Johne's disease, inflammatory bowel disease, and Mycobacterium paratuberculosis

Meta-analysis of prevalence of paratuberculosis in cattle using published estimates under serum and milk ELISA

Johne's disease (JD), caused by Mycobacterium avium subspecies paratuberculosis (MAP), poses significant challenges to the global livestock industry, particularly affecting bovine populations. To better understand the prevalence of paratuberculosis and its diagnostic nuances, a comprehensive meta-analysis was conducted. This analysis encompassed 21 studies involving 632,767 cows for milk enzyme-linked immunosorbent assay (ELISA) and 51 studies involving 256,409 cows for serum ELISA. The pooled prevalence estimate for paratuberculosis on a cow-basis was found to be 16% (95% CI: 14%; 18%) for milk ELISA and 8% (95% CI: 7%; 8%) for serum ELISA. Notably, higher confidence intervals (CI) were observed in milk ELISA, the Europe and Asia groups, suggesting variability in prevalence estimates within these regions. Conversely, lower CIs were noted in the USA and Canada groups, indicating greater consistency in prevalence estimates within these countries. However, serum ELISA exhibited high CI values across all regions, underscoring potential variability in diagnostic performance. These findings provide valuable insights for veterinarians, researchers, policymakers, and livestock producers in optimizing paratuberculosis detection and control strategies to mitigate its impact on bovine health and agricultural productivity.

Proteomic profiling of membrane vesicles from Mycobacterium avium subsp. paratuberculosis: Navigating towards an insilico design of a multi-epitope vaccine targeting membrane vesicle proteins

Bacteria typically produce membrane vesicles (MVs) at varying levels depending on the surrounding environments. Gram-negative bacterial outer membrane vesicles (OMVs) have been extensively studied for over 30 years, but MVs from Gram-positive bacteria only recently have been a focus of research. In the present study, we isolated MVs from Mycobacterium avium subsp. paratuberculosis (MAP) and analyzed their protein composition using LC-MS/MS. A total of 316 overlapping proteins from two independent preparations were identified in our study, and topology prediction showed these cargo proteins have different subcellular localization patterns. When MVs were administered to bovine-derived macrophages, significant up-regulation of pro-inflammatory cytokines was observed via qRT-PCR. Proteome functional annotation revealed that many of these proteins are involved in the cellular protein metabolic process, tRNA aminoacylation, and ATP synthesis. Secretory proteins with high antigenicity and adhesion capability were mapped for B-cell and T-cell epitopes. Antigenic, Immunogenic and IFN-γ inducing B-cell, MHC-I, and MHC-II epitopes were stitched together through linkers to form multi-epitope vaccine (MEV) construct against MAP. Strong binding energy was observed during the docking of the 3D structure of the MEV with the bovine TLR2, suggesting that the putative MEV may be a promising vaccine candidate against MAP. However, in vitro and in vivo analysis is required to prove the immunogenic concept of the MEV which we will follow in our future studies. SIGNIFICANCE: Johne's disease is a chronic infection caused by Mycobacterium avium subsp. paratuberculosis that has a potential link to Crohn's disease in humans. The disease is characterized by persistent diarrhea and enteritis, resulting in significant economic losses due to reduced milk yield and premature culling of infected animals. The dairy industry in the United States alone experiences losses of approximately USD 250 million due to Johne's disease. The current vaccine against Johne's disease is limited by several factors, including variable efficacy, limited duration of protection, interference with diagnostic tests, inability to prevent infection, and logistical and cost-related challenges. Nevertheless, a multiepitope vaccine design approach targeting M. avium subsp. paratuberculosis has the potential to overcome these challenges and offer improved protection against Johne's disease.

Regionally Distinct Immune and Metabolic Transcriptional Responses in the Bovine Small Intestine and Draining Lymph Nodes During a Subclinical Mycobacterium avium subsp. paratuberculosis Infection

Mycobacterium avium subsp. paratuberculosis (MAP) is the causative infectious agent of Johne’s disease (JD), an incurable granulomatous enteritis affecting domestic livestock and other ruminants around the world. Chronic MAP infections usually begin in calves with MAP uptake by Peyer’s patches (PP) located in the jejunum (JE) and ileum (IL). Determining host responses at these intestinal sites can provide a more complete understanding of how MAP manipulates the local microenvironment to support its long-term survival. We selected naturally infected (MAPinf, n=4) and naive (MAPneg, n=3) cows and transcriptionally profiled the JE and IL regions of the small intestine and draining mesenteric lymph nodes (LN). Differentially expressed (DE) genes associated with MAP infection were identified in the IL (585), JE (218), jejunum lymph node (JELN) (205), and ileum lymph node (ILLN) (117). Three DE genes (CD14, LOC616364 and ENSBTAG00000027033) were common to all MAPinf versus MAPneg tissues. Functional enrichment analysis revealed immune/disease related biological processes gene ontology (GO) terms and pathways predominated in IL tissue, indicative of an activated immune response state. Enriched GO terms and pathways in JE revealed a distinct set of host responses from those detected in IL. Regional differences were also identified between the mesenteric LNs draining each intestinal site. More down-regulated genes (52%) and fewer immune/disease pathways (n=5) were found in the ILLN compared to a higher number of up-regulated DE genes (56%) and enriched immune/disease pathways (n=13) in the JELN. Immunohistochemical staining validated myeloid cell transcriptional changes with increased CD172-positive myeloid cells in IL and JE tissues and draining LNs of MAPinf versus MAPneg cows. Several genes, GO terms, and pathways related to metabolism were significantly DE in IL and JE, but to a lesser extent (comparatively fewer enriched metabolic GO terms and pathways) in JELN suggesting distinct regional metabolic changes in IL compared to JE and JELN in response to MAP infection. These unique tissue- and regional-specific differences provides novel insight into the dichotomy in host responses to MAP infection that occur throughout the small intestine and mesenteric LN of chronically MAP infected cows.

An Embedded Multiscale Modelling to Guide Control and Elimination of Paratuberculosis in Ruminants

In recent years, multiscale modelling approach has begun to receive an overwhelming appreciation as an appropriate technique to characterize the complexity of infectious disease systems. In this study, we develop an embedded multiscale model of paratuberculosis in ruminants at host level that integrates the within-host scale and the between-host. A key feature of embedded multiscale models developed at host level of organization of an infectious disease system is that the within-host scale and the between-host scale influence each other in a reciprocal (i.e., both) way through superinfection, that is, through repeated infection before the host recovers from the initial infectious episode. This key feature is demonstrated in this study through a multiscale model of paratuberculosis in ruminants. The results of this study, through numerical analysis of the multiscale model, show that superinfection influences the dynamics of paratuberculosis only at the start of the infection, while the MAP bacteria replication continuously influences paratuberculosis dynamics throughout the infection until the host recovers from the initial infectious episode. This is largely because the replication of MAP bacteria at the within-host scale sustains the dynamics of paratuberculosis at this scale domain. We further use the embedded multiscale model developed in this study to evaluate the comparative effectiveness of paratuberculosis health interventions that influence the disease dynamics at different scales from efficacy data.

