Immunochemical characterization of a heat-stable surface antigen of Mycoplasma pulmonis expressing both species-specific and strain-specific determinants

Cross-reactive proteins among eight bovine mycoplasmas detected by monoclonal antibodies

Whole cell proteins of eight bovine mycoplasmas (M. bovoculi, M. bovis, M. dispar, M. bovirhinis, M. arginini, M. verecundum, M. canadense, M. alkalescens) were separated by SDS-PAGE and transferred to nitrocellulose paper. Rabbit anti-M. bovoculi serum was found to react with immunoblots of all mycoplasma species tested. These cross-reactive proteins were in the range of 35,000-100,000 molecular weight. Monoclonal antibody MA25.5 developed against a M. bovoculi 94 kDa surface protein cross-reacted with a band of 62 kDa from M. dispar and three bands of 89, 85 and 74 kDa from M. arginini only while MA18.13 that recognized a band of 57 kDa from M. bovoculi did not react with the other species. The role of MA25.5 monoclonal antibody in inhibiting the growth of M. bovoculi, M. dispar and M. arginini was tested using the metabolic-inhibition (MI) test. Monoclonal antibody MA25.5 inhibited the growth of M. bovoculi and also inhibited M. dispar growth but at lower MI titers, while it showed no effect on the growth of M. arginini.

Mycoplasma infection can sensitize host cells to apoptosis through contribution of apoptotic-like endonuclease(s)

Mycoplasma infection may lead to various pathologies in a broad range of hosts. It has been shown that Mycoplasma may trigger cell death in cell cultures; however, the mechanism remains unknown. In the present paper we show that Mycoplasma infection of different lymphocyte and epithelial tumour cell lines leads to the inhibition of proliferation, and increased cell death, accompanied by DNA fragmentation and the morphological features of apoptosis. We also showed that this infection leads to an increased sensitivity of cells to various inducers of apoptosis targeting different signalling pathways. Finally, we show that increased apoptosis is associated with overexpression of an endonuclease produced by Mycoplasma. This endonuclease is recovered in the nuclear fraction of host cells, introduces mostly DSB and is active at neutral pH in the presence of divalent cations. Activation of this endonuclease is connected with limited proteolysis, which may be reproduced in vitro by snake venom serine proteinase.

Comparison of Mycoplasma arthritidis strains by enzyme-linked immunosorbent assay, immunoblotting, and DNA restriction analysis

Twenty Mycoplasma arthritidis strains or isolates were compared by a combination of enzyme-linked immunosorbent assay by an antiserum adsorption technique, Western immunoblotting, and restriction analysis of chromosomal DNA. Antigenic markers that defined strains related to strains 158p10p9, PG6, and H606 were identified. In addition, restriction analysis allowed all 20 strains to be divided into six groups. Results of restriction analysis corresponded generally with antigenic similarities, although the former did not allow grouping with as fine a precision as the latter. However, intrastrain antigenic variability, which is common among many Mycoplasma species, including M. arthritidis, introduced a complicating factor into our attempts at antigenic analysis. While serologic and antigenic analyses remain useful, we recommend that they be used with caution and in combination with other techniques for identifying and characterizing new isolates and newly acquired strains. Combinations of these techniques have proven to be useful in our laboratory for quality control and for uncovering interesting relationships among strains subjected to animal passage and their less virulent antecedents and among strains originally classified as the same but obtained from different sources and maintained, sometimes for decades, in different laboratories.

Monoclonal antibodies that inhibit mitogenic activity of Mycoplasma pulmonis

Previous studies have suggested a correlation between mitogenic, polyclonal activation of host lymphocytes and the respiratory tract inflammatory diseases induced by Mycoplasma pulmonis. This study describes the generation of monoclonal antibodies (MAbs) to M. pulmonis membrane antigens with different capacities to inhibit stimulation of cultured rat lymphocytes by mycoplasmal membranes and with variable effects on M. pulmonis growth. We show that the inhibitory effects exerted on mitogenesis by purified MAbs are inversely related to the effects of MAbs on M. pulmonis growth. Immunoblotting of electrophoretically separated membrane proteins, with both growth- and mitogenesis-inhibiting antibodies, revealed significant changes in the reactions obtained with both types of MAb following short exposure of membranes to heat. Growth-inhibiting MAbs strongly react with heat-labile antigenic complexes with molecular weights of 65,000 to 75,000. Inhibition of mitogenesis is mainly associated with recognition of membrane complexes of 84 to 113 kDa that exhibit disperse smears and variable heat sensitivities. Following brief heating of membranes, more distinct bands of 103, 90, and 84 kDa are obtained with MAbs that inhibit mitogenesis. Experiments with other mitogenic mycoplasma species and MAb 3.3.10.2, a potent inhibitor of mitogenesis reveal that whereas the antigenic epitope recognized by this antibody is present on unheated membranes from different mycoplasmas, with heated membranes the MAb yields reactions only with M. pulmonis and M. arthritidis. Our studies suggest that M. pulmonis mitogens are unique membrane complexes of variable molecular weights, highly susceptible to heat and less sensitive to reducing agents.

