Molecular biology and pathogenicity of mycoplasmas.

The recent sequencing of the entire genomes of Mycoplasma genitalium and M. pneumoniae has attracted considerable attention to the molecular biology of mycoplasmas, the smallest self-replicating organisms. It appears that we are now much closer to the goal of defining, in molecular terms, the entire machinery of a self-replicating cell. Comparative genomics based on comparison of the genomic makeup of mycoplasmal genomes with those of other bacteria, has opened new ways of looking at the evolutionary history of the mycoplasmas. There is now solid genetic support for the hypothesis that mycoplasmas have evolved as a branch of gram-positive bacteria by a process of reductive evolution. During this process, the mycoplasmas lost considerable portions of their ancestors' chromosomes but retained the genes essential for life. Thus, the mycoplasmal genomes carry a high percentage of conserved genes, greatly facilitating gene annotation. The significant genome compaction that occurred in mycoplasmas was made possible by adopting a parasitic mode of life. The supply of nutrients from their hosts apparently enabled mycoplasmas to lose, during evolution, the genes for many assimilative processes. During their evolution and adaptation to a parasitic mode of life, the mycoplasmas have developed various genetic systems providing a highly plastic set of variable surface proteins to evade the host immune system. The uniqueness of the mycoplasmal systems is manifested by the presence of highly mutable modules combined with an ability to expand the antigenic repertoire by generating structural alternatives, all compressed into limited genomic sequences. In the absence of a cell wall and a periplasmic space, the majority of surface variable antigens in mycoplasmas are lipoproteins. Apart from providing specific antimycoplasmal defense, the host immune system is also involved in the development of pathogenic lesions and exacerbation of mycoplasma induced diseases. Mycoplasmas are able to stimulate as well as suppress lymphocytes in a nonspecific, polyclonal manner, both in vitro and in vivo. As well as to affecting various subsets of lymphocytes, mycoplasmas and mycoplasma-derived cell components modulate the activities of monocytes/macrophages and NK cells and trigger the production of a wide variety of up-regulating and down-regulating cytokines and chemokines. Mycoplasma-mediated secretion of proinflammatory cytokines, such as tumor necrosis factor alpha, interleukin-1 (IL-1), and IL-6, by macrophages and of up-regulating cytokines by mitogenically stimulated lymphocytes plays a major role in mycoplasma-induced immune system modulation and inflammatory responses.

Subversion and exploitation of host cells by mycoplasmas.

Mycoplasmas are minute wall-less bacterial parasites that exhibit strict host and tissue specificities. They enter, multiply and survive within the host for extended periods by circumventing host defenses. Their intimate interaction with eukaryotic cells, and in some cases the subsequent invasion into or fusion with these cells, mediates cell damage. Mycoplasmas also modulate the activity of host cells by a variety of direct mechanisms and/or indirectly by cytokine-mediated effects.

Use of enzyme-linked immunosorbent assays (ELISA) for detection of monoclonal antibodies: experience with antigens of Toxoplasma gondii.

The usefulness of enzyme-linked immunosorbent assay (ELISA) systems for detection of monoclonal antibodies to Toxoplasma gondii was studied. Seven monoclonal antibodies with specificities for membrane antigens, cytoplasmic antigens, or both membrane and cytoplasmic antigens of T. gondii were tested in a "sandwich" or in a "double sandwich" assay. Whereas both ELISA systems were sensitive and specific for detection of monoclonal antibodies to T. gondii, the double sandwich ELISA proved more sensitive than did the sandwich assay. Using different T. gondii antigen preparations in both assays, we demonstrated that the ELISA systems are specific, sensitive, rapid, and easy to perform and are therefore useful for screening and detection of monoclonal antibodies of desired isotypes and defined specificities.

IgM and IgG antibody response in two immunosuppressed patients with Legionnaires' disease. Evidence of reactivation of latent infection.

Two patients in whom pneumonia due to Legionella pneumophila developed while they were receiving immunosuppressive therapy had serologic evidence of prior infection with the same serogroup of L. pneumophila two and eight months prior to their clinical pneumonia. This suggests that the pneumonia in these patients may have been due to the reactivation of a latent infection, possibly due to their immunosuppressed state. A new enzyme-linked immunosorbent assay (ELISA) was developed to detect IgG and IgM antibodies to L. pneumophila, and the kinetics of these antibody responses were useful diagnostically.

Histamine levels in ovarian hyperstimulation syndrome.

Ovarian hyperstimulation syndrome was produced in rabbits by administration of human menopausal gonadotropin (hMG) and human chorionic gonadotropin (hCG). Histamine levels in the animals' plasma were determined by an enzymatic-isotopic assay. The results of this study show that there is no statistically significant difference between histamine levels in ovarian hyperstimulated animals as compared with control animals. Furthermore, no differences in the number of mast cells in the ovaries could be demonstrated between the 2 groups. It is concluded that histamine probably does not play a role in the pathogenesis of this syndrome. The relevance of this suggestion to other proposed mechanisms on the etiology of ovarian hyperstimulation syndrome is discussed.

Membrane lipids of Mycoplasma fermentans.

