Mycoplasma arginini TUH-14 membrane lipoproteins induce production of interleukin-1, interleukin-6, and tumor necrosis factor alpha by human monocytes

Interaction between alveolar macrophages and epithelial cells during Mycoplasma pneumoniae infection

Mycoplasma pneumoniae, as one of the most common pathogens, usually causes upper respiratory tract infections and pneumonia in humans and animals. It accounts for 10% to 40% of community-acquired pneumonia in children. The alveolar epithelial cells (AECs) are the first barrier against pathogen infections, triggering innate immune responses by recruiting and activating immune cells when pathogens invade into the lung. Alveolar macrophages (AMs) are the most plentiful innate immune cells in the lung, and are the first to initiate immune responses with pathogens invasion. The cross-talk between the alveolar epithelium and macrophages is necessary to maintain physiological homeostasis and to eradicate invaded pathogen by regulating immune responses during Mycoplasma pneumoniae infections. This review summarizes the communications between alveolar macrophages and epithelial cells during Mycoplasma pneumoniae infections, including cytokines-medicated communications, signal transduction by extracellular vesicles, surfactant associated proteins-medicated signal transmission and establishment of intercellular gap junction channels.

TLR2 agonists and their structure–activity relationships

We review the structure–activity relationships and synthetic studies of TLR2 agonists – important chemical targets in immunotherapy.

Vaccination of cattle with the N terminus of LppQ of Mycoplasma mycoides subsp. mycoides results in type III immune complex disease upon experimental infection

Contagious bovine pleuropneumonia (CBPP) is a serious respiratory disease of cattle caused by Mycoplasma mycoides subsp. mycoides. Current vaccines against CBPP induce short-lived immunity and can cause severe postvaccine reactions. Previous studies have identified the N terminus of the transmembrane lipoprotein Q (LppQ-N') of M. mycoides subsp. mycoides as the major antigen and a possible virulence factor. We therefore immunized cattle with purified recombinant LppQ-N' formulated in Freund's adjuvant and challenged them with M. mycoides subsp. mycoides. Vaccinated animals showed a strong seroconversion to LppQ, but they exhibited significantly enhanced postchallenge glomerulonephritis compared to the placebo group (P = 0.021). Glomerulonephritis was characterized by features that suggested the development of antigen-antibody immune complexes. Clinical signs and gross pathological scores did not significantly differ between vaccinated and placebo groups. These findings reveal for the first time the pathogenesis of enhanced disease as a result of antibodies against LppQ during challenge and also argue against inclusion of LppQ-N' in a future subunit vaccine for CBPP.

Exosomes released from Mycoplasma infected tumor cells activate inhibitory B cells

Mycoplasmas cause numerous human diseases and are common opportunistic pathogens in cancer patients and immunocompromised individuals. Mycoplasma infection elicits various host immune responses. Here we demonstrate that mycoplasma-infected tumor cells release exosomes (myco+ exosomes) that specifically activate splenic B cells and induce splenocytes cytokine production. Induction of cytokines, including the proinflammatory IFN-γ and the anti-inflammatory IL-10, was largely dependent on the presence of B cells. B cells were the major IL-10 producers. In splenocytes from B cell deficient μMT mice, induction of IFN-γ+ T cells by myco+ exosomes was greatly increased compared with wild type splenocytes. In addition, anti-CD3-stimulated T cell proliferation was greatly inhibited in the presence of myco+ exosome-treated B cells. Also, anti-CD3-stimulated T cell signaling was impaired by myco+ exosome treatment. Proteomic analysis identified mycoplasma proteins in exosomes that potentially contribute to the effects. Our results demonstrate that mycoplasma-infected tumor cells release exosomes carrying mycoplasma components that preferentially activate B cells, which in turn, are able to inhibit T cell activity. These results suggest that mycoplasmas infecting tumor cells can exploit the exosome pathway to disseminate their own components and modulate the activity of immune cells, in particular, activate B cells with inhibitory activity.

CBLB613: a TLR 2/6 agonist, natural lipopeptide of Mycoplasma arginini , as a novel radiation countermeasure

To date, there are no safe and effective drugs available for protection against ionizing radiation damage. Therefore, a great need exists to identify and develop non-toxic agents that will be useful as radioprotectors or postirradiation therapies under a variety of operational scenarios. We have developed a new pharmacological agent, CBLB613 (a naturally occurring Mycoplasma-derived lipopeptide ligand for Toll-like receptor 2/6), as a novel radiation countermeasure. Using CD2F1 mice, we investigated CBLB613 for toxicity, immunogenicity, radioprotection, radiomitigation and pharmacokinetics. We also evaluated CBLB613 for its effects on cytokine induction and radiation-induced cytopenia in unirradiated and irradiated mice. The no-observable-adverse-effect level of CBLB613 was 1.79 mg/kg and 1 mg/kg for single and repeated doses, respectively. CBLB613 significantly protected mice against a lethal dose of (60)Co γ radiation. The dose reduction factor of CBLB613 as a radioprotector was 1.25. CBLB613 also mitigated the effects of (60)Co γ radiation on survival in mice. In both irradiated and unirradiated mice, the drug stimulated induction of interleukin-1β (IL-1β), IL-6, IL-10, IL-12, keratinocyte-derived chemokine, granulocyte colony-stimulating factor, granulocyte-macrophage colony-stimulating factor, and tumor necrosis factor-1α. CBLB613 also reduced radiation-induced cytopenia and increased bone marrow cellularity in irradiated mice. Our immunogenicity study demonstrated that CBLB613 is not immunogenic in mice, indicating that it could be developed as a radioprotector and radiomitigator for humans against the potentially lethal effects of radiation exposure.

Mycoplasma bovis pneumonia in cattle

Mycoplasma bovis is an important and emerging cause of respiratory disease and arthritis in feedlot cattle and young dairy and veal calves, and has a variety of other disease manifestations in cattle. M. bovis is certainly capable of causing acute respiratory disease in cattle, yet the attributable fraction has been difficult to estimate. In contrast, M. bovis is more accepted as a cause of chronic bronchopneumonia with caseous and perhaps coagulative necrosis, characterized by persistent infection that seems poorly responsive to many antibiotics. An understanding of the disease has been recently advanced by comparisons of natural and experimentally induced disease, development of molecular diagnostic tools, and understanding some aspects of virulence, yet uncertainties regarding protective immunity, the importance of genotypic diversity, mechanisms of virulence, and the role of co-pathogens have restricted our understanding of pathogenesis and our ability to effectively control the disease. This review critically considers the relationship between M. bovis infection and the various manifestations of the bovine respiratory disease complex, and addresses the pathogenesis, clinical and pathologic sequelae, laboratory diagnosis and control of disease resulting from M. bovis infection in the bovine respiratory tract.

