Mycoplasmas and oncogenesis: persistent infection and multistage malignant transformation

Mycoplasma fermentans infection promotes immortalization of human peripheral blood mononuclear cells in culture

Chronic infection or colonization by mycoplasma(s) could gradually and significantly alter many biologic properties of mammalian host cells in culture, including induction of malignant transformation. We examined effects of Mycoplasma fermentans infection on the continuing survival and immortality of human peripheral blood mononuclear cells (PBMCs) from healthy blood donors. Without specific supplemental growth factors, human PBMCs normally die rapidly, with few cells other than macrophages/monocytes surviving after 2 weeks in cultures. Only occasional Epstein-Barr virus (EBV)–positive B lymphocytes would continue to proliferate and undergo spontaneous immortalization. Our present study revealed that infection of human PBMCs in culture with the incognitus and PG18 strains of M fermentans, but surprisingly not with some other strains tested in parallel, markedly enhanced the rate of EBV-positive B lymphocytes to undergo immortalization (74% vs 17%). Compared with spontaneously immortalized PBMCs, the PBMCs immortalized in cultures infected with the mycoplasmas often had prominent karyotype changes with chromosomal loss, gain, or translocations. Furthermore, many of these immortalized B lymphocytes were found to be monoclonal in nature. The in vitro findings would be of relevance to lymphoproliferative disorders that occurred in patients with immune suppression. The mycoplasma-mediated promotional effect in cell immortalization and its potential clinical implications warrant further study.

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.

Hemotrophic mycoplasmas (hemoplasmas): a review and new insights into pathogenic potential

The red cell parasites formerly known as Haemobartonella and Eperythrozoon spp have been reclassified as hemotrophic mycoplasmas (hemoplasmas) based on strong phylogenetic evidence and 16S ribosomal RNA gene sequences. The latter form the basis for polymerase chain reaction assays used to detect infection. Candidatus designation was given to incompletely characterized species. Like other mycoplasmas, hemoplasmas are small epicellular parasites that lack a cell wall and are susceptible to tetracyclines; their circular, double-stranded DNA encodes only those gene products essential for life. Diseases caused by infection with hemoplasmas range from overt life-threatening hemolytic anemia to subtle chronic anemia, ill-thrift, and infertility. In addition, the organisms may act as cofactors in the progression of retroviral, neoplastic, and immune-mediated diseases. Intimate contact of hemoplasma organisms with RBCs leads to cell injury through immune-mediated and other mechanisms that have not yet been defined. Despite an intense immune response and even with antibiotic treatment, infected animals probably remain chronic carriers after clinical signs have resolved.

Mitochondrial activities in human cultured skin fibroblasts contaminated by Mycoplasma hyorhinis

Background

Mycoplasma contaminations are a recurrent problem in the use of cultured cells, including human cells, especially as it has been shown to impede cell cycle, triggering cell death under various conditions. More specific consequences on cell metabolism are poorly known.

Results

Here we report the lack of significant consequence of a heavy contamination by the frequently encountered mycoplasma strain, M. hyorhinis, on the determination of respiratory chain activities, but the potential interference when assaying citrate synthase. Contamination by M. hyorhinis was detected by fluorescent imaging and further quantified by the determination of the mycoplasma-specific phosphate acetyltransferase activity. Noticeably, this latter activity was not found equally distributed in various mycoplasma types, being exceptionally high in M. hyorhinis.

Conclusion

While we observed a trend for respiration reduction in heavily contaminated cells, no significant and specific targeting of any respiratory chain components could be identified. This suggested a potential interference with cell metabolism rather than direct interaction with respiratory chain components.

Identification of antigens by monoclonal antibody PD4 and its expression in Escherichia coli

AIM

To clone and express the antigen of monoclonal antibody (MAb) PD4 for further investigation of its function.

