Opsonin-reversible resistance of Mycoplasma pneumoniae to in vitro phagocytosis by alveolar macrophages

Altered chemokine profile in Refractory Mycoplasma pneumoniae pneumonia infected children

BACKGROUND

Mycoplasma pneumoniae is one of the major pathogens causing community-acquired pneumonia in children. Although usually self-limited, Mycoplasma pneumoniae pneumonia (MPP) may lead to complicated morbidity that can even be life-threatening. Upon MPP infection, alveolar macrophage becomes attracted and activated and will induce subsequent cytokine and chemokine reaction. Refractory Mycoplasma pneumoniae pneumonia (RMPP) is manifested by clinical or radiological deterioration despite proper antibiotic therapy. RMPP is characterized with excessive inflammation and may need subsequent glucocorticoid treatment.

AIM

The aim of this study was to investigate the change of plasma chemokines in non-refractory Mycoplasma pneumoniae pneumonia (NRMPP) and RMPP before and after antibiotic or methylprednisolone treatment.

METHOD

A total of 42 children with MPP were enrolled in this study. Plasma specimens were collected at admission and one to two weeks after antibiotic or methylprednisolone treatment with declined fever. Plasma specimens were then indicated to chemokines detection.

RESULTS

Mycoplasma pneumoniae pneumonia altered the chemokine profile through the observation of decreased plasma M1 related chemokines (CCL2, CCL8 and CXCL10) and increased M2 related chemokines (CCL17 and CCL22) after treatment.When the patients were divided into RMPP and NRMPP groups and the chemokines before treatment were compared, the RMPP group showed higher CXCL10 but lower CCL3 and CCL11 than the NRMPP group.

CONCLUSION

Unique changes in macrophage related chemokines is observed in the course of MPP infection. NRMPP and RMPP infection in children showed distinct manifestation in chemokine profiles.

Mycoplasma hyopneumoniae evades phagocytic uptake by porcine alveolar macrophages in vitro

Mycoplasma hyopneumoniae, the agent of porcine enzootic pneumonia (EP), is able to persist in the lung tissue and evade destruction by the host for several weeks. To understand the mechanism of pathogen survival, phagocytic uptake of M. hyopneumoniae by primary porcine alveolar macrophages was investigated. Intracellular location and survival of the pathogen were explored using gentamicin survival assays, flow cytometry and confocal microscopy of M. hyopneumoniae 232 labelled with green fluorescent protein (GFP). Following 1 h and 16 h of co-incubation, few viable M. hyopneumoniae were recovered from inside macrophages. Flow cytometric analysis of macrophages incubated with M. hyopneumoniae expressing GFP indicated that the mycoplasmas became associated with macrophages, but were shown to be extracellular when actin-dependent phagocytosis was blocked with cytochalasin D. Confocal microscopy detected GFP-labelled M. hyopneumoniae inside macrophages and the numbers increased modestly with time of incubation. Neither the addition of porcine serum complement or convalescent serum from EP-recovered pigs was able to enhance engulfment of M. hyopneumoniae. This investigation suggests that M. hyopneumoniae evades significant uptake by porcine alveolar macrophages and this may be a mechanism of immune escape by M. hyopneumoniae in the porcine respiratory tract.

Successful Additional Corticosteroid Treatment in a Patient with Mycoplasma pneumoniae Pneumonia in whom a Monobacterial Infection was Confirmed by a Molecular Method Using Bronchoalveolar Lavage Fluid

A 23-year-old Japanese woman was admitted to A hospital due to pneumonia. IgM for Mycoplasma pneumoniae was positive, and the patient was treated with imipenem/cilastatin, clindamycin, pazufloxacin and minocycline. However, both the chest radiological findings and the symptoms became exacerbated, and she was therefore transferred to our hospital. The bronchoalveolar lavage fluid was obtained, and a 16S rRNA gene sequencing analysis revealed a monobacterial infection of Mycoplasma pneumoniae. Therefore, corticosteroid treatment in addition to minocycline was administered, and the patients symptoms, laboratory data and chest radiographs improved. Corticosteroid therapy may therefore be considered for patients with refractory M. pneumoniae pneumonia.

