Mycoplasma hyopneumoniae increases intracellular calcium release in porcine ciliated tracheal cells

Cough associated with the detection of Mycoplasma hyopneumoniae DNA in clinical and environmental specimens under controlled conditions

Background

The association of cough with Mycoplasma hyopneumoniae (MHP) DNA detection in specimens was evaluated under conditions in which the MHP status of inoculated and contact-infected pen mates was closely monitored for 59 days post-inoculation (DPI).

Methods

Seven-week-old pigs (n = 39) were allocated to five rooms (with one pen). Rooms contained 9 pigs each, with 1, 3, 6, or 9 MHP-inoculated pigs, respectively, except Room 5 (three sham-inoculated pigs). Cough data (2 × week) and specimens, tracheal swabs (2 × week), oral fluids (daily), drinker wipes (~ 1 × week), and air samples (3 × week) were collected. At 59 DPI, pigs were euthanized, and lung and trachea were evaluated for gross and microscopic lesions. Predictive cough value to MHP DNA detection in drinker and oral fluid samples were estimated using mixed logistic regression.

Results

Following inoculation, MHP DNA was first detected in tracheal swabs from inoculated pigs (DPI 3), then oral fluids (DPI 8), air samples (DPI 10), and drinker wipes (21 DPI). MHP DNA was detected in oral fluids in 17 of 59 (Room 1) to 43 of 59 (Room 3) samples, drinker wipes in 4 of 8 (Rooms 2 and 3) to 5 of 8 (Rooms 1 and 4) samples, and air samples in 5 of 26 (Room 2) or 3 of 26 (Room 4) samples. Logistic regression showed that the frequency of coughing pigs in a pen was associated with the probability of MHP DNA detection in oral fluids (P < 0.01) and nearly associated with drinker wipes (P = 0.08). Pathology data revealed an association between the period when infection was first detected and the severity of gross lung lesions.

Conclusions

Dry, non-productive coughs suggest the presence of MHP, but laboratory testing and MHP DNA detection is required for confirmation. Based on the data from this study, oral fluids and drinker wipes may provide a convenient alternative for MHP DNA detection at the pen level when cough is present. This information may help practitioners in specimen selection for MHP surveillance.

Intracellular changes of a swine tracheal cell line infected with a Mycoplasma hyopneumoniae pathogenic strain

Mycoplasma hyopneumoniae is the etiological agent of enzootic pneumonia (EP), a widespread disease that causes major economic losses to the pig industry. The swine host response plays an important role in the outcome of M. hyopneumoniae infections. The whole proteome of newborn pig trachea (NPTr) epithelial cells infected with the M. hyopneumoniae pathogenic strain 7448 was analyzed using an LC-MS/MS approach to shed light on intracellular processes triggered in response to the pathogen. Overall, 853 swine protein species were identified, 156 of which were differentially represented in response to M. hyopneumoniae 7448 infection in comparison with non-infected control cells. These differentially represented proteins were categorized by function. Fifty-seven of them were assigned to the immune system and/or response to stimulus functional subcategories. Comparative expression analysis of these immune-related proteins in NPTr cells infected with attenuated or non-pathogenic mycoplasmas (M. hyopneumoniae J strain and M. flocculare, respectively) revealed proteins whose abundance was altered only in response to the pathogenic M. hyopneumoniae 7448 strain. Among these proteins, calcium homeostasis and endoplasmic reticulum stress-related biomarkers were detected, providing evidence of molecular mechanisms that might lead to swine cell apoptosis.

The effects of phospholipase C on oestradiol and progesterone secretion in porcine granulosa cells cultured in vitro