Mycoplasma genitalium-derived lipid-associated membrane proteins induce activation of MAPKs, NF-kappaB and AP-1 in THP-1 cells

Mycoplasma genitalium lipid-associated membrane proteins (LAMPg) can induce human monocytic cell line THP-1 to produce proinflammatory cytokines, including tumor necrosis factor-alpha (TNF-alpha), IL-1beta and IL-6, as demonstrated by an enzyme-linked immunosorbent assay and reverse transcription-PCR (RT-PCR). This study also investigated the signaling transduction pathways involved in the production of these cytokines. THP-1 cells were stimulated with LAMPg and then examined for the activation of MAPKs, such as SAPK/JNK, p38, extracellular signal-regulated kinase (ERK)1/2 and NF-kappaB and AP-1. Western blot clearly showed that stress-activated protein kinase (SAPK)/c-Jun-N-terminal kinase (JNK), p38 and ERK1/2 were activated in response to LAMPg, peaking at 30 min. SAPK/JNK-specific inhibitor SP600125 slightly suppressed IL-6 production although no evident effects were obtained for TNF-alpha and IL-1beta; ERK1/2 inhibitor PD98059 blocked both TNF-alpha and IL-1beta, but not IL-6 production. However, p38 inhibitor SB203580 abrogated TNF-alpha, IL-1beta and IL-6 production. The DNA-binding activity of NF-kappaB and AP-1 was also assessed by an electrophoretic mobility gel shift assay, and an NF-kappaB specific inhibitor, pyrrolidine dithiocarbamate, profoundly inhibited the synthesis and production of the proinflammatory cytokines. Based on these results, this study concludes that MAPKs, NF-kappaB and AP-1 may play important roles in the genital tract inflammatory reaction after mycoplasma infection.

Domain analysis of lipoprotein LppQ in Mycoplasma mycoides subsp. mycoides SC

The lipoprotein LppQ is the most prominent antigen of Mycoplasma mycoides subsp. mycoides small colony type (SC) during infection of cattle. This pathogen causes contagious bovine pleuropneumonia (CBPP), a devastating disease of considerable socio-economic importance in many countries worldwide. The dominant antigenicity and high specificity for M. mycoides subsp. mycoides SC of lipoprotein LppQ have been exploited for serological diagnosis and for epidemiological investigations of CBPP. Scanning electron microscopy and immunogold labelling were used to provide ultrastructural evidence that LppQ is located to the cell membrane at the outer surface of M. mycoides subsp. mycoides SC. The selectivity and specificity of this method were demonstrated through discriminating localization of extracellular (i.e., in the zone of contact with host cells) vs. integral membrane domains of LppQ. Thus, our findings support the suggestion that the accessible N-terminal domain of LppQ is surface exposed and such surface localization may be implicated in the pathogenesis of CBPP.

Molecular mechanisms of pathogenicity of Mycoplasma mycoides subsp. mycoides SC

Mycoplasma mycoides subsp. mycoides SC, the aetiological agent of contagious bovine pleuropneumonia (CBPP), is considered the most pathogenic of the Mycoplasma species. Its virulence is probably the result of a coordinated action of various components of an antigenically and functionally dynamic surface architecture. The different virulence attributes allow the pathogen to evade the host's immune defence, adhere tightly to the host cell surface, persist and disseminate in the host causing mycoplasmaemia, efficiently import energetically valuable nutrients present in the environment, and release and simultaneously translocate toxic metabolic pathway products to the host cell where they cause cytotoxic effects that are known to induce inflammatory processes and disease. This strategy enables the mycoplasma to exploit the minimal genetic information in its small genome, not only to fulfil the basic functions for its replication but also to damage host cells in intimate proximity thereby acquiring the necessary bio-molecules, such as amino acids and nucleic acid precursors, for its own biosynthesis and survival.

Beta-D-glucoside utilization by Mycoplasma mycoides subsp. mycoides SC: possible involvement in the control of cytotoxicity towards bovine lung cells

Background

Contagious bovine pleuropneumonia (CBPP) caused by Mycoplasma mycoides subsp. mycoides small-colony type (SC) is among the most serious threats for livestock producers in Africa. Glycerol metabolism-associated H₂O₂ production seems to play a crucial role in virulence of this mycoplasma. A wide number of attenuated strains of M. mycoides subsp. mycoides SC are currently used in Africa as live vaccines. Glycerol metabolism is not affected in these vaccine strains and therefore it does not seem to be the determinant of their attenuation. A non-synonymous single nucleotide polymorphism (SNP) in the bgl gene coding for the 6-phospho-β-glucosidase (Bgl) has been described recently. The SNP differentiates virulent African strains isolated from outbreaks with severe CBPP, which express the Bgl isoform Val₂₀₄, from strains to be considered less virulent isolated from CBPP outbreaks with low mortality and vaccine strains, which express the Bgl isoform Ala₂₀₄.

Results

Strains of M. mycoides subsp. mycoides SC considered virulent and possessing the Bgl isoform Val₂₀₄, but not strains with the Bgl isoform Ala₂₀₄, do trigger elevated levels of damage to embryonic bovine lung (EBL) cells upon incubation with the disaccharides (i.e., β-D-glucosides) sucrose and lactose. However, strains expressing the Bgl isoform Val₂₀₄ show a lower hydrolysing activity on the chromogenic substrate p-nitrophenyl-β-D-glucopyranoside (pNPbG) when compared to strains that possess the Bgl isoform Ala₂₀₄. Defective activity of Bgl in M. mycoides subsp. mycoides SC does not lead to H₂O₂ production. Rather, the viability during addition of β-D-glucosides in medium-free buffers is higher for strains harbouring the Bgl isoform Val₂₀₄ than for those with the isoform Ala₂₀₄.

Conclusion

Our results indicate that the studied SNP in the bgl gene is one possible cause of the difference in bacterial virulence among strains of M. mycoides subsp. mycoides SC. Bgl does not act as a direct virulence factor, but strains possessing the Bgl isoform Val₂₀₄ with low hydrolysing activity are more prone to survive in environments that contain high levels of β-D-glucosides, thus contributing in some extent to mycoplasmaemia.

Biofilm formation by mycoplasma species and its role in environmental persistence and survival

Although mycoplasmas possess a very limited genome, little is known about their virulence mechanisms and methods of persistence in the host. Examination of a wide range of mycoplasma species found considerable variation in their ability to form a biofilm. Mycoplasma putrefaciens, M. cottewii, M. yeatsii, M. agalactiae and M. bovis produced prolific biofilms. Conversely, the highly pathogenic mycoplasma and causative agent of contagious bovine pleuropneumonia, Mycoplasma mycoides subsp. mycoides SC, was unable to produce a biofilm. Biofilms were found to be considerably more resistant to stress, including heat and desiccation, than planktonic cells. A link between the biofilm phenotype and genotype as determined by molecular typing was found for M. bovis. Analysis of biofilms using fluorescent staining combined with confocal microscopy demonstrated that mycoplasma biofilms formed a highly differentiated structure with stacks and channels. Biofilm formation may indicate that mycoplasmas are capable of surviving in the environment.

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.

