Mycoplasma membrane lipoproteins induced proinflammatory cytokines by a mechanism distinct from that of lipopolysaccharide

Suppressing neutrophil itaconate production attenuates Mycoplasma pneumoniae pneumonia

Mycoplasma pneumoniae is a common cause of community-acquired pneumonia in which neutrophils play a critical role. Immune-responsive gene 1 (IRG1), responsible for itaconate production, has emerged as an important regulator of inflammation and infection, but its role during M. pneumoniae infection remains unknown. Here, we reveal that itaconate is an endogenous pro-inflammatory metabolite during M. pneumoniae infection. Irg1 knockout (KO) mice had lower levels of bacterial burden, lactate dehydrogenase (LDH), and pro-inflammatory cytokines compared with wild-type (WT) controls after M. pneumoniae infection. Neutrophils were the major cells producing itaconate during M. pneumoniae infection in mice. Neutrophil counts were positively correlated with itaconate concentrations in bronchoalveolar lavage fluid (BALF) of patients with severe M. pneumoniae pneumonia. Adoptive transfer of Irg1 KO neutrophils, or administration of β-glucan (an inhibitor of Irg1 expression), significantly attenuated M. pneumoniae pneumonia in mice. Mechanistically, itaconate impaired neutrophil bacterial killing and suppressed neutrophil apoptosis via inhibiting mitochondrial ROS. Moreover, M. pneumoniae induced Irg1 expression by activating NF-κB and STAT1 pathways involving TLR2. Our data thus identify Irg1/itaconate pathway as a potential therapeutic target for the treatment of M. pneumoniae pneumonia.

Korean Nationwide Exploration of Sarcopenia Prevalence and Risk Factors in Late Middle-Aged Women

This study examined specific clinical risk factors for age-related loss of skeletal muscle mass in late middle-aged women with sarcopenia. This Korean nationwide cross-sectional study analyzed data from 2814 community-dwelling women aged from 50 to 64 years old and screened them for sarcopenia. This study examined various risk factors such as age; height; weight; body mass index; waist circumference; skeletal muscle mass index; systolic and diastolic blood pressure; smoking and drinking habits; fasting glucose levels; triglyceride; and cholesterol levels. Complex sampling analysis was used for the data set. Prevalence of sarcopenia with a weighted prevalence of 13.43% (95% confidence interval: 2.15-15.78). The risk factors for sarcopenia were height, body mass index, waist circumference, skeletal muscle mass index, systolic blood pressure, diastolic blood pressure, triglyceride level, and total cholesterol level (p < 0.05). Weight, fasting glucose level, drinking status, and smoking status were not significant (p > 0.05). These results are expected to contribute to the existing literature on sarcopenia and identify potential risk factors associated with the development of sarcopenia in late middle-aged females. By acknowledging prevalence and recognized risk factors, healthcare professionals may augment their proficiency in recognizing and discerning potential instances of sarcopenia in female patients.

Screening of immunogenic proteins and evaluation of vaccine candidates against Mycoplasma synoviae

Mycoplasma synoviae (M. synoviae) is a serious avian pathogen that causes significant economic losses to chicken and turkey producers worldwide. The currently available live attenuated and inactivated vaccines provide limited protection. The objective of this study was to identify potential subunit vaccine candidates using immunoproteomics and reverse vaccinology analyses and to evaluate their preliminary protection. Twenty-four candidate antigens were identified, and five of them, namely RS01790 (a putative sugar ABC transporter lipoprotein), BMP (a substrate-binding protein of the BMP family ABC transporter), GrpE (a nucleotide exchange factor), RS00900 (a putative nuclease), and RS00275 (an uncharacterized protein), were selected to evaluate their immunogenicity and preliminary protection. The results showed that all five antigens had good immunogenicity, and they were localized on the M. synoviae cell membrane. The antigens induced specific humoral and cellular immune responses, and the vaccinated chickens exhibited significantly greater body weight gain and lower air sac lesion scores and tracheal mucosal thicknesses. Additionally, the vaccinated chickens had lower M. synoviae loads in throat swabs than non-vaccinated chickens. The protective effect of the RS01790, BMP, GrpE, and RS00900 vaccines was better than that of the RS00275 vaccine. In conclusion, our study demonstrates the potential of subunit vaccines as a new approach to developing M. synoviae vaccines, providing new ideas for controlling the spread of M. synoviae worldwide.

Long COVID and the Neuroendocrinology of Microbial Translocation Outside the GI Tract: Some Treatment Strategies

Similar to previous pandemics, COVID-19 has been succeeded by well-documented post-infectious sequelae, including chronic fatigue, cough, shortness of breath, myalgia, and concentration difficulties, which may last 5 to 12 weeks or longer after the acute phase of illness. Both the psychological stress of SARS-CoV-2 infection and being diagnosed with COVID-19 can upregulate cortisol, a stress hormone that disrupts the efferocytosis effectors, macrophages, and natural killer cells, leading to the excessive accumulation of senescent cells and disruption of biological barriers. This has been well-established in cancer patients who often experience unrelenting fatigue as well as gut and blood–brain barrier dysfunction upon treatment with senescence-inducing radiation or chemotherapy. In our previous research from 2020 and 2021, we linked COVID-19 to myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) via angiotensin II upregulation, premature endothelial senescence, intestinal barrier dysfunction, and microbial translocation from the gastrointestinal tract into the systemic circulation. In 2021 and 2022, these hypotheses were validated and SARS-CoV-2-induced cellular senescence as well as microbial translocation were documented in both acute SARS-CoV-2 infection, long COVID, and ME/CFS, connecting intestinal barrier dysfunction to disabling fatigue and specific infectious events. The purpose of this narrative review is to summarize what is currently known about host immune responses to translocated gut microbes and how these responses relate to fatiguing illnesses, including long COVID. To accomplish this goal, we examine the role of intestinal and blood–brain barriers in long COVID and other illnesses typified by chronic fatigue, with a special emphasis on commensal microbes functioning as viral reservoirs. Furthermore, we discuss the role of SARS-CoV-2/Mycoplasma coinfection in dysfunctional efferocytosis, emphasizing some potential novel treatment strategies, including the use of senotherapeutic drugs, HMGB1 inhibitors, Toll-like receptor 4 (TLR4) blockers, and membrane lipid replacement.

Vaccination with Mycoplasma pneumoniae membrane lipoproteins induces IL-17A driven neutrophilia that mediates Vaccine-Enhanced Disease

Bacterial lipoproteins are an often-underappreciated class of microbe-associated molecular patterns with potent immunomodulatory activity. We previously reported that vaccination of BALB/c mice with Mycoplasma pneumoniae (Mp) lipid-associated membrane proteins (LAMPs) resulted in lipoprotein-dependent vaccine enhanced disease after challenge with virulent Mp, though the immune responses underpinning this phenomenon remain poorly understood. Herein, we report that lipoprotein-induced VED in a mouse model is associated with elevated inflammatory cytokines TNF-α, IL-1β, IL-6, IL-17A, and KC in lung lavage fluid and with suppurative pneumonia marked by exuberant neutrophilia in the pulmonary parenchyma. Whole-lung-digest flow cytometry and RNAScope analysis identified multiple cellular sources for IL-17A, and the numbers of IL-17A producing cells were increased in LAMPs-vaccinated/Mp-challenged animals compared to controls. Specific IL-17A or neutrophil depletion reduced disease severity in our VED model—indicating that Mp lipoproteins induce VED in an IL-17A-dependent manner and through exuberant neutrophil recruitment. IL-17A neutralization reduced levels of TNF-α, IL-1β, IL-6, and KC, indicating that IL-17A preceded other inflammatory cytokines. Surprisingly, we found that IL-17A neutralization impaired bacterial clearance, while neutrophil depletion improved it—indicating that, while IL-17A appears to confer both maladaptive and protective responses, neutrophils play an entirely maladaptive role in VED. Given that lipoproteins are found in virtually all bacteria, the potential for lipoprotein-mediated maladaptive inflammatory responses should be taken into consideration when developing vaccines against bacterial pathogens.

