Newly discovered mycoplasma isolated from patients infected with HIV

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.

Intracerebral administration of Mycoplasma fermentans produces sickness behavior: role of prostaglandins

Mycoplasmas are small microorganisms, which cause various diseases in animals and in humans, activate the immune system, and induce the release of various cytokines. Some of the effects of mycoplasmas are mediated by the CNS. Moreover, Mycoplasma fermentans (MF) has recently been found in the brain, as well as other tissues of some AIDS patients, who usually display severe neurobehavioral disturbances. The present study was designed to examine the behavioral effects of central administration of MF, and the role of prostaglandins in mediating these effects. In one set of experiments, rats were injected intracerebroventricularly (i.c.v.) with either saline or a dose of MF (5.1-36 microg per rat), and several behavioral parameters were measured. In addition, body temperature and locomotor activity were continuously monitored by a biotelemetric system. MF induced a significant elevation in body temperature and suppression of motor activity levels. MF also significantly reduced the time spent in social exploration, decreased locomotor and exploratory activity in the open field test, suppressed the consumption of food and saccharine solution, and reduced body weight. In a second set of experiments, i.c.v. administration of MF (7.2 microg) was found to produce a significant increase in the production of prostaglandin E2 (PGE2) in hypothalamic, hippocampal, and cortical tissues. This effect was blocked by indomethacin, a prostaglandin synthesis inhibitor. Indomethacin also attenuated the effects of MF on body temperature, motor activity and body weight, suggesting the involvement of prostaglandins in mediating some of the effects of MF. Together, these findings suggest that the presence of MF in the brain may be responsible for some of the neurobehavioral abnormalities in HIV-infected patients.

Mycoplasma fermentans enhances concanavalin A-induced apoptosis of mouse splenic T cells

Mycoplasma fermentans, an AIDS-associated mycoplasma, possessed the activity of enhancing concanavalin A-induced apoptosis of T cells purified from mouse spleen by a nylon wool column, and tumor necrosis factor-alpha played an important role in expression of the activity. M. salivarium, an oral mycoplasma, used for comparative purposes also possessed the activity, the level of which was lower than that of M. fermentans.

Search for the presence of six Mycoplasma species in peripheral blood mononuclear cells of subjects seropositive and seronegative for human immunodeficiency virus

The prevalence of Mycoplasma fermentans, Mycoplasma pirum, Mycoplasma genitalium, Mycoplasma pneumoniae, Mycoplasma hominis, and Mycoplasma penetrans was investigated by using specific PCR assays with peripheral blood mononuclear cells from subjects infected or not infected with the human immunodeficiency virus (HIV). Only M. fermentans was detected in 5.8% of 154 HIV-seropositive and 11.1% of 90 HIV-seronegative subjects.

Detection of Mycoplasma sp. in bronchoalveolar lavage of AIDS patients with pulmonary infiltrates

We examined 486 bronchoalveolar lavages (BAL) including 32 from AIDS patients with pulmonary infiltrates and 20 from patients with leukemia or after transplantation. Mycoplasmas were found in 4/32 (12.5%) HIV-positive patients compared to 4/454 (< 0.9%) HIV-negative patients (p < 0.001). All of these four HIV-positive patients suffered from advanced infection (CD4 counts < 100/microL) and developed complications (Pcp, n = 2, recurrent bacterial pneumonia, n = 1, pulmonary Kaposi sarcoma, n = 1). No mycoplasmas were detected in 20 immunosuppressed patients with leukemia or after transplantation. Our data indicate that AIDS patients may be more often colonised or infected by mycoplasmas than HIV-negative patients or other immunocompromised persons. Although the etiological role of mycoplasmas for pulmonary infections in these patients remains unclear, the finding of mycoplasmas was associated with rapid progress and development of severe complications in our study.