Granulosa cells play important roles in the regulation of ovarian functions. Phospholipase C is crucial in several signalling pathways and could participate in the molecular mechanisms of cell proliferation, differentiation and ageing. The objective of this study was to identify the effects of phospholipase C on the steroidogenesis of oestradiol and progesterone in porcine granulosa cells cultured in vitro. Inhibitor U73122 or activator m-3M3FBS of phospholipase C was added to the in vitro medium of porcine granulosa cells, respectively. The secretion of oestradiol decreased after 2 hr, 8 hr, 12 hr, 24 hr and 48 hr of treatment with 500 nM U73122 (p < .05) and decreased after 2 hr of treatment in the 500 nM m-3M3FBS addition group (p < .05). The secretion of progesterone increased after 4 hr of treatment with 500 nM U73122 (p < .05) and increased after 2 hr and 8 hr of treatment in the 500 nM m-3M3FBS addition group (p < .05). The ratio of oestradiol to progesterone decreased at each time point, except 8 hr after the addition of 500 nM U73122 (p < .05). The ratio of oestradiol to progesterone decreased after 2 hr (p < .05) of treatment with 500 nM m-3M3FBS. In genes that regulate the synthesis of oestradiol or progesterone, the mRNA expression of CYP11A1 was markedly increased (p < .05), and the mRNA expression of other genes did not change significantly in the U73122 treatment group, while the addition of m-3M3FBS did not change those genes significantly despite the contrary trend. Our results demonstrated that phospholipase C can be a potential target to stimulate the secretion of oestradiol and suppress progesterone secretion in porcine granulosa cells cultured in vitro, which shed light on a novel biological function of phospholipase C in porcine granulosa cells.

Mycoplasma hyopneumoniae variability: Current trends and proposed terminology for genomic classification

Mycoplasma hyopneumoniae (M. hyopneumoniae) is the aetiologic agent of enzootic pneumonia in swine, a prevalent chronic respiratory disease worldwide. Mycoplasma hyopneumoniae is a small, self-replicating microorganism that possesses several characteristics allowing for limited biosynthetic abilities, resulting in the fastidious, host-specific growth and unique pathogenic properties of this microorganism. Variation across several isolates of M. hyopneumoniae has been described at antigenic, proteomic, transcriptomic, pathogenic and genomic levels. The microorganism possesses a minimal number of genes that regulate the transcription process. Post-translational modifications (PTM) occur frequently in a wide range of functional proteins. The PTM by which M. hyopneumoniae regulates its surface topography could play key roles in cell adhesion, evasion and/or modulation of the host immune system. The clinical outcome of M. hyopneumoniae infections is determined by different factors, such as housing conditions, management practices, co-infections and also by virulence differences among M. hyopneumoniae isolates. Factors contributing to adherence and colonization as well as the capacity to modulate inflammatory and immune responses might be crucial. Different components of the cell membrane (i.e. proteins, glycoproteins and lipoproteins) may serve as adhesins and/or be toxic for the respiratory tract cells. Mechanisms leading to virulence are complex and more research is needed to identify markers for virulence. The utilization of typing methods and complete or partial-gene sequencing for M. hyopneumoniae characterization has increased in diagnostic laboratories as control and elimination strategies for this microorganism are attempted worldwide. A commonly employed molecular typing method for M. hyopneumoniae is Multiple-Locus Variable number tandem repeat Analysis (MLVA). The agreement of a shared terminology and classification for the various techniques, specifically MLVA, has not been described, which makes inferences across the literature unsuitable. Therefore, molecular trends for M. hyopneumoniae have been outlined and a common terminology and classification based on Variable Number Tandem Repeats (VNTR) types has been proposed.

Differential secretome profiling of a swine tracheal cell line infected with mycoplasmas of the swine respiratory tract