Experimental contagious caprine pleuropneumonia: a long term study on the course of infection and pathology in a flock of goats infected with Mycoplasma capricolum subsp. capripneumoniae

Contagious caprine pleuropneumonia (CCPP) is a major threat to goat farming in parts of Africa and Asia. It classically causes acute high morbidity and mortality early in infection, but little is known of its long term epizootiology and course. In this study, 10 goats were inoculated with Mycoplasma capricolum subsp. capripneumoniae (M. capripneumoniae) and then mixed with 15 goats for contact transmission. The disease course was monitored in each goat for 56-105 days, whereafter the goats were killed and necropsied. Varying features signifying infection occurred in altogether 17 goats (7 inoculated, 10 in-contact). Clinical signs were severe in 8 goats but no fatalities occurred. Only 6 goats had serum antibody titres against M. capripneumoniae in ELISA. Fourteen goats (5 inoculated, 9 in-contact) had chronic pleuropulmonary lesions compatible with CCPP at necropsy and 7 of those showed M. capripneumoniae antigen in the lung by immunohistochemistry. Neither cultivation nor PCR tests were positive for the agent in any goat. The results indicate that the clinical course of CCPP in a flock may be comparatively mild, M. capripneumoniae-associated lung lesions may be present at a late stage of infection, and chronic infection may occur without a significant serological response.

Severe acute lung injury caused by Mycoplasma pneumoniae: potential role for steroid pulses in treatment

Published evidence of pathogenetic mechanisms of acute respiratory distress syndrome (ARDS) in mycoplasmal lung infections suggests that the pulmonary injury is related to a cell-mediated immune response. Therefore, steroids may play a role in the treatment of severe cases. We describe a patient who had Mycoplasma pneumoniae pneumonia that progressed to severe ARDS requiring mechanical ventilation and who had improvement with prednisolone pulses.

Roles of innate and adaptive immunity in respiratory mycoplasmosis

Current evidence suggests that host defense in respiratory mycoplasmosis is dependent on both innate and humoral immunity. To further delineate the roles of innate and adaptive immunity in antimycoplasmal defenses, we intranasally infected C3H/HeSnJ-scid/scid (C3H-SCID), C3H/HeSnJ (C3H), C57BL/6J-scid/scid (C57-SCID), and C57BL/6N (C57BL) mice with Mycoplasma pulmonis and at 14 and 21 days postinfection performed quantitative cultures of lungs and spleens, quantification of lung lesions, and histopathologic assessments of all other major organs. We found that numbers of mycoplasmas in lungs were associated with genetic background (C3H susceptible, C57BL resistant) rather than functional state of adaptive immunity, indicating that innate immunity is the main contributor to antimycoplasmal defense of the lungs. Extrapulmonary dissemination of mycoplasmas with colonization of spleens and histologic lesions in multiple organs was a common occurrence in all mice. The absence of adaptive immune responses in severe combined immunodeficient (SCID) mice resulted in increased mycoplasmal colonization of spleens and lesions in extrapulmonary sites, particularly spleens, hearts, and joints, and also reduced lung lesion severity. The transfer of anti-M. pulmonis serum to infected C3H-SCID mice prevented extrapulmonary infection and disease, while the severity of lung lesions was restored by transfer of naive spleen cells to infected C3H-SCID mice. Collectively, our results strongly support the conclusions that innate immunity provides antimycoplasmal defense of the lungs and humoral immunity has the major role in defense against systemic dissemination of mycoplasmal infection, but cellular immune responses may be important in exacerbation of mycoplasmal lung disease.