Comparison of four Mycoplasma arthritidis strains by enzyme immunoassay, metabolism inhibition, one- and two-dimensional electrophoresis, and immunoblotting

Four Mycoplasma arthritidis strains, two virulent (158p10p9 and 14124p10) and two avirulent (PG6 and H606), were examined for differences in their antigenic compositions. Rabbit antisera prepared against each strain were compared for their reactivities against both homologous and heterologous strains by enzyme-linked immunosorbent assay and metabolism inhibition assay. These tests confirmed a close serologic relationship among the four strains. Only by cross-absorbing each antiserum with intact cells from both homologous and heterologous strains could serologic differences be detected. Interestingly, antigenic variability was minimal among those antigens involved in the metabolism inhibition reaction, suggesting that they may be highly conserved within this species. No differences in protein composition could be detected by one-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis. However, slight variation was apparent on two-dimensional gels, and antigens possessing strain-specific epitopes were detected by two-dimensional immunoblotting experiments performed with cross-absorbed antisera. The enzyme-linked immunosorbent assay, two-dimensional electrophoresis, and immunoblotting experiments showed that the two virulent strains were closely related to each other, while the avirulent strains were more distantly related to each other and to the other two strains. The relationship of M. arthritidis serologic diversity to virulence remains unclear: however, this study has demonstrated that it may be possible to subdivide M. arthritidis into serogroups on the basis of cross-absorption patterns and to identify those antigens bearing strain-specific epitopes by immunoblotting with cross-absorbed antisera.

Protein variability among strains of Mycoplasma pulmonis

The proteins of Mycoplasma pulmonis were examined by two-dimensional polyacrylamide gel electrophoresis and immunoblotting. Comparison of profiles from silver-stained two-dimensional polyacrylamide gel electrophoresis of 18 strains of M. pulmonis allowed identification of five proteins that were strain variable. These variable proteins were not dependent on the medium used to grow the organisms and were shown by reaction with serum samples from naturally infected rats and mice to be produced in vivo and not to be medium components. Identification of strain-variable proteins may lead to an explanation of the differences in properties found among M. pulmonis strains.

Enzymatic release of germ tube-specific antigens from cell walls of Candida albicans

The differences between blastospores and germ tubes of Candida albicans, as previously shown by immunofluorescence, were further studied by comparing digests of cell walls of both growth forms. Organisms were surface labeled with 125I, and cell walls were digested enzymatically. When Zymolase digests were treated with polyclonal, polyspecific antiserum to C. albicans 441B, which stains only germ tubes in immunofluorescence assays, components of molecular weights 200,000 and 155,000 were immunoprecipitated from digests of germ tubes of strain B311, but nothing was recovered from blastospores. Whereas the 200,000-molecular-weight component was found in the three strains tested, the 155,000-molecular-weight component was found only in strain B311. When Zymolase digests were treated with unadsorbed antiserum, which stains both blastospores and germ tubes in immunofluorescence assays, an additional component was precipitated from digests of both growth forms with a molecular weight greater than the 200,000-molecular-weight marker. All three antigens were mannoproteins, as was shown by their abilities to bind concanavalin A and to be labeled by 125I. Also, all antigens were located on the cell surface, as was shown by the following criteria: adsorption of antisera with live organisms removed antibody to these components, and antibody eluted from surfaces of whole organisms precipitated all components. Components common to both growth forms, as well as germ tube-specific components, were detected in trypsin and chymotrypsin digests, but their molecular weights differed from those of Zymolase digests. Thus, germ tube-specific surface determinants as well as determinants common to both growth forms were detected on enzymatically released cell wall components.

Surface proteins of Mycoplasma hyopneumoniae identified from an Escherichia coli expression plasmid library

A genomic library of Mycoplasma hyopneumoniae was constructed by cloning random DNA fragments approximately 300 base pairs long in a fusion expression plasmid, pEx29, containing the N terminus of the phage MS2 polymerase under the control of the PL promoter of phage lambda. Clones that produced fusion proteins carrying surface-specific antigenic determinants were identified by using antiserum raised in a pig by intranasal inoculation of viable mycoplasmas. Rabbit antisera produced against gel-purified fusion proteins synthesized in Escherichia coli were analyzed by Western blotting to identify antigenically related mycoplasma components. Distinct mycoplasma proteins termed P90, P68, P50, P30, and P26 were identified. Evidence for the surface location of P90, P68, and P50 was provided by their sensitivity to trypsin and their comigration with lactoperoxidase-catalyzed iodinated proteins of intact mycoplasmas. Immune electron microscopy, performed with antiserum against the hybrid MS2-mycoplasma protein produced in E. coli and corresponding to P90, also showed that its antigenic determinant is associated with the mycoplasma surface.

Demonstration of cross-reactive antigens in F38 and related mycoplasmas by enzyme-linked immunosorbent assay (ELISA) and immunoblotting

The ELISA and an immunoblotting technique were used to study F38-type mycoplasmas - an important cause of contagious caprine pleuropneumonia - and a number of related mycoplasma species, subspecies, types or serogroups. Two-way ELISA cross-reactivity was demonstrated between five mycoplasmas, namely strain F38, Mycoplasma mycoides subsp. mycoides (LC strain), M. equigenitalium, M. primatum and bovine serogroup 7. In addition one-way cross-reactivity was demonstrated between F38 and each of the following mycoplasmas: M. mycoides subsp. mycoides (two SC strains), M. mycoides subsp. capri, and bovine serogroup L. F38 and M. capricolum did not cross-react. Immunoblot analysis, unlike ELISA, revealed that F38 and M. capricolum were closely related. At least four major protein antigens were shared between F38, M. mycoides subsp. mycoides (SC and LC strains), M. mycoides subsp. capri and bovine serogroup 7. The ELISA cross-reactions (above) shown by M. equigenitalium and M. primatum with each other, with F38 and with other mycoplasmas were not apparent by immunoblotting.