Mycoplasma penetrans bacteremia and primary antiphospholipid syndrome

Characterization of Virulence-Associated Traits in Mycoplasma penetrans Strains Acting as Likely Etiological Agents of Idiopathic Nongonococcal Urethritis

Mycoplasma penetrans is an emerging pathogen with a reduced genome. This bacterium has only previously been cultured from individuals with chronic immunodeficiencies. Here we report the characteristics of 4 M. penetrans isolates from the urine of immunocompetent males with nongonococcal urethritis, in comparison with strain HF-2 from an immunocompromised patient. Several features exhibited distinct differences between these isolates and HF-2. Unlike HF-2, all 4 were resistant to azithromycin. They exhibited greater sialic acid-dependent binding to erythrocytes, gliding motility speed, and H2O2 production than HF-2. All new isolates produced thinner capsules than HF-2. Invasiveness varied, with some isolates being more invasive than HF-2 and some less invasive. Cytotoxicity to HeLa cells was similar to HF-2, and all strains could clear extracellular traps produced by innate immune cells. We conclude that subtle differences among M. penetrans strains may be critical for this organism to establish an infection in an otherwise healthy individual.

[Clinical implications of the genus Mycoplasma]

Dentro del género Mycoplasma, las especies que tradicionalmente se han relacionado con cuadros infecciosos han sido principalmente M. pneumoniae, M. genitalium, M. hominis o U. urealyticum. Sin embargo, existen otras muchas que están implicadas y, que muchas veces, son desconocidas para los profesionales sanitarios. El objetivo de esta revisión es identificar todas las especies del género Mycoplasma que se han aislado en el hombre y determinar su participación en la patología infecciosa humana.

Mycoplasma penetrans bacteremia in an immunocompromised patient detected by metagenomic sequencing: a case report

BACKGROUND

Mycoplasma sp. are well recognized as etiological agents of respiratory and sexually transmitted disease. Mycoplasma penetrans, a species of Mycoplasma sp., has been frequently detected in HIV-positive patients and associated with the progression of HIV-associated disease. To date, there is only a single case report describing M. penetrans as the causative agent of a severe respiratory tract infection in a HIV-negative patient.

CASE PRESENTATION

In this report, we describe the case of M. penetrans bacteremia in a HIV-negative, 38-year-old, female, immunocompromised, solid organ transplant patient (combined kidney and pancreas transplantation in 2016), who was admitted to our hospital with anemic uterine bleeding and fever of 38.3 °C. Several hours before her admission at our university hospital, a latex bladder catheter was inserted into her uterus and she complained about fatigue, dizziness and ongoing vaginal bleeding. Laboratory examination showed severe anemia, but microbiological examination was inconspicuous (culture negative vaginal and cervical smears, negative urine culture). Bacterial blood cultures showed a growth signal after 4 h, but microscopic examination with Gram staining and subcultures on different agar media did not identify bacterial pathogens. To identify the bacterial cause of malignancy in the patient, metagenomic sequencing of the blood culture was performed that identified M. penetrans.

CONCLUSION

Metagenomic sequencing identified M. penetrans in an immunosuppressed patient with culture-negative bacteremia. Clinicians should be aware of the opportunistic potential of M. penetrans that may cause severe infections in certain vulnerable patient populations and the limitations of culture and Gram staining for confirming the presence of fastidious bacterial pathogens like Mycoplasma spp.

The Variable Internal Structure of the Mycoplasma penetrans Attachment Organelle Revealed by Biochemical and Microscopic Analyses: Implications for Attachment Organelle Mechanism and Evolution

Although mycoplasmas have small genomes, many of them, including the HIV-associated opportunist Mycoplasma penetrans, construct a polar attachment organelle (AO) that is used for both adherence to host cells and gliding motility. However, the irregular phylogenetic distribution of similar structures within the mycoplasmas, as well as compositional and ultrastructural differences among these AOs, suggests that AOs have arisen several times through convergent evolution. We investigated the ultrastructure and protein composition of the cytoskeleton-like material of the M. penetrans AO with several forms of microscopy and biochemical analysis, to determine whether the M. penetrans AO was constructed at the molecular level on principles similar to those of other mycoplasmas, such as Mycoplasma pneumoniae and Mycoplasma mobile We found that the M. penetrans AO interior was generally dissimilar from that of other mycoplasmas, in that it exhibited considerable heterogeneity in size and shape, suggesting a gel-like nature. In contrast, several of the 12 potential protein components identified by mass spectrometry of M. penetrans detergent-insoluble proteins shared certain distinctive biochemical characteristics with M. pneumoniae AO proteins, although not with M. mobile proteins. We conclude that convergence between M. penetrans and M. pneumoniae AOs extends to the molecular level, leading to the possibility that the less organized material in both M. pneumoniae and M. penetrans is the substance principally responsible for the organization and function of the AO.IMPORTANCEMycoplasma penetrans is a bacterium that infects HIV-positive patients and may contribute to the progression of AIDS. It attaches to host cells through a structure called an AO, but it is not clear how it builds this structure. Our research is significant not only because it identifies the novel protein components that make up the material within the AO that give it its structure but also because we find that the M. penetrans AO is organized unlike AOs from other mycoplasmas, suggesting that similar structures have evolved multiple times. From this work, we derive some basic principles by which mycoplasmas, and potentially all organisms, build structures at the subcellular level.