Heterologous Expression, Purification, and Immunomodulatory Effects of Recombinant Lipoprotein GUDIV-103 Isolated from Ureaplasma diversum

Ureaplasma diversum is a bacterial pathogen that infects cattle and can cause severe inflammation of the genital and reproductive systems. Lipid-associated membrane proteins (LAMPs), including GUDIV-103, are the main virulence factors in this bacterium. In this study, we heterologously expressed recombinant GUDIV-103 (rGUDIV-103) in Escherichia coli, purified it, and evaluated its immunological reactivity and immunomodulatory effects in bovine peripheral blood mononuclear cells (PBMCs). Samples from rabbits inoculated with purified rGUDIV-103 were analysed using indirect enzyme-linked immunosorbent assay and dot blotting to confirm polyclonal antibody production and assess kinetics, respectively. The expression of this lipoprotein in field isolates was confirmed via Western blotting with anti-rGUDIV-103 serum and hydrophobic or hydrophilic proteins from 42 U. diversum strains. Moreover, the antibodies produced against the U. diversum ATCC 49783 strain recognised rGUDIV-103. The mitogenic potential of rGUDIV-103 was evaluated using a lymphoproliferation assay in 5(6)-carboxyfluorescein diacetate succinimidyl ester−labelled bovine PBMCs, where it induced lymphocyte proliferation. Quantitative polymerase chain reaction analysis revealed that the expression of interleukin-1β, toll-like receptor (TLR)-α, TLR2, TLR4, inducible nitric oxide synthase, and caspase-3−encoding genes increased more in rGUDIV-103−treated PBMCs than in untreated cells (p < 0.05). Treating PBMCs with rGUDIV-103 increased nitric oxide and hydrogen peroxide levels. The antigenic and immunogenic properties of rGUDIV-103 suggested its suitability for immunobiological application.

Diving into Inflammation: A Pilot Study Exploring the Dynamics of the Immune-Microbiota Axis in Ileal Tissue Layers of Patients with Crohn's Disease

BACKGROUND AND AIMS

The pathogenesis of Crohn's disease [CD] is still unclear. Disorders in the mucosal immunoregulation and its crosstalk with the microbiota may represent an important component in tissue injury. We aimed to characterize the molecular immune response distribution within the ileal layers and to evaluate the correlated microbiota in pathological/healthy settings comparing first surgery/relapse clinical conditions.

METHODS

We enrolled 12 CD patients. A comprehensive analysis of an ileal mucosa, submucosa and serosa broad-spectrum cytokine panel was performed through a multiplex approach. In addition, ileal microbiota composition was assessed through next generation sequencing.

RESULTS

We observed a distinct profile [of IL1-α, IL-1β, IL-4, IL-8, ICAM-1, E-Selectin, P-Selectin, IP-10, IL 6 and IL 18] across the CD vs healthy ileal layers; and a different distribution of IFN- γ, P-Selectin, IL-27 and IL-21 in first surgery vs relapse patients. In addition, the phylum Tenericutes, the family Ruminococcaceae, and the genera Mesoplasma and Mycoplasma were significantly enriched in the pathological setting. Significant microbiota differences were observed between relapse and first surgery patients regarding the class Bacteroidia, and the genera Prevotella, Flavobacterium, Tepidimonas and Escherichia/Shigella. Finally, the abundance of the genus Mycoplasma was positively correlated with IL-18.

CONCLUSIONS

We describe a dissimilarity of cytokine distribution and microbiota composition within CD and adjacent healthy ileal tissue layers and between first operation and surgical relapse. Our results give potential insight into the dynamics of the gut microbiota-immune axis in CD patients, leading to detection of new biomarkers.

A Review of Ureaplasma diversum: A Representative of the Mollicute Class Associated With Reproductive and Respiratory Disorders in Cattle

The Mollicutes class encompasses wall-less microbes with a reduced genome. They may infect plants, insects, humans, and animals including those on farms and in livestock. Ureaplasma diversum is a mollicute associated with decreased reproduction mainly in the conception rate in cattle, as well as weight loss and decreased quality in milk production. Therefore, U. diversum infection contributes to important economic losses, mainly in large cattle-producing countries such as the United States, China, Brazil, and India. The characteristics of Mollicutes, virulence, and pathogenic variations make it difficult to control their infections. Genomic analysis, prevalence studies, and immunomodulation assays help better understand the pathogenesis of bovine ureaplasma. Here we present the main features of transmission, virulence, immune response, and pathogenesis of U. diversum in bovines.

Novel antigenic proteins of Mycoplasma agalactiae as potential vaccine and serodiagnostic candidates

Contagious agalactia (CA) is a serious disease notifiable to the World Organisation for Animal Health (OIE) causing severe economic losses to sheep and goat producers worldwide. Mycoplasma agalactiae, considered as its main etiological agent, inflicts a variety of symptoms in infected animals, including keratoconjunctivitis, mastitis, arthritis, ankylosis, abortions, stillbirths and granular vulvovaginitis. Despite its significance, developing a successful vaccine remains elusive, mostly due to the lack of knowledge about M. agalactiae's pathogenicity factors and pathogenic mechanisms, including its "core" antigens. The aim of this study was to identify, characterize and express antigenic proteins of M. agalactiae as potential vaccine candidates. Predicted proteins of type strain PG2 were analyzed using bioinformatic algorithms to assess their cellular localization and to identify their linear and conformational epitopes for B cells. Out of a total of 156 predicted membrane proteins, three were shortlisted as potential antigenic surface proteins, namely [MAG_1560 (WP_011949336.1), MAG_6130 (WP_011949770.1) and P40 (WP_011949418.1)]. These proteins were expressed in recombinant Escherichia coli strains. Purified proteins were evaluated for their antigenicity using Western blot and ELISA using sera of M. agalactiae-naturally infected and non-infected sheep and goats. All 3 proteins were specifically recognized by the tested sera of M. agalactiae-infected animals. Also, specific rabbit antisera raised against each of these 3 proteins confirm their membrane localization using TritonX-114 phase partioning, Western and colony immunoblotting. In conclusion, our study successfully identified P40 (as proof of concept and validation) and two novel antigenic M. agalactiae proteins as potential candidates for developing effective CA vaccines.

Mycoplasmas-Host Interaction: Mechanisms of Inflammation and Association with Cellular Transformation

Mycoplasmas are the smallest and simplest self-replicating prokaryotes. Located everywhere in nature, they are widespread as parasites of humans, mammals, reptiles, fish, arthropods, and plants. They usually exhibiting organ and tissue specificity. Mycoplasmas belong to the class named Mollicutes (mollis = soft and cutis = skin, in Latin), and their small size and absence of a cell wall contribute to distinguish them from other bacteria. Mycoplasma species are found both outside the cells as membrane surface parasites and inside the cells, where they become intracellular residents as "silent parasites". In humans, some Mycoplasma species are found as commensal inhabitants, while others have a significant impact on the cellular metabolism and physiology. Mollicutes lack typical bacterial PAMPs (e.g., lipoteichoic acid, flagellin, and some lipopolysaccharides) and consequently the exact molecular mechanisms of Mycoplasmas' recognition by the cells of the immune system is the subjects of several researches for its pathogenic implications. It is well known that several strains of Mycoplasma suppress the transcriptional activity of p53, resulting in reduced apoptosis of damaged cells. In addition, some Mycoplasmas were reported to have oncogenic potential since they demonstrated not just accumulation of abnormalities but also phenotypic changes of the cells. Aim of this review is to provide an update of the current literature that implicates Mycoplasmas in triggering inflammation and altering critical cellular pathways, thus providing a better insight into potential mechanisms of cellular transformation.

Toll-Like Receptor 2 (TLR2) and TLR4 Mediate the IgA Immune Response Induced by Mycoplasma hyopneumoniae

IgA plays an important role in mucosal immunity against infectious pathogens; however, the molecular mechanism of IgA secretion in response to infection remains largely unknown, particularly in Mycoplasma spp. In this study, we found that the levels of IgA in the peripheral blood serum, bronchoalveolar lavage fluid, nasal mucosa, trachea, hilar lymph nodes, and lung tissues of pigs increased significantly after infection with Mycoplasma hyopneumoniae.

