Hormonal modulation of phagocytosis and intracellular growth of Mycobacterium avium ss. paratuberculosis In bovine peripheral blood monocytes

Genomic comparison of two strains of Mycobacterium avium subsp. paratuberculosis with contrasting pathogenic phenotype

In a previous study, we evaluated the degree of virulence of Mycobacterium avium subsp. paratuberculosis (Map) strains isolated from cattle in Argentina in a murine model. This assay allowed us to differentiate between high-virulent MapARG1347 and low-virulent MapARG1543 strains. To corroborate whether the differences in virulence could be attributed to genetic differences between the strains, we performed Whole Genome Sequencing and compared the genomes and gene content between them and determined the differences related to the reference strain MapK10. We found 233 SNPs/INDELS in one or both strains relative to Map K10. The two strains share most of the variations, but we found 15 mutations present in only one of the strains. Considering NS-SNP/INDELS that produced a severe effect in the coding sequence, we focus the analysis on four predicted proteins, putatively related to virulence. Survival of MapARG1347 strain in bMDM was higher than MapARG1543 and was more resistant to acidic pH and H₂O₂ stresses than MapK10. The genomic differences between the two strains found in genes MAP1203 (a putative peptidoglycan hydrolase), MAP0403 (a putative serine protease) MAP1003c (a member of the PE-PPE family) and MAP4152 (a putative mycofactocin binding protein) could contribute to explain the contrasting phenotype previously observed in mice models.

Effect of the deletion of lprG and p55 genes in the K10 strain of Mycobacterium avium subspecies paratuberculosis

The lprG-p55 operon of Mycobacterium tuberculosis, M. bovis and M. avium strain D4ER has been identified as a virulence factor involved in the transport of toxic compounds. LprG is a lipoprotein that modulates the host immune response against mycobacteria, whereas P55 is an efflux pump that provides resistance to several drugs. In the present study we search for, and characterize, lprg and p55, putative virulence genes in Mycobacterium avium subsp. paratuberculosis (MAP) to generate a live-attenuated strain of MAP that may be useful in the future as live-attenuated vaccine. For this purpose, we generated and evaluated two mutants of MAP strain K10: one mutant lacking the lprG gene (ΔlprG) and the other lacking both genes lprG and p55 (ΔlprG-p55). None of the mutant strains showed altered susceptibility to first-line and second-line antituberculosis drugs or ethidium bromide, only the double mutant had two-fold increase in clarithromycin susceptibility compared with the wild-type strain. The deletion of lprG and of lprG-p55 reduced the replication of MAP in bovine macrophages; however, only the mutant in lprG-p55 grew faster in liquid media and showed reduced viability in macrophages and in a mouse model. Considering that the deletion of both genes lprG-p55, but not that of lprG alone, showed a reduced replication in vivo, we can speculate that p55 contributes to the survival of MAP in this animal model.

Interaction between stress hormones and phagocytic cells and its effect on the health status of dairy cows: A review

Dairy cows are exposed to various stressors during their production cycle that makes them more susceptible to various diseases. Phagocytes (neutrophils and macrophages) are important soldiers of the innate immune system. Neutrophils are the first responders to an inflammatory response and stress and kill pathogens by generating reactive oxygen species and by the release of various antimicrobial peptides, enzymes, neutrophil extracellular trap formation, etc. Macrophages, the other phagocytes, are also the cleanup crew for the innate immune system that removes debris, pathogens, and dead neutrophils later on after an inflammatory response. The neuroendocrine system along with phagocytes exhibits an immunomodulatory potential during stressful conditions. Neuroendocrine system directly affects the activity of phagocytes by communicating bidirectionally through shared receptors and messenger molecules such as hormones, neurotransmitters, or cytokines. Different immune cells may show variable responses to each hormone. Short time exposure to stress can be beneficial, but repeated or extended exposure to stress may be detrimental to the overall health and well-being of an animal. Although some stresses associated with farming practices in dairy cows are unavoidable, better understanding of the interactions occurring between various stress hormones and phagocytic cells can help to reduce stress, improve productivity and animal welfare. This review highlights the role played by various stress hormones in modulating phagocytic cell performance of dairy cattle under inflammatory conditions.