Systematic review of case reports of antiphospholipid syndrome following infection

OBJECTIVE

The objective of this study was to conduct a systematic review of case reports documenting the development of antiphospholipid syndrome or antiphospholipid syndrome-related features after an infection.

METHODS

We searched Medline, EMBASE, Web of Science, PubMed ePubs, and The Cochrane Library - CENTRAL through March 2015 without restrictions. Studies reporting cases of antiphospholipid syndrome or antiphospholipid syndrome-related features following an infection were included.

RESULTS

Two hundred and fifty-nine publications met inclusion criteria, reporting on 293 cases. Three different groups of patients were identified; group 1 included patients who fulfilled the criteria for definitive antiphospholipid syndrome (24.6%), group 2 included patients who developed transient antiphospholipid antibodies with thromboembolic phenomena (43.7%), and group 3 included patients who developed transient antiphospholipid antibodies without thromboembolic events (31.7%). The most common preceding infection was viral (55.6%). In cases that developed thromboembolic events Human immunodeficiency and Hepatitis C viruses were the most frequently reported. Parvovirus B19 was the most common in cases that developed antibodies without thromboembolic events. Hematological manifestations and peripheral thrombosis were the most common clinical manifestations. Positive anticardiolipin antibodies were the most frequent antibodies reported, primarily coexisting IgG and IgM isotypes. Few patients in groups 1 and 2 had persistent antiphospholipid antibodies for more than 6 months. Outcome was variable with some cases reporting persistent antiphospholipid syndrome features and others achieving complete resolution of clinical events.

CONCLUSIONS

Development of antiphospholipid antibodies with all traditional manifestations of antiphospholipid syndrome were observed after variety of infections, most frequently after chronic viral infections with Human immunodeficiency and Hepatitis C. The causal relationship between infection and antiphospholipid syndrome cannot be established, but the possible contribution of various infections in the pathogenesis of antiphospholipid syndrome need further longitudinal and controlled studies to establish the incidence, and better quantify the risk and the outcomes of antiphospholipid-related events after infection.

Conserved terminal organelle morphology and function in Mycoplasma penetrans and Mycoplasma iowae

Within the genus Mycoplasma are species whose cells have terminal organelles, polarized structures associated with cytadherence and gliding motility. Mycoplasma penetrans, found mostly in HIV-infected patients, and Mycoplasma iowae, an economically significant poultry pathogen, are members of the Mycoplasma muris phylogenetic cluster. Both species have terminal organelles that interact with host cells, yet the structures in these species, or any in the M. muris cluster, remain uncharacterized. Time-lapse microcinematography of two strains of M. penetrans, GTU-54-6A1 and HF-2, and two serovars of M. iowae, K and N, show that the terminal organelles of both species play a role in gliding motility, with differences in speed within and between the two species. The strains and serovars also differed in their hemadsorption abilities that positively correlated with differences in motility speeds. No morphological differences were observed between M. penetrans and M. iowae by scanning electron microscopy (SEM). SEM and light microscopy of M. penetrans and M. iowae showed the presence of membranous filaments connecting pairs of dividing cells. Breaking of this filament during cell division was observed for M. penetrans by microcinematography, and this suggests a role for motility during division. The Triton X-100-insoluble fractions of M. penetrans and M. iowae consisted of similar structures that were unique compared to those identified in other mycoplasma species. Like other polarized mycoplasmas, M. penetrans and M. iowae have terminal organelles with cytadherence and gliding functions. The difference in function and morphology of the terminal organelles suggests that mycoplasmas have evolved terminal organelles independently of one another.

Characterization of a unique ADP-ribosyltransferase of Mycoplasma penetrans

Mycoplasma penetrans is a urogenital tract pathogen implicated in the deterioration of the immune system in human immunodeficiency virus-infected AIDS patients. Here, we describe a 78-kDa protein from M. penetrans, designated MYPE9110, that exhibits sequence similarity to known ADP-ribosyltransferases (ADPRTs) such as Bordetella pertussis pertussis toxin and Mycoplasma pneumoniae community-acquired respiratory distress syndrome toxin. MYPE9110 possesses key amino acid residues found in all ADPRTs that are essential for ADPRT activity. Several mammalian cell proteins are ADP-ribosylated by MYPE9110, and the full-length recombinant protein exhibits a strong auto-ADP-ribosylating activity. In the absence of target proteins, MYPE9110 demonstrates a NAD-glycohydrolase activity by hydrolyzing NAD. Furthermore, this toxin elicits cytopathology in HeLa cells by inducing cytoplasmic vacuolization in the presence of ammonium chloride. The deletion of the C-terminal region of MYPE9110 significantly diminishes its binding to host cells while still exhibiting an ADPRT activity, suggesting that MYPE9110 is a member of the family of A-B ADPRT toxins.