Detection of Mycoplasma fermentans in human saliva with a polymerase chain reaction-based assay

Mycoplasma fermentans and other mycoplasma species may be associated with human immunodeficiency virus infection. Little is known about the ecology of this micro-organism and its natural habitat. A polymerase chain reaction (PCR)-based assay was used to detect M. fermentans in whole saliva. The hypothesis was tested that M. fermentans is present on the mucosal surfaces of the mouth and oropharynx. Whole saliva was collected from 110 adults. The 206-bp amplification product of DNA purified from these samples was detected in ethidium bromide-stained 6% polyacrylamide gels in 49 (44%) samples tested. All samples were confirmed by Southern blotting with a probe based on an internal sequence of the expected amplification product. The data suggest that this organism is often found in saliva and on oropharyngeal mucosal surfaces. Saliva may play a part in its transmission between individuals. Saliva sampling may be helpful in further studies of the ecology and distribution of the micro-organism in human populations.

Failure to detect Mycoplasma fermentans, Mycoplasma penetrans, or Mycoplasma pirum in the urethra of patients with acute nongonococcal urethritis

Urethral swab specimens collected from 108 male Japanese patients with acute nongonococcal urethritis (NGU) and from 50 Japanese men without NGU were examined for the presence of Mycoplasma fermentans, Mycoplasma penetrans, and Mycoplasma pirum by means of polymerase chain reaction-based assays. These mycoplasmas were not detected in any of the specimens, which suggests that they are unlikely to have a pathogenic role in acute NGU.

Adherence, fibronectin binding, and induction of cytoskeleton reorganization in cultured human cells by Mycoplasma penetrans

Mycoplasma penetrans adhered to cultured human cells, forming clusters that localized to specific areas of the host cell surface. Adherence and cluster formation were inhibited by anti-M. penetrans antibodies, suggesting the involvement of specific adhesin-receptor interactions. Ultrastructural studies showed that after 2 h of infection, mycoplasmas attach to and penetrate the host cell surface. M. penetrans bound selectively to immobilized fibronectin, an interaction which was not inhibited by a 70-kDa fragment containing a heparin-gelatin-binding domain of fibronectin, other matrix glycoproteins, or an RGD tripeptide, suggesting the recognition of other specific binding sites on the fibronectin molecule. A ca. 65-kDa fibronectin-binding protein of M. penetrans was eluted following Sepharose-fibronectin affinity chromatography. Confocal, light, and immunofluorescence microscopy demonstrated that the interaction of M. penetrans with target cells triggers a signal that causes recruitment of several cytoskeletal components, including tubulin and alpha-actinin, and aggregation of phosphorylated proteins. Detergent-soluble mycoplasma proteins with apparent molecular masses of 18, 28, 32, 36, 39, and 41 kDa selectively bound to glutaraldehyde-fixed HEp-2 cells. Our findings offer new insights into understanding the interaction of this human mycoplasma with host target cells.

Induction of tumor necrosis factor alpha (TNF alpha) and enhancement of HIV-1 replication in the J22HL60 cell line by Mycoplasma penetrans

Mycoplasma penetrans isolated from clinical specimens of AIDS patients showed potent activity in tumor necrosis factor alpha (TNF alpha) production in THP-1, U937 and J22HL60 cell lines, and in the enhancement of HIV-1 replication in a dormantly-infected J22HL60 cell line as compared with the activities of other mycoplasmas. Both activities were found in the methanol layer but not in the chloroform layer of the membrane extracted by the Bligh-Dyer method. TNF alpha production was observed in the peritoneal macrophages from both lipopolysaccharide-responsive and -unresponsive mouse strains, and was not inhibited by polymyxin B. The induction of TNF alpha production and enhancement of HIV-1 replication were strongly inhibited by Concanavalin A-Sepharose. The inhibitory effect of Concanavalin A-Sepharose was partially prevented by sugars in the order methyl-alpha-D-mannopyranoside and methyl-alpha-D-glucopyranoside but not methyl-alpha-D-galactopyranoside. Anti-human TNF alpha antibody, however, did not reduce the activity of the methanol layer to enhance HIV-1 replication, suggesting that the methanol layer could enhance HIV-1 replication directly. These results suggest that the carbohydrate derived from M. penetrans might be responsible for the progression of HIV-1 infection.