An Escherichia coli carrier vaccine with surface-displayed protein MAP3061c elicits protective immunity against Mycobacterium paratuberculosis in mice

Johne's disease, or paratuberculosis, is a chronic granulomatous enteritis of ruminants caused by Mycobacterium avium subsp. paratuberculosis (MAP). This disease occurs worldwide and results in considerable economic losses in the livestock industry. There are no effective treatments for Johne's disease, so there is an urgent need to develop an efficient, economical, and stable vaccine for MAP control. Here, a live Escherichia coli (E. coli) surface display vaccine harboring the MAP3061c gene was developed through an ice nucleation protein (INP) surface display system. The experimental data demonstrated that MAP3061c has strong immunogenicity and that the surface displayed vaccine can stimulate mice to produce high levels of antibodies. Both CD4⁺ and CD8⁺ T cell counts as well as several cytokines - including IFN-γ, IL-4, IL-10, IL-17A and IL-23 - were significantly increased in the display vaccine group. Post-vaccination challenge with MAP in mice resulted in improved fitness of the mice as demonstrated by a lack of weight loss. Pathological results revealed that the surface display vaccine could reduce the degree of pathological damage and slowed the course of disease. Taken together, our data suggests that the E. coli carrier vaccine with surface-displayed MAP3061c elicits protective immunity against MAP, providing new insights into the development of a MAP vaccine.

Welfare Assessment of 30 Dairy Goat Farms in the Midwestern United States

Dairy goat animal welfare assessment protocols have been developed and conducted in Europe and the United Kingdom for dairy goats; however, there are no published reports of large-scale welfare assessment for dairy goats on farms in the Midwestern United States (US). Therefore, the objective of this study was to perform welfare assessment of lactating dairy goats and identify the most prevalent welfare issues on 30 farms across the Midwestern US. Thirty dairy goat farms (self-selected) were enrolled in the study if they shipped milk for human consumption (regardless of herd size). The number of lactating does on each farm ranged from 34 to 6,500 goats, with a median number of 158 lactating does (mean ± SD: 602 ± 1,708 lactating does). The protocol used was developed from available literature on goat welfare assessment but modified for use in the Midwestern US. Observations were made without handling the animals and included 22 animal-based indicators evaluated at the group- and individual-level. The observations were conducted during ~3-5 h during a milking session (either morning or afternoon) and time in the home pen. Principal components analysis (PCA) was carried out on the welfare assessment data from each farm. The first two dimensions of the PCA explained 34.8% of the variation. The PCA biplot indicated correlations between indicators. The most prevalent conditions observed across the 30 farms included any knee calluses (80.9%), any claw overgrowth (51.4%), poor hygiene (14.9%), skin lesions (8.9%), poor hair coat condition (8.3%) and any ear pathology (8.0%). These results are the first to provide the Midwestern US dairy goat industry with information to improve commercial dairy goat welfare.

miRNA Regulatory Functions in Farm Animal Diseases, and Biomarker Potentials for Effective Therapies

MicroRNAs (miRNAs) are small endogenous RNAs that regulate gene expression post-transcriptionally by targeting either the 3′ untranslated or coding regions of genes. They have been reported to play key roles in a wide range of biological processes. The recent remarkable developments of transcriptomics technologies, especially next-generation sequencing technologies and advanced bioinformatics tools, allow more in-depth exploration of messenger RNAs (mRNAs) and non-coding RNAs (ncRNAs), including miRNAs. These technologies have offered great opportunities for a deeper exploration of miRNA involvement in farm animal diseases, as well as livestock productivity and welfare. In this review, we provide an overview of the current knowledge of miRNA roles in major farm animal diseases with a particular focus on diseases of economic importance. In addition, we discuss the steps and future perspectives of using miRNAs as biomarkers and molecular therapy for livestock disease management as well as the challenges and opportunities for understanding the regulatory mechanisms of miRNAs related to disease pathogenesis.

Serum Metabolomic Profiles of Paratuberculosis Infected and Infectious Dairy Cattle by Ambient Mass Spectrometry

Mycobacterium avium subsp. paratuberculosis (MAP) is the causative agent of paratuberculosis [Johne's disease (JD)], a chronic disease that causes substantial economic losses in the dairy cattle industry. The long incubation period means clinical signs are visible in animals only after years, and some cases remain undetected because of the subclinical manifestation of the disease. Considering the complexity of JD pathogenesis, animals can be classified as infected, infectious, or affected. The major limitation of currently available diagnostic tests is their failure in detecting infected non-infectious animals. The present study aimed to identify metabolic markers associated with infected and infectious stages of JD. Direct analysis in real time coupled with high resolution mass spectrometry (DART-HRMS) was, hence, applied in a prospective study where cohorts of heifers and cows were followed up annually for 2–4 years. The animals' infectious status was assigned based on a positive result of both serum ELISA and fecal PCR, or culture. The same animals were retrospectively assigned to the status of infected at the previous sampling for which all JD tests were negative. Stored sera from 10 infected animals and 17 infectious animals were compared with sera from 20 negative animals from the same herds. Two extraction protocols and two (-/+) ionization modes were tested. The three most informative datasets out of the four were merged by a mid-level data fusion approach and submitted to partial least squares discriminant analysis (PLS-DA). Compared to the MAP negative subjects, metabolomic analysis revealed the m/z signals of isobutyrate, dimethylethanolamine, palmitic acid, and rhamnitol were more intense in infected animals. Both infected and infectious animals showed higher relative intensities of tryptamine and creatine/creatinine as well as lower relative abundances of urea, glutamic acid and/or pyroglutamic acid. These metabolic differences could indicate altered fat metabolism and reduced energy intake in both infected and infectious cattle. In conclusion, DART-HRMS coupled to a mid-level data fusion approach allowed the molecular features that identified preclinical stages of JD to be teased out.

Economic losses due to Johne's disease (paratuberculosis) in dairy cattle

Johne's disease (JD), or paratuberculosis, is an infectious inflammatory disorder of the intestines primarily associated with domestic and wild ruminants including dairy cattle. The disease, caused by an infection with Mycobacterium avium subspecies paratuberculosis (MAP) bacteria, burdens both animals and producers through reduced milk production, premature culling, and reduced salvage values among MAP-infected animals. The economic losses associated with these burdens have been measured before, but not across a comprehensive selection of major dairy-producing regions within a single methodological framework. This study uses a Markov chain Monte Carlo approach to estimate the annual losses per cow within MAP-infected herds and the total regional losses due to JD by simulating the spread and economic impact of the disease with region-specific economic variables. It was estimated that approximately 1% of gross milk revenue, equivalent to US$33 per cow, is lost annually in MAP-infected dairy herds, with those losses primarily driven by reduced production and being higher in regions characterized by above-average farm-gate milk prices and production per cow. An estimated US$198 million is lost due to JD in dairy cattle in the United States annually, US$75 million in Germany, US$56 million in France, US$54 million in New Zealand, and between US$17 million and US$28 million in Canada, one of the smallest dairy-producing regions modeled.