Identification of a site-specific tyrosine recombinase that mediates promoter inversions of phase-variable mpl lipoprotein genes in Mycoplasma penetrans

Mycoplasma penetrans has the ability to change its surface lipoprotein profiles frequently. The P35 family lipoproteins encoded by the mpl genes are key players in this profile variation. The M. penetrans HF-2 genome has 38 mpl genes that form three gene clusters. Most of these mpl genes have an invertible promoter sequence that is responsible for the ON/OFF switching of individual mpl gene expression. Here, we identified the recombinase that catalyses inversions of the mpl gene promoters. We focused on two open reading frames of the M. penetrans HF-2 genome, namely MYPE2900 and MYPE8180, which show significant homology to the tyrosine site-specific recombinase (Tsr) family proteins. Since genetic tools for M. penetrans are still not developed, we cloned the MYPE2900 and MYPE8180 genes and expressed them in Mycoplasma pneumoniae and Escherichia coli. The promoter regions of the mpl genes [p35 (MYPE6810) or p42 (MYPE6630) genes] were also introduced into M. pneumoniae and E. coli cells expressing MYPE2900 or MYPE8180. Inversion of these promoters occurred in the presence of the MYPE2900 gene but not in the presence of the MYPE8180 gene, indicating that the MYPE2900 gene product is the recombinase that catalyses mpl gene promoter inversions. We used a PCR-based method to detect mpl promoter inversion. This method also enabled us to detect inversions of 10 mpl gene promoters in M. penetrans HF-2 cells. All these promoter inversions occurred at the 12 bp inverted repeat (IR) sequences flanking the promoter sequence. The consensus sequence of these IRs was proposed as TAAYNNNDATTA (Y=C or T; D=A, G or T).

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

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

Antiphospholipid syndromes in infectious diseases

Antiphospholipid antibodies are essential in the diagnosis of antiphospholipid syndrome (APS), or the classic "Hughes syndrome," which is a systemic disorder that is autoimmune in nature. They are also found in various infections in low titers without any evidence of thrombotic manifestations of APS. However, in a few infections, when antiphospholipid antibodies are associated with protein cofactor, there can be associated thrombosis. Different infections are also responsible for triggering a subset of lethal APS, acute catastrophic APS. This situation requires prompt diagnosis and aggressive treatment of the infection to prevent severe complications.

Are antiphospholipid antibodies an essential requirement for an effective immune response to infections?

Antiphospholipid antibodies show a close association to a variety of infections. Recent data implicate that parvovirus B19 may be used as a model-system for studying the interaction of viral infection and the development of these autoantibodies. B19-related diseases commonly associated with the acute infection show flu-like symptoms, transient arthralgias, leukopenia and thrombocytopenia, and, in pregnant women, spontaneous abortion and hydrops fetalis. Hepatitis, myocarditis, meningitis, encephalitis, as well as pure red cell anemia may occur occasionally. In addition, parvovirus B19 infections have been frequently described as the cause or trigger of various forms of autoimmune diseases affecting all blood cell lines, joints, connective tissue, uvea, and large and small vessels. Molecular mimicry may be one major contribution to the appearance of autoimmune antibodies, for example, antiphospholipid and antineutrophil cytoplasmic antibodies as well as antinuclear antigens. These mechanisms implicated in the pathogenesis of parvovirus B19-triggered autoimmune diseases, especially focused on the development of antiphospholipid antibodies, will be discussed in this mini review.

Rapid and efficient preparation of monoclonal antibodies against 35 kDa lipoprotein of Mycoplasma penetrans

To develop a rapid and efficient method for preparing monoclonal antibodies (MAb) against 35 kDa lipoprotein of Mycoplasma penetrans, BALB/c mice were injected into the footpads for immunization, and the popliteal lymph nodes were isolated 19 days later for MAb-producing hybridomas, from which the mAbs against the 35 kDa lipoprotein were screened. The identification of the mAb against the 35 kDa lipoprotein was performed using indirect enzyme-linked immunosorbent assay (ELISA) and immunoblotting. Using popliteal lymph node procedures, we generated several positive clones, one of which we characterized by ELISA and immunoblot. The clone 1D41B8 was identified as the immunoglobulin G1 (IgG1) isotype, kappa chain with affinity constants (Ka) of 2.95 x 10(9) M(-1). The MAbs did not cross-react with a number of control bacteria, which included Mycoplasma fermentans, Mycoplasma hominis, and Mycoplasma genitalium. This is the first report on the preparation of mAbs against M. penetrans that is specific to 35 kDa lipoprotein using popliteal lymph nodes. The high-specificity and high-affinity MAbs produced by two methodologies used of hybridomas provide a basis for further research on the pathogenesis and early diagnosis of M. penetrans. This simple approach may become a method of choice for the generation and production of MAbs in a short period of time.