Mycoplasma hyopneumoniae and Mycoplasma flocculare are genetically similar. However, M. hyopneumoniae causes porcine enzootic pneumonia, while M. flocculare is a commensal bacterium. M. hyopneumoniae and M. flocculare do not penetrate their host cells, and secreted proteins are important for bacterium-host interplay. Thus, the secretomes of a swine trachea cell line (NPTr) infected with M. hyopneumoniae 7448 (a pathogenic strain), M. hyopneumoniae J (a non-pathogenic strain) and M. flocculare were compared to shed light in bacterium-host interactions. Medium from the cultures was collected, and secreted proteins were identified by a LC-MS/MS. Overall numbers of identified host and bacterial proteins were, respectively, 488 and 58, for NPTr/M. hyopneumoniae 7448; 371 and 67, for NPTr/M. hyopneumoniae J; and 203 and 81, for NPTr/M. flocculare. The swine cells revealed different secretion profiles in response to the infection with each M. hyopneumoniae strain or with M. flocculare. DAMPs and extracellular proteasome proteins, secreted in response to cell injury and death, were secreted by NPTr cells infected with M. hyopneumoniae 7448. All three mycoplasmas secreted virulence factors during NPTr infection, but M. hyopneumoniae 7448 secreted higher number of adhesins and hypothetical proteins, that may be related with pathogenicity. SIGNIFICANCE: The enzootic pneumonia caused by mycoplasmas of swine respiratory tract has economic loss consequences in pig industry due to antibiotic costs and pig weight loss. However, some genetically similar mycoplasmas are pathogenic while others, such as Mycoplasma hyopneumoniae and Mycoplasma flocculare, are non-pathogenic. Here, we conducted an infection assay between swine cells and pathogenic and non-pathogenic mycoplasmas to decipher secreted proteins during host-pathogen interaction. Mycoplasma response to cell infection was also observed. Our study provided new insights on secretion profile of swine cells in response to the infection with pathogenic and non-pathogenic mycoplasmas. It was possible to observe that pathogenic M. hyopneumoniae 7448 secreted known virulence factors and swine cells responded by inducing cell death. Otherwise, M. hyopneumoniae J and M. flocculare, non-pathogenic mycoplasmas, secreted a different profile of virulence factors in response to swine cells. Consequently, swine cells altered their secretome profile, but the changes were not sufficient to cause disease.

Biofilm formation and determination of minimum biofilm eradication concentration of antibiotics in Mycoplasma hyopneumoniae

The study was aimed to investigate biofilm forming ability of Mycoplasma hyopneumoniae and to determine the minimum biofilm eradication concentrations of antibiotics. Biofilm forming ability of six strains of M. hyopneumoniae was examined using crystal violet staining on coverslips. The results demonstrated an apparent line of biofilm growth in 3 of the strains isolated from swine with confirmed cases of enzootic pneumonia. BacLight bacterial viability assay revealed that the majority of the cells were viable after 336 hr of incubation. Moreover, M. hyopneumoniae persists in the biofilm after being exposed to 10 fold higher concentration of antibiotics than the minimum inhibitory concentrations in planktonic cells. To the best of our knowledge, this is the first report of biofilm formation in M. hyopneumoniae. However, comprehensive studies on the mechanisms of biofilm formation are needed to combat swine enzootic pneumonia caused by resistant M. hyopneumoniae.

Potential use of local and systemic humoral immune response parameters to forecast Mycoplasma hyopneumoniae associated lung lesions

Immunopathological events are key for the development of enzootic pneumonia (EP), which is macroscopically observed as cranioventral pulmonary consolidation (CVPC). This study aimed to investigate the putative association between the humoral immune response against Mycoplasma hyopneumoniae (M. hyopneumoniae) and prevalence and extension of CVPC in 1) experimentally infected pigs, 2) slaughtered pigs and 3) sequentially necropsied pigs in a longitudinal study. CVPC was scored by means of the European Pharmacopoeia recommended methodology. Specific IgG, IgG1 and IgG2 antibodies were assessed in serum. In addition, mucosal IgG and IgA antibodies were analyzed in broncho-alveolar lavage fluid (BALF) from experimentally challenged pigs. The systemic humoral immune response in experimentally infected pigs was delayed in onset whereas humoral respiratory mucosal immune response appeared more rapidly but declined earlier. Although low, BALF IgG antibodies showed the highest correlation with CVPC scores (r = 0.49, p<0.05). In slaughter-aged pigs, both percentage of lungs with CVPC and mean lung lesion score were significantly higher in M. hyopneumoniae seropositive farms compared to the seronegative ones (p<0.001). Similarly, seropositive sequentially necropsied pigs showed more severe CVPC than seronegative ones. Overall, mean serological values might help to forecast prevalence and severity of EP-like lung lesions using a population based approach. Remarkably, the specific systemic humoral immune response was found to be predominated by the IgG2 subclass, suggesting a dominant Th1-mediated immune response to M. hyopneumoniae.