IgA plays an important role in mucosal immunity against infectious pathogens; however, the molecular mechanism of IgA secretion in response to infection remains largely unknown, particularly in Mycoplasma spp. In this study, we found that the levels of IgA in the peripheral blood serum, bronchoalveolar lavage fluid, nasal mucosa, trachea, hilar lymph nodes, and lung tissues of pigs increased significantly after infection with Mycoplasma hyopneumoniae. Furthermore, IgA and CD11c were detected in the lungs and hilar lymph nodes by immunohistochemical analysis, and colocalization of these two markers indicates that CD11c⁺ cells play an important role in IgA mucosal immunity induced by M. hyopneumoniae. To investigate the regulatory mechanism of IgA, we separated mouse dendritic cells (DCs) from different tissues and mouse macrophages from the lungs and then cultured mouse B cells together with either DCs or macrophages in vitro. In the mouse lung-DC/B (LDC/B) cell coculture, IgA secretion was increased significantly after the addition of whole-cell lysates of M. hyopneumoniae. The expression of both Toll-like receptor 2 (TLR2) and TLR4 was also upregulated, as determined by mRNA and protein expression analyses, whereas no obvious change in the expression of TLR3 and TLR7 was detected. Moreover, the IgA level decreased to the same as the control group when TLR2 or TLR4 was inhibited instead of TLR8 or TLR7/9. In conclusion, M. hyopneumoniae can stimulate the response of IgA through TLR2 and TLR4 in a mouse LDC/B cell coculture model, and the coculture model is an ideal tool for studying the IgA response mechanism, particularly that with Mycoplasma spp.

The Role of Lipoproteins in Mycoplasma-Mediated Immunomodulation

Mycoplasma infections, such as walking pneumonia or pelvic inflammatory diseases, are a major threat to public health. Despite their relatively small physical and genomic size, mycoplasmas are known to elicit strong host immune responses, generally inflammatory, while also being able to evade the immune system. The mycoplasma membrane is composed of approximately two-thirds protein and one-third lipid and contains several lipoproteins that are known to regulate host immune responses. Herein, the immunomodulatory effects of mycoplasma lipoproteins are reviewed. A better understanding of the immunomodulatory effects, both activating and evasive, of Mycoplasma surface lipoproteins will contribute to understanding mechanisms potentially relevant to mycoplasma disease vaccine development and treatment.

Activation of NLRP3 inflammasome in macrophages by mycoplasmal lipoproteins and lipopeptides

The NLRP3 inflammasome, an intracellular sensor consisting of the nucleotide-binding oligomerization domain-like receptor family, pyrin domain containing 3 (NLRP3), the adaptor protein apoptosis-associated speck-like protein containing a caspase-recruitment domain (ASC), and procaspase-1, plays critical roles in host defense against microbial pathogens by inducing production of interleukin-1β (IL-1β) and IL-18. Mycoplasma salivarium and Mycoplasma pneumoniae cells activated murine bone marrow-derived macrophages (BMMs) to induce production of IL-1α, IL-1β, and IL-18. The IL-1β production-inducing activities of these mycoplasmas toward BMMs from Toll-like receptor 2 (TLR2)-deficient mice were significantly attenuated compared with those from C57BL/6 mice (B6BMMs). This result suggests the possibility that their lipoproteins as TLR2 agonists are involved in the activity. Lipoproteins of M. salivarium and M. pneumoniae (MsLP and MpLP), and the M. salivarium-derived lipopeptide FSL-1 induced IL-1β production by B6BMMs, but not by BMMs from caspase-1-, NLRP3- or ASC-deficient mice. The activities of MsLP and MpLP were not downregulated by the proteinase K treatment, suggesting that the active sites are their N-terminal lipopeptide moieties. B6BMMs internalized the mycoplasmal N-terminal lipopeptide FSL-1 at least 30 min after incubation, FSL-1-containing endosomes started to fuse with the lysosomes around 2 hours, and then FSL-1 translocated into the cytosol from LAMP-1⁺ endosomes. The artificial delivery of FSL-1 into the cytosol of B6BMMs drastically enhanced the IL-1β production-inducing activity. FSL-1 as well as the representative NLRP3 inflammasome activator nigericin induced the NLRP3/ASC speck, but FSL-1 located in a compartment different from the NLRP3/ASC speck.

The Putative Role of Viruses, Bacteria, and Chronic Fungal Biotoxin Exposure in the Genesis of Intractable Fatigue Accompanied by Cognitive and Physical Disability

Patients who present with severe intractable apparently idiopathic fatigue accompanied by profound physical and or cognitive disability present a significant therapeutic challenge. The effect of psychological counseling is limited, with significant but very slight improvements in psychometric measures of fatigue and disability but no improvement on scientific measures of physical impairment compared to controls. Similarly, exercise regimes either produce significant, but practically unimportant, benefit or provoke symptom exacerbation. Many such patients are afforded the exclusionary, non-specific diagnosis of chronic fatigue syndrome if rudimentary testing fails to discover the cause of their symptoms. More sophisticated investigations often reveal the presence of a range of pathogens capable of establishing life-long infections with sophisticated immune evasion strategies, including Parvoviruses, HHV6, variants of Epstein-Barr, Cytomegalovirus, Mycoplasma, and Borrelia burgdorferi. Other patients have a history of chronic fungal or other biotoxin exposure. Herein, we explain the epigenetic factors that may render such individuals susceptible to the chronic pathology induced by such agents, how such agents induce pathology, and, indeed, how such pathology can persist and even amplify even when infections have cleared or when biotoxin exposure has ceased. The presence of active, reactivated, or even latent Herpes virus could be a potential source of intractable fatigue accompanied by profound physical and or cognitive disability in some patients, and the same may be true of persistent Parvovirus B12 and mycoplasma infection. A history of chronic mold exposure is a feasible explanation for such symptoms, as is the presence of B. burgdorferi. The complex tropism, life cycles, genetic variability, and low titer of many of these pathogens makes their detection in blood a challenge. Examination of lymphoid tissue or CSF in such circumstances may be warranted.

Genetic variation in SP-A2 leads to differential binding to Mycoplasma pneumoniae membranes and regulation of host responses

Mycoplasma pneumoniae is an extracellular pathogen that colonizes mucosal surfaces of the respiratory tract and is associated with asthma exacerbations. Previous reports demonstrate that surfactant protein-A (SP-A) binds live M. pneumoniae and mycoplasma membrane fractions (MMF) with high affinity. Humans express a repertoire of single-amino acid genetic variants of SP-A that may be associated with lung disease, and our findings demonstrate that allelic differences in SP-A2 (Gln223Lys) affect the binding to MMF. We show that SP-A(-/-) mice are more susceptible to MMF exposure and have significant increases in mucin production and neutrophil recruitment. Novel humanized SP-A2-transgenic mice harboring the hSP-A2 223K allele exhibit reduced neutrophil influx and mucin production in the lungs when challenged with MMF compared with SP-A(-/-) mice. Conversely, mice expressing hSP-A2 223Q have increased neutrophil influx and mucin production that are similar to SP-A(-/-) mice. Using tracheal epithelial cell cultures, we show that enhanced mucin production to MMF occurs in the absence of SP-A and is not dependent upon neutrophil recruitment. Increased phosphorylation of the epidermal growth factor receptor (EGFR) was evident in the lungs of MMF-challenged mice when SP-A was absent. Pharmacologic inhibition of EGFR prior to MMF challenge dramatically reduced mucin production in SP-A(-/-) mice. These findings suggest a protective role for SP-A in limiting MMF-stimulated mucin production that occurs through interference with EGFR-mediated signaling. SP-A interaction with the EGFR signaling pathway appears to occur in an allele-specific manner that may have important implications for SP-A polymorphisms in human diseases.