Proteome of the bacterium Mycoplasma penetrans

A proteome map of Mycoplasma penetrans has been constructed using two-dimensional gel electrophoresis in combination with mass spectrometry (MS). Mycoplasma penetrans infects the urogenital and respiratory tracts of humans. A total of 207 spots were characterized with MS and, in comparing the experimental data with the DNA sequence-derived predictions, it was possible to assign these 207 spots to 153 genes. The Pro-Q Diamond phosphoprotein dye technology was used for the fluorescent detection of 26 phosphoproteins in the 4-7 pH range.

Antiphospholipid antibodies in pediatric patients with prolonged activated partial thromboplastin time during infection

OBJECTIVE

To investigate the close association between different antiphospholipid antibodies (aPL) caused by infection and their appearance together with a prolonged activated partial thromboplastin time (aPTT).

METHODS

Sera from 122 children were evaluated in this study. Thirty-seven children with mild to medium prolonged aPTT (>37.2s) and elevated C-reactive protein (CRP) levels during various forms of infections (group 2), 18 children without infections (group 3) but with mild to medium prolonged aPTT and 13 children with infections (group 4) and with elevated CRP-level as well as a control group (group 1) of 54 patients without any infection and normal aPTT and negative CRP levels were investigated with commercially available ELISA tests (AESKU.Diagnostics, Wendelsheim, Germany) for the presence of antibodies directed against cardiolipin (CL), phosphatidylserine (PS) and beta2-glycoprotein I (beta 2GPI). The cutoff for positive results was defined with the healthy, aged matched control group (group 1) using the mean OD values plus 2 standard deviations. The lupus anticoagulant (dilute Russell's Viper Venom time, dRVVT) and coagulation Factor XII were determined with routine tests (Dade Behring).

RESULTS

Detection of at least one antibody to phospholipids was possible in 89.2% of group 2. It could be shown that IgM anti-beta 2GPI antibodies were found in 27 (59.5%) of group 2, but only in 1 (5.6%) of group 3 (p=0.024) and only in 4 (7.4%) of the controls (p=0.014). The presence of IgG-anti-beta 2GPI antibodies showed no significant difference in the different groups. Furthermore, children of groups 2, 3 and 4 had statistically significant higher levels of antibodies against PS IgG and PS IgM than controls. Also, antibodies to CL of the IgG-type were more frequently detected in children of group 2 than in controls (p=0.038). Detection of CL-IgM antibodies did not reach a significant level in the comparison of the different groups.

CONCLUSION

During commonly acquired infections elevation of aPL of nearly all types seems to be a common process. Mild prolongation of aPTT might reflect this presence of aPL in the course of the infectious disease. Our data suggest that there exists no differences in specificity in comparison to the "pathogenic" aPL but the presence over time might be the trigger for the autoimmune activity to begin.

Mycoplasmas and ureaplasmas as neonatal pathogens

The genital mycoplasmas represent a complex and unique group of microorganisms that have been associated with a wide array of infectious diseases in adults and infants. The lack of conclusive knowledge regarding the pathogenic potential of Mycoplasma and Ureaplasma spp. in many conditions is due to a general unfamiliarity of physicians and microbiology laboratories with their fastidious growth requirements, leading to difficulty in their detection; their high prevalence in healthy persons; the poor design of research studies attempting to base association with disease on the mere presence of the organisms in the lower urogenital tract; the failure to consider multifactorial aspects of diseases; and considering these genital mycoplasmas only as a last resort. The situation is now changing because of a greater appreciation of the genital mycoplasmas as perinatal pathogens and improvements in laboratory detection, particularly with regard to the development of powerful molecular nucleic acid amplification tests. This review summarizes the epidemiology of genital mycoplasmas as causes of neonatal infections and premature birth; evidence linking ureaplasmas with bronchopulmonary dysplasia; recent changes in the taxonomy of the genus Ureaplasma; the neonatal host response to mycoplasma and ureaplasma infections; advances in laboratory detection, including molecular methods; and therapeutic considerations for treatment of systemic diseases.

Antiphospholipid syndrome associated with infections: clinical and microbiological characteristics of 100 patients

OBJECTIVE

To describe and analyse the clinical characteristics of 100 patients with antiphospholipid syndrome (APS) associated with infections.