In vitro influence of Mycoplasma penetrans on activation of peripheral T lymphocytes from healthy donors or human immunodeficiency virus-infected individuals

Mycoplasma penetrans is a mycoplasma species newly isolated from the urine of human immunodeficiency virus (HIV)-infected individuals and presents the only case in which an association has been found between antibodies against a mycoplasma and HIV infection. To further explore the effects of M. penetrans on the immune system, we studied the influence of this mycoplasma on peripheral blood mononuclear cells (PBMCs) from healthy donors and HIV-infected individuals. M. penetrans induced, in addition to blastogenesis of PBMCs, a significant proliferative response associated with the expression of some activation markers such as CD69, HLA-DR, and CD25. This M. penetrans-dependent lymphocyte activation was observed not only in healthy donors but also in HIV-infected persons at different stages of the disease. In addition, our study revealed that both CD4+ and CD8+ T lymphocytes were responsive to M. penetrans. Interestingly, the mitogenic activity of M. penetrans was associated with mycoplasma cells but not with the supernatants of mycoplasma culture. The potent stimulating activity of M. penetrans on T lymphocytes from HIV-infected individuals is of particular interest in view of the supposed contribution of immune activation to HIV replication and disease progression.

Release of hydrogen peroxide from human T cell lines and normal lymphocytes co-infected with HIV-1 and mycoplasma

Human T-cell lines and normal lymphocytes persistently or acutely co-infected with the human immunodeficiency virus type 1 (HIV-1) and mycoplasmas were found to release hydrogen peroxide (H2O2), a likely cause of oxidative stress in these cells. The spectrofluorometric measurement of H2O2 release from these cells, using the scopoletin fluorescence quenching technique, gave values of 16-84 p moles/10(6) cells/min. In CEM cells, H2O2 was released only when acutely co-infected with HIV-1 and mycoplasmas, and not when infected with either organism alone. Anti-mycoplasmal antibiotics strongly reduced H2O2 release, and improved cell viability without blocking virus replication. These results suggest that the simultaneous infection by HIV-1 and mycoplasma leads to the release of H2O2, a toxic and potentially lethal metabolite, which in vivo may contribute to HIV-1 pathogenicity.

Characterization of a major Mycoplasma penetrans lipoprotein and of its gene

A novel mycoplasmal species designated as Mycoplasma penetrans has been isolated recently from patients infected with human immunodeficiency virus. p35, a major antigen extracted from the membrane of this mycoplasma using Triton X-114 has been found to be a lipoprotein. After proteolytic treatment of p35, the sequence of one of the resulting peptides was determined and a corresponding oligonucleotide was deduced. Using this oligonucleotide as a probe the p35 gene was cloned and sequenced. Sequence analysis revealed an amino-terminal signal peptide with a potential acylation site which would result in a 35.3 kDa mature product. In addition, the p35 gene was followed by an open reading frame with a corresponding polypeptide partially homologous to p35, in particular to the N-terminus region.

In vitro antibiotic susceptibility testing of clinical isolates of Mycoplasma penetrans from patients with AIDS

In vitro susceptibilities of Mycoplasma penetrans were determined. MICs and MBCs were determined. The MICs at which 50% of the isolates are inhibited (micrograms per milliliter) for broth dilution testing were as follows: azithromycin, 0.039; chloramphenicol, 0.625; ciprofloxacin, 0.156; clindamycin, 0.078; doxycycline, 0.312; erythromycin, 0.312; gentamicin. > 10; levofloxacin, 0.078; lincomycin, 0.625; streptomycin, > 10; and tetracycline, 1.25. Bactericidal activity was significant only for ciprofloxacin (MBC at which 50% of the isolates are killed, 0.312 microgram/ml) and levofloxacin (MBC at which 50% of the isolates are killed, 0.312 microgram/ml).