METHODS

MGC803 cDNA expression library was constructed and screened with PD4 as probes to clone the antigen. After failed in the library screening, immunoprecipitation and SDS-polyacrylamide gel electrophoresis were applied to purify the antigen for sequence analysis. The antigen coming from Mycoplasma hyorhinis (M. hyorhinis) was further confirmed with Western blot analysis by infecting M. hyorhinis -free HeLa cells and eliminating the M. hyorhinis from MGC803 cells. The full p37 gene was cloned by PCR and expressed successfully in Escherichia coli after site-directed mutations. Immunofluorescence assay was used to demonstrate if p37 protein could directly bind to gastric tumor cell AGS.

RESULTS

The cDNA library constructed with MGC803 cells was screened by MAb PD4 as probes. Unfortunately, the positive clones identified with MAb PD4 were also reacted with unrelated antibodies. Then, immunoprecipitation was performed and the purified antigen was identified to be a membrane protein of Mycoplasma hyorhinis (M. hyorhinis) by sequencing of N-terminal amino acid residues. The membrane protein was intensively verified with Western blot by eliminating M. hyorhinis from MGC803 cells and by infecting M. hyorhinis-free HeLa cells. The full p37 gene was cloned and expressed successfully in Escherichia coli after site-directed mutations. Immunofluorescence demonstrated that p37 protein could directly bind to gastric tumor cell AGS.

CONCLUSION

The antigen recognized by MAb PD4 is from M. hyorhinis, which suggests the actions involved in MAb PD4 is possibly mediated by p37 protein or M. hyorhinis. As p37 protein can bind directly to tumor cells, the pathogenic role of p37 involved in tumorigenesis justifies further investigation.

APAF-1-ALT, a novel alternative splicing form of APAF-1, potentially causes impeded ability of undergoing DNA damage-induced apoptosis in the LNCaP human prostate cancer cell line

We have found a novel alternative splicing product of the apoptotic protease activating factor 1 (APAF-1), termed APAF-1-ALT, in the LNCaP human prostate cancer cell line. APAF-1-ALT harbors the caspase recruitment domain and an incomplete CED-4 like/ATPase domain, but lacks the WD-40 repeat units. The LNCaP cell expressed the full-length APAF-1 weakly and APAF-1-ALT rather abundantly, especially after mycoplasma infection. LNCaP underwent a retarded DNA damage-induced apoptosis, which was independent of caspase 9 activity. APAF-1-ALT functioned less effectively in inducing apoptosis than did APAF-1-XL, the full-length APAF-1, in transient transfection. Moreover, APAF-1-ALT interfered with APAF-1-XL's ability to induce apoptosis in transient double transfection experiment. These results indicate that APAF-1-ALT is a molecule that is deficient and impeded for mediating apoptosis and that it may contribute to the resistance to DNA damage-induced treatment observed in LNCaP.

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.

Identification and characterization of cytopathogenic Mycoplasma hyorhinis from swine farms with a history of abortions

A virus-like cytopathic agent isolated from swine farms with a history of recurrent abortion episodes was investigated. We employed a differential display reverse transcription-polymerase chain reaction (ddRT-PCR) to obtain genetic information of the cytopathic agent. Partial nucleotide sequence (527 bp) obtained from differentially displayed PCR fragments showed 88.7% similarity with the 23S rRNA gene of Mycoplasma hyopneumoniae. Unexpectedly, the 5' portion (1-333 bp) of the sequence shared 96.1% similarity with 5' untranslated region (UTR) of human prostate tumor inducing gene 1 (PTI-1). Cytopathic effects and extranuclear DNA fluorescence were no longer observed when BM-cyclin was added in the culture medium, suggesting that BM-cyclin sensitive mycoplasma-like organisms caused the cell death. Further evidence supporting the cytopathic agent as a mycoplasma-like organism was obtained by the capability of (3)H-thymidine and (3)H-uridine incorporation, a single peak in buoyant density gradient profile (1.20-1.24 g/ml), and ultrastructural morphology. Unlike M. hyopneumoniae, the organism was not propagated in Friis medium. Nucleotide sequence of 16S rRNA obtained from the cytopathic agent showed 0.8-1.0% divergences with other M. hyorhinis strains, suggesting that the newly isolated cytopathogenic swine mycoplasma was a variant form of M. hyorhinis. Striking homology between a portion of the 23S rRNA gene of M. hyorhinis and 5' UTR of human PTI-1 implicated that M. hyorhinis might potentially be related to the evolution of human PTI-1.