METHODS

Patients were identified by a computer assisted search (Medline) of published reports to locate all cases of APS published in English, Spanish, and French from 1983 to 2003. The bilateral Fisher exact test was used for statistics.

RESULTS

59 female and 41 male patients were identified (mean (SD) age, 32 (18) years (range 1 to 78)): 68 had primary APS, 27 had systemic lupus erythematosus, two had "lupus-like" syndrome, two had inflammatory bowel disease, and one had rheumatoid arthritis. APS presented as a catastrophic syndrome in 40% of cases. The main clinical manifestations of APS included: pulmonary involvement (39%), skin involvement (36%), and renal involvement (35%; nine with renal thrombotic microangiopathy, RTMA). The main associated infections and agents included skin infection (18%), HIV (17%), pneumonia (14%), hepatitis C (13%), and urinary tract infection (10%). Anticoagulation was used in 74%, steroids in 53%, intravenous immunoglobulins in 20%, cyclophosphamide in 12%, plasma exchange in 12%, and dialysis in 9.6%. Twenty three patients died following infections and thrombotic episodes (16 with catastrophic APS). Patients given steroids had a better prognosis (p = 0.024). The presence of RTMA and requirement for dialysis carried a worse prognosis (p = 0.001 and p = 0.035, respectively).

CONCLUSIONS

Various different infections can be associated with thrombotic events in patients with APS, including the potentially lethal subset termed catastrophic APS. Aggressive treatment with anticoagulation, steroids, and appropriate antibiotic cover is necessary to improve the prognosis.

Antiphospholipid antibodies in pediatric and adult patients with rheumatic disease are associated with parvovirus B19 infection

OBJECTIVE

To show a possible association between parvovirus B19 infection and the presence of antiphospholipid antibodies (aPL) in patients with rheumatic diseases.

METHODS

Serum samples obtained from 88 children with various forms of juvenile rheumatic disease and from 40 adults with systemic lupus erythematosus, the antiphospholipid syndrome, or other rheumatic disease, who had previously been tested and shown to be positive for IgG aPL, were analyzed for the presence of B19 DNA, for antibodies against the B19 viral proteins VP1, VP2, and NS1, and for IgG aPL (anticardiolipin, anti-beta(2)-glycoprotein I, and antiphosphatidylserine). As controls, serum samples obtained from 135 children with noninflammatory bone diseases or growth retardation were also analyzed.

RESULTS

Twenty-four (27%) of the 88 children with rheumatic diseases had detectable amounts of IgG aPL. Fourteen (58%) of these 24 IgG aPL-positive patients showed IgG against VP1/VP2 and viral genomes, indicating the presence of acute (2 patients) or persistent (12 patients) infection. Past parvovirus B19 infection was identified in 7 (29%) of 24 IgG aPL-positive children, as indicated by VP1/VP2-specific IgG in the absence of viral DNA. Three (12%) of 24 IgG aPL-positive children had not been infected with B19. Sixty-nine (51%) of 135 control children displayed VP1/VP2-specific IgG. Three (2%) of these 135 children were IgG aPL positive (2 children had past parvovirus B19 infection, and 1 was negative for parvovirus B19). Analysis of the parvovirus B19 status of 40 adult IgG aPL-positive patients showed that 33 (83%) were anti-IgG VP1/VP2-positive, and viral DNA was detected in 11 patients (28%). Ten of these 11 viremic patients were in the subgroup of 28 IgG aPL-positive SLE patients.

CONCLUSION

Antiphospholipid antibodies are preferentially found in serum of children with juvenile idiopathic arthritis who have been previously infected with parvovirus B19 and have established, persistent infection. Adult patients with IgG aPL positivity have a high incidence of persistent parvovirus B19 infection. We conclude that parvovirus B19 might be directly involved in the elicitation of autoimmune reactions partly mediated by aPL.

Detection of several Mycoplasma species at various anatomical sites of homosexual men

In order to determine the colonisation patterns of several Mycoplasma species in homosexual men, urethral, oral and rectal specimens from 10 homosexual men with acute non-gonococcal urethritis (NGU) and 18 without NGU were examined using sensitive methods. Mycoplasma hominis and Ureaplasma urealyticum existed in both groups, which is in keeping with previous studies of heterosexual men. Mycoplasma genitalium was detected in the rectum of both NGU-positive and NGU-negative men and in the urethra of one man with chlamydia-negative NGU, but not in those without urethritis. Mycoplasma fermentans was found in the throat and rectum only and Mycoplasma penetrans in all three anatomical sites. In contrast, Mycoplasma pirum was found in the rectum only, that is, in 5 of the 28 men studied. Infrequent examination of this site is a possible explanation for previous failures to detect Mycoplasma pirum at a mucosal surface.