Membranes of Mycoplasma fermentans, incognitus strain, were isolated by a combination of osmotic lysis and sonication. Analysis of membrane lipids revealed, in addition to free and esterified cholesterol, six major polar lipids dominated by a de novo synthesized compound (compound X), which accounts for 64% of the total lipid phosphorus. Compound X was labeled by palmitate, but not by oleate. Mass spectrometry and gas liquid chromatography analyses of compound X revealed two molecular species with molecular masses of 1048 and 1076 representing, a dipalmitoyl- and a stearoyl-palmitoyl-glycerodiphosphatidylcholine. Compound X has the ability to stimulate human monocytes to secret TNF alpha and to enhance the fusion of small unilamellar vesicles with MOLT-3 lymphocytes.

Mycoplasma infection in pregnant rats: low viability of foetuses and newborn offspring.

The controversy regarding the possible role of genital mycoplasma infection in human reproductive failure gave rise to a study in which pregnant rats, previously shown to be of normal fertility, were inoculated 7-11 days after conception with either Mycoplasma arthritidis or an equal volume of sterile broth medium. Repeated observations during the course of pregnancy revealed several pathogenic effects. A statistically significant decrease was observed in the mean litter size of infected mothers. Furthermore, the offspring showed low viability at birth and, still more, at 10 days after birth. Our data are compatible with the hypothesis that genital mycoplasma infection plays a role in reproductive failure.

Identification of human sperm antigens reacting with antisperm antibodies from sera and genital tract secretions.

OBJECTIVE: To identify sperm antigens reacting with antisperm antibodies relevant in human infertility. DESIGN: The reactions of separated sperm antigens with antibodies present in sera and genital tract secretions from infertile and fertile females and males were examined by immunoblotting techniques. SETTING: The patients were followed in an outpatient setting of a hospital clinic. PATIENTS: One hundred consecutive infertile males and females, referred for determinations of antisperm antibodies, comprised the study group. Fifty hospital and faculty employees with proven fertility served as a control group. RESULTS: A high proportion of sera from fertile and infertile humans contained antibodies reacting with at least one sperm antigen. However, two discrete bands of antigenic proteins with molecular weights of 44 and 72 kd reacted significantly more frequently with serum antibodies from infertile females than from fertile females. No apparent correlation could be demonstrated between any particular antigen and serum antibodies from infertile males. Nevertheless, antigenic proteins of 62 kd were identified as the major sperm antigens reacting with antibodies present in seminal plasmas from infertile males. CONCLUSIONS: The major sperm antigens reacting with systemic antibodies differ from the antigens recognized by local antisperm antibodies. Sperm antigens exhibiting relative molecular weights of 62 kd are major antigens reactive with local antisperm antibodies from infertile humans.

Characterization of a potent sperm-agglutinating monoclonal antibody and its cognate antigens.

OBJECTIVE: To identify sperm antigens that are capable of eliciting infertility-related sperm-agglutinating antibodies. DESIGN: In vitro laboratory experiments. SETTING: University research laboratory. PATIENT(S): Fertile semen donors. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): Sperm agglutination, immunofluorescence localization, and flow cytometric analysis of surface expression of A36 antigens. Antigen analysis by Western immunoblotting. RESULT(S): Monoclonal antibody A36 induced intensive head-to-head, tail-to-tail, and head-to-tail agglutination of motile human spermatozoa. Antigens recognized by A36 were localized on the acrosomal cap and in the principal tail regions of motile, noncapacitated human sperm. Changes in subcellular levels and localization of the A36-recognized epitope occurred after capacitation and acrosomal loss. A36 reacted with a polymorphic series of proteins in Western blots of sperm extracts from humans and various other animal species, including mouse testis extracts. A common 53-kd antigen was recognized by the antibody in the different antigenic preparations. CONCLUSION(S): A mouse antibody to human sperm, monoclonal antibody A36, caused intensive agglutination of noncapacitated human spermatozoa and reacted with antigens on the acrosomal cap and in the principal tail regions. Of the multiple polypeptides that were reactive with the monoclonal antibody in sperm extracts from humans and other animal species, a common 53-kd antigen was recognized.

A reverse (antibody capture) enzyme-linked immunosorbent assay for detection of antisperm antibodies in sera and genital tract secretions.

A reverse (antibody capture) enzyme-linked immunosorbent assay (ELISA) for detection of antisperm antibodies has been developed. The assay enables detection of immunoglobulin (Ig) M, IgG, IgA, or IgM, IgG, and IgA--antisperm antibodies in serum, cervical mucus, and seminal plasma samples. The reverse ELISA is more specific and sensitive than conventional ELISA in detecting human antisperm antibodies of different isotypes. Using this assay, statistically significant differences in levels of antibodies between infertile and fertile individuals were demonstrated in sera and in genital tract secretions. Studies with 143 infertile couples revealed that the presence of antibodies in sera was not necessarily reflected in individual's genital tract secretion and vice versa. These data emphasize the importance of detecting antisperm antibodies in sera as well as in genital tract secretions for correct evaluation of sperm immunity.