Mycoplasma hyopneumoniae-derived lipid-associated membrane proteins induce inflammation and apoptosis in porcine peripheral blood mononuclear cells in vitro

Mycoplasma hyopneumoniae is the causative agent of swine enzootic pneumonia (EP), a disease that causes considerable economic losss in swine industry. Lipid-associated membrane proteins (LAMPs) of mycoplasma play important roles in causing mycoplasma diseases. The present study explores the pathogenic mechanisms of M. hyopneumoniae LAMPs by elucidating their role in modulating the inflammation, apoptosis, and relevant signaling pathways of peripheral blood mononuclear cells (PBMCs) of pig. LAMP treatment inhibited the growth of PBMCs. Up-regulation of cytokines, such as IL-6 and IL-1β, as well as increased production of nitric oxide (NO) and superoxide anion were all detected in the supernatant of LAMPs-treated PBMCs. Furthermore, flow cytometric analysis using dual staining with annexin-V-FITC and propidium iodide (PI) showed that LAMPs of M. hyopneumoniae induced a time-dependent apoptosis in lymphocyts and monocytes from PBMCs, which was blocked by NOS inhibitor or antioxidant. In addition, LAMPs induced the phosphorylation of p38, the ratio of pro-apoptotic Bax protein to anti-apoptotic Bcl-2, activation of caspase-3 and caspase-8, and poly ADP-ribose polymerase (PARP) cleavage in PBMCs. These findings demonstrated that M. hyopneumoniae LAMPs induced the production of proinflammatory cytokines, NO and reactive oxygen species (ROS), and apoptosis of PBMCs in vitro through p38 MAPK and Bax/Bcl-2 signaling pathways, as well as caspase activation.

Sulfur compounds block MCP-1 production by Mycoplasma fermentans-infected macrophages through NF-κB inhibition

Background and aims

Hydrogen sulfide (H₂S), together with nitric oxide (NO) and carbon monoxide (CO), belongs to a family of endogenous signaling mediators termed “gasotransmitters”. Recent studies suggest that H₂S modulates many cellular processes and it has been recognized to play a central role in inflammation, in the cardiovascular and nervous systems. By infecting monocytes/macrophages with Mycoplasma fermentans (M.F.), a well-known pro-inflammatory agent, we evaluated the effects of H₂S.

Methods

M.F.-infected cells were analyzed by ELISA and real time RT-PCR to detect the M.F. effects on MCP-1 and on MMP-12 expression. The role of two different H₂S donors (NaHS and GYY4137) on MF-infected cells was determined by treating infected cells with H₂S and then testing the culture supernatants for MCP-1 and on MMP-12 production by ELISA assay. In order to identify the pathway/s mediating H₂S- anti-inflammatory activity, cells were also treated with specific pharmaceutical inhibitors. Cytoplasmic and nuclear accumulation of NF-κB heterodimers was analyzed.

Results

We show that H₂S was able to reduce the production of pro-inflammatory cytokine MCP-1, that was induced in monocytes/macrophages during M.F. infection. Moreover, MCP-1 was induced by M.F. through Toll-like receptor (TLR)-mediated nuclear factor-κB (NF-κB) activation, as demonstrated by the fact that TLR inhibitors TIRAP and MyD88 and NF-κB inhibitor IKK were able to block the cytokine production. In contrast H₂S treatment of M.F. infected macrophages reduced nuclear accumulation of NF-κB heterodimer p65/p52.

Conclusions

Our data demonstrate that under the present conditions H₂S is effective in reducing Mycoplasma-induced inflammation by targeting the NF-κB pathway. This supports further studies for possible clinical applications.

Mycoplasma hyorhinis activates the NLRP3 inflammasome and promotes migration and invasion of gastric cancer cells

BACKGROUND

Mycoplasma hyorhinis (M.hyorhinis, M.hy) is associated with development of gastric and prostate cancers. The NLRP3 inflammasome, a protein complex controlling maturation of important pro-inflammatory cytokines interleukin (IL)-1β and IL-18, is also involved in tumorigenesis and metastasis of various cancers.

METHODOLOGY/PRINCIPAL FINDINGS

To clarify whether M.hy promoted tumor development via inflammasome activation, we analyzed monocytes for IL-1β and IL-18 production upon M.hy challenge. When exposed to M.hy, human monocytes exhibited rapid and robust IL-1β and IL-18 secretion. We further identified that lipid-associated membrane protein (LAMP) from M.hy was responsible for IL-1β induction. Applying competitive inhibitors, gene specific shRNA and gene targeted mice, we verified that M.hy induced IL-1β secretion was NLRP3-dependent in vitro and in vivo. Cathepsin B activity, K(+) efflux, Ca(2+) influx and ROS production were all required for the NLRP3 inflammasome activation by M.hy. Importantly, it is IL-1β but not IL-18 produced from macrophages challenged with M.hy promoted gastric cancer cell migration and invasion.

CONCLUSIONS

Our data suggest that activation of the NLRP3 inflammasome by M.hy may be associated with its promotion of gastric cancer metastasis, and anti-M.hy therapy or limiting NLRP3 signaling could be effective approach for control of gastric cancer progress.

Modulation of IL-8 boosted by Mycoplasma pneumoniae lysate in human airway epithelial cells

Mycoplasma pneumoniae, a major cause of community-acquired pneumonia, has been recognized as a trigger for asthma inception and exacerbation. The epithelial cells on the respiratory tract parasitized by M. pneumoniae exhibit a number of cytopathic effects as a result of local inflammation and stimulated host immune response. We investigated the interactions of signaling molecules regulating the release of IL-8 by the direct stimulation of M. pneumoniae lysate (MPL) in human airway epithelial cells. In human airway epithelial cells, MPL-induced IL-8 proteins were decreased by monoclonal anti-TLR2 antibody in a dose-dependent fashion, and significantly blocked by siRNA TLR2. The pharmacologic inhibitors of ERK, U0126 and PD98059, effectively reduced IL-8 expression and the active forms of ERK signaling molecules, as detected by anti-phosphorylated p44/42 antibody. The region spanning from -132 to +41 in the IL-8 promoter demonstrated the highest luciferase activity against MPL and the mutations of NF-κB and NF-IL6 entirely diminished the activity. After investigating transfections of the NF-κB and NF-IL6 reporter vectors, NF-IL6 activation was significantly induced by MPL stimulation, which was considerably decreased by U0126 and monoclonal anti-TLR2 antibody. These results indicate that MPL-induced IL-8 increase is transcriptionally regulated by NF-IL6 more than by NF-κB. Additionally, the activation of NF-IL6 is influenced by TLR2 and ERK signaling pathways in airway epithelial cells.

Identification of genes coding for B cell antigens of Mycoplasma mycoides subsp. mycoides Small Colony (MmmSC) by using phage display

Background

Contagious bovine pleuropneumonia (CBPP) is a mycoplasmal disease caused by Mycoplasma mycoides subsp. mycoides SC (MmmSC). Since the disease is a serious problem that can affect cattle production in parts of Africa, there is a need for an effective and economical vaccine. Identifying which of the causative agent's proteins trigger potentially protective immune responses is an important step towards developing a subunit vaccine. Accordingly, the purpose of this study was to determine whether phage display combined with bioinformatics could be used to narrow the search for genes that code for potentially immunogenic proteins of MmmSC. Since the production of IgG2 and IgA are associated with a Th₁ cellular immune response which is implicated in protection against CBPP, antigens which elicit these immunoglobulin subclasses may be useful in developing a subunit vaccine.

Results

A filamentous phage library displaying a repertoire of peptides expressed by fragments of the genome of MmmSC was constructed. It was subjected to selection using antibodies from naturally- and experimentally-infected cattle. Mycoplasmal genes were identified by matching the nucleotide sequences of DNA from immunoselected phage particles with the mycoplasmal genome. This allowed a catalogue of genes coding for the proteins that elicited an immune response to be compiled. Using this method together with computer algorithms designed to score parameters that influence surface accessibility and hence potential antigenicity, five genes (abc, gapN, glpO, lppB and ptsG) were chosen to be expressed in Escherichia coli. After appropriate site-directed mutagenesis, polypeptides representing portions of each of these proteins were tested for immunoreactivity. Of these five, polypeptides representing expression products of abc and lppB were recognised on immunoblots by sera obtained from cattle during a natural outbreak of the disease.

Conclusion

Since phage display physically couples phenotype with genotype, it was used to compile a list of sequences that code for MmmSC proteins bearing epitopes which were recognised by antibodies in the serum of infected animals. Together with the appropriate bioinformatic analyses, this approach provided several potentially useful vaccine or diagnostic leads. The phage display step empirically identified sequences by their interaction with antibodies which accordingly reduced the number of ORFs that had to be expressed for testing. This is a particular advantage when working with MmmSC since the mycoplasmal codon for tryptophan needs to be mutated to prevent it from being translated as a stop in E. coli.