Multiple promoter inversions generate surface antigenic variation in Mycoplasma penetrans

Mycoplasma penetrans is a newly identified species of the genus MYCOPLASMA: It was first isolated from a urine sample from a human immunodeficiency virus (HIV)-infected patient. M. penetrans changes its surface antigen profile with high frequency. The changes originate from ON<==>OFF phase variations of the P35 family of surface membrane lipoproteins. The P35 family lipoproteins are major antigens recognized by the human immune system during M. penetrans infection and are encoded by the mpl genes. Phase variations of P35 family lipoproteins occur at the transcriptional level of mpl genes; however, the precise genetic mechanisms are unknown. In this study, the molecular mechanisms of surface antigen profile change in M. penetrans were investigated. The focus was on the 46-kDa protein that is present in M. penetrans strain HF-2 but not in the type strain, GTU. The 46-kDa protein was the product of a previously reported mpl gene, pepIMP13, with an amino-terminal sequence identical to that of the P35 family lipoproteins. Nucleotide sequencing analysis of the pepIMP13 gene region revealed that the promoter-containing 135-bp DNA of this gene had the structure of an invertible element that functioned as a switch for gene expression. In addition, all of the mpl genes of M. penetrans HF-2 were identified using the whole-genome sequence data that has recently become available for this bacterium. There are at least 38 mpl genes in the M. penetrans HF-2 genome. Interestingly, most of these mpl genes possess invertible promoter-like sequences, similar to those of the pepIMP13 gene promoter. A model for the generation of surface antigenic variation by multiple promoter inversions is proposed.

The complete genomic sequence of Mycoplasma penetrans, an intracellular bacterial pathogen in humans

The complete genomic sequence of an intracellular bacterial pathogen, Mycoplasma penetrans HF-2 strain, was determined. The HF-2 genome consists of a 1 358 633 bp single circular chromosome containing 1038 predicted coding sequences (CDSs), one set of rRNA genes and 30 tRNA genes. Among the 1038 CDSs, 264 predicted proteins are common to the Mycoplasmataceae sequenced thus far and 463 are M.penetrans specific. The genome contains the two-component system but lacks the essential cellular gene, uridine kinase. The relatively large genome of M.penetrans HF-2 among mycoplasma species may be accounted for by both its rich core proteome and the presence of a number of paralog families corresponding to 25.4% of all CDSs. The largest paralog family is the p35 family, which encodes surface lipoproteins including the major antigen, P35. A total of 44 genes for p35 and p35 homologs were identified and 30 of them form one large cluster in the chromosome. The genetic tree of p35 paralogs suggests the occurrence of dynamic chromosomal rearrangement in paralog formation during evolution. Thus, M.penetrans HF-2 may have acquired diverse repertoires of antigenic variation-related genes to allow its persistent infection in humans.

Immunization of naive BALB/c mice with human beta2-glycoprotein I breaks tolerance to the murine molecule

OBJECTIVE

Immunization of naive mice with beta2-glycoprotein I (beta2GPI) leads to the generation of pathogenic anticardiolipin antibodies associated with clinical manifestations of the antiphospholipid syndrome (APS). The aim of this study was to determine whether immunization of naive mice with human beta2GPI, which shares homology with mouse beta2GPI molecules, breaks tolerance to murine beta2GPI and leads to the generation of anti-mouse beta2GPI.

METHODS

Twenty-four female BALB/c mice were immunized in the footpads with 10 microg of human beta2GPI. Twelve age- and sex-matched BALB/c mice were immunized in the same manner with Freund's complete adjuvant and served as controls. The reactivity of whole sera, polyclonal IgG, and affinity-purified anti-beta2GPI IgG antibodies against human, bovine, and mouse beta2GPI was evaluated by enzyme-linked immunosorbent assay.

RESULTS

High titers of anti-human beta2GPI IgG antibodies were detected 1 month after immunization. Progressively increasing titers against murine and bovine beta2GPI were recorded 1-4 months after injection.

CONCLUSION

Immunization of mice with human beta2GPI resulted in the generation of antibodies reacting with human, bovine, and murine beta2GPI. The loss of tolerance to mouse beta2GPI is attributable to the high interspecies homology of beta2GPI. These results may point to molecular mimicry as a possible cause of APS.