Is this the historical 'cancer germ'?

A highly pleomorphic bacterium, isolated from a canine mammary tumour was found to share many characteristics with recently described cancer-related bacteria and with the Glover organism, a historically important 'cancer germ'. We suggest that both the Glover organism, and possibly other cancer-related bacteria, are likely to be a strain of the highly pleomorphic bacterium, Bacillus licheniformis.

A lipoprotein family from Mycoplasma fermentans confers host immune activation through Toll-like receptor 2

Mycoplasma have been reported to be associated with human diseases. Three forms of a mycoplasma lipopeptide/protein with the ability to modulate the host immune system were independently identified and named macrophage-activating lipopeptide 2 (MALP-2), P48 and M161Ag (identical to MALP-404). Although these molecules had polypeptides of different sizes, they exerted similar immunomodulatory effects on macrophages/dendritic cells, such as cytokine induction, NO production and maturation of antigen-presenting cells (APCs). M161Ag exhibited complement-activating ability and bound macrophages via complement C3b/C3bi and their receptors. The diacylated N-terminal palmitates were involved in these activities. Toll-like receptor 2 (TLR2) was found to be responsible for these functional features of these mycoplasma products, except for complement activation. Here, we summarize the functional properties of this family of proteins, namely pathogen-associated molecular pattern (PAMP) and discuss its relationship to the reported pathogenesis of latent mycoplasma infection.

Detection of Mycoplasma ribosomal DNA sequences in ovarian tumors by nested PCR

OBJECTIVE

The aim of this study was to investigate the reported association between mycoplasma infection and ovarian cancer by screening ovarian tumor tissues for the presence of mycoplasma DNA.

METHODS

Forty-six benign and malignant ovarian tumors were obtained from patients undergoing pelvic surgery at a regional cancer center. DNA was isolated from snap-frozen tumor tissues, and commercial nested polymerase chain reaction (PCR) kits were used to detect the presence of 12 species of mycoplasma in tumor DNA samples. PCR products were isolated from ethidium bromide-stained agarose gels, and sequenced with an automated DNA sequencer. Species were identified through nucleotide sequence similarity searches using the National Center for Biotechnology Information BLAST program.

RESULTS

Mycoplasma DNA was detected in 6 (13.0%) of the 46 tumor DNA samples. Nucleotide sequence similarity searches of nested PCR products revealed that one Mycoplasma salivarium and five M. arginini DNA sequences were amplified from the ovarian tissues.

CONCLUSIONS

Since M. salivarium and M. arginini are frequently encountered laboratory contaminants that do not have a recognized role as human pathogens, our findings do not support an association between human mycoplasma pathogens and ovarian cancer.

Do mycoplasmas cause human cancer?

A linkage between mycoplasmas and malignancy was mainly proposed in the 1960s when human-associated mycoplasmas were becoming of interest given the novel characterization of the human respiratory pathogen Mycoplasma pneumoniae. Associations with leukemia and other malignancies, however, were largely ascribed to tissue-culture contamination, which is now recognized as a significant potential problem in molecular biology circles. A few epidemiological studies, however, continue to raise concern over such a linkage. As well, in vitro data have demonstrated the potential for some mycoplasmas to induce karyotypic changes and malignant transformation during chronic tissue-culture infestation. As cellular and molecular mechanisms for such transformation become studied, a resurgence of interest in this area is inevitable. A role for mycoplasmas in malignancy of any sort is conjectural, but there remains a need to continue with focussed epidemiological and laboratory investigations.Key words: mycoplasma, cancer, oncogenesis, leukemia.