Mycoplasma genitalium lipoproteins induce human monocytic cell expression of proinflammatory cytokines and apoptosis by activating nuclear factor kappaB

This study was designed to investigate the molecular mechanisms responsible for the induction of proinflammatory cytokines gene expression and apoptosis in human monocytic cell line THP-1 stimulated by lipoproteins (LPs) prepared from Mycoplasma genitalium. Cultured cells were stimulated with M. genitalium LP to analyze the production of proinflammatory cytokines and expression of their mRNA by ELISA and RT-PCR, respectively. Cell apoptosis was also detected by Annexin V-FITC-propidium iodide (PI) staining and acridine orange (AO)-ethidium bromide (EB) staining. The DNA-binding activity of nuclear factor-κB (NF-κB) was assessed by electrophoretic mobility shift assay (EMSA). Results showed that LP stimulated THP-1 cells to produce tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and IL-6 in a dose-dependent manner. The mRNA levels were also upregulated in response to LP stimulation. LPs were also found to increase the DNA-binding activity of NF-κB, a possible mechanism for the induction of cytokine mRNA expression and the cell apoptosis. These effects were abrogated by PDTC, an inhibitor of NF-κB. Our results indicate that M. genitalium-derived LP may be an important etiological factor of certain diseases due to the ability of LP to produce proinflammatory cytokines and induction of apoptosis, which is probably mediated through the activation of NF-κB.

Apoptosis induced by lipid-associated membrane proteins from Mycoplasma penetrans is mediated by nuclear factor kappaB activation in mouse macrophage

Mycoplasma penetrans was shown to be involved in alteration of several eukaryotical cells functions and a causative agent in urogenital infectious diseases. Lipid-associated membrane proteins (LAMPs) may be responsible for the pathogenicity of some mycoplamas. In this study, we investigated whether M. penetrans LAMPs have pathogenic potential by inducing apoptosis in mouse macrophages. As analyzed by annexin-V - fluorescein isothiocyanate staining, significant early- and late-stage apoptosis was induced in M. penetrans LAMPs-challenged mouse macrophages. And agarose gel electrophoresis of the DNA of M. penetrans LAMPs-challenged cells revealed a ladder-like pattern of migration of DNA indicative of apoptosis. The possible molecular mechanisms responsible for the induction of apoptosis were also investigated by characterizing the activation of nuclear transcription factor kappaB (NFkappaB). NFkappaB was activated and translocated into the nucleus in mouse macrophages stimulated by M. penetrans LAMPs. The activation of NFkappaB and M. penetrans LAMPs-induced apoptosis in mouse macrophages was partially inhibited by the NFkappaB-specific inhibitor pyrrolidine dithiocarbamate. Thus, this study demonstrates that M. penetrans LAMPs may be an important etiological factor owing to their ability to induce apoptosis in mouse macrophages, which is probably mediated through the activation of NFkappaB.

Induction of IL-8 by Mycoplasma pneumoniae membrane in BEAS-2B cells

Mycoplasma pneumoniae is an extracellular pathogen, residing on mucosal surfaces of the respiratory and genital tracts. The lack of cell walls in mycoplasmas facilitates the direct contact of the bacterial membrane with the host cell. The cell membrane of mycoplasma is the major inducer of the host pathogenic response. Airway diseases caused by M. pneumoniae include bronchiolitis, bronchitis, and rarely bronchiectasis. In such disorders, neutrophil infiltration of the airways predominates. More recently, M. pneumoniae has been implicated in the pathogenesis of asthma. Epithelial cells play an important role in recruiting inflammatory cells into the airways. Since M. pneumoniae infection of human epithelial cells induces expression of IL-8-a potent activator of neutrophils-we investigated the signaling and transcriptional mechanisms by which mycoplasma membrane induces expression of this chemokine. In BEAS-2B human bronchial epithelial cells, mycoplasma membrane fraction (MMF) increased IL-8 mRNA and protein production. Activation of the transcriptional elements activating protein-1, nuclear factor-interleukin-6, and particularly NF-kappaB are essential for optimal IL-8 production by MMF. The mitogen-activated protein kinases individually played a modest role in MMF-induced IL-8 production. Toll-like receptor-2 did not play a significant role in MMF-induction of IL-8. Antibiotics with microbicidal activity against M. pneumoniae are also known to have anti-inflammatory effects. Whereas clarithromycin, azithromycin, and moxifloxacin individually were able to inhibit TNF-alpha-induction of IL-8, each failed to inhibit MMF-induction of IL-8.

Mycoplasma pneumoniae-an emerging extra-pulmonary pathogen

Mycoplasma is a well-recognised pathogen that colonises mucosal surfaces of humans and animals. Mycoplasma pneumoniae infects the upper and lower respiratory tracts of children and adults, leading to a wide range of respiratory and non-respiratory clinical conditions. M. pneumoniae infection is frequently considered in the differential diagnosis of patients with respiratory illnesses, and is commonly managed empirically with macrolides and fluoroquinolones. This contrasts with patients who present with non-respiratory symptoms in the context of a recent or current unrecognised M. pneumoniae infection, for whom this pathogen is rarely considered in the initial differential diagnosis. This review considers the microbiological, epidemiological, pathogenic and clinical features of this frequent pathogen that need to be considered in the differential diagnosis of respiratory and non-respiratory infections.

The inducibility of TNF-alpha production is different in the granulocytic and monocytic differentiated forms of wild type and CGD-mutant PLB-985 cells

Chronic granulomatous disease is an inherited disorder associated with a defect in phagocytic cell oxidative metabolism resulting in ineffective microbicidal activity. Consequently, patients with chronic granulomatous disease suffer from recurrent infections. Published data show that besides the failure to produce superoxide and its derivatives, other functional problems can also be found in chronic granulomatous disease-mutant cells. Since in innate immune responses other mediators, such as cytokines, also play an important role, we hypothesized that there may be a disturbance in cytokine production by chronic granulomatous disease-mutant cells as well. To prove this hypothesis, the production of tumour necrosis factor-alpha, an important proinflammatory cytokine, was determined by enzyme-linked immunosorbent assay in wild-type and chronic granulomatous disease-mutant myelomonoblastic PLB-985 cells in their immature, granulocytic and monocytic/macrophage differentiated forms. Tumour necrosis factor-alpha production was induced with N-formyl-L-methionyl-L-leucyl-L-phenylalanine (100 nmol/L), lipopolysaccharide (10 micro g/mL), opsonized zymosan (100 micro g/mL) or phorbol 12-myristate 13-acetate (100 nmol/L) for 24 h. We could demonstrate that: (i) there were marked differences in tumour necrosis factor-alpha production only in the differentiated forms of both wild-type and chronic granulomatous disease-mutant cells, while there were no differences in the case of their immature counterparts; (ii) only chronic granulomatous disease-mutant cells retained sensitivity to phorbol 12-myristate 13-acetate both in their granulocytic and monocytic forms, although phorbol 12-myristate 13-acetate responsiveness was a characteristic of both types of immature cells; (iii) the granulocytic form of wild-type cells produced tumour necrosis factor-alpha after opsonized zymosan stimulation, but such a response was not observed in cells originating from the chronic granulomatous disease-mutant cell line; (iv) with the monocytic forms, significantly higher tumour necrosis factor-alpha production could be induced by lipopolysaccharide in the wild-type cells than in the chronic granulomatous disease-mutant cells, although there was no difference in their lipopolysaccharide receptor CD14 expression. In summary, these data show an altered inducibility of tumour necrosis factor-alpha production by chronic granulomatous disease-mutant cells. Our observations suggest a further defect in differentiated chronic granulomatous disease-mutant cells in addition to the known defect in reduced nicotinamide adenine dinucleotide phosphate oxidase, which may contribute to the development of susceptibility to infections in people with chronic granulomatous disease.