The cell membrane of Mycoplasma penetrans: lipid composition and phospholipase A1 activity

Analysis of Mycoplasma penetrans membrane lipids revealed that, in addition to large amounts of unesterified cholesterol, M. penetrans incorporated exogenous phospholipids, preferentially sphingomyelin, from the growth medium. The major phospholipids synthesized de novo by M. penetrans were phosphatidylglycerol (PG) and diphosphatidylglycerol (DPG). In vivo labeling of PG and DPG by growing the cells with radioactive palmitate or oleate, followed by snake venom phospholipase A2 treatment, enabled us to assess the positional distribution of fatty acids in these lipids. Saturated fatty acids were found preferentially in position 2 of the glycerol backbone, and not in position 1 as found elsewhere in nature, while unsaturated fatty acids prefer position 1. M. penetrans membranes contain phospholipase activity of the A1 type, removing a fatty acid from the sn-1 ester bond of phospholipids. The activity was neither stimulated by Ca2+ nor inhibited by EGTA and had a broad pH spectrum. The substrate specificity of the enzyme was investigated with various natural lipids and with a fluorescent analog of the phosphatidylcholine. The enzyme was equally active toward phosphatidylcholine and phosphatidylglycerol, but did not hydrolyze diphosphatidylglycerol. The enzyme did not act on triacylglycerol, diacylglycerol or cholesteryl ester, but low activity was detected toward monoacylglycerol. The enzyme was heat-sensitive and detergent-sensitive, and was almost completely inhibited by p-bromophenacylbromide (50 microM), but was not affected by SH reagents. This study is the first one reporting phospholipase A1 activity in Mollicutes. A possible role of this enzyme in forming lipid mediators upon the interaction of M. penetrans cells with eukaryotic cells is suggested.

Mycoplasmas in plaque and saliva of children and their relationship to gingivitis

Gingivitis is common in children but its etiology is not well understood. Results of earlier studies have suggested that mycoplasmas may have a role in the disease. In this study two plaque samples and one stimulated saliva sample were taken from each of a group of sixty (60) 5 to 9 year-old children and cultured selectively for mycoplasmas. Subjects had been selected on the basis of gingival status buccal to the most posterior tooth in an upper quadrant, 20 each having scores 0, 1, or 2 at this site using the Löe and Silness index. Plaque samples were taken from the adjacent tooth surface and from a second posterior site where the adjacent gingiva was free of signs of inflammation. Mycoplasmas were cultured from 54 saliva samples and from 57 plaque samples. Isolation frequency and numbers of mycoplasmas in relation to total anaerobic counts were consistently related to gingivitis scores in both plaque and saliva samples, with higher frequencies and proportions with increasing levels of gingival inflammation at the selected site. In plaque samples this finding held good for both comparisons between groups of subjects and for those between test and control sites within subjects. Findings would appear to confirm the suggestions of earlier studies that mycoplasmas in the oral cavity are associated with gingivitis in children.

AIDS as immune system activation. Key questions that remain

Immune system activation is gaining attention as a central part of HIV pathogenesis. Although there is no consensus yet as to the source of the signal or the result of the signalling, this line of thinking represents a significant shift in the paradigm away from considering HIV disease like any other cytopathic viral infection. Hopefully, completion of studies focussed on this approach will lead to more complete understanding of AIDS and more effective therapies, and will at least bring to the fore some of the central unanswered questions in modern cellular immunology.

Links and interactions between mycoplasmas and viruses: past confusions and present realities

Links between mycoplasmas and viruses are ancient, multiple and complex, from past confusions during the first decades of the virus era to present realities illustrated by the possible implication of mycoplasmas as co-factors in natural infections of AIDS. Mycoplasma viruses (phages) may also be responsible for modifying the pathogenic power of mycoplasmas, at least for plants and insects. In addition, several mycoplasmas are able to act as undesirable cell culture contaminants that induce erroneous results in both applied and general virology. These problems are examined within a historical context.