Presence of Infection by Mycobacterium avium subsp. paratuberculosis in the Blood of Patients with Crohn's Disease and Control Subjects Shown by Multiple Laboratory Culture and Antibody Methods

Mycobacterium avium subspecies paratuberculosis (MAP) has long been suspected to be involved in the etiology of Crohn's disease (CD). An obligate intracellular pathogen, MAP persists and influences host macrophages. The primary goals of this study were to test new rapid culture methods for MAP in human subjects and to assess the degree of viable culturable MAP bacteremia in CD patients compared to controls. A secondary goal was to compare the efficacy of three culture methods plus a phage assay and four antibody assays performed in separate laboratories, to detect MAP from the parallel samples. Culture and serological MAP testing was performed blind on whole blood samples obtained from 201 subjects including 61 CD patients (two of the patients with CD had concurrent ulcerative colitis (UC)) and 140 non-CD controls (14 patients in this group had UC only). Viable MAP bacteremia was detected in a significant number of study subjects across all groups. This included Pozzato culture (124/201 or 62% of all subjects, 35/61 or 57% of CD patients), Phage assay (113/201 or 56% of all subjects, 28/61 or 46% of CD patients), TiKa culture (64/201 or 32% of all subjects, 22/61 or 36% of CD patients) and MGIT culture (36/201 or 18% of all subjects, 15/61 or 25% of CD patients). A link between MAP detection and CD was observed with MGIT culture and one of the antibody methods (Hsp65) confirming previous studies. Other detection methods showed no association between any of the groups tested. Nine subjects with a positive Phage assay (4/9) or MAP culture (5/9) were again positive with the Phage assay one year later. This study highlights viable MAP bacteremia is widespread in the study population including CD patients, those with other autoimmune conditions and asymptomatic healthy subjects.

Nutrition in New Zealand: Can the Past Offer Lessons for the Present and Guidance for the Future?

Over the last century, nutrition research and public health in New Zealand have been inspired by Dr Muriel Bell, the first and only state nutritionist. Some of her nutritional concerns remain pertinent today. However, the nutritional landscape is transforming with extraordinary changes in the production and consumption of food, increasing demand for sustainable and healthy food to meet the requirements of the growing global population and unprecedented increases in the prevalence of both malnutrition and noncommunicable diseases. New Zealand’s economy is heavily dependent on agrifoods, but there is a need to integrate interactions between nutrition and food-related disciplines to promote national food and nutrition security and to enhance health and well-being. The lack of integration between food product development and health is evident in the lack of investigation into possible pathological effects of food additives. A national coherent food strategy would ensure all components of the food system are optimised and that strategies to address the global syndemic of malnutrition and climate change are prioritised. A state nutritionist or independent national nutrition advocacy organisation would provide the channel to communicate nutrition science and compete with social media, lead education priorities and policy development, engage with the food industry, facilitate collaboration between the extraordinary range of disciplines associated with food production and optimal health and lead development of a national food strategy.

Mycobacterium avium Subspecies paratuberculosis Infects and Replicates within Human Monocyte-Derived Dendritic Cells

BACKGROUND

Mycobacterium avium subspecies paratuberculosis (MAP), a member of the mycobacteriaceae family, causes Johne's disease in ruminants, which resembles Crohn's disease (CD) in humans. MAP was proposed to be one of the causes of human CD, but the evidence remains elusive. Macrophages were reported to be the only cell where MAP proliferates in ruminants and humans and is likely the major producer of TNFα-associated inflammation. However, whether human dendritic cells (DCs), another major antigen-presenting cell (APC), have the ability to harbor MAP and disseminate infection, remains unknown.

METHODS

Human monocyte-derived dendritic cells (moDCs) were infected with MAP and phagocytosis and intracellular survival were quantified by immunofluorescence (IF) and colony counts, respectively. MoDC cytokine expression was measured via ELISA and their activation state was measured via flow cytometry.

RESULTS

We showed that MAP can infect and replicate in human moDCs as means to evade the immune system for successful infection, through inhibition of the phago-lysosome fusion via the secretion of protein tyrosine phosphatase PtpA. This mechanism initially led to a state of tolerance in moDCs and then subsequently caused a pro-inflammatory response as infection persisted, characterized by the upregulation of IL-6 and TNFα, and downregulation of IL-10. Moreover, we showed that moDCs have the ability to phagocytose up to 18% of MAP, when exposed at a multiplicity of infection of 1:1.

CONCLUSION

Infection and subsequent proliferation of MAP within moDCs could provide a unique means for the dissemination of MAP to lymphoid tissue, while altering immune responses to facilitate the persistence of infection of host tissues in CD.

The development and use of Actiphage® to detect viable mycobacteria from bovine tuberculosis and Johne's disease-infected animals

Here, we describe the development of a method that exploits bacteriophage D29 as a lysis agent for efficient DNA extraction from low numbers of mycobacterial cells. This method (Actiphage® ) used in combination with PCR achieved rapid and sensitive (LOD ≤ 10 cell ml-1 ) detection and identification of viable, pathogenic mycobacteria in blood samples within 6 h. We demonstrate that mycobacteriophage D29 can be used to detect a range of mycobacteria from clinical blood samples including both Mycobacterium tuberculosis complex and Mycobacterium avium subsp. paratuberculosis without the need for culture and confirms our earlier observations that a low-level bacteraemia is associated with these infections in cattle. In a study of M. bovis-infected cattle (n = 41), the sensitivity of the Actiphage® method was 95 % (95 % CI; 0.84-0.99) and specificity was 100 % (95% CI; 0.92-1). We further used Actiphage® to demonstrate viable Mycobacterium avium subsp. paratuberculosis is present in the blood of Johne's infected cattle. This method provides a revolutionary new tool for the study of infections caused by these difficult to grow pathogens.

Evaluation of Mycobacterium smegmatis as indicator of the efficacy of high hydrostatic pressure and ultra-high pressure homogenization treatments for pasteurization-like purposes in milk

The objectives of this study were: to assess the efficiency of high hydrostatic pressure or ultra-high pressure homogenization against Mycobacterium smegmatis in milk and to discuss whether M. smegmatis can be considered a suitable surrogate for other Mycobacterium spp. in high pressure inactivation trials using milk. Three strains of this specie (CECT 3017, 3020 and 3032) were independently inoculated into both skimmed (0.2% fat) and whole milk (3.4% fat) at an approximate load of 6.5 Log CFU/ml and submitted to HHP treatments at 300, 400 or 500 MPa for 10 m at 6°C and 20°C. Evolution of the surviving cells of the inoculated strains was evaluated analysing milk immediately after the treatments and after 5 and 8 d of storage at 6°C. HHP treatments at 300 MPa were seldom efficient at inactivating M. smegmatis strains, but lethality increased with pressure applied in all cases. Generation of sub-lethal injured cells was observed only after 400 MPa treatments since inactivation at 500 MPa was shown to be complete. Significant differences were not observed due to either temperature of treatment or fat content of milk, except for strain CECT3032, which was shown to be the most sensitive to HHP treatments. Milk inoculated with strain CECT3017 was submitted to ultra-high pressure homogenization (UHPH) treatments at 200, 300 and 400 MPa. Maximum reductions were obtained after 300 and 400 MPa treatments, although less than 3.50 Log CFU/ml were inactivated. UHPH did not cause significant number of injured cells. The usefulness of this species as a marker for pressure-based processing seems limited since it showed greater sensitivity than some pathogenic species including other Mycobacteria reported in previous studies.