Mycoplasma synoviae lipoprotein MSPB, the N-terminal part of VlhA haemagglutinin, induces secretion of nitric oxide, IL-6 and IL-1β in chicken macrophages

Mycoplasma synoviae is a major pathogen of chickens and turkeys, causing respiratory disease and infectious synovitis. M. synoviae haemagglutinin VlhA is an abundant surface-exposed lipoprotein and immunodominant antigen. Post-translational cleavage of VlhA generates two proteins, MSPB and MSPA. MSPB, the amino-terminal end of VlhA, is a lipoprotein of about 40-50 kDa but can appear in truncated forms (tMSPB) of about 20-30 kDa. The aim of this study was to determine whether MSPB and tMSPB can stimulate chicken macrophages to secrete NO and cytokines. Macrophages derived from chicken monocytes (MDM) or the MQ-NCSU macrophage cell line were stimulated with M. synoviae protein extracts containing MSPB or tMSPB, as well as with purified MSPB and tMSPB. Proteins from detergent extractions induced IL-6 secretion in MDM and NO secretion in MQ-NCSU. Both MSPB and tMSPB were capable of inducing NO secretion in MQ-NCSU, as well as IL-6 and IL-1beta in MDM. The activity of IL-6 induced by purified tMSPB was similar to the effect of 60 pg/ml of recombinant chicken IL-6. The effect of IL-1beta induced by tMSPB was comparable to the effect of 10 ng/ml of recombinant IL-1beta. Whereas all samples containing MSPB were able to induce NO, IL-6 and IL-1beta, it seemed that the purified tMSPB of about 20 kDa was the most potent in its ability to induce IL-6 and IL-1beta in MDM. Compared to MSPB, tMSPB lacks about 200 amino acids in its carboxyl-terminal part. Therefore, our results suggest that the major part of the stimulating activity is associated with the amino-terminal part of MSPB, most likely with its lipid moiety.

Mycoplasma fermentans and TNF-beta interact to amplify immune-modulating cytokines in human lung fibroblasts

Mycoplasma can establish latent infections and are associated with arthritis, leukemia, and chronic lung disease. We developed an experimental model in which lung cells are deliberately infected with Mycoplasma fermentans. Human lung fibroblasts (HLF) were exposed to live M. fermentans and immune-modulating cytokine release was assessed with and without known inducers of cytokine production. M. fermentans increased IL-6, IL-8/CXCL8, MCP-1/CCL2, and Gro-alpha/CXCL1 production. M. fermentans interacted with TNF-beta to release more IL-6, CXCL8, and CXCL1 than predicted by the responses to either stimulus alone. The effects of live infection were recapitulated by exposure to M. fermentans-derived macrophage-activating lipopeptide-2 (MALP-2), a Toll-like receptor-2- and receptor-6-specific ligand. The synergistic effect of combined stimuli was more pronounced with prolonged incubations. Preexposure to TNF-beta sensitized the cells to subsequent MALP-2 challenge, but preexposure to MALP-2 did not alter the IL-6 response to TNF-beta. Exposure to M. fermentans or MALP-2 did not enhance nuclear localization, DNA binding, or transcriptional activity of NF-kappaB and did not modulate early NF-kappaB activation in response to TNF-beta. Application of specific inhibitors of various MAPKs suggested that p38 and JNK/stress-activated protein kinase were involved in early IL-6 release after exposure to TNF-beta and M. fermentans, respectively. The combined response to M. fermentans and TNF-beta, however, was uniquely sensitive to delayed application of SP-600125, suggesting that JNK/stress-activated protein kinase contributes to the amplification of IL-6 release. Thus M. fermentans interacts with stimuli such as TNF-beta to amplify lung cell production of immune-modulating cytokines. The mechanisms accounting for this interaction can now be dissected with the use of this in vitro model.

Mycoplasma pneumoniae subtype-independent induction of proinflammatory cytokines in THP-1 cells

Mycoplasma pneumoniae can be divided into two main subtypes depending on the amino acid sequences of the P1 adhesin and the P65 protein, both located in the attachment organelle. Differences between these subtypes in infectivity, virulence and interaction with host cells have not been extensively studied. Using ELISA to measure released protein and real-time PCR to quantify mRNA, we have demonstrated that both M. pneumoniae subtypes significantly increased tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6) and interleukin-8 (IL-8) at comparable levels in THP-1 cells over a 72 h period of time. However, subtype 2 induced a statistically significant increase (P<0.001) in the release of interleukin-1beta at 24 h post-infection compared to subtype 1. These data provide evidence that the induction of proinflammatory cytokine gene and protein expression by M. pneumoniae is not dependent on the infecting subtype.

The Sulfogalactose Moiety of Sulfoglycosphingolipids Serves as a Mimic of Tyrosine Phosphate in Many Recognition Processes

Multiple ligand co-recognition of 3'-sulfogalactosylceramide (SGC) and sulfotyrosine initiated the comparison of SGC and sulfotyrosine and, subsequently, phosphotyrosine (pY) binding. SGC is a receptor for ligands involved in cell adhesion/microbial pathology. pY forms a Src homology domain 2 recognition motif in intracellular signaling. Using hsp70, anti-SGC, and anti-pY antibodies, ligand binding is retained following phosphate/sulfate and tyrosine/galactose substitution in SGC and sulfate/phosphate exchange in pY. Remarkable lipid-dependent binding to phosphatidylethanolamine-conjugated sulfotyrosine suggests "microenvironmental" modulation of sulfotyrosine-containing receptors, similar to glycosphingolipids. Based on an aryl substrate-bound co-crystal of arylsulfatase A, a sulfogalactose and phosphotyrosine esterase, modeling provides a solvation basis for co-recognition. c-Src/Src homology domain 2:SGC/phosphogalactosylceramide binding confirms our hypothesis, heralding a carbohydrate-based approach to regulation of phosphotyrosine-mediated recognition.

Microbial stimulation by Mycoplasma fermentans synergistically amplifies IL-6 release by human lung fibroblasts in response to residual oil fly ash (ROFA) and nickel

Mycoplasma (MP), such as the species M. fermentans, possess remarkable immunoregulatory properties and can potentially establish chronic latent infections with little signs of disease. Atmospheric particulate matter (PM) is a complex and diverse component of air pollution associated with adverse health effects. We hypothesized that MP modulate the cellular responses induced by chemical stresses such as residual oil fly ash (ROFA), a type of PM rich in transition metals. We assessed the release of interleukin-6 (IL-6), a prototypic immune-modulating cytokine, in response to PM from different sources in human lung fibroblasts (HLF) deliberately infected with M. fermentans. We found that M. fermentans and ROFA together synergistically stimulated production of IL-6 compared to either stimuli alone. Compared to several other PM, ROFA appeared most able to potentiate IL-6 release. The potentiating effect of live MP infection could be mimicked by M. fermentans-derived macrophage-activating lipopeptide-2 (MALP-2), a known Toll-like receptor-2 agonist. The aqueous fraction of ROFA also contained potent IL-6 inducing activity in concert with MALP-2, and exposure to several defined metal salts indicated that Ni and, to a lesser extent V, (but not Cu) could synergistically act with MALP-2 to induce IL-6. These data indicate that microorganisms like MP can interact with environmental stimuli such as PM-derived metals to synergistically activate signaling pathways that control lung cell cytokine production and, thus, can potentially modulate adverse health effects of PM exposure.

Presence of human mycoplasma DNA in gastric tissue samples from Korean chronic gastritis patients

We aimed to determine whether mycoplasmas are present in Korean chronic gastritis, and to understand their roles in gastric cancer tumorigenesis, because mycoplasmas resemble Helicobacter pylori in terms of ammonia production and induction of inflammatory cytokines in immune and non-immune cells. The presence and identity of mycoplasmas were assessed by semi-nested PCR and sequencing, and the results were compared with pathologic data. Fifty-six samples collected from Korean chronic gastritis patients were used for this study. Twenty-three (41.1%) were positive for mycoplasmas. Eighteen sequenced samples contained a single human mycoplasma or two mycoplasmas, which were identified as Mycoplasma faucium (13/18), M. fermentans (3/18), M. orale (1/18), M. salivarium (2/18), and M. spermatophilum (1/18). Mycoplasma-infected chronic gastritis samples showed significantly more severe neutrophil infiltration than non-infected samples (P = 0.0135). Mycoplasma profiles in the oral cavity (M. salivarium is major) and stomach were different, and the presence of significant proinflammatory responses in mycoplasma-positive patients suggests that the mycoplasmas are not simply contaminants. Further studies are required to understand whether mycoplasmas play a role in gastric tumorigenesis.