Expression of inflammatory cytokines in pigs experimentally infected with Mycoplasma hyopneumoniae

The expression of interleukin-1 (IL-1), tumour necrosis factor-alpha (TNF-alpha) and IL-6 were studied over a period of 35 days in the lungs of pigs experimentally infected with Mycoplasma hyopneumoniae, by semiquantitative reverse transcription-polymerase chain reaction (RT-PCR), morphometric analysis and in-situ hybridization. Fifteen colostrum-deprived pigs aged 14 days were inoculated intranasally with M. hyopneumoniae. IL-1, TNF-alpha and IL-6 were detected by RT-PCR in the lungs of the infected pigs from 7 days post-inoculation (dpi) onwards, but not in the uninfected control pigs. Concurrent expression of all three cytokines was always observed, in association with lung lesions. Inflammatory cytokine-positive cells were detected in the lungs at 7 dpi, their number increasing at 21dpi, and decreasing thereafter. The results suggest that such cytokines play a role in mediating and regulating inflammation in M. hyopneumoniae infection.

Interaction of mycoplasmas with host cells

The mycoplasmas form a large group of prokaryotic microorganisms with over 190 species distinguished from ordinary bacteria by their small size, minute genome, and total lack of a cell wall. Owing to their limited biosynthetic capabilities, most mycoplasmas are parasites exhibiting strict host and tissue specificities. The aim of this review is to collate present knowledge on the strategies employed by mycoplasmas while interacting with their host eukaryotic cells. Prominant among these strategies is the adherence of mycoplasma to host cells, identifying the mycoplasmal adhesins as well as the mammalian membrane receptors; the invasion of mycoplasmas into host cells including studies on the role of mycoplasmal surface molecules and signaling mechanisms in the invasion; the fusion of mycoplasmas with host cells, a novel process that raises intriguing questions of how microinjection of mycoplasma components into eukaryotic cells subvert and damage the host cells. The observations of diverse interactions of mycoplasmas with cells of the immune system and their immunomodulatory effects and the discovery of genetic systems that enable mycoplasmas to rapidly change their surface antigenic composition have been important developments in mycoplasma research over the past decade, showing that mycoplasmas possess an impressive capability of maintaining a dynamic surface architecture that is antigenically and functionally versatile, contributing to the capability of the mycoplasmas to adapt to a large range of habitats and cause diseases that are often chronic in nature.

Opposing roles of activator protein-1 and CCAAT/enhancer binding protein beta in the regulation of inducible granulysin gene expression in a human monocytic cell line, THP-1

We previously reported that inducible granulysin gene expression in a human monocytic cell line, THP-1 is dominantly dependent on transcription factor activator protein-1 (AP-1). Here, we further examined the precise regulatory mechanisms underlying granulysin gene expression using THP-1 cells treated with Acholeplasma laidlawii. Transfection of reporter gene constructs into THP-1 cells indicated that the presence of a positive regulatory element(s) is located from -329 to -85 base pairs, containing two distinct AP-1 binding sites and one nuclear factor-kappaB (NF-kappaB) binding site. Deletion or mutation of the NF-kappaB binding site failed to affect inducible promoter activity, whereas deletion or mutation of both the AP-1 binding sites abrogated the promoter activity. Interestingly, deletion of the putative CCAAT/enhancer binding protein beta (C/EBPbeta) binding site upstream of the positive regulatory element induced the augmentation of granulysin promoter activity. Electrophoretic mobility shift assays demonstrated that nuclear extract prepared from A. laidlawii-treated THP-1 cells generated a specific binding to oligonucleotides, including AP-1, C/EBPbeta, and NF-kappaB element. Furthermore, over-expression of liver-enriched transcriptional activator protein, a subunit of C/EBPbeta, augmented A. laidlawii-induced granulysin promoter activity, whereas over-expression of liver-enriched transcriptional inhibitory protein inhibited the promoter activity. NF-kappaB p50 homodimer had no transactivation property, although it bound to the NF-kappaB site. These results indicate that AP-1 and C/EBPbeta, but not NF-kappaB participate in the regulation of inducible granulysin gene expression in THP-1 cells. Moreover, the Toll-like receptor 2-dependent signalling pathway may be involved in A. laidlawii-induced transactivation of the granulysin promoter. Thus, these results suggest that the gene expression of granulysin in macrophages would be exquisitely regulated by positive and negative transcription factors when microbial invasion occurs.

Essential roles of CD14 and lipopolysaccharide-binding protein for activation of toll-like receptor (TLR)2 as well as TLR4 Reconstitution of TLR2- and TLR4-activation by distinguishable ligands in LPS preparations

Although genetic studies have revealed a critical role for the toll-like receptor (TLR) 4 in the biological response to lipopolysaccharide (LPS), the activities of ectopically expressed TLR4 and TLR2 are controversial. We have found that under appropriate transfection conditions, both TLR2 and TLR4 mediate LPS-induced NF-kappaB activation in human embryonic kidney 293 cells. The reconstitution systems we established here allow direct biochemical characterization and comparison of activation of each receptor. TLR4 is approximately 100-fold more sensitive to LPS than TLR2. In contrast to the response to commercial LPS preparations, TLR2 is unresponsive to repurified LPS or synthetic lipid A, indicating the requirement for an additional molecule(s). On the other hand, a lipid A-neutralizing reagent, polymyxin B, blocks the ability of the LPS preparation to stimulate both receptors, suggesting that lipid A is also involved in the activation of TLR2. Mutant TLRs harboring a point mutation in the cytoplasmic domain is inactive in transducing the signal upon stimulation, and act as dominant-negative mutants specifically inhibiting the activation of corresponding type of the receptor but not the other type. Thus, the two receptors are independently activated by distinguishable ligands. Nevertheless, the responses of both TLRs to the LPS preparation are strongly dependent on serum and CD14 and LPS-binding protein are essential for the activation of both of the two receptors. Supporting its functional significance, both receptors are found to associate with CD14.

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.

Role of porin of Shigella dysenteriae type 1 in modulation of lipopolysaccharide mediated nitric oxide and interleukin-1 release by murine peritoneal macrophages

The ability of Shigella dysenteriae type 1 porin to induce the release of nitric oxide (NO) and interleukin-1 (IL-1) from peritoneal macrophages of mouse and to regulate lipopolysaccharide (LPS) and gamma interferon (IFN-gamma) mediated release of the two proinflammatory mediators was investigated. Porin released nitrite when added to macrophage cultures. A maximum of 3.2-fold nitrite release by macrophages was observed with 100 ng ml(-1) of porin. The nitrite release of LPS was enhanced significantly by lower concentrations of porin, whereas the effect of IFN-gamma was enhanced by porin at higher concentrations. Polysaccharide (PS) moiety of LPS stimulated the nitrite release of elicited macrophages by 1.6-fold compared to untreated control. It also enhanced the stimulatory effect of 1 and 10 ng ml(-1) of porin by 1.3-fold. Lipid A (LPA) moiety of LPS did not release nitrite, nor did it increase the porin mediated nitrite production. Porin treated 24 h old macrophage culture supernatants were applied for ConA activated thymocyte proliferation as a measure for determination of IL-1 release. Sixty percent depletion of thymocyte proliferation was observed when the porin treated macrophage supernatants were absorbed with anti-IL-1 antibody. A maximum of 5.5-fold increase of thymocyte proliferation over control was found with 1 and 10 ng ml(-1) of porin. One or 10 ng ml(-1) of porin and LPS augmented the thymocyte growth, 1.5-fold beyond that obtained by porin and 1.8-/1. 7-fold more than that obtained by LPS, alone. Similarly, porin and IFN-gamma co-stimulated the cell growth also. PS enhanced the thymocyte proliferation by 5-fold. It also enhanced the thymocyte growth by co-stimulating 1.4-fold the effect observed by 1 or 10 ng ml(-1) of porin alone. LPA could not participate in the cell proliferating activity nor did it enhance the stimulatory effect of porin. Therefore, both nitrite release and thymocyte proliferation by LPS could be substituted by PS only. The tight association of the two bacterial outer membrane components, porin and LPS, could be a necessary co-signal for boosting the release of the two proinflammatory mediators, namely NO and IL-1, which may be associated with the inflammatory response of the colon during Shigella invasion.