Characterization of the Mycobacterium avium subsp. paratuberculosis laminin-binding/histone-like protein (Lbp/Hlp) which reacts with sera from patients with Crohn's disease

Mycobacterium avium subsp. paratuberculosis (Map) causes a chronic enteric disease in ruminants, called paratuberculosis or Johne's disease. The current model proposes that after ingestion by the host, Map crosses the intestinal barrier via internalization by the M cells. Experimental observations suggest, however, that Map may also transcytose the intestinal wall via the enterocytes, but the mechanisms involved in this process remain poorly understood. Cytoadherence assays performed on epithelial cells with Map revealed that the addition of laminin to the cell culture increases adhesion. A Map protein was isolated by heparin-Sepharose chromatography and identified as a laminin-binding protein like. The gene encoding this protein named Lbp/Hlp was identified in the Map genome sequence at locus MAP3024 (annotated Hup B). The deduced Map Lbp/Hlp amino acid sequence reveals 80% identity with that reported for other mycobacteria. The C-terminal domain involved in adhesion is mainly composed of arginine and lysine residues modified by methylation. In vitro tests demonstrated that recombinant Lbp/Hlp binds laminin, heparin, collagen and epithelial cells. Interestingly, we found that this adhesin corresponds to the antigen described as the target of pANCA and serum antibodies of patients with Crohn's disease.

Vaccination against paratuberculosis

Johne's disease, or paratuberculosis, is a chronic granulomatous enteritis in ruminants caused by Mycobacterium avium subsp. paratuberculosis (MAP) affecting principally cattle, sheep and goats. Primarily, there are two clinical signs: cachexia and chronic diarrhea (less common in goats and sheep). This disease results in considerable economic losses in livestock industry, particularly the dairy sector. The route of transmission is mostly by the fecal-oral route, but hygienic measures and culling of shedding animals are not sufficient to eradicate this disease. Moreover, diagnostic tools available at this moment are not powerful enough to perform early and specific diagnosis. Existing vaccines, based on whole killed or live-attenuated bacteria, can delay the onset of clinical symptoms but do not protect against infection. Moreover, vaccinated animals develop antibodies that interfere with existing serodiagnostic tests for paratuberculosis and they become reactive in the tuberculin skin test, used for the control of bovine tuberculosis. This review summarizes the current knowledge of the immune responses induced by MAP infection, with focus on cattle studies. It provides an overview of the existing MAP vaccines and comments on the development of second-generation subunit vaccines based on new technologies.

Comparison of the proteosomes and antigenicities of secreted and cellular proteins produced by Mycobacterium paratuberculosis

The protein expression profiles and antigenicities of both culture filtrates (CF) and cellular extracts (CE) of Mycobacterium paratuberculosis were compared by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), one-dimensional electrophoresis (1-DE) and 2-DE immunoblotting, and enzyme-linked immunosorbent assay (ELISA). The CF proteins were harvested from supernatants of stationary-phase liquid cultures and concentrated by size exclusion filtration. The CE proteins were extracted by mechanical disruption of cells using glass beads and a high-speed agitator. Analysis of SDS-PAGE gels showed that the majority of CF proteins had low molecular masses (<50 kDa), whereas CE protein mass ranged more evenly over a broader range up to 100 kDa. By 2-DE, CF proteins had a narrow array of pI values, with most being between pH 4.0 and 5.5; CE proteins spanned pI values from pH 4.0 to 7.0. The antigenicities of CF and CE proteins were first determined by 1-DE and 2-DE immunoblotting with serum from a cow naturally infected with M. paratuberculosis. The serum reacted strongly to more proteins in the CF than the CE. Sera from 444 infected and 412 uninfected cattle were tested by ELISA with CF and CE as solid-phase antigens. Receiver-operator characteristic curve analysis of the ELISA results showed a significantly greater area under the curve for CF compared to CE (P<0.05). A high degree of variability in protein binding patterns was shown with 1-DE immunoblot analysis with 31 sera from M. paratuberculosis-infected cattle. Collectively, these results indicate that serologic tests for bovine paratuberculosis may be improved by using proteins derived from CF instead of CE. To maximize the diagnostic sensitivity of serologic tests, multiple proteins will be required. Even so, a CF ELISA may not be able to detect all M. paratuberculosis-infected cattle, in particular those in the early stages of infection that have yet to mount an antibody response.