Bacterial induction of autoantibodies to beta2-glycoprotein-I accounts for the infectious etiology of antiphospholipid syndrome

The antiphospholipid syndrome (APS) is characterized by the presence of pathogenic autoantibodies against beta2-glycoprotein-I (beta2GPI). The factors causing production of anti-beta2GPI remain unidentified, but an association with infectious agents has been reported. Recently, we identified a hexapeptide (TLRVYK) that is recognized specifically by a pathogenic anti-beta2GPI mAb. In the present study we evaluated the APS-related pathogenic potential of microbial pathogens carrying sequences related to this hexapeptide. Mice immunized with a panel of microbial preparations were studied for the development of anti-beta2GPI autoantibodies. IgG specific to the TLRVYK peptide were affinity purified from the immunized mice and passively infused intravenously into naive mice at day 0 of pregnancy. APS parameters were evaluated in the infused mice on day 15 of pregnancy. Following immunization, high titers of antipeptide [TLRVYK] anti-beta2GPI Ab's were observed in mice immunized with Haemophilus influenzae, Neisseria gonorrhoeae, or tetanus toxoid. The specificity of binding to the corresponding target molecules was confirmed by competition and immunoblot assays. Naive mice infused with the affinity-purified antipeptide Ab's had significant thrombocytopenia, prolonged activated partial thromboplastin time and elevated percentage of fetal loss, similar to a control group of mice immunized with a pathogenic anti-beta2GPI mAb. Our study establishes a mechanism of molecular mimicry in experimental APS, demonstrating that bacterial peptides homologous with beta2GPI induce pathogenic anti-beta2GPI Ab's along with APS manifestations.

Bacterial induction of autoantibodies to beta2-glycoprotein-I accounts for the infectious etiology of antiphospholipid syndrome

The antiphospholipid syndrome (APS) is characterized by the presence of pathogenic autoantibodies against beta2-glycoprotein-I (beta2GPI). The factors causing production of anti-beta2GPI remain unidentified, but an association with infectious agents has been reported. Recently, we identified a hexapeptide (TLRVYK) that is recognized specifically by a pathogenic anti-beta2GPI mAb. In the present study we evaluated the APS-related pathogenic potential of microbial pathogens carrying sequences related to this hexapeptide. Mice immunized with a panel of microbial preparations were studied for the development of anti-beta2GPI autoantibodies. IgG specific to the TLRVYK peptide were affinity purified from the immunized mice and passively infused intravenously into naive mice at day 0 of pregnancy. APS parameters were evaluated in the infused mice on day 15 of pregnancy. Following immunization, high titers of antipeptide [TLRVYK] anti-beta2GPI Ab's were observed in mice immunized with Haemophilus influenzae, Neisseria gonorrhoeae, or tetanus toxoid. The specificity of binding to the corresponding target molecules was confirmed by competition and immunoblot assays. Naive mice infused with the affinity-purified antipeptide Ab's had significant thrombocytopenia, prolonged activated partial thromboplastin time and elevated percentage of fetal loss, similar to a control group of mice immunized with a pathogenic anti-beta2GPI mAb. Our study establishes a mechanism of molecular mimicry in experimental APS, demonstrating that bacterial peptides homologous with beta2GPI induce pathogenic anti-beta2GPI Ab's along with APS manifestations.

Phase variation among major surface antigens of Mycoplasma penetrans

The pathogenicity and prevalence of Mycoplasma penetrans, a Mycoplasma species recently isolated from humans, are still debated. A major P35 antigen, which is used as target epitope in serological assays, was shown to be a phase-variable lipid-associated membrane protein (LAMP). In this study, we performed a comparative analysis of the LAMP patterns from five M. penetrans clinical isolates and from the type strain. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis profiles and immunoblots with sera serially collected from an M. penetrans-infected patient indicated that these strains expressed different LAMP repertoires. Furthermore, the intraclonal variation in the expression of LAMPs (P34A, P34B, P35, and P38) was monitored by immunoblot analysis with three specific monoclonal antibodies (MAbs) developed in this study and MAb 7 to P35. The phase variation of these LAMPs occurs in an independent manner, with frequencies of variation ranging from 10(-2) to 10(-4) per cell per generation. Consistent with their amphipathic nature, the P34B and P38 antigens were found exposed at the cell surface. The DNA sequence encoding the P38 antigen was defined and found to be related to those of the P35 gene and other putative LAMP-encoding genes, suggesting that these variable antigens are encoded by a family of related genes. Finally, the serum samples from an M. penetrans-infected patient contained antibodies that reacted with a P36 antigen expressed in different M. penetrans strains but not in the isolate recovered from this patient. This result suggested that in vivo phase variation of P36 occurred, which would support a role for these LAMP variations in avoiding the host's immune vigilance.

The antiphospholipid syndrome and infection

Infectious agents have been implicated in the induction of antiphospholipid (aPL) antibodies and the development of the antiphospholipid syndrome (APS). This review focuses on the types of aPL antibodies detected in infections and addresses whether these antibodies are of clinical importance in patients with infections. Hepatitis C virus (HCV) infection is given special attention because this virus has the propensity to induce various autoimmune phenomena. Several aspects are emphasized that should be considered carefully when interpreting results. Most of the published data agree that thrombophilia is not observed in patients with infections (including HCV) because aPL antibodies are mostly the natural or nonpathogenic type. Thus, we do not recommend routinely testing for HCV in patients with APS. However, not all infection-associated aPL antibodies are cofactor independent. For instance, infections are increasingly recognized as a major precipitating condition of the catastrophic variant of APS, perhaps via mechanisms of molecular mimicry. Therefore, it may be possible to prevent this devastating evolution if the infectious process is promptly recognized and exhaustively treated.