Antigenic and genetic characterization of lipoprotein LppQ from Mycoplasma mycoides subsp. mycoides SC

Lipoprotein LppQ, a predominant 48-kDa antigen, and its corresponding gene, lppQ, were characterized in Mycoplasma mycoides subsp. mycoides SC, the etiological agent of contagious bovine pleuropneumonia. The lppQ gene is specific to M. mycoides subsp. mycoides SC and was found in the type strain and in field strains isolated in Europe, Africa, and Australia, as well as in vaccinal strains. LppQ is encoded as a precursor with a consensus sequence for prokaryotic signal peptidase II and a lipid attachment site. The leader sequence shows significant prominent transmembrane helix structure with a predicted outside-to-inside helix formation capacity. The N-terminal domain of the mature LppQ was shown to be surface exposed. It induced a strong, specific, early, and persistent immune response in naturally and experimentally infected animals. The C-terminal domain of LppQ possesses an integral membrane structure built up of repeated units, rich in hydrophobic and aromatic amino acids, which have a pore formation potential. A recombinant peptide representing the N-terminal domain of LppQ was obtained by site-directed mutagenesis of nine Mycoplasma-specific TGA (Trp) codons into universal TGG (Trp) codons and expression in Escherichia coli hosts. It was used for serodetection of cattle infected with M. mycoides subsp. mycoides SC, in which it was detected postinfection for significantly longer than conventional serological test reactions.

Induction of leukemia cell differentiation and apoptosis by recombinant P48, a modulin derived from Mycoplasma fermentans

P48 is a 48-kDa monocytic differentiation/activation factor which was originally identified in the conditioned medium of the Reh and other leukemia cell lines and has recently been shown to be a Mycoplasma fermentans gene product. Previously, conditioned medium P48 has been shown to induce differentiation of HL-60 (human promyelocytic leukemia) cells. Recently our laboratory isolated cDNA clones for P48 from Reh cells and genomic clones from Mycoplasma fermentans and expressed the recombinant protein as a maltose binding protein (MBP) fusion protein in E. coli. In this report we present the initial characterization of this recombinant P48 fusion protein (rP48-MBP). We show that rP48-MBP induces differentiation of HL-60, U937 (human histiocytic lymphoma), and M1 (mouse myeloid leukemia) cell lines. Interestingly, rP48-MBP also induces apoptosis of U937 and HL-60 cells as assessed by terminal transferase (TUNEL) assays. This is the first report of induction of apoptosis by a Mycoplasma gene product. P48 is a Mycoplasma-derived immunomodulatory molecule which has differentiation and apoptosis-inducing activities and may be important in the pathophysiology of Mycoplasma infections. The recombinant protein may be useful in studying the mechanisms of differentiation, cytokine production, and apoptosis in malignant and nonmalignant hematopoietic cells.

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.

Cutting edge: preferentially the R-stereoisomer of the mycoplasmal lipopeptide macrophage-activating lipopeptide-2 activates immune cells through a toll-like receptor 2- and MyD88-dependent signaling pathway

Mycoplasmas and their membranes are potent activators of macrophages, the active principle being lipoproteins and lipopeptides. Two stereoisomers of the mycoplasmal lipopeptide macrophage-activating lipopeptide-2 (MALP-2) differing in the configuration of the lipid moiety were synthesized and compared in their macrophage-activating potential, the R-MALP being >100 times more active than the S-MALP in stimulating the release of cytokines, chemokines, and NO. To assess the role of the Toll-like receptor (TLR) family in mycoplasmal lipopeptide signaling, the MALP-2-mediated responses were analyzed using macrophages from wild-type, TLR2-, TLR4-, and MyD88-deficient mice. TLR2- and MyD88-deficient cells showed severely impaired cytokine productions in response to R- and S-MALP. The MALP-induced activation of intracellular signaling molecules was fully dependent on both TLR2 and MyD88. There was a strong preference for the R-MALP in the recognition by its functional receptor, TLR2.

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.

Expression of the monocytic differentiation/activation factor P48 in Mycoplasma species

P48 is a 48 kd monocytic differentiation/activation factor previously purified from the conditioned medium of the Reh human pre-B cell leukemia line. It induces differentiation of HL-60 promyelocytic leukemia cells along the monocytic pathway and production of IL1, TNF-alpha and IL6 in human monocytes and monocytic cell lines. Recently our laboratory isolated cDNA clones for P48 from Reh cells and genomic clones from Mycoplasma fermentans DNA and showed that P48 is a M. fermentans gene product. In this paper we report the analysis of P48 expression at the DNA, mRNA and protein levels in different Mycoplasma species. Polymerase Chain Reaction (PCR) analysis of extracted DNA using P48-specific oligonucleotide primers revealed P48 sequences in M. fermentans but not M. hominis, M. iowae, M. genitalium or M. capricolum. Southern analysis of Mycoplasma DNAs revealed hybridizing bands in M. fermentans and M. capricolum under low stringency, but only in M. fermentans under high stringency. Consistent with this, Northern blot studies revealed a single hybridizing transcript in M. fermentans but not in other Mycoplasma species tested. However, Western blot studies with anti-P48 antibodies revealed P48 antigenic material in M. fermentans, as well as M. hominis and M. iowae. These studies demonstrate that the gene for P48 is derived from M. fermentans or a closely related species and is absent in these other species tested. However, the P48 protein exhibits shared antigenic determinants among several Mycoplasma species which presently are of unknown function or significance. P48 is a Mycoplasma -derived immunomodulatory molecule which may be important in Mycoplasma pathophysiology and may be useful in understanding human haematopoietic differentiation and the control of cytokine biosynthesis.