Western Blot Immunoassay as a Confirmatory Test for the Presence of Anti-Mycoplasma Hyopneumoniae Antibodies in Swine Serum

A Western blot immunoassay (WBI) was developed as a confirmatory test for 2 commercial Mycoplasma hyopneumoniae (Mhyo) ELISAs. The WBI detected at least 5 antigen bands (150, 130, 74, 70, and 30 kDa) from Mhyo whole membrane proteins that were not present in the antigens prepared from M. hyorhinis and M. hyosynoviae. Among discrepant sera from vaccinated pigs ( n = 17) and field samples ( n = 91) assayed by WBI: 1) 2 of the ELISA-positive samples reacted with all 5 antigens bands; 2) all blocking ELISA-positive samples ( n = 53) bound 150-, 130-, 74-, and 70-kD antigen bands; and 3) all indirect ELISA-positive samples ( n = 55) bound 150-, 130-, and 30-kD antigens. We conclude that the WBI targeting the top 4 antigen bands is a useful confirmatory test for samples initially screened using the commercial Mhyo ELISAs.

Optimization of culture media of pathogenic Mycoplasma hyopneumoniae by a response surface methodology

Composition of culture medium for mass production of Mycoplasma hyopneumoniae was optimized using a response surface methodology (RSM). Initially, the influence of glucose, thallium acetate, fresh yeast extract, horse serum, and porcine serum on the production of mycoplasmal protein was assessed using a 'one factor at a time' technique. Next, factors with a significant effect, including fresh yeast extract, and horse and porcine sera, were selected for further optimization using a central composite design (CCD) of RSM. The experimental results were fitted into a second order polynomial model equation. Estimated optimal condition of the factors for maximum production of mycoplasmal protein (i.e., triple-fold increase from 0.8 mg/L produced by basal mycoplasma media to 2.5 mg/L) was 10.9% fresh yeast extract, 15% horse serum, and 31.5% porcine serum (v/v). For the optimized conditions, a 2.96 mg/L experimental result was observed, similar to the estimated optimal conditions result of the CCD.

The effect of intracellular calcium oscillations on fluid secretion in airway epithelium

Airway epithelium has been shown to elicit fluid secretion after a rise in intracellular calcium. This rise in intracellular calcium has been shown to display complex oscillations in many species after the binding of particular agonists to extracellular receptors. Fluid secreted by the airway epithelium is used to maintain the depth of the periciliary liquid (PCL) above the apical membrane of the epithelial cells lining the bronchial airways. Previous mathematical models have been published which separately consider the electrophysiology involved in regulating periciliary liquid depth, and the transmission of intracellular calcium waves in airway epithelial tissue. In this paper we present a mathematical model that combines these previous models and allows the effect of oscillations in intracellular calcium on fluid secretion by airway epithelial cells to be investigated. We show that an oscillatory calcium response produces different fluid secretion properties to that elicited by a tonic rise in intracellular calcium. These differences are shown to be due to saturation of the Ca(2+) activated ion channels.

Primary in vitro culture of porcine tracheal epithelial cells in an air-liquid interface as a model to study airway epithelium and Aspergillus fumigatus interactions

Since the airway epithelium is the first tissue encountered by airborne fungal spores, specific models are needed to study this interaction. We developed such a model using primary porcine tracheal epithelial cells (PTEC) as a possible alternative to the use of primary human cells. PTEC were obtained from pigs and were cultivated in an air-liquid interface. Fluorescent brightener was employed to quantify the internalization of Aspergillus fumigatus conidia. Potential differences (Vt) and transepithelial resistances (Rt) after challenge with the mycotoxin, verruculogen, were studied. Primers for porcine inflammatory mediator genes IL-8, TNF-alpha, and GM-CSF were designed for a quantitative real-time PCR procedure to study cellular responses to challenges with A. fumigatus conidia. TEM showed the differentiation of ciliated cells and the PTEC ability to internalize conidia. The internalization rate was 21.9 ± 1.4% after 8 h of incubation. Verruculogen (10(-6) M) significantly increased Vt without having an effect on the Rt. Exposure of PTEC to live A. fumigatus conidia for 24 h induced a 10- to 40-fold increase in the mRNA levels of inflammatory mediator genes. PTEC behave similarly to human cells and are therefore a suitable alternative to human cells for studying interaction between airway epithelium and A. fumigatus.