Expression of functions by normal sheep alveolar macrophages and their alteration by interaction with Mycoplasma ovipneumoniae

Normal sheep alveolar macrophages collected by bronchial lavage were exposed to live or heat-killed Mycoplasma ovipneumoniae organisms, and their capability to ingest Staphylococcus aureus and to elicit antibody-dependent cellular cytotoxicity against sensitized chicken red blood cells was tested. Controls consisted of non-infected macrophages in M199 medium. In addition, the effect of M. ovipneumoniae on expression of surface molecules on these sheep alveolar macrophages was determined. The percentage of S. aureus ingested by nontreated sheep alveolar macrophages was significantly higher than that of infected macrophages. Live mycoplasmas were more effective in suppressing the ingestion of S. aureus by these macrophages than killed mycoplasmas. Both live and killed mycoplasmas suppressed the cytolytic effect of the sheep alveolar macrophages to a similar degree. About 78% and 45% of the normal sheep alveolar macrophages had IgG and complement receptors, respectively. Infection of these macrophages with M. ovipneumoniae decreased significantly the expression of IgG receptors but had no effects on complement receptors. There were substantial increases in the expression of both MHC class I and class II by the mycoplasma-induced macrophages as compared with unstimulated macrophages. Live mycoplasmas were more effective in inducing expression of both classes than killed mycoplasmas. The results, taken together, suggest that M. ovipneumoniae induced alterations in macrophage activities and this may be a contributing factor in the pathogenesis of respiratory disease induced by the organism.

Adherence of Mycoplasma pneumoniae to human alveolar macrophages

The human pathogen Mycoplasma pneumoniac causes primary atypical-cold agglutinin-positive pneumonia. Since alveolar macrophages internalize mycoplasma as part of their immune defense, we studied characteristics of the human macrophage receptor for opsonized and nonopsonized M. pneumoniae. The glass-adhering subpopulation of M. pneumoniae attached more than the non-adherent subpopulation. The attachment was dose-dependent and enhanced by opsonization in the presence of human serum. It is inhibited by sulfated compounds such as dextran-sulfate and polyanetholsulfonic acid, but not by dextran or several monosaccharides, suggesting that sulfated glycolipids on the macrophage surface may act as receptors for M. pneumoniae binding. In addition, sialylated compounds, such as fetuin and alpha 1-acid glycoprotein, were found to be potent inhibitors of the attachment, also indicating the role of sialic acid residue in recognition and attachment of M. pneumoniae to human alveolar macrophages.

In vitro influence of Mycoplasma species on the stimulation of human polymorphonuclear granulocytes

The influence of Mycoplasma species (sp.) on the stimulation of human polymorphonuclear neutrophil granulocytes (PMNG) was determined by means of the luminol-dependent chemiluminescence (CL) method. When opsonized Mycoplasma sp. were used the CL response of PMNG was greater than in the presence of nonopsonized strains. Nonopsonized and nonspecifically opsonized Mycoplasma sp. showed a different CL response pattern. The stimulation of PMNG was with M. pneumoniae significantly weaker than with the other Mycoplasma sp. Using isolated M. hominis strains always the same CL-reaction of PMNG was observed. On the other hand, with 12 isolated U. urealyticum strains different results were obtained; 9 strains isolated from the upper urogenital tract lead to a slight PMNG stimulation comparable to that of M. pneumoniae. No correlation was found between CL response and bacterial killing. The weak stimulation of PMNG by M. pneumoniae and most of the U. urealyticum isolates suggest that this behaviour could be a factor of pathogenicity.