Lipid extract of Mycoplasma penetrans proteinase K-digested lipid-associated membrane proteins rapidly activates NF-kappaB and activator protein 1

Lipid-associated membrane proteins (LAMPs) of Mycoplasma penetrans rapidly induced macrophages to produce proinflammatory cytokines such as tumor necrosis factor alpha (TNF-alpha). Our analysis showed that the macrophage-stimulating activity of TNF-alpha production was mainly attributable to a lipid extractable component(s) in the LAMP preparation. Since induction of gene expression is normally preceded by activation of transcriptional factors that bind to their specific recognition elements located in the upstream promoter region, we examined the activity of transcriptional factors, namely, NF-kappaB and activator protein 1 (AP-1), in thioglycolate exudate peritoneal (TEP) macrophages treated with M. penetrans lipid extract of proteinase K (PK)-digested LAMPs. Initially, in the nuclei of unstimulated TEP cells, there was only a low basal level of active AP-1, and the active form of NF-kappaB could not be detected. M. penetrans lipid extract of PK-digested LAMPs activated both NF-kappaB and AP-1 in TEP macrophages within 15 min. The markedly increased activities of both factors gradually declined and dissipated after 2 h. Parallel to the rapid increase of NF-kappaB and AP-1, the TNF-alpha transcript also increased significantly 15 min after the stimulation. The high-level expression of TNF-alpha persisted over 2 h. Dexamethasone blocked the activation of both NF-kappaB and AP-1 and suppressed the production of TNF-alpha in TEP macrophages stimulated by M. penetrans lipid extract of PK-digested LAMPs. Our study demonstrates that the M. penetrans lipid extract of PK-digested LAMP is a potent activator for NF-kappaB and AP-1 in murine TEP macrophages. Our results also suggest that high-level expression of TNF-alpha in cells induced by M. penetrans lipid extract of PK-digested LAMPs is associated with rapid activation of transcriptional factors NF-kappaB and AP-1.

Molecular biology and pathogenicity of mycoplasmas

The recent sequencing of the entire genomes of Mycoplasma genitalium and M. pneumoniae has attracted considerable attention to the molecular biology of mycoplasmas, the smallest self-replicating organisms. It appears that we are now much closer to the goal of defining, in molecular terms, the entire machinery of a self-replicating cell. Comparative genomics based on comparison of the genomic makeup of mycoplasmal genomes with those of other bacteria, has opened new ways of looking at the evolutionary history of the mycoplasmas. There is now solid genetic support for the hypothesis that mycoplasmas have evolved as a branch of gram-positive bacteria by a process of reductive evolution. During this process, the mycoplasmas lost considerable portions of their ancestors' chromosomes but retained the genes essential for life. Thus, the mycoplasmal genomes carry a high percentage of conserved genes, greatly facilitating gene annotation. The significant genome compaction that occurred in mycoplasmas was made possible by adopting a parasitic mode of life. The supply of nutrients from their hosts apparently enabled mycoplasmas to lose, during evolution, the genes for many assimilative processes. During their evolution and adaptation to a parasitic mode of life, the mycoplasmas have developed various genetic systems providing a highly plastic set of variable surface proteins to evade the host immune system. The uniqueness of the mycoplasmal systems is manifested by the presence of highly mutable modules combined with an ability to expand the antigenic repertoire by generating structural alternatives, all compressed into limited genomic sequences. In the absence of a cell wall and a periplasmic space, the majority of surface variable antigens in mycoplasmas are lipoproteins. Apart from providing specific antimycoplasmal defense, the host immune system is also involved in the development of pathogenic lesions and exacerbation of mycoplasma induced diseases. Mycoplasmas are able to stimulate as well as suppress lymphocytes in a nonspecific, polyclonal manner, both in vitro and in vivo. As well as to affecting various subsets of lymphocytes, mycoplasmas and mycoplasma-derived cell components modulate the activities of monocytes/macrophages and NK cells and trigger the production of a wide variety of up-regulating and down-regulating cytokines and chemokines. Mycoplasma-mediated secretion of proinflammatory cytokines, such as tumor necrosis factor alpha, interleukin-1 (IL-1), and IL-6, by macrophages and of up-regulating cytokines by mitogenically stimulated lymphocytes plays a major role in mycoplasma-induced immune system modulation and inflammatory responses.

Genital mycoplasmas stimulate tumor necrosis factor-alpha and inducible nitric oxide synthase production from a murine macrophage cell line

Ureaplasma urealyticum and Mycoplasma hominis, two genital mycoplasmas, are the most common organisms isolated in the perinatal period and both either cause or are associated with poor perinatal outcomes. We speculate that these microbes could increase inflammation by stimulating macrophages to produce tumor necrosis factor-alpha (TNF-alpha) and inducible nitric oxide synthase because of their propensity to interact with the host's immune system. To test this hypothesis, RAW 264.7 cells, a murine macrophage cell line, were coincubated for 16 h with either U. urealyticum or M. hominis, and LPS and sterile broth were used as controls. Lipopolysaccharide (LPS) and both mycoplasmas induced TNF-alpha production, which was concentration-dependent, whereas sterile broth had little effect. TNF-alpha production was not inhibited by the addition of polymyxin B, excluding the possibility of contaminating endotoxin in this effect. Inducible nitric oxide synthase was produced only in the presence of recombinant inteferon-gamma. We conclude that both viable and nonviable U. urealyticum and M. hominis are capable of TNF-alpha induction from murine macrophages and that LPS is not involved in this event. Also, the genital mycoplasmas are capable of stimulating inducible nitric oxide synthase production from murine macrophages. We speculate that the genital mycoplasmas produce perinatal disease by producing proinflammatory mediators by their interaction with inflammatory cells and either induce or act as a catalyst and augment inflammation which in turn leads to a poor pregnancy outcome.

Structure and specific activity of macrophage-stimulating lipopeptides from Mycoplasma hyorhinis

Mycoplasmas are potent macrophage stimulators. We describe the isolation of macrophage-stimulatory lipopeptides S-[2, 3-bisacyl(C16:0/C18:0)oxypropyl]cysteinyl-GQTDNNSSQSQQPGS GTTNT and S-[2,3-bisacyl(C16:0/C18:0)oxypropyl]cysteinyl-GQTN derived from the Mycoplasma hyorhinis variable lipoproteins VlpA and VlpC, respectively. These lipopeptides were characterized by amino acid sequence and composition analysis and by mass spectrometry. The lipopeptides S-[2,3-bis(palmitoyloxy)propyl]cysteinyl-GQTNT and S-[2, 3-bis(palmitoyloxy)propyl]cysteinyl-SKKKK and the N-palmitoylated derivative of the latter were synthesized, and their macrophage-stimulatory activities were compared in a nitric oxide release assay with peritoneal macrophages from C3H/HeJ mice. The lipopeptides with the free amino terminus showed half-maximal activity at 3 pM regardless of their amino acid sequence; i.e., they were as active as the previously isolated M. fermentans-derived lipopeptide MALP-2. The macrophage-stimulatory activity of the additionally N-palmitoylated lipopeptide or of the murein lipoprotein from Escherichia coli, however, was lower by orders of magnitude. It is concluded that the lack of N-acyl groups in mycoplasmal lipoproteins explains their exceptionally high in vitro macrophage-stimulatory capacity. Certain features that lipopolysaccharide endotoxin and mycoplasmal lipopeptides have in common are discussed. Lipoproteins and lipopeptides are likely to be the main causative agents of inflammatory reactions to mycoplasmas. This may be relevant in the context of mycoplasmas as arthritogenic pathogens and their association with AIDS.