Higher prevalence of urogenital mycoplasmas in human immunodeficiency virus-positive patients as compared to patients with other sexually transmitted diseases

We determined the prevalence of three emergent urogenital mycoplasma species (M. fermentans, M. penetrans, and M. genitalium) in comparison to the most common species (M. hominis and U. urealyticum). M. genitalium is probably the third most frequent agent of nongonococcal urethritis (NGU) in men. It has been suggested that M. fermentans and M. penetrans play a role in the development of AIDS. We analysed the urine and the urethral swab samples from 106 HIV-1 infected individuals (HIV group) and 110 HIV-negative patients with NGU (STD group) by using PCR and culture methods. M. genitalium was detected in 0.9% of the urine and in 1.9% of the urethral samples from the HIV group, compared to 9.1% found only in urethral swab samples from the STD group. M. fermentans was detected in 5.7% urethral swabs from the HIV group and in 0.9% from the STD group. M. penetrans was detected in 6.6% urine samples from the HIV group. M. hominis and U. urealyticum showed infection rates of 7.5 and 18.9% in the HIV group, and 0.9 and 13.6% in the STD group. Overall there was a higher prevalence of mycoplasmas in the HIV group than in the STD group, but the significance of these results remains unclear.

Mycoplasma species in rapid and slow HIV progressors

We determined the relationship between the presence of Mycoplasma fermentans and Mycoplasma penetrans and the rate of progression of HIV-associated disease in a nested case-control study based on a cohort of 159 HIV-infected patients with different rates of disease progression. Study participants were divided into 3 progression groups: non-progressors who had been HIV-1 seropositive for at least 9 years and had remained asymptomatic with a CD4 cell count of > 500/mm3; slow progressors who had been HIV-1 seropositive for at least 9 years and whose CD4 cell count had fallen below 500 cells, and who had developed symptomatic disease or AIDS; and rapid progressors who had developed AIDS within 5 years of HIV infection. Peripheral blood mononuclear cells (PBMCs) were collected at enrollment and examined by mycoplasma polymerase chain reaction (PCR) assays. Three (7%) of 46 non-progressors, 3 (3%) of 86 slow progressors, and 2 (7%) of 27 rapid progressors were M. fermentans positive. The PBMCs from 91 subjects were tested for M. penetrans DNA and none was positive. The small proportion of M. fermentans-positive patients indicates that the mycoplasma cannot be important in the development of AIDS in the large majority of patients. Furthermore, no association was found between its presence and more rapid HIV disease progression.

Role of Mycoplasma penetrans endonuclease P40 as a potential pathogenic determinant

Recently, we reported the purification to homogeneity and characterization of Ca(2+)- and Mg(2+)-dependent endonuclease P40 produced by Mycoplasma penetrans (M. Bendjennat, A. Blanchard, M. Loutfi, L. Montagnier, and E. Bahraoui, J. Bacteriol. 179; 2210-2220, 1997), a mycoplasma which was isolated for the first time from the urine of human immunodeficiency virus-infected patients. To evaluate how this nuclease could interact with host cells, we tested its effect on CEM and Molt-4 lymphocytic cell lines and on peripheral blood mononuclear cells. We observed that 10(-7) to 10(-9) M P40 is able to mediate a cytotoxic effect. We found that 100% of cells were killed after 24 h of incubation with 10(-7) M P40 while only 40% cytotoxicity was obtained after 72 h of incubation with 10(-9) M P40. Phase-contrast microscopy observations of P40-treated cells revealed morphological changes, including pronounced blebbing of the plasma membrane and cytoplasmic shrinkage characteristic of programmed cell death, which is in agreement with the internucleosomal fragmentation of P40-treated cell DNA as shown by agarose gel electrophoresis. We showed that (125)I-radiolabeled or fluorescein isothiocyanate-labeled P40 was able to bind specifically in a dose-dependent manner to the cell membrane of CEM cells, which suggested that the cytotoxicity of P40 endonuclease was mediated by its interaction with the cell surface receptor(s). The concentration of unlabeled P40 required to inhibit by 50% the formation of (125)I-P40-CEM complexes was about 3 x 10(-9) M, indicating a high-affinity interaction. Both P40 interaction and cytotoxicity are Ca(2+) dependent. Our results suggest that the cytotoxicity of M. penetrans observed in vitro is mediated at least partially by secreted P40, which, after interaction with host cells, can induce an apoptosis-like death. These results strongly suggest a major role of mycoplasmal nucleases as potential pathogenic determinants.