In vitro studies on the mitogenic activity of mycoplasmal species toward lymphocytes.

The observed mitogenic activity of many mycoplasmal species provided the impetus for studies on this biologic manifestation. Studies designed to define the rat lymphocyte populations activated in vitro by Mycoplasma pulmonis showed that both B and T cells are activated. On the other hand, Mycoplasma neurolyticum induces nonspecific blastogenesis of the B-cell population of both rats and mice. These results and those of other workers suggest that the lymphocyte subpopulations activated by mycoplasmas differ with the mycoplasmal species and the origin of the lymphocytes. Further, one mycoplasmal species activates lymphocytes obtained from different species. Experiments performed to localize and define the biochemical nature of mitogens of M. pulmonis demonstrated that membranous outer-surface proteins are major constituents of the mitogenic factors. Membrane carbohydrates, but not lipids, may also be involved in the mitogenicity of M. pulmonis. Further studies establish a direct correlation between mitogenicity and pathogenicity of M. pulmonis in rats.

Activation of B lymphocytes by mycoplasma mitogen(s).

Various strains of the murine mycoplasma M. neurolyticum have been shown to induce extensive blast transformation of mouse lymphocytes, comparable in strength to mitogenicity exerted by these mycoplasma species on rat lymphocytes. The data summarized in this report demonstrate that this mitogenic effect is non-specific. Lymphoid cells from mycoplasma free, germ-free mice were activated to the same extent as those lymphocytes obtained from conventionally bred animals. Lymph node cell suspensions obtained from athymic nude mice were strongly activated by M. neurolyticum mitogen. Furthermore, mouse thymocytes and mouse T-cell enriched populations, were not stimulated by these mitogens. It was thus suggested that M. neurolyticum activates mouse B lymphocytes.

Role of gene 52 in bacteriophage T4 DNA synthesis.

In an attempt to elucidate the mechanism of delayed DNA synthesis in phage T4, Escherichia coli B cells were infected with H17 (an amber mutant defective in gene 52 possessing a "DNA-delay" phenotype). The fate of (14)C-labeled H17 parental DNA after infection was followed: we could show that this DNA sediments more slowly in neutral sucrose than wild-type DNA 3 min postinfection. In pulse-chase experiments progeny DNA was found to undergo detachment from the membrane at 12 min postinfection. Reattachment to the membrane was found to be related to an increase in rate of DNA synthesis. A nucleolytic activity that is absent from cells infected by wild-type phage and from uninfected cells could be detected in extracts prepared from mutant-infected cells. In contrast, degradation of host DNA was found to be less extensive in am H17 compared with wild-type infected cells. Addition of chloramphenicol to mutant-infected cells 10 min postinfection inhibited the appearance of a nuclease activity on one hand and suppressed the "DNA-delay" phenotype on the other hand. We conclude that the gene 52 product controls the activity of a nuclease in infected cells whose main function may be specific strand nicking in association with DNA replication. This gene product might directly attack both E. coli and phage T4 DNA, or indirectly determine their sensitivity to degradation by another nuclease.

Cloning of a glucose phosphate isomerase/neuroleukin-like sperm antigen involved in sperm agglutination.

The mouse monoclonal antibody (mAb) A36 produced by us and shown to induce extensive, "tangled" sperm agglutination was used to isolate cDNAs encoding its cognate antigen. Three overlapping cDNA clones specifically recognized by the mAb were isolated from a human testis cDNA expression library in lambdagt11. Sequencing of these cDNAs yielded the complete nucleotide sequence of a 3-kilobase cDNA that encodes the mAb-related polypeptide, designated sperm antigen-36 (SA-36), composed of 558 deduced amino acids. SA-36 cDNA contained a 5' untranslated region of 234 nucleotides (nt), an open reading frame of 1674 nt, and a 3' untranslated region of 1138 nt. SA-36 cDNA displayed > 99% homology to glucose phosphate isomerase (GPI)/neuroleukin (NLK) mRNA. This surprising homology was confirmed in Western blots demonstrating that mAb A36 reacted specifically with GPI obtained from rabbit muscle and from baker's yeast. Moreover, polyclonal, monospecific antibodies produced against beta-galactosidase/SA-36-3 fusion protein stained human spermatozoa and caused intensive agglutination of these cells in a manner similar to that with the mAb. Taken together, the data presented here demonstrated that mAb A36 cognate sperm surface antigen, encoded by SA-36 cDNA, is a GPI/NLK-like protein involved in sperm agglutination.

Defective concatemer formation in cells infected with deoxyribonucleic acid-delay mutants of bacteriophage T4.

Nonpermissive host cells infected with phage T4 mutants in genes 52, 39, and 58 through 61 are shown to form short intracellular single-stranded deoxyribonucleic acid in contrast to wild-type infected cells, which form dimers and trimers of T4 genome size.

Inhibition of mycoplasma-induced lymphocyte activation by sodium aurothiomalate.

Sodium aurothiomalate, at concentrations of 10 to 150 microgram/ml of culture, inhibited rat lymphocyte stimulation by Mycoplasma pulmonis mitogen in a dose-dependent manner.