Members of the 30- to 32-kilodalton mycolyl transferase family (Ag85) from culture filtrate of Mycobacterium avium subsp. paratuberculosis are immunodominant Th1-type antigens recognized early upon infection in mice and cattle

The characterization of protective antigens is essential for the development of an effective, subunit-based vaccine against paratuberculosis. Surface-exposed and secreted antigens, present abundantly in mycobacterial culture filtrate (CF), are among the well-known protective antigens of Mycobacterium tuberculosis and Mycobacterium bovis. Culture filtrate, prepared from Mycobacterium avium subsp. paratuberculosis ATCC 19698 grown as a surface pellicle on synthetic Sauton medium, was strongly and early recognized in experimentally infected B6 bg/bg beige mice and cattle, as indicated by elevated spleen cell gamma interferon (IFN-gamma) secretion and lymphoproliferative responses of peripheral blood mononuclear cells, respectively. Strong proliferative and ex vivo IFN-gamma responses against antigen 85 (Ag85) complex (a major protein component from M. bovis BCG culture filtrate) could be detected in cattle as early as 10 weeks after oral M. avium subsp. paratuberculosis infection. Synthetic peptides from the Ag85A and Ag85B components of this complex were strongly recognized, whereas T-cell responses were weaker against peptides from the Ag85C protein. A promiscuous T-cell epitope spanning amino acids 145 to 162 of Ag85B (identical sequence in M. bovis and M. avium subsp. paratuberculosis) was identified in experimentally infected cattle. Finally, young calves, born from cows with confirmed paratuberculosis, demonstrated proliferative responses to purified, recombinant Ag85A and Ag85B from M. avium subsp. paratuberculosis. These results indicate that the M. avium subsp. paratuberculosis Ag85 homologues are immunodominant T-cell antigens that are recognized early in experimental and natural infection of cattle.

The association of sub-clinical paratuberculosis with the fertility of Greek dairy ewes and goats varies with parity

Our cross-sectional study investigated the association of sub-clinical Mycobacterium avium subsp. paratuberculosis (MAP) infection with failing to produce a live offspring the season of lambing/kidding (November 2001 to January 2002) before testing (in April-May 2002), in four dairy-sheep and/or goat flocks in Greece (369 animals >or=1.5-year-old). From each selected animal 10 ml of blood and 10 g of feces from the rectum were obtained. The harvested sera were tested for antibodies to MAP with a commercial ELISA test kit; the feces were cultured on Herrold's egg-yolk medium supplemented with mycobactin J and antibiotics. An animal was considered sub-clinically infected when found either seropositive or culture positive. The true prevalence of sub-clinically infected animals, adjusted for the sensitivity and specificity of the parallel testing, was 14% (0.1-28%) and 35.9% (9.2-62.7%) in sheep and goats, respectively. The association of fertility of sheep and goats with sub-clinical paratuberculosis was investigated in random-effects logistic models. Sub-clinically infected animals (compared to uninfected) had OR for live offspring the previous year of 5.4 for parity <4, OR=0.05 for parity >6, and a non-significant OR for the middle parity category.

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

Johne's disease is a chronic diarrhea affecting all ruminants. Mycobacterium avium subsp. paratuberculosis (MAP), a slowly growing mycobacteria, is the etiologic agent. There is also a concern that MAP might be a causative agent of some cases of inflammatory bowel disease in humans, especially Crohn's disease. Food products including pasteurized bovine milk have been suggested as potential sources of human infection. This review addresses microbial factors that may contribute to its pathogenicity. In addition, the experimental evidence defining MAP as the cause of Johne's disease and the issues and controversies surrounding its potential pathogenic role in humans are discussed.