Sero-surveillance of Mycobacterium avium subspecies paratuberculosis infection in ruminants in Medina

Objective:

The present study aimed to assess for the first time, in Medina, the prevalence of Mycobacterium avium subsp. paratuberculosis in ruminants due to its potential zoonotic importance.

Materials and methods:

A total of 823 sera samples and 364 milk samples were used to determine the incidence of Mycobacterium avium subsp. Paratuberculosis (MAP) using the indirect Enzyme-Linked Immunosorbent Assay.

Results:

The seroprevalence of MAP was 11.1% in sheep and 13.8% in goats, while no infection was recorded among camels. MAP infection was not influenced by the animal’s gender, but it was influenced by its locality since the infection rate in local animals was higher than that in imported ones with a significant correlation (p < 0.05). MAP infection had a significant correlation (p < 0.05) with 2 years aged animals. On the other hand, the detection of MAP in milk revealed that 17 (13.8%) goats and 12 (4.9%) sheep were infected. The prevalence of MAP in milk samples was not influenced by either the animal’s age or locality.

Conclusion:

Sheep and goats may act as a reservoir for MAP to the Medina community. Since Medina is an active area of mass gatherings as a destination for pilgrims throughout the year, therefore, necessary control measures should be implemented to lower the economic losses, zoonotic infections, and the possibility of a global epidemic.

Presence of Mycobacterium avium Subspecies paratuberculosis Monitored Over Varying Temporal and Spatial Scales in River Catchments: Persistent Routes for Human Exposure

Mycobacterium avium subspecies paratuberculosis (Map) was monitored by quantitative PCR over a range of temporal and spatial scales in the River Tywi catchment. This study shows the persistence of Map over a 10-year period with little change, which correlates with the recognised levels of Johne’s disease in British herds over that period (aim 1). Map was quantified within the river at up to 10⁸ cell equivalents L⁻¹ and was shown to be consistently present when monitored over finer timescales (aim 4). Small wastewater treatment plants where the ingress of human-associated Map might be expected had no significant effect (aim 2). Map was found for the first time to be located in natural river foams providing another route for spread via aerosols (aim 5). This study provides evidence for the environmental continuum of Map from the grazing infected animal via rain driven runoff through field drains and streams into main rivers; with detection at a high frequency throughout the year. Should Map need to be monitored in the future, we recommend that weekly or monthly sampling from a fixed location on a river will capture an adequate representation of the flow dynamics of Map in a catchment (aim 3). The human exposure to Map during this process and its impact on human health remains unquantified.

Chronic regional intestinal inflammatory disease: A trans-species slow infection?

Crohn's disease and ulcerative colitis in humans and paratuberculosis in domestic and wild ruminants can be defined as chronic regional intestinal inflammatory diseases (CRIID). This review is a literature overview on these diseases in humans, non-human primates, dogs, cats, rabbits, equids and ruminants with a focus on pathological and microbiological features aimed identifying common characteristics that could lead to a unified pathological classification for a better understanding of their mechanisms and causes. The result is a framework of inflammatory forms throughout the different species indicative of common mechanisms of the slow infection type characterized by a time course varying from weeks to months or even years, and where the inflammatory component would be more prominent in the intestinal interphase between host and environment and be morphologically characterized by an infiltrate ranging from lymphoplasmacytic to histiocytic. This should provide new insights for causation demonstration and therapeutic approaches in human IBD.

High levels of antibodies against PtpA and PknG secreted by Mycobacterium avium ssp. paratuberculosis are present in neuromyelitis optica spectrum disorder and multiple sclerosis patients

Mycobacterium avium ssp. paratuberculosis (Map) is the etiological agent of Paratuberculosis in ruminants. Protein tyrosine phosphatase A (PtpA) and protein kinase G (PknG) are secreted proteins necessary for the survival of the pathogen within macrophages. In this study we analyzed if Map was able to grow within astrocytes and investigated on the presence of antibodies against PtpA and PknG proteins in MS and NMOSD patients by ELISA. Map was unable to proliferate in astrocytes after of 72 h post-infection, but we observed a high level of antibodies against both virulence factors, suggesting that these patients have been exposed/infected with Map.

Pathogenesis, Molecular Genetics, and Genomics of Mycobacterium avium subsp. paratuberculosis, the Etiologic Agent of Johne's Disease

Mycobacterium avium subsp. paratuberculosis (MAP) is the etiologic agent of Johne's disease in ruminants causing chronic diarrhea, malnutrition, and muscular wasting. Neonates and young animals are infected primarily by the fecal-oral route. MAP attaches to, translocates via the intestinal mucosa, and is phagocytosed by macrophages. The ensuing host cellular immune response leads to granulomatous enteritis characterized by a thick and corrugated intestinal wall. We review various tissue culture systems, ileal loops, and mice, goats, and cattle used to study MAP pathogenesis. MAP can be detected in clinical samples by microscopy, culturing, PCR, and an enzyme-linked immunosorbent assay. There are commercial vaccines that reduce clinical disease and shedding, unfortunately, their efficacies are limited and may not engender long-term protective immunity. Moreover, the potential linkage with Crohn's disease and other human diseases makes MAP a concern as a zoonotic pathogen. Potential therapies with anti-mycobacterial agents are also discussed. The completion of the MAP K-10 genome sequence has greatly improved our understanding of MAP pathogenesis. The analysis of this sequence has identified a wide range of gene functions involved in virulence, lipid metabolism, transcriptional regulation, and main metabolic pathways. We also review the transposons utilized to generate random transposon mutant libraries and the recent advances in the post-genomic era. This includes the generation and characterization of allelic exchange mutants, transcriptomic analysis, transposon mutant banks analysis, new efforts to generate comprehensive mutant libraries, and the application of transposon site hybridization mutagenesis and transposon sequencing for global analysis of the MAP genome. Further analysis of candidate vaccine strains development is also provided with critical discussions on their benefits and shortcomings, and strategies to develop a highly efficacious live-attenuated vaccine capable of differentiating infected from vaccinated animals.

Use of an Individual-based Model to Control Transmission Pathways of Mycobacterium avium Subsp. paratuberculosis Infection in Cattle Herds

Johne’s disease (JD) is a chronic enteric disease in cattle caused by Mycobacterium avian subsp. paratuberculosis (MAP). Eradicating JD is a difficult task due to the long incubation period of MAP, inefficient diagnostic tests, and delayed clinical signs. Effective control strategies can help farmers to reduce prevalence, but those most acceptable to farmers combine specific information about lactation performance and testing results, which existing models do not provide. This paper presents an individual-based model of MAP infection dynamics and assesses the relative performance of the applied alternative control strategies. The base dairy herd model included the daily life events of a dairy cow and reflects several current dairy management processes. We then integrated MAP infection dynamics into the model. The model adopted four different test-based control strategies based on risk-based culling decisions and three hygiene scenarios. The model tracked the source of each infection and quantified the efficacy of each control strategy in reducing the risks of different transmission routes. The results suggest that risk-based culling can reduce prevalence compared with no control, but cannot eliminate the infection. Overall, this work provides not only a valuable tool to investigate MAP transmission dynamics but also offers adaptability to model similar infectious diseases.