Interaction between Mycoplasma hyopneumoniae and swine influenza virus

An experimental respiratory model was used to investigate the interaction between Mycoplasma hyopneumoniae and swine influenza virus (SIV) in the induction of pneumonia in susceptible swine. Previous studies demonstrated that M. hyopneumoniae, which produces a chronic bronchopneumonia in swine, potentiates a viral pneumonia induced by the porcine reproductive and respiratory syndrome virus (PRRSV). In this study, pigs were inoculated with M. hyopneumoniae 21 days prior to inoculation with SIV. Clinical disease as characterized by the severity of cough and fever was evaluated daily. Percentages of lung tissue with visual lesions and microscopic lesions were assessed upon necropsy at 3, 7, 14, and 21 days following SIV inoculation. Clinical observations revealed that pigs infected with both SIV and M. hyopneumoniae coughed significantly more than pigs inoculated with a single agent. Macroscopic pneumonia on necropsy at days 3 and 7 was greatest in both SIV-infected groups, with minimal levels of pneumonia in the M. hyopneumoniae-only-infected pigs. At 14 days post-SIV inoculation, pneumonia was significantly more severe in pigs infected with both pathogens. However, by 21 days postinoculation, the level of pneumonia in the dual-infected pigs was similar to that of the M. hyopneumoniae-only-infected group, and the pneumonia in the pigs inoculated with only SIV was nearly resolved. Microscopically, there was no apparent increase in the severity of pneumonia in pigs infected with both agents compared to that of single-agent-challenged pigs. The results of this study found that while pigs infected with both agents exhibited more severe clinical disease, the relationship between the two pathogens lacked the profound potentiation found with dual infection with M. hyopneumoniae and PRRSV. These findings demonstrate that the relationship between mycoplasmas and viruses varies with the individual agent.

Mycoplasma infections and different human carcinomas

AIM: To explore relationships between human carcinomas and mycoplasma infection.

METHODS: Monoclonal antibody PD4, which specifically recognizes a distinct protein from mycoplasma hyorhinis, was used to detect mycoplasma infection in different paraffin embedded carcinoma tissues with immunohistochemistry. PCR was applied to amplify the mycoplasma DNA from the positive samples for confirming immunohistochemistry.

RESULTS: Fifty of 90 cases (56%) of gastric carcinoma were positive for mycoplasma hyorhinis. In other gastric diseases, the mycoplasma infection ratio was 28% (18/49) in chronic superficial gastritis, 30% (14/46) in gastric ulcer and 37% (18/49) in intestinal metaplasia. The difference is significant with gastric cancer (χ² = 12.06, P < 0.05). In colon carcinoma, the mycoplasma infection ratio was 55.1% (32/58),but it was 20.9% (10/ 49) in adenomarous polyp (χ² = 13.46, P < 0.005). Gastric and colon cancers with high differentiation had a higher mycoplasma infection ratio than those with low differentiation (P < 0.05). Mycoplasma infection in esophageal cancer, lung cancer, breast cancer and glioma was 50.9% (27/53), 52.6% (31/ 59), 39.7% (25/63)and 41% (38/91), respectively. The mycoplasma DNA was successfully amplified with the DNA extracted from the cancer tissues that were positive for mycoplasma infection (detected with antibody PD4).

CONCLUSION: There was high correlation between mycoplasma infection and different cancers, which suggests the possibility of an association between the two. The mechanism involved in oncogenesis by mycoplasma remains unknown.

Monoclonal antibody against Mycoplasma fermentans-specific aminoglycoglycerolipid

Previously, we reported that Mycoplasma fermentans has specific antigens (phosphocholine-containing glycoglycerolipids: GGPL-I and GGPL-III) and discussed the possibility of their pathogenic role. In this paper, we report the characterization of a monoclonal antibody (MF-III-1) specific to GGPL-III (phosphocholine-containing aminoglycoglycerolipid) using methods of electron microscopy, immunofluorescence cell surface staining, laser scanning microscopy, immunoelectron microscopy, and thin-layer chromatography immunostaining. The MF-III-1 antibody specifically recognized M. fermentans attached to the surface of HTLV-I-infected human helper T-cells, and it did not cross-react with other lipids nor with human T-cell antigens. Since MF-III-1 distinguishes GGPL-III from GGPL-I, the binding site may include a serinol (2-amino-1,3-propanediol) residue of GGPL-III. MF-III-1 is useful for the in vitro study of M. fermentans, and may also be useful as a tool for the study of the involvement of M. fermentans in human diseases.