A longitudinal study of seroreactivity against Mycoplasma penetrans in HIV-infected homosexual men: association with disease progression

We investigated the relationships between a putative cofactor of HIV infection, Mycoplasma penetrans, and the evolution of HIV disease. The evolution of titers of anti-M. penetrans antibodies in 58 randomly selected HIV-seropositive adult homosexual men was investigated. The median length of follow-up was 38 months. Thirty-six individuals was investigated. The median length of follow-up was 38 months. Thirty-six individuals (62.1%) remained M. penetrans seronegative (group 0). Fourteen patients (24.1%) had consistently low antibody titers or low antibody titer(s) in at least one sample and negative test(s) in the other(s). This pattern was possibly associated with latent or earlier infection (group 1). Eight patients (13.8%) had moderate to high antibody titers for long periods, indicating an active and persistent M. penetrans infection (group 2); four patients in this group presented a serological reactivation and thus probably developed an acute infection during the study; two had a stable and moderate level of antibody throughout the study; in two patients the antibody titers decreased substantially. Interestingly, CD4 cell counts declined more rapidly in group 2 than in group 0 (medians of -4.5 versus -2.1 cells/mm3/month, p < 0.05 and -0.16 versus 0 cell percentage/month, p < 0.05), whereas there was no significant difference between groups 1 and 0 (medians of -2.0 versus -2.1 cells/mm3/month and -0.15 versus 0 cell percentage/month). In patients with serological reactivation, the viral load was higher in sera with higher M. penetrans antibody titers. These findings suggest an association between active M. penetrans infection and progression of HIV disease.

Activation of Mitogen-Activated Protein Kinase Pathways by Mycoplasma fermentans Membrane Lipoproteins in Murine Macrophages: Involvement in Cytokine Synthesis

Stimulation of monocytes and resident macrophages by mycoplasmas induces production of numerous cytokines. We have previously reported that membrane lipoproteins derived from Mycoplasma fermentans are responsible for the induction of proinflammatory cytokines by monocytic cells and that triggering protein tyrosine kinase activation is an essential requirement for this biologic effect. In the present study, we have investigated the effect of M. fermentans-derived membrane lipoproteins (LAMPf) on mitogen-activated protein kinase (MAPK) cascades in the murine macrophage cell line RAW 264.7 and have analyzed the contribution of these pathways to the cytokine induction mediated by this agent. Treatment of murine macrophages with LAMPf resulted in significant activation of MAPK family members extracellular signal-regulated kinase 1 and 2 (ERK1/2), c-Jun NH2-terminal kinase (JNK), and p38. Unlike LPS, these effects were demonstrated to be independent of the presence of serum. The activation of MAPKs paralleled the tyrosine kinase activation and peaked at 30 min after stimulation. The specific p38 inhibitor SB203580 abrogated the mycoplasma-induced IL-6, IL-1β, and TNF-α synthesis. The selective MAPK/extracellular signal-regulated kinase 1 (MEK-1) inhibitor PD-98059 blocked both IL-1β and TNF-α but not IL-6 production by RAW 264.7 cells in response to LAMPf. Additionally, transfection of murine macrophages with a JNK dominant negative mutant significantly reduced only IL-6 production. These data underscore the role of MAPKs as signal transduction molecules controlling the expression of cytokines upon mycoplasma stimulation.

Humoral and bronchial immune responses in cattle experimentally infected with Mycoplasma mycoides subsp. mycoides small colony type

The course of immune reactions of the manifold antigens of Mycoplasma mycoides subsp. mycoides small colony type (SC) was analysed in serum and bronchial lavage of cattle experimentally infected with the African strain Afadé and the European strain L2 using Western-blots and complement fixation. Western-blot analysis of total antigens of both strains with sera from animals infected with the homologous and heterologous strain revealed the common dominant immunogenic antigens with the molecular masses of 110, 95, 85, 80, 72, 62, 48 and 39 kDa. The sequential sampling of the blood and bronchial lavages before and after contact infections allowed us to identify the antigens of 85, 80, 72, 48 and 39 kDa as particularly early immunogens. The IgA Western blots of the bronchial lavages showed distinct, early and persistent reactions to the 110, 85, 80, 72, 48 and 45 kDa proteins. These proteins were the predominant lipoproteins as determined by [14C]palmitic acid labelling. Only relatively weak reactions of the bronchial lavages were detected with IgG. In general immune responses were significantly stronger in the animals infected with the African strain Afadé, which gave positive results two weeks after contact infection. In contrast, the animals infected with the European strain L2 induced much lower reactions with a delay of three months after contact infection. In one animal strain L2 caused no sero-conversion and no infection. The results indicate a difference in virulence between the African strain Afadé and the European strain L2.

Mycoplasma salivarium induces interleukin-6 and interleukin-8 in human gingival fibroblasts

Analysis by an enzyme-linked immunosorbent assay for cytokines indicated that whole cells, intracellular materials and cell membranes of Mycoplasma salivarium induced interleukin-6 and interleukin-8 in a human gingival fibroblast cell line, Gin-1 cells. This was confirmed by reverse transcription-polymerase chain reaction analysis of mRNAs of these cytokines. Studies with inhibitors of second-messenger pathway indicated that a protein kinase C-dependent pathway was involved in the expression of the activity of the cell membranes. In addition, whole cells of other mycoplasmas (M. hominis, M. arthritidis, M. arginini, M. fermentans, M. penetrans, M. pirum and M. pneumoniae) tested for comparative purposes were also shown to possess the activity. Thus, this study demonstrated that mycoplasmas possess the activity to induce interleukin-6 and interleukin-8 in human fibroblasts.

Spiralin, a mycoplasmal membrane lipoprotein, induces T-cell-independent B-cell blastogenesis and secretion of proinflammatory cytokines

Mycoplasmas are bacteria which can cause respiratory, arthritic, and urogenital diseases. During the early phase of infection, mycoplasmas usually induce an inflammatory response and a humoral response preferentially directed against their membrane-bound, surface-exposed lipoproteins. In this report, we describe the effects on immune cells of spiralin, a well-characterized mycoplasmal lipoprotein. Purified spiralin stimulated the in vitro proliferation of human peripheral blood mononuclear cells and murine splenocytes. The stimulation pathway was probably different from that followed by Escherichia coli lipopolysaccharide because the effect of spiralin was not abolished by polymyxin B. Comparison of the effects of whole, native spiralin with those induced by proteinase K-digested spiralin or by the C-terminal half of spiralin (peptide p[13.5]T) revealed that the first half of the protein, which contains the lipoylated N terminus, is responsible for the mitogenic activity. In contrast to whole spiralin, proteinase K-digested spiralin did not trigger murine B-cell differentiation and immunoglobulin G and M secretion. Stimulation of human or murine immune cells led to early secretion of proinflammatory cytokines (human tumor necrosis factor alpha and murine interleukin 1 or 6). Spiralin induced the T-cell-independent blastogenesis of murine B cells but did not stimulate T cells. Altogether, our data demonstrate that spiralin possesses potent immunostimulating activity, similar to that reported for lipoproteins of pathogenic gracilicutes (gram-negative eubacteria; e.g., Borrelia burgdorferi OspA and E. coli Braun lipoprotein), and are consistent with the fact that lipoproteins are major antigens during mycoplasma infections.