Nod2: The intestinal gate keeper

Nucleotide-binding oligomerization domain 2 (NOD2) is an intracellular pattern recognition receptor that senses bacterial peptidoglycan (PGN)-conserved motifs in cytosol and stimulates host immune response. The association of NOD2 mutations with a number of inflammatory pathologies, including Crohn disease (CD), Graft-versus-host disease (GVHD), and Blau syndrome, highlights its pivotal role in host–pathogen interactions and inflammatory response. Stimulation of NOD2 by its ligand (muramyl dipeptide) activates pro-inflammatory pathways such as nuclear factor-κB (NF-κB), mitogen-activated protein kinases (MAPKs), and Caspase-1. A loss of NOD2 function may result in a failure in the control of microbial infection, thereby initiating systemic responses and aberrant inflammation. Because the ligand of Nod2 is conserved in both gram-positive and gram-negative bacteria, NOD2 detects a wide variety of microorganisms. Furthermore, current literature evidences that NOD2 is also able to control viruses’ and parasites’ infections. In this review, we present and discuss recent developments about the role of NOD2 in shaping the gut commensal microbiota and pathogens, including bacteria, viruses, and parasites, and the mechanisms by which Nod2 mutations participate in disease occurrence.

Bacterial Nucleoid Occlusion: Multiple Mechanisms for Preventing Chromosome Bisection During Cell Division

In most bacteria cell division is driven by the prokaryotic tubulin homolog, FtsZ, which forms the cytokinetic Z ring. Cell survival demands both the spatial and temporal accuracy of this process to ensure that equal progeny are produced with intact genomes. While mechanisms preventing septum formation at the cell poles have been known for decades, the means by which the bacterial nucleoid is spared from bisection during cell division, called nucleoid exclusion (NO), have only recently been deduced. The NO theory was originally posited decades ago based on the key observation that the cell division machinery appeared to be inhibited from forming near the bacterial nucleoid. However, what might drive the NO process was unclear. Within the last 10 years specific proteins have been identified as important mediators of NO. Arguably the best studied NO mechanisms are those employed by the Escherichia coli SlmA and Bacillus subtilis Noc proteins. Both proteins bind specific DNA sequences within selected chromosomal regions to act as timing devices. However, Noc and SlmA contain completely different structural folds and utilize distinct NO mechanisms. Recent studies have identified additional processes and factors that participate in preventing nucleoid septation during cell division. These combined data show multiple levels of redundancy as well as a striking diversity of mechanisms have evolved to protect cells against catastrophic bisection of the nucleoid. Here we discuss these recent findings with particular emphasis on what is known about the molecular underpinnings of specific NO machinery and processes.

Analysis of Mycobacterium avium subsp. paratuberculosis mutant libraries reveals loci-dependent transposition biases and strategies for novel mutant discovery

Mycobacterium avium subsp. paratuberculosis (MAP), the aetiological agent of Johne's disease, is one of the most important bacterial pathogens in ruminants. A thorough understanding of MAP pathogenesis is needed to develop new vaccines and diagnostic tests. The generation of comprehensive random transposon mutant libraries is a fundamental genetic technology to determine the role of genes in physiology and pathogenesis. In this study, whole MAP genome analysis compared the insertion sites for the mycobacterial transposon Tn5367 derived from the Mycobacterium smegmatis insertion sequence IS1096 and the mariner transposon MycoMarT7 carrying the Himar1 transposase. We determined that only MycoMarT7 provides a random representation of insertions in 99 % of all MAP genes. Analysis of the MAP K-10 genome indicated that 710 of all ORFs do not possess IS1096 recognition sites, while only 37 do not have the recognition site for MycoMarT7. Thus, a significant number of MAP genes remain underrepresented in insertion libraries from IS1096-derived transposons. Analysis of MycoMarT7 and Tn5367 mutants showed that Tn5367 has a predilection to insert within intergenic regions, suggesting that MycoMarT7 is the more adequate for generating a comprehensive library. However, we uncovered the novel finding that both transposons have loci-dependent biases, with Tn5367 being the most skewed. These loci-dependent transposition biases led to an underestimation of the number of independent mutants required to generate a comprehensive mutant library, leading to an overestimation of essential genes. Herein, we also demonstrated a useful platform for gene discovery and analysis by isolating three novel mutants for each transposon.

Invited review: The economic impact and control of paratuberculosis in cattle

Paratuberculosis (also called Johne's disease) is a chronic disease caused by Mycobacterium avium ssp. paratuberculosis (MAP) that affects ruminants and other animals. The epidemiology of paratuberculosis is complex and the clinical manifestations and economic impact of the disease in cattle can be variable depending on factors such as herd management, age, infection dose, and disease prevalence, among others. Additionally, considerable challenges are faced in the control of paratuberculosis in cattle, such as the lack of accurate and reliable diagnostic tests. Nevertheless, efforts are directed toward the control of this disease because it can cause substantial economic losses to the cattle industry mainly due to increased premature culling, replacement costs, decreased milk yield, reduced feed conversion efficiency, fertility problems, reduced slaughter values, and increased susceptibility to other diseases or conditions. The variability and uncertainty surrounding the estimations of paratuberculosis prevalence and impact influence the design, implementation, and efficiency of control programs in diverse areas of the world. This review covers important aspects of the economic impact and control of paratuberculosis, including challenges related to disease detection, estimations of the prevalence and economic effects of the disease, and the implementation of control programs. The control of paratuberculosis can improve animal health and welfare, increase productivity, reduce potential market problems, and increase overall business profitability. The benefits that can derive from the control of paratuberculosis need to be communicated to all industry stakeholders to promote the implementation of control programs. Moreover, if the suspected link between Johne's disease in ruminants and Crohn's disease in humans was established, significant economic losses could be expected, particularly for the dairy industry, making the control of this disease a priority across dairy industries internationally.

Variations in IL-23 and IL-25 receptor gene structure, sequence and expression associated with the two disease forms of sheep paratuberculosis

The immunopathology of paucibacillary and multibacillary sheep paratuberculosis is characterized by inflammatory T cell and macrophage responses respectively. IL-23 and IL-25 are key to the development of these responses by interaction with their complex receptors, IL-23R/IL-12RB1 and IL-17RA/IL-17RB. In humans, variations in structure, sequence and/or expression of these genes have been implicated in the different pathological forms of tuberculosis and leprosy, and in gastrointestinal inflammatory disorders such as Crohn’s disease. Sequencing has identified multiple transcript variants of sheep IL23R, IL12RB1 and IL17RB and a single IL17RA transcript. RT-qPCR assays were developed for all the identified variants and used to compare expression in the ileo-caecal lymph node of sheep with paucibacillary or multibacillary paratuberculosis and uninfected animals. With IL-23 receptor, only the IL12RB1v3 variant, which lacks the receptor activation motif was differentially expressed and was significantly increased in multibacillary disease; this may contribute to high Th2 responses. Of the IL17RB variants only full length IL17RB was differentially expressed and was significantly increased in multibacillary pathology; which may also contribute to Th2 polarization. IL17RA expression was significantly increased in paucibacillary disease. The contrast between the IL17RA and IL17RB results may indicate that, in addition to Th1 cells, Th17 T cells are also involved in paucibacillary pathology.