Phagocytosis of Mycoplasma pneumoniae and Acholeplasma laidlawii measured as inhibition of [3H]uridine uptake by macrophages

Many studies of the interaction between phagocytes and mycoplasmas have given controversial results. This is probably due both to the small size of the microorganisms and their ability to attach to the cell membrane, making it difficult to distinguish between adsorption and ingestion. To overcome these difficulties we took advantage of a phenomenon we noted occurring concomitantly with phase-contrast microscope-monitored phagocytosis of heat-killed C. albicans, i.e., a reduction of [3H]uridine uptake by macrophages from culture medium. This approach allowed us to measure the ability of mouse peritoneal macrophages and the macrophage-like P 388 D 1 continuous cell line to phagocytose Mycoplasma pneumoniae and Acholeplasma laidlawii. Live, UV-killed and specific antiserum-opsonized mycoplasmas were tested. A. laidlawii was ingested under all the conditions mentioned above, while live M. pneumoniae was not phagocytosed unless UV-killed. Phagocytosis of UV-killed M. pneumoniae was directly verified by transmission electron microscopy studies. Data obtained with opsonized M. pneumoniae indicated no ingestion by mouse peritoneal macrophages and incomplete phagocytosis with P388 D 1 macrophages, suggesting that different responses by different types of phagocytes can be observed. In spite of a lack of information concerning the biological meaning of the inhibition of macrophage RNA metabolism during phagocytosis, our data suggest that this phenomenon may be used to study the phagocytosis of microorganisms which are difficult to visualize.

Increased susceptibility to Mycoplasma infection in patients with hypogammaglobulinemia

The incidence and morbidity of Mycoplasma infections were examined in a group of 23 patients with hypogammaglobulinemia. Among this group of patients, 18 had one or more episodes of acute respiratory illness during which Ureaplasma urealyticum, Mycoplasma orale, or Mycoplasma pneumoniae were isolated from sputum. Resolution only followed institution of specific antibiotic therapy and elimination of the Mycoplasma. In addition to respiratory illness, U. urealyticum was isolated from the urine of two patients with urinary tract infection and from an area of cellulitis in another patient. M. pneumoniae was isolated from the joint of a patient with arthritis. In six patients with chronic lung disease, Mycoplasma was frequently isolated and clinical improvement, albeit transient, coincided with negative Mycoplasma culture results. These findings emphasize the unique susceptibility to Mycoplasma infection in patients with hypogammaglobulinemia.

Antigenic determinants of the attachment protein of Mycoplasma pneumoniae shared by other pathogenic Mycoplasma species

In previous studies with hyperimmune rabbit antisera, we found evidence of serologic cross-reactivity among Mycoplasma pneumoniae, Mycoplasma genitalium, and Mycoplasma gallisepticum. Because of certain biologic and morphologic similarities of these species, attempts were made to determine if this cross-reactivity related to the attachment protein (P1) of M. pneumoniae. Monoclonal and monospecific antibodies against P1 were used to probe proteins of the other species by immunoblotting. One of the P1 monoclonal antibodies was reactive with a smaller protein of M. genitalium; rabbit antiserum raised by immunization with P1 excised from a sodium dodecyl sulfate-polyacrylamide gel electrophoresis gel was found to react with a similar-sized protein of M. gallisepticum. These preliminary findings suggest antigenic sharing among the species examined; however, limitations of the methods used are discussed.

Demonstration of multiple antigenic determinants on Mycoplasma pneumoniae attachment protein by monoclonal antibodies

Distinct multiple antigenic determinants of the attachment protein of Mycoplasma pneumoniae have been identified by limited proteolytic cleavage, using specific monoclonal antibodies. Western blots prepared from the gels containing the cleaved fragments were probed with antiserum against M. pneumoniae or monoclonal antibodies. Five distinct bands with intact antigenic determinants were detected by the antiserum, of which two bands were each reactable with two monoclonal antibodies. A sequential binding assay suggested that these monoclonal antibodies recognized different antigenic sites of each band. These results demonstrate the existence of multiple antigenic sites on the attachment protein and describe procedures that should prove useful for identifying those antigenic sites critical to the specific attachment of M. pneumoniae.