Sensory reception is an attribute of both primary cilia and motile cilia

A recent cluster of papers has shown that motile cilia in the respiratory and reproductive tracts of humans and other mammals can exhibit sensory functions, a function previously attributed primarily to non-motile primary cilia. This leads to a new paradigm that all cilia and flagella (both motile and primary) can mediate sensory functions. However, examination of the literature shows that evidence of sensory functions of motile cilia and flagella is widespread in studies of invertebrates, and extends as back as far as 1899. In this Opinion article, I review the recent and historical findings that motile cilia have a variety of sensory functions, and discuss how this concept has in fact been evolving for the past century.

Initiation of Plasmodium sporozoite motility by albumin is associated with induction of intracellular signalling

Malaria infection is initiated when a mosquito injects Plasmodium sporozoites into a mammalian host. Sporozoites exhibit gliding motility both in vitro and in vivo. This motility is associated with the secretion of at least two proteins, circumsporozoite protein (CSP) and thrombospondin-related anonymous protein (TRAP). Both derive from micronemes, which are organelles that empty out of the apical end of the sporozoite. Sporozoite motility can be initiated in vitro by albumin added to the medium. To investigate how albumin functions in this process, we studied second messenger signalling within the sporozoite. Using pharmacological activators and inhibitors, we have concluded that gliding motility is initiated when albumin interacts with the surface of the sporozoite and that this leads to a signal transduction cascade within the sporozoite, including the elevation of intracellular cAMP, the modulation of sporozoite motility by Ca(2+) and the release of microneme proteins.

Mycoplasma hyopneumoniae Induces Grap, Gadd45β, and secreted phosphoprotein 1 Gene Expression as Part of the Inflammatory Response in RAW264.7 Cells

Genes related to Mycoplasma hyopneumoniae-induced inflammation were identified using the gene-fishing technology, an improved method for identifying differentially expressed genes (DEGs) using an annealing control primer (ACP) system in RAW264.7 cells. After treatment with M. hyopneumo-niae, 16 DEGs were expressed in RAW264.7 cells using a pre-screening system. Among these 16 DEGs, 11 DEGs (DEGs 1, 4, 5-10, 12-15) were selected and sequenced directly, revealing that DEG12 (Grap), DEG14 (Gadd45), and DEG15 (secreted phosphoprotein 1) were related to inflammatory cytokines. This is the first report that intact M. hyopneumoniae induces the expression of Grap, Gadd 45β, and secreted phosphoprotein 1 in RAW264.7 cells. Subsequently, these genes may be targets for screening novel inhibitors of the mycoplasmal inflammatory response.

Control of Mycoplasma hyopneumoniae infections in pigs

Mycoplasma hyopneumoniae, the primary pathogen of enzootic pneumonia, occurs worldwide and causes major economic losses to the pig industry. The organism adheres to and damages the ciliated epithelium of the respiratory tract. Affected pigs show chronic coughing, are more susceptible to other respiratory infections and have a reduced performance. Control of the disease can be accomplished in a number of ways. First, management practices and housing conditions in the herd should be optimized. These include all-in/all-out production, limiting factors that may destabilize herd immunity, maintaining optimal stocking densities, prevention of other respiratory diseases, and optimal housing and climatic conditions. Strategic medication with antimicrobials active against M. hyopneumoniae and, preferably, also against major secondary bacteria may be useful during periods when the pigs are at risk for respiratory disease. Finally, commercial bacterins are widely used to control M. hyopneumoniae infections. The main effects of vaccination include less clinical symptoms, lung lesions and medication use, and improved performance. However, bacterins provide only partial protection and do not prevent colonization of the organism. Different vaccination strategies (timing of vaccination, vaccination of sows, vaccination combined with antimicrobial medication) can be used, depending on the type of herd, the production system and management practices, the infection pattern and the preferences of the pig producer. Research on new vaccines is actively occurring, including aerosol and feed-based vaccines as well as subunit and DNA vaccines. Eradication of the infection at herd level based on age-segregation and medication is possible, but there is a permanent risk for re-infections.