Potential application of emerging diagnostic techniques to the diagnosis of bovine Johne's disease (paratuberculosis)

Mycobacterium avium subspecies paratuberculosis (MAP) causes Johne's disease (paratuberculosis), a chronic wasting disease in cattle with important welfare, economic and potential public health implications. Current tests are unable to recognise all stages of the disease, which makes it difficult to diagnose and control. This review explores emerging diagnostic techniques that could complement and enhance the diagnosis of MAP infection, including bacteriophage analysis, new MAP-specific antigens, host protein expression in response to infection, transcriptomic studies, analysis of microRNAs and investigation of the gastrointestinal microbiome. It emphasises the inherent challenges of diagnosing bovine Johne's disease and investigates novel areas which may have the potential both to advance our understanding of the immunopathology of MAP infection and to augment current diagnostic tests.

Inflammatory bowel disease

Scandinavian researchers have contributed to the present understanding of inflammatory bowel disease (IBD). Important epidemiological data and family risk factors have been reported from all the Nordic countries, original twin studies mainly from Denmark and Sweden, and relationships to cancer and surgery mostly from Sweden. In collaboration with the industry, development of medical compounds was for a long time in the front line of international research, and the Scandinavian countries participated in the clinical breakthrough of biologic treatment. At present, many Nordic centers are working in the forefront of IBD research. An increasing number of young investigators have entered the scene along with the extended distribution of University clinics and research laboratories in these countries. This presentation of IBD gives a brief overview in the fields of clinical epidemiology and molecular biology. Many areas are covered by International collaborations with partners from Nordic centers. IBD was a topic focused by the founders of Scandinavian Journal of Gastroenterology. After 50 years one may state that the journal's history reflects important pieces of scientific knowledge within these diseases. The early scope of Johannes Myren for IBD was shown through his work in the original World Association of Gastroenterology (OMG), and after 50 years we can clearly support the view that global perspectives in IBD are increasingly important.

Prevalence of Mycobacterium avium subsp. paratuberculosis and Escherichia coli in blood samples from patients with inflammatory bowel disease

Mycobacterium avium subsp. paratuberculosis (MAP) and adherent-invasive Escherichia coli (AIEC) have been implicated as primary triggers in Crohn's disease (CD). In this study, we evaluated the prevalence of MAP and E. coli (EC) DNA in peripheral blood from 202 inflammatory bowel disease (IBD) patients at various disease periods and compared against 24 cirrhotic patients with ascites (CIR) (non-IBD controls) and 29 healthy controls (HC). MAP DNA was detected by IS900-specific nested PCR, EC DNA by malB-specific nested PCR and AIEC identity, in selected samples, by sequencing of fimH gene. CD patients with active disease showed the highest MAP DNA prevalence among IBD patients (68 %). Infliximab treatment resulted in decreased MAP detection. CIR patients had high individual and coinfection rates (75 % MAP, 88 % EC and 67 % MAP and EC), whilst HC controls had lower MAP prevalence (38 %) and EC was undetectable in this control group. EC DNA prevalence in IBD patients was highly associated with CD, and 80 % of EC from the selected samples of CD patients analyzed carried the fimH30 allele, with a mutation strongly associated with AIEC. Our results show that coinfection with MAP and AIEC is common and persistent in CD, although the high MAP and EC detection in CIR patients suggested that colonization is, at least, partially dependent on increased gut permeability. Nevertheless, facilitative mechanisms between a susceptible host and these two potential human pathogens may allow their implication in CD pathogenesis.

Epidemiology and risk factors for IBD

IBD, comprising Crohn's disease and ulcerative colitis, is a chronic immunologically mediated disease at the intersection of complex interactions between genetics, environment and gut microbiota. Established high-prevalence populations of IBD in North America and Europe experienced the steepest increase in incidence towards the second half of the twentieth century. Furthermore, populations previously considered 'low risk' (such as in Japan and India) are witnessing an increase in incidence. Potentially relevant environmental influences span the spectrum of life from mode of childbirth and early-life exposures (including breastfeeding and antibiotic exposure in infancy) to exposures later on in adulthood (including smoking, major life stressors, diet and lifestyle). Data support an association between smoking and Crohn's disease whereas smoking cessation, but not current smoking, is associated with an increased risk of ulcerative colitis. Dietary fibre (particularly fruits and vegetables), saturated fats, depression and impaired sleep, and low vitamin D levels have all been associated with incident IBD. Interventional studies assessing the effects of modifying these risk factors on natural history and patient outcomes are an important unmet need. In this Review, the changing epidemiology of IBD, mechanisms behind various environmental associations and interventional studies to modify risk factors and disease course are discussed.

What Role Does Mycobacterium avium subsp. paratuberculosis Play in Crohn's Disease?

Crohn's disease (CD) is a chronic, debilitating inflammatory bowel disease with no etiological agent yet identified. Studies have demonstrated that the bacterium Mycobacterium avium subsp. paratuberculosis (MAP) is present in a high percentage of CD patients. Although MAP has been isolated from human specimens, current techniques fail to show the presence of MAP in 100 % of tissues or biopsies obtained from CD patient lesions, and thus MAP cannot meet Koch's postulate as the etiological agent of CD. In this report, the effect of genetic and immune factors as well as the presence of MAP as a potential environmental factor is analyzed.

Increased viability but decreased culturability of Mycobacterium avium subsp. paratuberculosis in macrophages from inflammatory bowel disease patients under Infliximab treatment

Mycobacterium avium subsp. paratuberculosis (MAP) has long been implicated as a triggering agent in Crohn's disease (CD). In this study, we investigated the growth/persistence of both M. avium subsp. hominissuis (MAH) and MAP, in macrophages from healthy controls (HC), CD and ulcerative colitis patients. For viability assessment, both CFU counts and a pre16SrRNA RNA/DNA ratio assay (for MAP) were used. Phagolysosome fusion was evaluated by immunofluorescence, through analysis of LAMP-1 colocalization with MAP. IBD macrophages were more permissive to MAP survival than HC macrophages (a finding not evident with MAH), but did not support MAP active growth. The lower MAP CFU counts in macrophage cultures associated with Infliximab treatment were not due to increased killing, but possibly to elevation in the proportion of intracellular dormant non-culturable MAP forms, as MAP showed higher viability in those macrophages. Increased MAP viability was not related to lack of phagolysosome maturation. The predominant induction of MAP dormant forms by Infliximab treatment may explain the lack of MAP reactivation during anti-TNF therapy of CD but does not exclude the possibility of MAP recrudescence after termination of therapy.