Isolation, structure elucidation, and synthesis of a macrophage stimulatory lipopeptide from Mycoplasma fermentans acting at picomolar concentration

Macrophages are typically stimulated by components of microbial cell walls. Surprisingly, cell wall-less mycoplasmas can also very efficiently stimulate macrophages. We showed recently that mycoplasma-derived lipopeptides constitute the active principle. We have now isolated a clone of Mycoplasma fermentans expressing mainly one macrophage-stimulating lipopeptide. This lipopeptide was detergent-extracted and isolated by reversed-phase high-performance liquid chromotography, using nitric oxide release from C3H/HeJ mouse macrophages as bioassay for detection. In contrast to "conventional" bacterial lipoproteins, this lipopeptide had a free NH2 terminus. Amino acid composition, sequence, and the molecular weight of 2,163. 3 are consistent with the following structure: S-(2, 3-bisacyloxypropyl)cysteine-GNNDESNISFKEK with one mole C16:0, and a further mole of a mixture of C18:0 and C18:1 fatty acid per lipopeptide molecule. The sequence could not be found in either the protein identification resource nor the Swiss Prot data bank. We named this 2-kD lipopeptide, macrophage-activating lipopeptide-2 (MALP-2). Synthetic dipalmitoyl MALP-2 and mycoplasma-derived MALP-2 were compared with the bioassay. Both lipopeptides showed an identical dose dependency with a half-maximal response at 10(-11) M concentration. MALP-2 may be one of the most potent natural macrophage stimulators besides endotoxin.

Chlamydia trachomatis growth stimulates interleukin 8 production by human monocytic U-937 cells

Growth of Chlamydia trachomatis serotypes L2 and L3 in a human monocytic cell line, U-937, increased the rate of interleukin 8 (IL-8) release 100-fold. Heat-killed chlamydiae induced a 10-fold-lower level of production of IL-8. IL-8 may play an important role in the inflammatory reaction to chlamydial infection.

cDNA and genomic cloning and expression of the P48 monocytic differentiation/activation factor, a Mycoplasma fermentans gene product

P48 is a 48 kDa monocytic differentiation/activation factor previously purified from the conditioned medium of the Reh human pre-B cell leukaemia cell line. It induces growth arrest and differentiation of HL-60 human promyelocytic leukaemia cells along the monocytic pathway and the production of the cytokines interleukin 1, tumour necrosis factor-alpha and interleukin 6 in human monocytes and monocytic cell lines. The cDNA for P48 was cloned from Reh cellular RNA using 3' reverse amplification of cDNA ends. Southern blot probing with P48 cDNA revealed hybridization with DNA from Reh and Molt-4 cells, but not with DNA from human peripheral blood mononuclear cells. Subsequent studies using PCR and Southern analysis revealed P48 sequences in DNA isolated from Mycoplasma fermentans but not M. hominis, M.iowae, M.synoviae or M.lypophilum. Although initial studies using Mycoplasma culture and hybridization techniques had failed to reveal Mycoplasma infection in our Reh and Molt-4 cell lines, subsequent PCR studies using Mycoplasma genus-specific rRNA primrs revealed Mycoplasma sequences in these cell lines. Using the P48 cDNA probe, we isolated a genomic clone from M. fermentans DNA which was found to be 98.5% identical with the P48 cDNA clone, and the deduced amino acid sequence agreed with N-terminal microsequencing data for P48 protein purified from the Reh cell line conditioned medium. The 5' end of the gene has a number of consensus sequences characteristic of prokaryotic genes, and the deduced amino acid sequence has a number of features suggesting that P48 is a lipoprotein. The P48 cDNA was expressed in pMAL in Escherichia coli, and the 60 kDa expressed fusion protein was found to react with anti-P48 antibodies on Western blots. This is consistent with a pMAL fusion protein representing the sum of the 42 kDa maltose-binding protein and 18 kDa of P48 recombinant protein, suggesting that native P48 has significant post-translational modification. Consistent with this, Northern blot studies revealed a single 1 kb transcript. The recombinant fusion protein was found to possess anti-proliferative activity against HL-60 cells, and antibodies against recombinant P48 were found to block the biological activity of native P48 isolated from conditioned medium. These studies demonstrate that P48, a molecule with immunomodulatory and haematopoietic differentiation activities, is derived from M. fermentans or a closely related species. P48 may be important in the pathophysiology of Mycoplasma infections and may be useful in dissecting the mechanisms involved in mammalian haematopoietic cell differentiation, immune function and cytokine biosynthesis.

Proteins of 30 and 36 kilodaltons, membrane constituents of the Staphylococcus aureus L form, induce production of tumor necrosis factor alpha and activate the human immunodeficiency virus type 1 long terminal repeat

We have previously demonstrated that the membrane of the Staphylococcus aureus L form induced tumor necrosis factor alpha (TNF-alpha) from murine macrophages. In this study, we purified two proteins which induce TNF-alpha production from a human monocytic cell line, THP-1, and murine macrophages. These molecules were purified from delipidated membranes by deoxycholic acid extraction, two-step anion-exchange chromatography, and preparative electrophoresis. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the purified proteins showed for each a single band with a molecular mass of 30, and 36 kDa. These proteins were heat stable. Polymyxin B did not affect the production of TNF-alpha induced by these proteins. Furthermore, these proteins induced comparable levels of TNF-alpha in both lipopolysaccharide-responsive and -nonresponsive mouse macrophages. Pretreatment of murine macrophages with gamma interferon enhanced 30- and 36-kDa protein-mediated TNF-alpha production. The 30-kDa protein showed lethal toxicity to D-galactosamine-treated mice. The 30- and 36-kDa proteins stimulated the human immunodeficiency virus type 1 long terminal repeat in a monocytic cell line but not a T-cell line. This effect appeared to be mediated through the induction of nuclear factor kappaB. These results indicate that the 30- and 36-kDa proteins, membrane constituents of the S. aureus L form, may play a role in S. aureus infection and/or in human immunodeficiency virus type 1-infected individuals.

Mycoplasma orale infection affects K+ and Cl- currents in the HSG salivary gland cell line

The relations between K+ channel and Cl- channel currents and mycoplasma infection status were studied longitudinally in HSG cells, a human submandibular gland cell line. The K+ channel currents were disrupted by the occurrence of mycoplasma infection: muscarinic activation of K+ channels and K+ channel expression as estimated by ionomycin- or hypotonically induced K+ current responses were all decreased. Similar decreases in ionomycin- and hypotonically induced responses were observed for Cl- channels, but only the latter decrease was statistically significant. Also, Cl- currents could be elicited more frequently than K+ currents (63% of cases versus 0%) in infected cells when tested by exposure to hypotonic media, indicating that mycoplasma infection affects K+ channels relatively more than Cl- channels. These changes occurred in the originally infected cells, were ameliorated when the infection was cleared with sparfloxacin, and recurred when the cells were reinfected. Such changes would be expected to result in hyposecretion of salivary fluid if they occurred in vivo.