Preliminary evidence for idiotype-antiidiotype immune complexes cross-reactive with lymphocyte antigens in AIDS and lupus

Several investigators have proposed that autoimmunity may be induced by idiotype-antiidiotype antibody networks. It is generally assumed that the antiidiotype is produced in response to the idiotype, and therefore that autoimmune diseases have single antigenic initiators. The theory of multiple-antigen-mediated autoimmunity (MAMA) proposes, on the other hand, that idiotype and antiidiotype result from two primary immune responses to two chemically complementary antigens. Because of the complementarity of the antigens, and the complementarity of the antibodies for the antigens, the antibodies will themselves be complementary. They will thus form circulating immune complexes, the self-nonself distinction diffusion (DAD) experiments (a modification of Ouchterlony immunodiffusion), in which 1800 pairs of antibodies were screened for their ability to form precipitating complexes. Four sets of antibodies associated with AIDS (HIV + Staphylococcus; HIV + Mycoplasma; CMV + Mycoplasma; and HBV + Mycoplasma) specifically precipitated each other, and one of the antibodies in each set also precipitated monoclonal antibodies against one or more lymphocyte protein markers. These results therefore demonstrate that idiotype-antiidiotype antibodies can be elicited by independent antigens and may induce AIDS-related forms of autoimmunity directed at lymphocytes.

Mycoplasma stimulates HIV-1 expression from acutely- and dormantly-infected promonocyte/monoblastoid cell lines

Treatment of a myelo-monocyte cell line, J22HL-60, dormantly infected with human immunodeficiency virus type 1 (HIV-1) with heat-inactivated extracts of Acholeplasma (A) laidlawii (250 micrograms/ml) enhanced virus production more than 45-fold as assessed by p24 viral core antigen assay. When treated with a suboptimal dose of TPA or TNF-alpha, Acholeplasma extracts further augmented virus production in J22HL-60 cells. H7, an inhibitor of protein kinase C(PKC), almost completely abrogated HIV-1-inducing ability of Acholeplasma extracts in the cells. A. laidlawii and several other mycoplasmas also enhanced acute infection of U937 cells as shown by increased virus-positive cells and augmentation of HIV-1 production in the culture supernatant independent of their pathogenicity to humans.

Induced mouse spleen B-cell proliferation and secretion of immunoglobulin by lipid-associated membrane proteins of Mycoplasma fermentans incognitus and Mycoplasma penetrans

Mycoplasmas have been implicated as a possible cofactor in AIDS pathogenesis. Mycoplasma fermentans and M. penetrans infect human immunodeficiency virus-positive patients at a significantly higher frequency than non-human immunodeficiency virus-infected control subjects. Various mycoplasmal membrane preparations are known to affect the functions of immune cells both in vitro and in vivo. A group of lipid-associated membrane proteins (LAMPs) extracted by Triton X-114 from mycoplasmas are major antigenic targets of human host antibody responses. In this study, LAMPs prepared from both M. fermentans and M. penetrans nonspecifically stimulated spleen cells of CBA/CaH mice to proliferate. LAMPs were also stimulatory to spleen cells from athymic mice. On the other hand, enriched splenic T cells from CBA/CaH mice with or without accessory cells responded poorly. Thus, the mitogenic effect of mycoplasmal LAMPs appeared mainly on B cells. High levels of immunoglobulin (Ig) M and low but detectable amounts of IgG were found in the supernatant of LAMP-treated splenic cell culture. M. penetrans LAMPs had a much more potent effect on murine spleen cells than did M. fermentans incognitus LAMPs in inducing both B-cell proliferation and Ig secretion. In conclusion, the mycoplasmal LAMPs contained an active component(s) with T-independent B-cell mitogenic effect.