Mycobacterium paratuberculosis as a cause of Crohn's disease

Crohn's disease is a chronic inflammatory bowel disease of unknown cause, affecting approximately 1.4 million North American people. Due to the similarities between Crohn's disease and Johne's disease, a chronic enteritis in ruminant animals caused by Mycobacterium avium paratuberculosis (MAP) infection, MAP has long been considered to be a potential cause of Crohn's disease. MAP is an obligate intracellular pathogen that cannot replicate outside of animal hosts. MAP is widespread in dairy cattle and because of environmental contamination and resistance to pasteurization and chlorination, humans are frequently exposed through contamination of food and water. MAP can be cultured from the peripheral mononuclear cells from 50-100% of patients with Crohn's disease, and less frequently from healthy individuals. Association does not prove causation. We discuss the current data regarding MAP as a potential cause of Crohn's disease and outline what data will be required to firmly prove or disprove the hypothesis.

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.

Experimental colitis is exacerbated by concomitant infection with Mycobacterium avium ssp. paratuberculosis

BACKGROUND

Crohn's disease (CD) is a chronic inflammatory disorder of the human gastrointestinal tract. Although genetic, immunological, environmental, and bacterial factors have been implicated, the pathogenesis is incompletely understood. The histopathological appearance of CD strikingly resembles Johne's disease, a ruminant inflammatory bowel disease, caused by Mycobacterium avium ssp. paratuberculosis (MAP), but a causative role of MAP in CD has not been established. In this work, we hypothesized that MAP might exacerbate an already existing intestinal disease.

METHODS

We combined dextran sulfate sodium (DSS)-induced colitis with MAP infection in mice and monitored the immune response and bacterial count in different organs.

RESULTS

An increased size of liver and spleen was observed in DSS-treated and MAP-infected animals (DSS + MAP) as compared with DSS-treated uninfected (DSS + PBS) mice. Similarly, DSS treatment increased the number and size of MAP-induced liver granulomas and enhanced the MAP counts in enteric tissue. MAP infection in turn delayed the mucosal healing of DSS-induced tissue damage. Finally, high numbers of MAP were found in mesenteric fat tissue causing large granuloma and necrotic regions.

CONCLUSIONS

Taken together, we present an in vivo model to study the role of MAP infection in CD. Our results confirm the hypothesis that MAP is able to exacerbate existing intestinal inflammation.

Enhanced expression of codon optimized Mycobacterium avium subsp. paratuberculosis antigens in Lactobacillus salivarius

It is well documented that open reading frames containing high GC content show poor expression in A+T rich hosts. Specifically, G+C-rich codon usage is a limiting factor in heterologous expression of Mycobacterium avium subsp. paratuberculosis (MAP) proteins using Lactobacillus salivarius. However, re-engineering opening reading frames through synonymous substitutions can offset codon bias and greatly enhance MAP protein production in this host. In this report, we demonstrate that codon-usage manipulation of MAP2121c can enhance the heterologous expression of the major membrane protein (MMP), analogous to the form in which it is produced natively by MAP bacilli. When heterologously over-expressed, antigenic determinants were preserved in synthetic MMP proteins as shown by monoclonal antibody mediated ELISA. Moreover, MMP is a membrane protein in MAP, which is also targeted to the cellular surface of recombinant L. salivarius at levels comparable to MAP. Additionally, we previously engineered MAP3733c (encoding MptD) and show herein that MptD displays the tendency to associate with the cytoplasmic membrane boundary under confocal microscopy and the intracellularly accumulated protein selectively adheres to the MptD-specific bacteriophage fMptD. This work demonstrates there is potential for L. salivarius as a viable antigen delivery vehicle for MAP, which may provide an effective mucosal vaccine against Johne's disease.

Facts, myths and hypotheses on the zoonotic nature of Mycobacterium avium subspecies paratuberculosis

Mycobacterium avium subspecies paratuberculosis (MAP) is the causative agent of paratuberculosis (Johne's disease [JD]), a chronic granulomatous enteritis in ruminants. JD is one of the most widespread bacterial diseases of domestic animals with significant economic impact. The histopathological picture of JD resembles that of Crohn's disease (CD), a human chronic inflammatory bowel disease of still unresolved aetiology. An aetiological relevance of MAP for CD has been proposed. This and the ambiguity of other published epidemiological findings raise the question whether MAP represents a zoonotic agent. In this review, we will discuss evidence that MAP has zoonotic capacity.

Mycobacterium avium Subspecies paratuberculosis: Human Exposure through Environmental and Domestic Aerosols

Mycobacterium avium subspecies paratuberculosis (Map) causes Johne's disease in animals and is significantly associated with Crohn's disease (CD) in humans. Our previous studies have shown Map to be present in U.K. rivers due to land deposition from chronic livestock infection and runoff driven by rainfall. The epidemiology of CD in Cardiff showed a significant association with the River Taff, in which Map can be detected on a regular basis. We have previously hypothesized that aerosols from the river might influence the epidemiology of CD. In this preliminary study, we detected Map by quantitative PCR in one of five aerosol samples collected above the River Taff. In addition, we examined domestic showers from different regions in the U.K. and detected Map in three out of 30 independent samples. In detecting Map in river aerosols and those from domestic showers, this is the first study to provide evidence that aerosols are an exposure route for Map to humans and may play a role in the epidemiology of CD.

Disruption of Mycobacterium avium subsp. paratuberculosis-specific genes impairs in vivo fitness

Background

Mycobacterium avium subsp. paratuberculosis (MAP) is an obligate intracellular pathogen that infects many ruminant species. The acquisition of foreign genes via horizontal gene transfer has been postulated to contribute to its pathogenesis, as these genetic elements are absent from its putative ancestor, M. avium subsp. hominissuis (MAH), an environmental organism with lesser pathogenicity. In this study, high-throughput sequencing of MAP transposon libraries were analyzed to qualitatively and quantitatively determine the contribution of individual genes to bacterial survival during infection.

Results

Out of 52384 TA dinucleotides present in the MAP K-10 genome, 12607 had a MycoMarT7 transposon in the input pool, interrupting 2443 of the 4350 genes in the MAP genome (56%). Of 96 genes situated in MAP-specific genomic islands, 82 were disrupted in the input pool, indicating that MAP-specific genomic regions are dispensable for in vitro growth (odds ratio = 0.21). Following 5 independent in vivo infections with this pool of mutants, the correlation between output pools was high for 4 of 5 (R = 0.49 to 0.61) enabling us to define genes whose disruption reproducibly reduced bacterial fitness in vivo. At three different thresholds for reduced fitness in vivo, MAP-specific genes were over-represented in the list of predicted essential genes. We also identified additional genes that were severely depleted after infection, and several of them have orthologues that are essential genes in M. tuberculosis.

Conclusions

This work indicates that the genetic elements required for the in vivo survival of MAP represent a combination of conserved mycobacterial virulence genes and MAP-specific genes acquired via horizontal gene transfer. In addition, the in vitro and in vivo essential genes identified in this study may be further characterized to offer a better understanding of MAP pathogenesis, and potentially contribute to the discovery of novel therapeutic and vaccine targets.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2164-15-415) contains supplementary material, which is available to authorized users.