Targeting proteins to the ciliary membrane

Most vertebrate cell types display solitary nonmotile cilia on their surface that serve as cellular antennae to sense the extracellular environment. These organelles play key roles in the development of mammals by coordinating the actions of a single cell with events occurring around them. Severe defects in cilia lead to midgestational lethality in mice while more subtle defects lead to pathology in most organs of the body. These pathologies range from cystic diseases of the kidney, liver, and pancreas, to retinal degeneration, to bone and skeletal defects, hydrocephaly, and obesity. The sensory functions of cilia rely on proteins localized specifically to the ciliary membrane. Even though the ciliary membrane is a subdomain of the plasma membrane and is continuous with the plasma membrane, cells have the ability to specifically localize proteins to this domain. In this chapter, we will review what is currently known about the structure and function of the ciliary membrane. We will further discuss ongoing work to understand how the ciliary membrane is assembled and maintained, and discuss protein machinery that is thought to play a role in sorting or trafficking proteins to the ciliary membrane.

Surfactin C inhibits Mycoplasma hyopneumoniae-induced transcription of proinflammatory cytokines and nitric oxide production in murine RAW 264.7 cells

Intact pathogenic Mycoplasma hyopneumoniae at 100 microg protein ml(-1) induced transcription of proinflammatory cytokines such as cyclooxygenase (COX)-2, tumor necrosis factor (TNF)-alpha, interleukin(IL)-1, IL-6 and inducible nitric oxide synthase (iNOS) in RAW 264.7 cells. After pretreatment with 50 microg surfactin C/ml, purified from Bacillus subtilis, transcription of the COX-2, IL-1beta, IL-6 and iNOS genes induced by M. hyopneumoniae was inhibited by 43%, 82%, 72% and 59%, respectively.

The effect of polyclonal antibody on intracellular calcium increase induced by Mycoplasma hyopneumoniae in porcine tracheal cells

An investigation was undertaken to assess whether polyclonal convalescent and hyperimmune sera obtained from pigs inhibit Mycoplasma hyopneumoniae induced increases in intracellular calcium [Ca2+](i) in ciliated porcine tracheal cells. Basal [Ca2+](i) in the tracheal cells was 97+/-13 nM (n=22 cells in four experiments) and after exposure to M. hyopneumoniae (300 micro g/mL or 10(11) CCU/mL), [Ca2+](i) increased by 246+/-56 nM within 100 s. After pre-treatment with hyperimmune or convalescent serum, M. hyopneumoniae increased [Ca2+](i) by 196+/-43 and 223+/-65 nM, respectively. It was found that neither hyperimmune nor convalescent serum significantly prevented the increase in [Ca2+](i) compared with M. hyopneumoniae alone. It was concluded that polyclonal antibodies produced by mycoplasma vaccination or exposure to the pathogen do not prevent M. hyopneumoniae-induced increase in [Ca2+](i).

The genome sequence of Mycoplasma hyopneumoniae strain 232, the agent of swine mycoplasmosis

We present the complete genome sequence of Mycoplasma hyopneumoniae, an important member of the porcine respiratory disease complex. The genome is composed of 892,758 bp and has an average G+C content of 28.6 mol%. There are 692 predicted protein coding sequences, the average protein size is 388 amino acids, and the mean coding density is 91%. Functions have been assigned to 304 (44%) of the predicted protein coding sequences, while 261 (38%) of the proteins are conserved hypothetical proteins and 127 (18%) are unique hypothetical proteins. There is a single 16S-23S rRNA operon, and there are 30 tRNA coding sequences. The cilium adhesin gene has six paralogs in the genome, only one of which contains the cilium binding site. The companion gene, P102, also has six paralogs. Gene families constitute 26.3% of the total coding sequences, and the largest family is the 34-member ABC transporter family. Protein secretion occurs through a truncated pathway consisting of SecA, SecY, SecD, PrsA, DnaK, Tig, and LepA. Some highly conserved eubacterial proteins, such as GroEL and GroES, are notably absent. The DnaK-DnaJ-GrpR complex is intact, providing the only control over protein folding. There are several proteases that might serve as virulence factors, and there are 53 coding sequences with prokaryotic lipoprotein lipid attachment sites. Unlike other mycoplasmas, M. hyopneumoniae contains few genes with tandem repeat sequences that could be involved in phase switching or antigenic variation. Thus, it is not clear how M. hyopneumoniae evades the immune response and establishes a chronic infection.