Antibiotic susceptibilities of AIDS-associated mycoplasmas

Because mycoplasmas may be a cofactor in the progression of human immunodeficiency virus infection to AIDS, their susceptibilities to antibiotics need to be known in the event that appropriate therapy is required. The mycoplasmas studied were a stock culture strain of Mycoplasma fermentans, two strains of M. fermentans isolated from patients with AIDS, M. fermentans var. incognitus, Mycoplasma penetrans, and Mycoplasma pirum. The antibiotics tested were doxycycline, tetracycline, clindamycin, ofloxacin, erythromycin, azithromycin, and clarithromycin at levels consistent with the attainable levels in serum. By the macrodilution metabolic inhibition method, all six mycoplasma strains were susceptible to doxycycline, tetracycline, clindamycin, ofloxacin, azithromycin, and clarithromycin. M. penetrans was susceptible to erythromycin. The M. fermentans strains and M. pirum were resistant to erythromycin. The macrodilution metabolic inhibition method results showed agreement with the Sensititre Gram Positive MIC Panel results for tetracycline, clindamycin, and erythromycin. MICs of clarithromycin for all six mycoplasma isolates tested were low, indicating susceptibility.

Murine AIDS: a model for the human disease or a distinct entity?

The LP-BM5 mixture of murine retroviruses elicits a disease in mice referred to as murine immunodeficiency syndrome (MAIDS) that is considered by some to be an animal homologue of human AIDS. In this article, we present and discuss some recent findings on the pathogenesis of the murine disease and their implications for the proposed homology between murine and human syndromes. The murine disease seems to display as many similarities to as it does differences from human AIDS. Among the latter are: definitive and exclusive viral etiology, a strong genetic effect on susceptibility to infection, expansion of the CD4+ cell population in spleen and peripheral blood, consistent transmissibility by a single transfusion of the minute amounts of blood or plasma from infected donors, and striking similarity between virus-induced alteration of the in vitro spleen cell proliferation and those caused by treatment with a protein kinase inhibitor K252a. With this in mind, the use of the noncommittal term retrovirus-induced murine lymphoproliferative disease instead of MAIDS appears to be more appropriate at this time.

Mycoplasmas and ureaplasmas in patients with hypogammaglobulinaemia and their role in arthritis: microbiological observations over twenty years

OBJECTIVES

To study the occurrence of mycoplasmas and ureaplasmas in patients with hypogammaglobulinaemia and the relationship of these micro-organisms to septic arthritis.

METHODS

Over a period of about 20 years, 53 men and 38 women with hypogammaglobulinaemia, most of whom were less than 50 years old, were examined clinically and microbiologically. Mycoplasmas and ureaplasmas were sought in the throat, urogenital tract and joints by standard cultural methods, although not consistently in the three sites of all patients.

RESULTS

Arginine-hydrolysing mycoplasmas and ureaplasmas occurred with similar frequency in the sputum/throat of the hypogammaglobulinaemic patients, but no more often than might be expected in immunocompetent patients. Ureaplasmas, however, dominated in the urogenital tracts of both men and women, being found in 75% of vaginal specimens. Arginine-hydrolysing mycoplasmas occurred two to six times more frequently and ureaplasmas two to three times more frequently in urine specimens from hypogammaglobulinaemic patients than they did in such specimens from sex- and age-matched non-venereal disease, hospital patients or healthy subjects; these differences were statistically significant (p < 0.05). Enhanced mucosal colonisation probably increases the chance of spread to distant sites, such as the joints. Of the 91 patients, 21 (23%) had septic arthritis involving one or more joints. Mycoplasmas and/or ureaplasmas, but not bacteria, were isolated from the joints of eight (38%) of these patients. However, dissemination to joints apparently had not occurred in some despite the opportunity by virtue of mycoplasmal or ureaplasmal colonisation at a mucosal site. Sometimes antibiotic therapy failed clinically, and microbiologically and recommendations for management are outlined.