Intracellular DNA replication and long-term survival of pathogenic mycoplasmas

We examined intracellular survival and growth of pathogenic mycoplasmas (Mycoplasma penetrans, Mycoplasma pneumoniae and Mycoplasma genitalium) in cultured human cells. By using the eukaryotic nuclear DNA synthesis inhibitor, aphidicolin, we detected the selective synthesis of mycoplasma (My) and mitochondria (Mt) DNA, which could be further differentiated by restriction enzyme analyses. Also, intracellular M. pneumoniae and M. penetrans infectivity of human cells was detected over 6 months using subfractionation of infected cells and determination of mycoIplasma colony forming units (cfu). For M. genitalium, which we failed to re-grow from infected cells, species-specific PCR primers were used to implicate long-term mycoplasma survivability. Data indicated that pathogenic mycoplasmas reside and replicate intracellularly over extended periods in human cells, consistent with the ability of mycoplasmas to circumvent antibiotic therapy and immune surveillance and establish chronic infections.

Mycoplasmal infections alter gene expression in cultured human prostatic and cervical epithelial cells

To better understand how infections by mycoplasmas affect gene expression in human cells, we quantitatively measured the transcripts of 38 cytokine genes in HPV E6- and E7-immortalized cervical and prostatic epithelial cells before and after infection by four human urogenital mycoplasmas, M. fermentans, M. genitalium, M. hominis and M. penetrans. Using the multi-probe RNase protection assay (RPA), 22 and 23 cytokine gene transcripts were detected in the non-infected control prostatic and cervical epithelial cells, respectively. Although there were no discernible changes in cell morphology and growth kinetics following 72 h of mycoplasmal infection, 55-74% of the cytokine genes expressed in the two human epithelial cell lines were altered. Most changes reflected an increased expression of these cytokine genes, while expression of some cytokine genes significantly decreased. The effects varied with host cell type and species of infecting mycoplasmas. These alterations in gene expression were more profound in the cervical epithelial cells than in the prostatic cells. M. fermentans produced the most significant effects, followed by M. penetrans, M. genitalium and M. hominis. Some alterations in the gene expression were transient, but most persisted over the course of chronic (9 months) mycoplasmal infection. Prolonged gene expression changes induced by chronic mycoplasmal infection may gradually alter important biological properties in the infected mammalian cells and produce a unique form of disease process.

Mycoplasmal infections prevent apoptosis and induce malignant transformation of interleukin-3-dependent 32D hematopoietic cells

32D cells, a murine myeloid cell line, rapidly undergo apoptosis upon withdrawal of interleukin-3 (IL-3) supplement in culture. We found that 32D cells, if infected by several species of human mycoplasmas that rapidly activated NF-kappaB, would live and continue to grow in IL-3-depleted culture. Mycoplasma-infected cells showed no evidence of autocrine production of IL-3. Pyrrolidine dithiocarbamate (PDTC) blocked activation of NF-kappaB and led to prominent cell death. Heat-killed mycoplasmas or mycoplasmal membrane preparations alone could support continued growth of 32D cells in culture without IL-3 supplement for a substantial period of time. However, upon removal of heat-inactivated mycoplasmas, 32D cells quickly became apoptotic. In comparison, live Mycoplasma fermentans or M. penetrans infection for 4 to 5 weeks induced malignant transformation of 32D cells. Transformed 32D cells grew autonomously and no longer required support of growth-stimulating factors including IL-3 and mycoplasmas. The transformed 32D cells quickly formed tumors when injected into nude mice. Karyotyping showed that development of chromosomal changes and trisomy 19 was often associated with malignant transformation and tumorigenicity of 32D cells. Mycoplasmal infections apparently affected the fidelity of genomic transmission in cell division as well as checkpoints coordinating the progression of cell cycle events.

Mycoplasma-mediated uptake of the exogenous human BRCA1 gene by hatching blastocysts

PURPOSE

Biological vectors for cell transfection are mainly viral in origin, with inherent shortcomings. Mycoplasmas are ubiquitous organisms that traverse cells easily. The objective was to determine if Ureaplasma urealyticum (T-mycoplasma) would vector exogenous BRCA1 DNA into blastocysts.