Recombinant human heat shock protein 60 does not induce the release of tumor necrosis factor alpha from murine macrophages

Recent studies have shown that commercially available recombinant human heat shock protein 60 (rhHSP60) could induce tumor necrosis factor alpha (TNF-alpha) release from macrophages and monocytes in a manner similar to that of lipopolysaccharide (LPS), e.g. via CD14 and Toll-like receptor 4 complex-mediated signal transduction pathway. In this study, we demonstrated that a highly purified rhHSP60 preparation with low endotoxin activity (designated rhHSP60-1) was unable to induce TNF-alpha release from murine macrophages at concentrations of up to 10 microg/ml. In contrast, a less purified rhHSP60 preparation (designated rhHSP60-2) was able to induce a marked TNF-alpha release at concentrations as low as 1 microg/ml. Failure of rhHSP60-1 to induce TNF-alpha release was not due to defective physical properties because rhHSP60-1 and rhHSP60-2 contained a similar amount of HSP60 as determined by SDS gels stained with Coomassie Blue and Western blots probed with an anti-rhHSP60 antibody. Both rhHSP60 preparations also had similar enzymatic activities as judged by their ability to hydrolyze ATP. Polymyxin B added in the incubation media abolished the endotoxin activity but inhibited only about 50% of the TNF-alpha-inducing activity of rhHSP60-2. However, both the endotoxin activity and the TNF-alpha-inducing activity of rhHSP60-2 were essentially eliminated after passing through a polymyxin B-agarose column that removes LPS and LPS-associated molecules from the rhHSP60 preparation. The TNF-alpha-inducing activities of both rhHSP60-2 and LPS with equivalent endotoxin activity present in rhHSP60-2 were equally sensitive to heat inactivation. These results suggest that rhHSP60 does not induce TNF-alpha release from macrophages. Approximately 50% of the observed TNF-alpha-inducing activity in the rhHSP60-2 preparation is due to LPS contamination, whereas the rest of the activity was due to the contamination of LPS-associated molecule(s).

Identification and functional mapping of the Mycoplasma fermentans P29 adhesin

Initial adherence interactions between mycoplasmas and mammalian cells are important for host colonization and may contribute to subsequent pathogenic processes. Despite significant progress toward understanding the role of specialized, complex tip structures in the adherence of some mycoplasmas, particularly those that infect humans, less is known about adhesins through which other mycoplasmas of this host bind to diverse cell types, even though simpler surface components are likely to be involved. We show by flow cytometric analysis that a soluble recombinant fusion protein (FP29), representing the abundant P29 surface lipoprotein of Mycoplasma fermentans, binds human HeLa cells and inhibits M. fermentans binding to these cells, in both a quantitative and a saturable manner, whereas analogous fusion proteins representing other mycoplasma surface proteins did not. Constructs representing nested N- or C-terminal truncations of FP29 allowed initial mapping of this specific adherence function to a central region of the P29 sequence containing a 36-amino-acid disulfide loop. A derivative of FP29 containing a mutation converting one participating Cys to Ser, precluding intrachain disulfide bond formation, retained full activity. Together these results suggest that the direct interaction of M. fermentans with a ligand on the HeLa cell surface involves a limited segment of the P29 surface lipoprotein and requires neither the disulfide bond nor the contribution of adjacent portions of the protein. Earlier results indicating phase-variable display of monoclonal antibody surface epitopes on P29, now recognized to be outside this ligand binding region, raise the possibility that variation of mycoplasma surface architecture might alter the presentation of the binding region and the adherence phenotype. Preliminary results further indicated that FP29 could inhibit binding to HeLa cells by Mycoplasma hominis, a distinct human mycoplasma species displaying the phase-variable adhesin Vaa, but not that by Mycoplasma capricolum, an organism infecting caprine species. This result raises the additional, testable possibility that a common host cell ligand for two human mycoplasma species may be recognized through structurally dissimilar adhesins that undergo phase variation by two distinct mechanisms, governing protein expression (Vaa) or surface masking (P29).

Regulation of proinflammatory cytokines in human lung epithelial cells infected with Mycoplasma pneumoniae

Mycoplasma pneumoniae is a small bacterium without a cell wall that causes tracheobronchitis and atypical pneumonia in humans. It has also been associated with chronic conditions, such as arthritis, and extrapulmonary complications, such as encephalitis. Although the interaction of mycoplasmas with respiratory epithelial cells is a critical early phase of pathogenesis, little is known about the cascade of events initiated by infection of respiratory epithelial cells by mycoplasmas. Previous studies have shown that M. pneumoniae can induce proinflammatory cytokines in several different study systems including cultured murine and human monocytes. In this study, we demonstrate that M. pneumoniae infection also induces proinflammatory cytokine expression in A549 human lung carcinoma cells. Infection of A549 cells resulted in increased levels of interleukin-8 (IL-8) and tumor necrosis factor alpha mRNA, and both proteins were secreted into culture medium. IL-1 beta mRNA also increased after infection and IL-1 beta protein was synthesized, but it remained intracellular. In contrast, levels of IL-6 and gamma interferon mRNA and protein remained unchanged or undetectable. Using protease digestion and antibody blocking methods, we found that M. pneumoniae cytoadherence is important for the induction of cytokines. On the other hand, while M. pneumoniae protein synthesis and DNA synthesis do not appear to be prerequisites for the induction of cytokine gene expression, A549 cellular de novo protein synthesis is responsible for the increased cytokine protein levels. These results suggest a novel role for lung epithelial cells in the pathogenesis of M. pneumoniae infection and provide a better understanding of M. pneumoniae pathology at the cellular level.

The macrophage inflammatory protein-1beta in the supernatants of Mycoplasma gallisepticum-infected chicken leukocytes attracts the migration of chicken heterophils and lymphocytes

Chicken monocytes, macrophages, heterophils and thrombocytes were infected with Mycoplasma gallisepticum, and their supernatants were collected and tested for the presence of chemotactic activities. The supernatants from MG-infected monocytes and macrophages were able to attract the migration of both heterophils and lymphocytes. The chemotactic activity in these supernatants could be abolished by antibodies prepared against the 10 amino acid peptides of the macrophage inflammatory protein (MIP)-1beta, indicating that the released chemoattractant was a MIP-1beta-like compound. The supernatant from MG-infected heterophils was also able to attract the migration of chicken lymphocytes, but its activity could not be neutralized by the antibody to MIP-1beta, indicating that the chemoattractant is not related to MIP-1beta. The supernatants from both control and MG-infected thrombocytes were able to attract the migration of lymphocytes. These results indicate that there is more than one chemotactic factor that is released by these cells; one of the chemoattractants has been identified as a MIP-1beta. These results also show that MIP-1beta may play a role in the recruitment and accumulation of heterophils and lymphocytes to the sites of mycoplasma infection.

Escherichia coli Braun lipoprotein induces a lipopolysaccharide-like endotoxic response from primary human endothelial cells

All bacteria contain proteins in which their amino-terminal cysteine residue is modified with N-acyl S-diacylglycerol functions, and peptides and proteins bearing this modification are immunomodulatory. The major outer membrane lipoprotein of Escherichia coli, the Braun lipoprotein (BLP), is the prototypical triacylated cysteinyl-modified protein. We find it is as active as LPS in stimulating human endothelial cells to an inflammatory phenotype, and a BLP-negative mutant of E. coli was less inflammatory than its parental strain. While the lipid modification was essential, the lipidated protein was more potent than a lipid-modified peptide. BLP associates with CD14, but this interaction, unlike that with LPS, was not required to elicit endothelial cell activation. BLP stimulated endothelial cell E-selectin surface expression, IL-6 secretion, and up-regulation of the same battery of cytokine mRNAs induced by LPS. Quantitative microarray analysis of 4400 genes showed the same 30 genes were induced by BLP and LPS, and that there was near complete concordance in the level of gene induction. We conclude that the lipid modification of at least one abundant Gram-negative protein is essential for endotoxic activity, but that the protein component also influences activity. The equivalent potency of BLP and LPS, and their complete concordance in the nature and extent of endothelial cell activation show that E. coli endotoxic activity is not due to just LPS. The major outer membrane protein of E. coli is a fully active endotoxic agonist for endothelial cells.