Virulence and immunity orchestrated by the global gene regulator sigL in Mycobacterium avium subsp. paratuberculosis

Mycobacterium avium subsp. paratuberculosis causes Johne's disease in ruminants, a chronic enteric disease responsible for severe economic losses in the dairy industry. Global gene regulators, including sigma factors are important in regulating mycobacterial virulence. However, the biological significance of such regulators in M. avium subsp. paratuberculosis rremains elusive. To better decipher the role of sigma factors in M. avium subsp. paratuberculosis pathogenesis, we targeted a key sigma factor gene, sigL, activated in mycobacterium-infected macrophages. We interrogated an M. avium subsp. paratuberculosis ΔsigL mutant against a selected list of stressors that mimic the host microenvironments. Our data showed that sigL was important in maintaining bacterial survival under such stress conditions. Survival levels further reflected the inability of the ΔsigL mutant to persist inside the macrophage microenvironments. Additionally, mouse infection studies suggested a substantial role for sigL in M. avium subsp. paratuberculosis virulence, as indicated by the significant attenuation of the ΔsigL-deficient mutant compared to the parental strain. More importantly, when the sigL mutant was tested for its vaccine potential, protective immunity was generated in a vaccine/challenge model of murine paratuberculosis. Overall, our study highlights critical role of sigL in the pathogenesis and immunity of M. avium subsp. paratuberculosis infection, a potential role that could be shared by similar proteins in other intracellular pathogens.

Pathogenesis of adherent-invasive Escherichia coli

The etiology of Crohn's disease (CD) is complex and involves both host susceptibility factors (i.e., the presence of particular genetic alleles) and environmental factors, including bacteria. In this regard, adherent-invasive Escherichia coli (AIEC), have recently emerged as an exciting potential etiological agent of CD. AIEC are distinguished from commensal strains of E. coli through their ability to adhere to and invade epithelial cells and replicate in macrophages. Recent molecular analyses have identified genes required for both invasion of epithelial cells and replication in the macrophage. However, these genetic studies, in combination with recent genome sequencing projects, have revealed that the pathogenesis of this group of bacteria cannot be explained by the presence of AIEC-specific genes. In this article, we review the role of AIEC as a pathobiont in the pathology of CD. We also describe the emerging link between AIEC and autophagy, and we propose a model for AIEC pathogenesis.

Complete Genome Sequence of Mycobacterium avium subsp. paratuberculosis, Isolated from Human Breast Milk

Mycobacterium avium subsp. paratuberculosis is the etiologic agent of Johne’s disease in ruminants and has also been associated with human Crohn’s disease. We report the complete genome sequence of M. avium subsp. paratuberculosis, isolated from the breast milk of a Crohn’s disease patient. This sequence has high identity with characterized strains recovered from cattle.

Effect of inflammatory bowel disease therapies on immunogenicity of Mycobacterium paratuberculosis proteins

BACKGROUND AND AIMS

The link between Mycobacterium avium subsp. paratuberculosis (MAP) and Crohn's disease (CD) is supported by several studies that have reported the detection and isolation of MAP from human tissues, but causation has not yet been proven. Preliminary studies have shown higher levels of antibodies in sera from CD patients against secreted protein from MAP within human macrophages when compared to healthy controls. The immunogenicity of this protein in CD patients under different treatment regimes was evaluated.

MATERIALS AND METHODS

Sera of 110 CD patients, 82 ulcerative colitis (UC), and 150 healthy controls were collected and the presence of antibodies against the mycobacterial protein tyrosine phosphatase PtpA was assayed using ELISA.

RESULTS

A statistically significant difference in the level of antibodies against PtpA was measured in untreated CD patients versus healthy controls, but variation in the antibody levels was observed when patients were subjected to different treatment regimens. UC patients showed no differences in the levels of antibodies against PtpA when compared to healthy controls.

CONCLUSIONS

CD patients under different drug treatments show a clear difference in the levels of antibodies against a protein secreted by MAP, suggesting that if MAP is active in the progress of CD, some treatments can be detrimental to its survival.

Competition for antigen between Th1 and Th2 responses determines the timing of the immune response switch during Mycobaterium avium subspecies paratuberulosis infection in ruminants

Johne's disease (JD), a persistent and slow progressing infection of ruminants such as cows and sheep, is caused by slow replicating bacilli Mycobacterium avium subspecies paratuberculosis (MAP) infecting macrophages in the gut. Infected animals initially mount a cell-mediated CD4 T cell response against MAP which is characterized by the production of interferon (Th1 response). Over time, Th1 response diminishes in most animals and antibody response to MAP antigens becomes dominant (Th2 response). The switch from Th1 to Th2 response occurs concomitantly with disease progression and shedding of the bacteria in feces. Mechanisms controlling this Th1/Th2 switch remain poorly understood. Because Th1 and Th2 responses are known to cross-inhibit each other, it is unclear why initially strong Th1 response is lost over time. Using a novel mathematical model of the immune response to MAP infection we show that the ability of extracellular bacteria to persist outside of macrophages naturally leads to switch of the cellular response to antibody production. Several additional mechanisms may also contribute to the timing of the Th1/Th2 switch including the rate of proliferation of Th1/Th2 responses at the site of infection, efficiency at which immune responses cross-inhibit each other, and the rate at which Th1 response becomes exhausted over time. Our basic model reasonably well explains four different kinetic patterns of the Th1/Th2 responses in MAP-infected sheep by variability in the initial bacterial dose and the efficiency of the MAP-specific T cell responses. Taken together, our novel mathematical model identifies factors of bacterial and host origin that drive kinetics of the immune response to MAP and provides the basis for testing the impact of vaccination or early treatment on the duration of infection.

Mycobacterium avium subsp. paratuberculosis (MAP) is the causative agent of Johne's disease, a chronic enteric disease of ruminants such as sheep and cows. Due to early culling and reduction in milk production of affected animals, MAP inflicts high economic cost to diary farms. MAP infection has a long incubation period of several years, and during the asymptomatic stage a strong cellular (T helper 1) immune response is thought to control MAP replication. Over time, Th1 response is lost and ineffective antibody response driven by Th2 cells becomes predominant. We develop the first mathematical model of helper T cell response to MAP infection to understand impact of various mechanisms on the dynamics of the switch from Th1 to Th2 response. Our results suggest that in contrast to the generally held belief, Th1/Th2 switch may be driven by the accumulation of long-lived extracellular bacteria, and therefore, may be the consequence of the disease progression of MAP-infected animals and not its cause. Our model highlights limitations of our current understanding of regulation of helper T cell responses during MAP infection and identifies areas for future experimental research.

Genetic diversity and phylogeny of Mycobacterium avium

Mycobacterium avium, one of the species of the M. avium complex (MAC), includes 4 subspecies, i.e., M. avium subsp. hominissuis (MAH), M. avium subsp. avium (MAA), M. avium subsp. silvaticum (MAS) and M. avium subsp. paratuberculosis (MAP), in turn classified into the S (sheep) and C (cattle) types. These subspecies, although closely related, represent distinct organisms, each endowed with specific pathogenetic and host range characteristics, ranging from environmental opportunistic bacteria that cause infections in swine and immunocompromised patients to pathogens of birds and ruminants. The present review summarizes the basic epidemiological and pathological features of the M. avium subspecies, describes the major genomic events responsible of M. avium subspecies diversity (insertion sequences, sequence variations in specific chromosome loci or genes, deletions, duplications and insertions of large genomic regions) and then reconstructs the phylogenetic relationships among the M. avium subspecies.