METHODS

Hatching mouse blastocysts (N = 70) were incubated in the presence of either viable or dead Ureaplasma urealyticum at 37 degrees C for 1 hr. The blastocysts were exposed to human BRCA1 DNA lacking homology in the mouse genome for 2 hr, followed by DNase-1 treatment and wash. Polymerase chain reaction and agarose gel electrophoresis analysis of amplified products were performed.

RESULTS

The BRCA1 gene was detected in the blastocysts only when viable Ureaplasma was present. PCR analyses of control Ureaplasma and untreated blastocysts were negative.

CONCLUSION

Viable Ureaplasma organisms were shown to mediate the uptake of DNA fragments into blastocysts, resulting in transgenic mouse blastocysts with a normal human BRCA1 exon 11 gene.

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.

Mycoplasma hyopneumoniae potentiation of porcine reproductive and respiratory syndrome virus-induced pneumonia

An experimental model that demonstrates a mycoplasma species acting to potentiate a viral pneumonia was developed. Mycoplasma hyopneumoniae, which produces a chronic, lymphohistiocytic bronchopneumonia in pigs, was found to potentiate the severity and the duration of a virus-induced pneumonia in pigs. Pigs were inoculated with M. hyopneumoniae 21 days prior to, simultaneously with, or 10 days after inoculation with porcine reproductive and respiratory syndrome virus (PRRSV), which induces an acute interstitial pneumonia in pigs. PRRSV-induced clinical respiratory disease and macroscopic and microscopic pneumonic lesions were more severe and persistent in M. hyopneumoniae-infected pigs. At 28 or 38 days after PRRSV inoculation, M. hyopneumoniae-infected pigs still exhibited lesions typical of PRRSV-induced pneumonia, whereas the lungs of pigs which had received only PRRSV were essentially normal. On the basis of macroscopic lung lesions, it appears that PRRSV infection did not influence the severity of M. hyopneumoniae infection, although microscopic lesions typical of M. hyopneumoniae were more severe in PRRSV-infected pigs. These results indicate that M. hyopneumoniae infection potentiates PRRSV-induced disease and lesions. Most importantly, M. hyopneumoniae-infected pigs with minimal to nondetectable mycoplasmal pneumonia lesions manifested significantly increased PRRSV-induced pneumonia lesions compared to pigs infected with PRRSV only. This discovery is important with respect to the control of respiratory disease in pigs and has implications in elucidating the potential contribution of mycoplasmas in the pathogenesis of viral infections of other species, including humans.

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.

Assessment of archived paraffin-embedded cervical condyloma tissues for mycoplasma-conserved DNA using sensitive PCR-ELISA

Clinically, it is important to detect mycoplasmas because these organisms have been implicated in gastric and ovarian cancer, pneumonia, postabortal fever, pelvic inflammatory disease, pyelonephritis, endometritis, urethritis, perinatal mortality, arthritis, spontaneous abortion, infertility and interference with sperm development and they act as cofactors catalyzing the HIV disease state. Recently, the combined polymerase chain reaction and enzyme-linked immunosorbent assay method targeting the consensus DNA of over 15 species of mycoplasmas was shown to be superior for the detection of mycoplasmas. The objective was to determine if there was an association between mycoplasmas and cervical neoplasia. Cervical tissues, histopathologically categorized by cervical intraepithelial neoplasia (CIN) grade, flat or exophytic, and acanthosis or koilocytotic, were used. The results showed that mycoplasmas DNA were present in 21.4% of the condyloma tissues and in 33.3% of condyloma tissues with CIN. In contrast, mycoplasmas DNA were not detected when there were no CIN. The presence or absence of human papillomavirus (HPV) did not make a difference. Mycoplasmas DNA were present in 40.0 and 12.5% of the exophytic and flat condylomas, respectively. A higher percentage of cervical tissues graded with slight koilocytosis had (P = 0.05) mycoplasmas DNA compared with tissues graded with moderate koilocytosis. The detection of mycoplasmas DNA in archived cervical condyloma tissues with CIN corroborated previous reports of an association between mycoplasmas and CIN. However, the association between mycoplasmas and the presence of HPV could not be made in this study.