Genetic and biochemical characterization of glycerol uptake in mycoplasma mycoides subsp. mycoides SC: its impact on H(2)O(2) production and virulence

Highly virulent strains of Mycoplasma mycoides subsp. mycoides SC belonging to the African cluster contain an operon with the genes gtsA, gtsB, and gtsC, encoding membrane ATP binding cassette transporter proteins GtsA, GtsB, and GtsC, which are involved in glycerol transport. Strain Afadé from the African cluster incorporated [U-(14)C]glycerol with a time-dependent increase. The less virulent strain L2 of the European cluster, which lacks gtsB and gtsC, failed to incorporate glycerol. Antibodies against GtsB noncompetitively inhibited glycerol uptake. L-alpha-Glycerophosphate was not transported by M. mycoides subsp. mycoides SC. It is postulated to be synthesized by phosphorylation of glycerol during transport and subsequently metabolized further to dihydroxyacetone phosphate accompanied by release of H(2)O(2). Peroxide production in glycerol-containing growth medium was high for the African strain Afadé but very low for the European strain L2. Virtually no H(2)O(2) was produced by both strains without glycerol. Hence, the efficient glycerol uptake system found in the virulent strain of the African cluster leads to a strong release of peroxide, a potential virulence factor which is lacking in the less virulent European strains. M. mycoides subsp. mycoides SC might have adopted, as a strategy for virulence, a highly efficient uptake system for glycerol which allows the production of an active metabolic intermediate that damages host cells.

Mycoplasma fermentans interaction with monocytes/macrophages: molecular basis

Mycoplasmas are the smallest free-living self-replicating bacteria - having diameters of 200 to 800 nm - widely distributed in animals and plants. Mycoplasma fermentans is a human pathogen suspected to be involved in the progression of autoimmune diseases. Although pathogenesis mechanisms of M. fermentans are currently poorly understood, the role of these microorganisms as immunomodulatory agents is well established. In the present paper, we will review and discuss recent breakthroughs in the field.

Genomic and antigenic differences between the European and African/Australian clusters of Mycoplasma mycoides subsp. mycoides SC

Mycoplasma mycoides subsp. mycoides small-colony type (SC), the aetiological agent of contagious bovine pleuropneumonia (CBPP), can be grouped into two major, epidemiologically distinct, clusters. One cluster contains strains isolated from different European countries since 1980 and a second cluster contains African and Australian strains collected over the last 50 years. Genetic analysis of representative strains from the two clusters revealed a genomic segment of 8.84 kb, located close to a copy of IS1296, which is present in all strains of the African cluster but lacking in all strains of the European cluster. This segment contains a copy of IS1634, a gene for a potential lipoprotein, IppB, open reading frames encoding a putative surface-located membrane protein and a hypothetical proline-rich membrane protein, and two open reading frames showing similarity to putative ABC transporters. The product of the IppB gene, lipoprotein B (LppB), has an apparent molecular mass of 70 kDa and was shown to be surface located. It is detected with monospecific antibodies in all strains of the African cluster tested, but not in European-cluster strains. DNA sequence analysis of the splicing site at which European strains differ from African-cluster strains by the lack of the 8.84 kb segment showed that the European cluster has arisen by deletion from a strain of the African cluster. Hence, M. mycoides subsp. mycoides SC strains isolated in different European countries from the newly reemerging outbreaks of CBPP, which occurred after the eradication of the epizootic in Europe in the middle of the 20th century, represent a phylogenetically newer cluster that has been derived from a strain of the older cluster of M. mycoides subsp. mycoides SC which is still endemic on the African continent.

Effect of MALP-2, a lipopeptide from Mycoplasma fermentans, on bone resorption in vitro

Mycoplasmas may be associated with rheumatoid arthritis in various animal hosts. In humans, mycoplasma arthritis has been recorded in association with hypogammaglobulinemia. Mycoplasma fermentans is one mycoplasma species considered to be involved in causing arthritis. To clarify which mycoplasmal compounds contribute to the inflammatory, bone-destructive processes in arthritis, we used a well-defined lipopeptide, 2-kDa macrophage-activating lipopeptide (MALP-2) from M. fermentans, as an example of a class of macrophage-activating compounds ubiquitous in mycoplasmas, to study its effects on bone resorption. MALP-2 stimulated osteoclast-mediated bone resorption in murine calvaria cultures, with a maximal effect at around 2 nM. Anti-inflammatory drugs inhibited MALP-2-mediated bone resorption by about 30%. This finding suggests that MALP-2 stimulates bone resorption partially by stimulating the formation of prostaglandins. Since interleukin-6 (IL-6) stimulates bone resorption, we investigated IL-6 production in cultured calvaria. MALP-2 stimulated the liberation of IL-6, while no tumor necrosis factor was detectable. Additionally, MALP-2 stimulated low levels of NO in calvaria cultures, an effect which was strongly increased in the presence of gamma interferon, causing an inhibition of bone resorption. MALP-2 stimulated the bone-resorbing activity of osteoclasts isolated from long bones of newborn rats and cultured on dentine slices without affecting their number. In bone marrow cultures, MALP-2 inhibited the formation of osteoclasts. It appears that MALP-2 has two opposing effects: it increases the bone resorption in bone tissue by stimulation of mature osteoclasts but inhibits the formation of new ones.

Induction of cytokines and chemokines in human monocytes by Mycoplasma fermentans-derived lipoprotein MALP-2

Bacterial infections are characterized by strong inflammatory reactions. The responsible mediators are often bacterially derived cell wall molecules, such as lipopolysaccharide or lipoteichoic acids, which typically stimulate monocytes and macrophages to release a wide variety of inflammatory cytokines and chemokines. Mycoplasmas, which lack a cell wall, may also stimulate monocytes very efficiently. This study was performed to identify mycoplasma-induced mediators. We investigated the induction of cytokines and chemokines in human monocytes exposed to the Mycoplasma fermentans-derived membrane component MALP-2 (macrophage-activating lipopeptide 2) by dose response and kinetic analysis. We found a rapid and strong MALP-2-inducible chemokine and cytokine gene expression which was followed by the release of chemokines and cytokines with peak levels after 12 to 20 h. MALP-2 induced the neutrophil-attracting CXC chemokines interleukin-8 (IL-8) and GRO-alpha as well as the mononuclear leukocyte-attracting CC chemokines MCP-1, MIP-1alpha, and MIP-1beta. Production of the proinflammatory cytokines tumor necrosis factor alpha and IL-6 started at the same time as chemokine release but required 10- to 100-fold-higher MALP-2 doses. The data show that the mycoplasma-derived lipopeptide MALP-2 represents a potent inducer of chemokines and cytokines which may, by the attraction and activation of neutrophils and mononuclear leukocytes, significantly contribute to the inflammatory response during mycoplasma infection.

Interactions between mycoplasma lipoproteins and the host immune system

Mycoplasmas typically have a number of distinct lipoproteins anchored on the outer face of the plasma membrane. These surface antigens have a potent modulin activity and are preferential targets of the host immune response. However, the variation of some of these lipoproteins provides mycoplasmas with an effective means of evading the host immune defence system.

Involvement of small GTPases in Mycoplasma fermentans membrane lipoproteins-mediated activation of macrophages

Mycoplasma fermentans lipoproteins (LAMPf) are capable of activating macrophages and inducing the secretion of proinflammatory cytokines. We have recently reported that mitogen-activated protein kinase (MAPK) pathways and NF-kappaB and activated protein 1 (AP-1) play a crucial role in the activation induced by this bacterial compound. To further elucidate the mechanisms by which LAMPf mediate the activation of macrophages, we assessed the effects of inhibiting small G proteins Rac, Cdc42, and Rho. The Rho-specific inhibitor C3 enzyme completely abolished the secretion of tumor necrosis factor alpha by macrophages stimulated with LAMPf and also inhibited the activation of extracellular signal-regulated kinase (ERK), c-Jun NH(2)-terminal kinase (JNK), and p38 kinase. In addition, we have shown that LAMPf stimulate Cdc42 and that inhibition of Cdc42 or Rac by dominant negative mutants abrogates LAMPf-mediated activation of JNK and transactivation of NF-kappaB and AP-1 in the murine macrophage cell line RAW 264.7. These results indicate that small G proteins Rho, Cdc42, and Rac are involved in the cascade of events leading to the macrophage activation by mycoplasma lipoproteins.