Bacterial modulins: a novel class of virulence factors which cause host tissue pathology by inducing cytokine synthesis

Cytokines are a diverse group of proteins and glycoproteins which have potent and wide-ranging effects on eukaryotic cell function and are now recognized as important mediators of tissue pathology in infectious diseases. It is increasingly recognized that for many bacterial species, cytokine induction is a major virulence mechanism. Until recent years, the only bacterial component known to stimulate cytokine synthesis was lipopolysaccharide (LPS). It is only within the past decade that it has been clearly shown that many components associated with the bacterial cell wall, including proteins, glycoproteins, lipoproteins, carbohydrates, and lipids, have the capacity to stimulate mammalian cells to produce a diverse array of cytokines. It has been established that many of these cytokine-inducing molecules act by mechanisms distinct from that of LPS, and thus their activities are not due to LPS contamination. Bacteria produce a wide range of virulence factors which cause host tissue pathology, and these diverse factors have been grouped into four families: adhesins, aggressins, impedins, and invasins. We suggest that the array of bacterial cytokine-inducing molecules represents a new class of bacterial virulence factor, and, by analogy with the known virulence families, we suggest the term "modulin" to describe these molecules, because the action of cytokines is to modulate eukaryotic cell behavior. This review summarizes our current understanding of cytokine biology in relation to tissue homeostasis and disease and concisely reviews the current literature on the cytokine-inducing molecules produced by gram-negative and gram-positive bacteria, with an emphasis on the cellular mechanisms responsible for cytokine induction. We propose that modulins, by controlling the host immune and inflammatory responses, maintain the large commensal flora that all multicellular organisms support.

Mycoplasma fermentans-derived lipid inhibits class II major histocompatibility complex expression without mediation by interleukin-6, interleukin-10, tumor necrosis factor, transforming growth factor-beta, type I interferon, prostaglandins or nitric oxide

Mycoplasma cause several diseases in man and animals. Some strains can chronically infect humans, leading to fever or inflammatory syndromes such as arthritis, particularly in immunosuppressed patients. A set of pathogenicity factors shared by many mollicutes may be membrane components that activate macrophages to secrete cytokines and other inflammatory mediators. Mycoplasma-derived high molecular weight material (MDHM) is a macrophage-activating amphiphilic lipid which was purified from Mycoplasma fermentans. We studied the influence of MDHM on the expression of major histocompatibility complex (MHC) class II molecules by mouse resident peritoneal macrophages with an ELISA. Highly purified MDHM at 4 ng/ml and 0.8 microgram/ml crude heat-killed M. fermentans (concentrations chosen to give maximal responses) suppressed interferon (IFN)-gamma-dependent class II MHC induction when added simultaneously with IFN-gamma. MDHM was not toxic and did not result in loss of adherent cells. Kinetic data showed that MDHM first up-regulated, then down-regulated the expression of preformed class II MHC molecules, while expression of Mac-1 and F4/80 antigens remained constant. MDHM-dependent suppression of class II MHC molecule expression resulted in impaired antigen presentation to the helper T cell line D10.G4.1. We further attempted to identify hypothetical products of MDHM-stimulated macrophages as secondary mediators of class II MHC suppression such as were described for lipopolysaccharide (LPS)-stimulated macrophages. Type I IFN, prostaglandins and nitric oxide, all reported to cause down-regulation of class II MHC, could be excluded in this context. Of the cytokines tumor necrosis factor, interleukin (IL)-6, IL-10 and transforming growth factor-beta, only IL-10 inhibited class II MHC expression, although less effectively than MDHM. The involvement of IL-10 was ruled out, as no evidence for its MDHM-dependent formation could be found. Our data suggest that MDHM interferes with class II MHC expression by up-regulating its turnover, and at the same time, inhibits the formation of new class II MHC molecules.

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

To gain a clear understanding of the mechanisms by which mycoplasmas induced the expression of proinflammatory cytokines in monocytic cells, we have studied the induction of interleukin-1 beta (IL-1 beta), tumor necrosis factor alpha, and IL-6 by mycoplasmas in three distinct human myelomonocytic cell lines in comparison with induction by lipopolysaccharide (LPS). HL-60 cell line did not release cytokines when induced with either LPS or mycoplasmas. In contrast to LPS, mycoplasmas failed to increase the weak levels of tumor necrosis factor alpha secreted by phorbol myristate acetate-differentiated U937 cells. In addition, Northern (RNA) blot analysis of cytokine expression in these cells showed that the induction of IL-1 beta by mycoplasmas involves, unlike that by LPS, posttranscriptional events. Interestingly, in THP-1 cells, cytokine induction pathways triggered by mycoplasmas remained operational under conditions where LPS pathways were abolished, suggesting functional independence. The study of cytokine-inducing activity displayed by distinct fractions derived from a series of different mycoplasma species demonstrated that lipid membrane constituents were largely responsible for these effects. Finally, we have demonstrated that tyrosine phosphorylation is a crucial event in the mycoplasma-mediated induction of proinflammatory cytokines in either THP-1 cells or human monocytes.

Mycoplasma hyorhinis molecules that induce tumor necrosis factor alpha secretion by human monocytes

Mycoplasma hyorhinis has been shown to induce the secretion of tumor necrosis factor alpha (TNF-alpha) from monocytes. To identify the molecules responsible for this activity, we separated sonicated M. hyorhinis lysate material by centrifugation at 100,000 x g into soluble (S) and particulate (P) fractions. The fractions were assayed for TNF-alpha-inducing activity by the L929 bioassay. Both the soluble and particulate fractions were able to induce TNF-alpha in roughly equal amounts. The optimum dose for both fractions was 1 micrograms/ml. Proteinase K treatment of either fraction eliminated the activity, suggesting that a protein component is involved in induction. Phase partitioning into Triton X-114 aqueous (A) and detergent (D) phases showed that the soluble fraction was composed of 80% aqueous-phase proteins, while the particulate fraction was > 75% detergent-phase proteins. All four fractions (SA, SD, PA, and PD) were able to induce TNF-alpha release. Treatment with NaIO4 to remove carbohydrate reduced the inducing activity of the SA phase by 80%, whereas that of the other fractions was unaffected by this treatment. The M(r)S of the inducing activity were determined by the monocyte Western (immunoblot) technique. The SA phase activity was associated with a single periodate-sensitive peak of 69 to 75 kDa. The two detergent phases had similar profiles of inducing activity, containing four peaks of activity. These peaks corresponded to 48 to 52, 43 to 45, 39 to 40, and 31 to 32 kDa. The PA fraction also contained four peaks of activity, 69 to 75, 55 to 57, 48 to 52, and 39 to 40 kDa. Thus, both a protein and glycan moiety from M. hyorhinis are capable of inducing TNF-alpha release from human monocytes.