Structural and functional properties of complement-activating protein M161Ag, a Mycoplasma fermentans gene product that induces cytokine production by human monocytes

Human malignant cells are targeted by homologous complement C3b if they express M161Ag, a 43-kDa protein with C3-activating property. cDNA of M161Ag cloned from human leukemia cell lines predicted M161Ag as a novel secretory protein comprised of 428 amino acids including 5 amino acids encoded by TGA codons (Matsumoto M., Takeda, J., Inoue, N., Hara, T., Hatanaka, M., Takahashi, K., Nagasawa, S., Akedo, H., and Seya, T. (1997) Nat. Med. 3, 1266-1270), although the origin of this gene was obscure. Here we clarified this point through genomic and biochemical analysis: 1) 5'-UT and genomic sequences represented the prokaryote promoter and ribosomal binding site; 2) the TGA codons in M161Ag cDNA were translated not into selenocysteines but into tryptophans; 3) M161Ag anchored onto the membrane secondary to its N-terminal palmitoylation like prokaryote lipoproteins; 4) genomic and cDNA clones of M161Ag were highly homologous to Mycoplasma fermentans gene encoding P48, a monocytic differentiation/activation factor, recently released in the data base, although the resultant proteins were different in the amino acid sequences. Additionally, purified soluble M161Ag efficiently provoked IL-1beta, tumor necrosis factor alpha, and IL-6 like P48, and further IL-10 and IL-12 in human peripheral blood monocytes. Thus, M161Ag originates from M. fermentans, and latently infected M. fermentans allows human cells to produce M161Ag. The liberated protein serves as a potent modulator of innate and cellular immune responses via its complement-activating and cytokine-producing activities.

Mycoplasma genitalium infection and host antibody immune response in patients infected by HIV, patients attending STD clinics and in healthy blood donors

Prevalence of Mycoplasma genitalium in humans is still not clear. We have developed a sensitive and specific serological assay for M. genitalium using lipid-associated membrane proteins (LAMPs) as antigens. Antibodies to LAMPs from M. genitalium showed little cross-reactivity to LAMPs from antigenically similar M. pneumoniae. For validity testing, urines from 104 patients were tested by PCR for M. genitalium. All 15 PCR+ patients had M. genitalium-LAMPs antibodies. Moreover, none of 64 antibody-negative patients were PCR+. Serological study of 1800 patients of various diseased groups and healthy blood donors showed M. genitalium was primarily a sexually transmitted microbe that infected patients with AIDS (44.0%), intravenous drugs users with or without HIV infection (42.5%), and also HIV- patients attending STD clinics (42.6%). Only 5.5% HIV- healthy blood donors and 1.3% HIV+ hemophiliacs tested positive. M. genitalium has been associated with acute non-gonococcal urethritis in male patients. However, many sexually active men and women appear to be chronically infected or colonized by the microbe without apparent clinical symptoms and may continue to transmit the organism through sexual contacts.

Mycoplasmas: sophisticated, reemerging, and burdened by their notoriety

Mycoplasmas are most unusual self-replicating bacteria, possessing very small genomes, lacking cell wall components, requiring cholesterol for membrane function and growth, using UGA codon for tryptophan, passing through "bacterial-retaining" filters, and displaying genetic economy that requires a strict dependence on the host for nutrients and refuge. In addition, many of the mycoplasmas pathogenic for humans and animals possess extraordinary specialized tip organelles that mediate their intimate interaction with eucaryotic cells. This host-adapted survival is achieved through surface parasitism of target cells, acquisition of essential biosynthetic precursors, and in some cases, subsequent entry and survival intracellularly. Misconceptions concerning the role of mycoplasmas in disease pathogenesis can be directly attributed to their biological subtleties and to fundamental deficits in understanding their virulence capabilities. In this review, we highlight the biology and pathogenesis of these procaryotes and provide new evidence that may lead to increased appreciation of their role as human pathogens.