Mycoplasma pneumoniae infections of man: integration of attachment mechanism, cellular responses and clinical manifestations

Research advances of recent years are permitting new understanding of M. pneumoniae disease pathogenesis, although our knowledge remains incomplete. Colonization of the respiratory tract mucosa, mediated by an attachment protein, leads to specialized cell injury and altered muco-ciliary clearance. Pulmonary cellular infiltrates and airway exudates are a mixture of both non-specific and specific host immune responsiveness to the mycoplasma. It is now possible to begin integration of the organism's molecular biology and the clinical manifestations of infection.

Demonstration of antibodies to Mycoplasma pneumoniae attachment protein in human sera and respiratory secretions

Antibodies specific to the attachment protein of Mycoplasma pneumoniae were demonstrated in sera and respiratory secretions of human patients. The results indicate that the attachment protein is a major immunogen.

Effect of corynebacterium parvum in the induction and course of mycoplasma arthritis of mice

The effect of the immunostimulant C. parvum on the establishment and course of mycoplasma arthritis of mice was investigated. Male Swiss albino mice were injected intra-venously with M. arthritidis culture and intraperitoneally with C. parvum. It was shown that mice immunostimulated with C. parvum were significantly protected against the establishment of arthritis if the mycoplasma was given 9 days after the immunostimulant. However, when the arthritis was established C. parvum had no effect on the course of the arthritis. A close association between mycoplasma arthritidis and synovial cells in proposed as a possible explanation of this observation.

Release of Mycoplasma pneumoniae substances after phagocytosis by guinea pig alveolar macrophages

Antibody-opsonized Mycoplasma pneumoniae cells with various radioactive markers were sedimented onto monolayers of guinea pig alveolar macrophages (AM). After 2 h of incubation, about 50% of the activity of [3H]palmitate-labeled mycoplasmas was associated with AM. Nonspecific attachment of the opsonized mycoplasmas to AM-free plastic surface areas was negligible. The occurrence of phagocytosis was proven by electron microscopy and monitoring of AM surface-bound antigen by 125I-labeled F(ab)2 fragments. The activity of [3H]palmitic acid-labeled mycoplasmas was only slowly released into the supernatant. About 55% of the activity remained AM-associated up to 70 h after phagocytosis. After phagocytosis of [3H]thymidine-labeled cells, about 70% of the radioactivity found non-precipitable by trichloracetic acid. 3H-amino acid-labeled protein was released to 50% within 8 h. Supernatants and AM were tested for M. pneumoniae antigen with enzyme-linked immunosorbent assay. Considerable amounts of antigenically active material could be found in the supernatant within 8 h. This antigen was totally inactivated by heat (80 degrees C). Trypsin treatment (1 mg/ml, 10 min) reduced the antigenicity by 80%. The results suggest a selective release of microbial material after phagocytosis.

Interactions between murine alveolar macrophages and Mycoplasma pulmonis in vitro

In comparison to syngeneic fibroblasts, alveolar macrophages collected from Fischer 344 rats demonstrated a significant ability to decrease the growth rate of cell-associated Mycoplasma pulmonis, even in the absence of specific actimycoplasmal antibodies. However, when exposed to thallium acetate (a cytotoxic heavy metal), macrophages supported growth of mycoplasmas almost as well as did untreated fibroblasts. This suggests an active antimycoplasmal process operative in untreated macrophages. In contrast, mouse alveolar macrophages were not capable of exerting an antimycoplasmal effect unless rabbit anti-M. pulmonis antibodies were present. Paradoxically, mouse anti-M. pulmonis antibodies did not promote this effect.

Experimental infection of the respiratory tract with Mycoplasma pneumoniae

M. pneumoniae, a common human respiratory pathogen, has been studied experimentally for years using intranasal inoculation of the golden Syrian hamster. Because of recent evidence outlining the role in pulmonary immune development of particle size and depth of mycoplasma deposition in the hamster lung, we developed an aerosol chamber for the reproducible aerosolization of radiolabeled M. pneumoniae. Organisms were labeled to high specific activity by the incorporation of 3H-oleic acid and aerosolized under airflow and humidity conditions creating a mean particle diameter of 2.0 micrometers. Under these conditions, viable mycoplasmas were reproducibly and evenly distributed to all major lobes of the lung. Examination of radioactive clearance and organism viability within the lung during the first 48 hr after aerosolization have suggested a minimal role for macrophage mycoplasmacidal activity and a more prominent role for ciliary clearance. Data from aerosol infections of hamsters with radio-labeled M. pneumoniae should provide a unique opportunity to examine in a highly controlled manner the effects of air pollutants on the initial stages of infection as well as effects on the development of pulmonary immunity and histologic alterations.