Application of the Genome Sequence to Address Concerns ThatMycobacterium aviumSubspeciesParatuberculosisMight Be a Foodborne Pathogen

Johne's disease, a chronic inflammatory disease caused by infection with Mycobacterium avium subspecies paratuberculosis (M. paratuberculosis), is one of the most prevalent and costly diseases of dairy cattle worldwide. This ruminant pathogen is closely related to the ubiquitous animal and human pathogen Mycobacterium avium subspecies avium (M. avium), confounding the development of specific diagnostic reagents. Exacerbating this problem further is that most existing microbiological, serological, and immunologic assays for the identification of infected animals are inadequate. This is primarily because of the slow-growing nature of the organism, genetic intractability and the previous lack of information on M. paratuberculosis subspecies-specific genes or proteins that may enable the development of specific and sensitive assays. New detection tools are critically needed to definitively answer questions surrounding M. paratuberculosis as a foodborne pathogen as well as aid in determining if it is a contributing factor in Crohn's disease. Thus, the recent characterization of the complete genome sequence of M. paratuberculosis in our laboratories has been a major step forward in meeting this need. We have performed studies that utilize genomic information for the identification of specific DNA sequences and protein antigens in M. paratuberculosis. Based on a preliminary in silico comparison of the M. paratuberculosis genome sequence with that of M. avium, we have now identified at least 35 novel coding sequences that are unique to M. paratuberculosis. These in silico data were then confirmed and expanded by PCR amplification analysis with DNA from several species and isolates of mycobacteria. Finally, these unique sequences have been incorporated into an antigen discovery project that may allow reliable detection of the bacterium in antigen-based diagnostic tests. Application of these new tools in addressing foodborne related issues of M. paratuberculosis is discussed.

Use of growth indices from radiometric culture for quantification of sheep strains of Mycobacterium avium subsp. paratuberculosis

A simple method for using growth indices from radiometric BACTEC cultures was evaluated for the enumeration of Australian sheep strains of Mycobacterium avium subsp. paratuberculosis. The numbers of viable organisms in inocula were determined by end-point titration in BACTEC cultures. Growth indices were measured by using a BACTEC 460 machine. There was a linear relationship between the number of days taken for the cumulative growth index to reach 1,000 (dCGI1000) and log(10) inoculum size. The use of dCGI1000 was shown to be as effective as the use of growth index data from the entire growth cycle for the estimation of inoculum size. For particular isolates characterized by end-point titration, the dCGI1000 of a single BACTEC vial provided estimates of viable numbers within narrow prediction limits. Predictive relationships were also established for the enumeration of M. avium subsp. paratuberculosis from field samples by using the dCGI1000 of a single BACTEC vial, with prediction limits of +/-1 to 2 log units. Organisms from feces or contaminated soil grew more slowly than those from cultures or tissues, and separate equations were developed for enumeration from these sources.

Mycobacterium avium subsp. paratuberculosis in Veterinary Medicine

Mycobacterium avium subsp. paratuberculosis (basonym M. paratuberculosis) is the etiologic agent of a severe gastroenteritis in ruminants known as Johne's disease. Economic losses to the cattle industry in the United States are staggering, reaching $1.5 billion annually. A potential pathogenic role in humans in the etiology of Crohn's disease is under investigation. In this article, we review the epidemiology, pathogenesis, diagnostics, and disease control measures of this important veterinary pathogen. We emphasize molecular genetic aspects including the description of markers used for strain identification, diagnostics, and phylogenetic analysis. Recent important advances in the development of animal models and genetic systems to study M. paratuberculosis virulence determinants are also discussed. We conclude with proposals for the applications of these models and recombinant technology to the development of diagnostic, control, and therapeutic measures.

Use of Hoechst 33342 staining to detect apoptotic changes in bovine mononuclear phagocytes infected with Mycobacterium avium subsp. paratuberculosis

Mycobacterium avium subsp. paratuberculosis is an intracellular pathogen of macrophages that causes a chronic enteritis (Johne's disease) in ruminants. The purpose of this study was to determine whether M. avium subsp. paratuberculosis infection causes apoptosis in bovine monocytes. Using Hoechst 33342 staining, we observed increased numbers of apoptotic monocytes within 6 h of infection with M. avium subsp. paratuberculosis, and these numbers increased further at 24 and 48 h. This effect appeared to require viable bacilli, because monocytes infected with heat-killed M. avium subsp. paratuberculosis did not exhibit a significant increase in apoptosis. Preincubation of monocytes with bovine growth hormone prior to infection with M. avium subsp. paratuberculosis did not significantly alter the number of apoptotic cells.