CONCLUSIONS

Hypogammaglobulinaemic patients appear to be more susceptible to colonisation of mucous membranes, especially of the urogenital tract, with mycoplasmas and ureaplasmas than are immunocompetent individuals. These micro-organisms are responsible for about two fifths of the septic arthritides occurring in these patients.

Phylogenetic analysis of Mycoplasma penetrans, isolated from HIV-infected patients

A novel mycoplasmal species designated as Mycoplasma penetrans has recently been isolated from patients infected with human immunodeficiency virus. The 16S rRNA gene from this mycoplasma was cloned and its nucleotide sequence determined. This sequence was aligned with previously published homologous sequences from several mycoplasmas and with related Gram-positive bacteria and a phylogenetic tree was constructed. The results indicate that M. penetrans belongs to the evolutionary group Pneumoniae.

Evaluation of intraspecies genetic variation within the 16S rRNA gene of Mycoplasma hominis and detection by polymerase chain reaction

Mycoplasma hominis is a heterogeneous species with DNA-DNA hybridization values ranging from 51 to 100%. We report here the sequencing of the 16S rRNA gene of a strain (183) that greatly differs from the type strain (PG21) of this species. Comparison of 16S rDNA sequences from these two strains showed limited differences, indicating that the two strains belong to the same rRNA species complex. Using these nucleotide sequence data, we established a rapid method for the detection of M. hominis by using polymerase chain reaction. This method was shown to be sensitive and specific when tested with reference strains and clinical isolates.

High frequency of antibodies to Mycoplasma penetrans in HIV-infected patients

Mycoplasma penetrans, a novel mycoplasma isolated from HIV-1-infected patients with AIDS, has pathogenic properties associated with in-vivo virulence. Enzyme-linked immunosorbent assay and western blotting detected a more than 100 times higher frequency of antibodies to the mycoplasma in serum from HIV-1-infected patients with AIDS (40%) than from HIV-negative controls (0.3%). Serum from 20% of HIV-1-infected, symptom-free individuals also had M penetrans specific antibodies. The antibodies' major immunoreactivity was directed against P35 and P38, the two main lipid-associated membrane protein antigens of the organism. Patients attending sexually transmitted disease clinics had a low frequency of antibody (0.9%). None of 178 HIV-negative patients with different non-AIDS diseases, many associated with immune dysfunction and/or low white cell counts, tested positive for the antibodies. M penetrans, apparently not a commensal and not a simple opportunist, is uniquely associated with HIV-1 infection and AIDS.

No direct neuronotoxicity by HIV-1 virions or culture fluids from HIV-1-infected T cells or monocytes

Macrophages and microglia are the principal target cells for human immunodeficiency virus (HIV) in brain, and as such, are likely participants in the neuropathology of HIV infection. In a model system for this process, we found that fluids from human monocyte cultures enhanced survival and differentiation of the neurons in fetal rat brain explants. In contrast, fluids from HIV-infected monocyte cultures were strongly toxic to neurons and paradoxically enhanced the proliferation of glial cells. Further, neuronotoxic activity in these fluids was mediated through activation of NMDA binding receptors on the neurons and was inhibited by any of several different NMDA antagonists. Neuronotoxic activity was directly related to contamination of the HIV virus stock with Mycoplasma arginini and M. hominis. Pure cultures of mycoplasma, bacterial lipopolysaccharide (LPS), or murine recombinant tumor necrosis factor alpha (rTNF alpha) each induced neuronotoxicity which exactly mirrored that induced by the contaminated HIV stock. It is likely that mycoplasma or components of the mycoplasma plasma membrane stimulate TNF alpha production by the glial cells in the brain explants. Indeed, careful depletion of glial cells in these explants prevented mycoplasma or LPS-mediated neuronotoxicity. No neuronotoxicity was evident with HIV-1 virus stock, HIV-1 gp120, or culture fluids from HIV-infected T cells or monocytes when these preparations were free of contamination by mycoplasma and LPS. These findings suggest caution in interpretation of those experiments in which similar contamination has not been rigorously excluded.