterium avium subspecies paratuberculosis (MAP); infection of sheep results in two disease forms - paucibacillary (tuberculoid) and multibacillary (lepromatous) associated with the differential polarization of the immune response. In addition the majority of MAP-infected animals show no pathology and remain asymptomatic. Microarray and real-time RT-qPCR analyses were used to compare gene expression in ileum from sheep with the two disease forms and asymptomatic sheep, to further understand the molecular basis of the pathologies. Microarrays identified 36 genes with fold-change of >1.5 and P< or = 0.05 in at least one comparison; eight candidates were chosen for RT-qPCR validation. Sequence analysis of two candidates, CXCR4 and IGFBP6, identified three SNPs in each; five were found in all three forms of disease and showed no significant relationship to pathological type. The IGFBP6 G(3743) A SNP was not detected in asymptomatic sheep. The data show that the two forms of disease are associated with distinct molecular profiles highlighted by the differential expression of chemokine and chemokine receptor transcripts, the protein products of which might be implicated in the different cell infiltrates of the pathologies. The cells within the lesions also show evidence of abnormal activation; they express high levels of cytokine transcripts but have reduced expression levels of transcripts for T cell receptor associated molecules.

Identification of differentially expressed genes in ileum, intestinal lymph node and peripheral blood mononuclear cells of sheep infected with Mycobacterium avium subsp. paratuberculosis using differential display polymerase chain reaction

Discovery of differentially expressed genes aids in understanding molecular mechanisms underpinning normal and pathological states. When studying animals such as sheep where the entire genome has not been characterized, techniques that do not require knowledge of gene sequences are particularly advantageous. We used one such technique, differential display polymerase chain reaction (DD-PCR), to identify genes that had different degrees of expression in response to Mycobacterium avium subsp. paratuberculosis (M. ptb), the organism that causes Johne's disease in ruminants. Differentially expressed genes were validated by quantitative PCR using especially selected reference genes established in this study. Sheep (n=47) were classified according to history of exposure to M. ptb and infection status by histology and faecal and tissue culture. Differences in levels of gene expression were analyzed using restricted maximum likelihood (REML) in a linear mixed model. Five genes from the ileum and 17 genes from lymph node were differentially expressed in ovine Johne's disease. Expression of seven of these genes was also significantly different in peripheral blood mononuclear cells. Genes identified in association with M. ptb infection had a wide range of functions in pathways including: antigen presentation, signal transduction and cell differentiation, TLR signaling, immune cell activation and chemokine functions, granulomatous inflammation, Th1 suppression and apoptosis.

Macrophage polarization in bacterial infections

Converging studies have shown that M1 and M2 macrophages are functionally polarized in response to microorganisms and host mediators. Gene expression profiling of macrophages reveals that various Gram-negative and Gram-positive bacteria induce the transcriptional activity of a "common host response," which includes genes belonging to the M1 program. However, excessive or prolonged M1 polarization can lead to tissue injury and contribute to pathogenesis. The so-called M2 macrophages play a critical role in the resolution of inflammation by producing anti-inflammatory mediators. These M2 cells cover a continuum of cells with different phenotypic and functional properties. In addition, some bacterial pathogens induce specific M2 programs in macrophages. In this review, we discuss the relevance of macrophage polarization in three domains of infectious diseases: resistance to infection, infectious pathogenesis, and chronic evolution of infectious diseases.

Transcriptional analysis of diverse strains Mycobacterium avium subspecies paratuberculosis in primary bovine monocyte derived macrophages

In this study we analyzed the macrophage-induced gene expression of three diverse genotypes of Mycobacterium avium subsp. paratuberculosis (MAP). Using selective capture of transcribed sequences (SCOTS) on three genotypically diverse MAP isolates from cattle, human, and sheep exposed to primary bovine monocyte derived macrophages for 48 h and 120 h we created and sequenced six cDNA libraries. Sequence annotations revealed that the cattle isolate up-regulated 27 and 241 genes; the human isolate up-regulated 22 and 53 genes, and the sheep isolate up-regulated 35 and 358 genes, at the two time points respectively. Thirteen to thirty-three percent of the genes identified did not have any annotated function. Despite variations in the genes identified, the patterns of expression fell into overlapping cellular functions as inferred by pathway analysis. For example, 10-12% of the genes expressed by all three strains at each time point were associated with cell-wall biosynthesis. All three strains of MAP studied up-regulated genes in pathways that combat oxidative stress, metabolic and nutritional starvation, and cell survival. Taken together, this comparative transcriptional analysis suggests that diverse MAP genotypes respond with similar modus operandi for survival in the host.