Interaction of Mycoplasma pneumoniae with alveolar macrophages: viability of adherent and ingested mycoplasmas

Guinea pig peritoneal or alveolar macrophages were inoculated with Mycoplasma pneumoniae cells. Extracellular mycoplasms were killed by complement treatment, and the effect of macrophage action on the number of the remaining viable mycoplasmas was observed. The complement killing was to some extent inhibited by the presence of the macrophages, but the mechanism of this protection remains unknown. Opsonized mycoplasmas were ingested, and approximately 98% were killed within 4 h. The killing rate was somewhat lower than comparable data for bacteria, but lack of cell wall and high lipid content of the membrane apparently do not cause a significant delay in intracellular destruction.

Ciliated respiratory epithelial monolayers: new model for Mycoplasma pneumoniae infection

Hamster respiratory epithelial cells were cultured in a monolayer format, and 20% of the cells were ciliated. Mycoplasma pneumoniae attached to the epithelial cells in a neuraminidase-specific fashion and induced ciliostasis and cytonecrosis.

Interaction of Mycoplasma dispar and Mycoplasma agalactiae subsp. bovis with bovine alveolar macrophages and bovine lacteal polymorphonuclear leukocytes

Mycoplasma dispar and Mycoplasma agalactiae subsp. bovis survived or grew in cultures of bovine lacteal polymorphonuclear leukocytes or bovine alveolar macrophages. In the presence of specific bovine antibody, macrophages and polymorphonuclear leukocytes appeared to kill both species of mycoplasma. Specific rabbit antisera also promoted the killing of these mycoplasmas by bovine macrophages but had no demonstrable activity for bovine polymorphonuclear leukocytes. It is suggested that phagocytosis of these mycoplasmas by bovine cells occurs only in the presence of specific antibody. The experiments also indicate that differences exist between bovine polymorphonuclear leukocytes and macrophages with regard to their receptor sites for immunoglobulins.

Pathogenicity factors of mycoplasmas

The pathogenicity of mycoplasmas is caused by several factors, e.g. exotoxin, toxic properties of membrane components, exoenzymes, peroxide, and immunological factors. The absence of a rigid cell wall and the small genome tend to influence the interactions between mycoplasmas and host tissue. Mycoplasmas do not have a cell wass and are therefore resistant to the action of the host's lysozymes. They appear in some patients to be immunologically inconspicuous and in other patients they have been reported to have an immuno-suppressive effect. Recently there have been reports of central nervous system disorders due to mycoplasma. The pathogenic factors involved in these reactions have not been elucidated. Other aspects of Mycoplasma pneumoniae pathogenicity are also discussed.

Mycoplasma pneumoniae in hamster tracheal organ culture studied by scanning electron microscopy

Hamster tracheal rings in organ culture were inoculated with a virulent strain of Mycoplasma pneumoniae and examined by scanning electron microscopy. A progressive increase in epithelial cell injury was detected from 48 to 96 h post-inoculation and was characterized by apparent loss of the apical portion of ciliated cells. M. pneumoniae attaching to the epithelial cell surfaces could be identified by comparison with the surface morphology of mycoplasmas grown on glass cover slips.

Phagocytosis by macrophages of mycoplasma pneumoniae after opsonization by complement

Mycoplasma pneumoniae cells are not phagocytized by peritoneal macrophages without opsonization. They are taken up after treatment with complement or antibody.