A safe and efficient method for elimination of cell culture mycoplasmas using ciprofloxacin

Growth Dynamics and Antibiotic Elimination of Symbiotic Rickettsia buchneri in the Tick Ixodes scapularis (Acari: Ixodidae)

Rickettsia buchneri is the principal symbiotic bacterium of the medically significant tick Ixodes scapularis This species has been detected primarily in the ovaries of adult female ticks and is vertically transmitted, but its tissue tropism in other life stages and function with regard to tick physiology is unknown. In order to determine the function of R. buchneri, it may be necessary to produce ticks free from this symbiont. We quantified the growth dynamics of R. buchneri naturally occurring in I. scapularis ticks throughout their life cycle and compared it with bacterial growth in ticks in which symbiont numbers were experimentally reduced or eliminated. To eliminate the bacteria, we exposed ticks to antibiotics through injection and artificial membrane feeding. Both injection and membrane feeding of the antibiotic ciprofloxacin were effective at eliminating R. buchneri from most offspring of exposed females. Because of its effectiveness and ease of use, we have determined that injection of ciprofloxacin into engorged female ticks is an efficient means of clearing R. buchneri from the majority of progeny.IMPORTANCE This paper describes the growth of symbiotic Rickettsia buchneri within Ixodes scapularis through the life cycle of the tick and provides methods to eliminate R. buchneri from I. scapularis ticks.

On-Demand Modulation of Bacterial Cell Fates on Multifunctional Dynamic Substrates

This paper reports unprecedented dynamic surfaces based on zwitterionic low-density self-assembled monolayers (LDSAMs) of alkanethiolates on gold, which integrate three interconvertible states-bacteria-adherable, bactericidal, and nonfouling states-through electrical modulations. The conformations of alkanethiolates were electrically modulated to generate zwitterionic, anionic, and cationic surfaces, which responded differently to bacteria and determined the fate of bacteria. Furthermore, the reversible switching of multifunctions of the surface was realized for killing bacteria and subsequently releasing dead bacteria from the surface. For practical application of our strategy, we examined the selective antibacterial effect of our surface for eradication of mycoplasma contaminants in contaminated mammalian cell cultures.

N-Terminal Polypeptide of Annexin A2 Decreases Infection of Mycoplasma hyorhinis to Gastric Cancer Cells

Mycoplasma infection in human and its contamination in cell cultures are worldwide problems. The drugs currently available for preventing or treating mycoplasma infection suffer from low sensitivity, strong resistance and high toxicity. Our previous work showed that Mycoplasma hyorhinis (M. hyorhinis) infection was mediated by the interaction between p37 of M. hyorhinis and Annexin A2 (ANXA2) of host cells, however the translational value of this mechanism was unknown. Herein, we synthesized the N-terminal of ANXA2 polypeptide (A2PP) and found that A2PP could decrease the infection of M. hyorhinis to gastric cancer cells and block M. hyorhinis infection-induced cell migration. Furthermore, we found that A2PP could reduce M. hyorhinis contamination of passage cells. Moreover, compared with the commercial antibiotics commonly used in cell culture to prevent M. hyorhinis infection, A2PP demonstrated a more effectiveness but a low toxicity on cell growth. Thus, our study for the first time revealed A2PP’s potential for the treatment and prevention of M. hyorhinis infection.

Diagnosis and treatment of mycoplasma-contaminated cell cultures

Mycoplasma contamination is a serious and frequent problem in the culture laboratory. Although mycoplasma contamination may be suspected by the failure of cells to thrive, the formal diagnosis rests on the detection of adenosine phosphorylase secretion by infected cell lines. This appendix describes how to test for mycoplasma contamination, and also presents methods for antibiotic treatment of infected cultures.

Diagnosis and treatment of Mycoplasma-contaminated cell cultures

Mycoplasma contamination is a serious and frequent problem in the culture laboratory. Although mycoplasma contamination may be suspected by the failure of cells to thrive, the formal diagnosis rests on the detection of adenosine phosphorylase secretion by infected cell lines. This appendix describes how to test for mycoplasma contamination, and also presents methods for antibiotic treatment of infected cultures.

Comparison of the measurement of lysosomal hydrolase activity in mycoplasma-contaminated and non-contaminated human fibroblast cultures treated with mycoplasma removal agent

OBJECTIVES

To investigate the effect of both mycoplasma contamination and of its remover (MRA), through human fibroblasts culture over the activity of some lysosomal hydrolases.

DESIGN AND METHODS

Activity was measured in contaminated fibroblasts before and after the addition of MRA. Results were compared with the enzymatic activity in control fibroblasts with and without MRA.

RESULTS

Only beta-glucosidase showed no significant alteration in the presence of either mycoplasma or MRA. Total hexosaminidase and beta-galactosidase underwent significant interference in the presence of the mycoplasma and the MRA. The % of hexosaminidase A and arylsulphatase A altered their activity only in the presence of MRA. Beta-glucuronidase changed its activity only in the presence of mycoplasma.

CONCLUSIONS

The fibroblast enzymes behaved differently in the presence of MRA and/or mycoplasma, demonstrating the sensitivity of these hydrolases. Our work suggests that mycoplasma and MRA alter the activity of some lysosomal hydrolases.

Mitochondrial activities in human cultured skin fibroblasts contaminated by Mycoplasma hyorhinis

Background

Mycoplasma contaminations are a recurrent problem in the use of cultured cells, including human cells, especially as it has been shown to impede cell cycle, triggering cell death under various conditions. More specific consequences on cell metabolism are poorly known.

Results

Here we report the lack of significant consequence of a heavy contamination by the frequently encountered mycoplasma strain, M. hyorhinis, on the determination of respiratory chain activities, but the potential interference when assaying citrate synthase. Contamination by M. hyorhinis was detected by fluorescent imaging and further quantified by the determination of the mycoplasma-specific phosphate acetyltransferase activity. Noticeably, this latter activity was not found equally distributed in various mycoplasma types, being exceptionally high in M. hyorhinis.

Conclusion

While we observed a trend for respiration reduction in heavily contaminated cells, no significant and specific targeting of any respiratory chain components could be identified. This suggested a potential interference with cell metabolism rather than direct interaction with respiratory chain components.

Hsp27, Hsp70, and metallothionein in MDCK and LLC-PK1 renal epithelial cells: effects of prolonged exposure to cadmium

Cadmium is a widely distributed industrial and environmental toxin. The principal target organ of chronic sublethal cadmium exposure is the kidney. In renal epithelial cells, acute high-dose cadmium exposure induces differential expression of proteins, including heat shock proteins. However, few studies have examined heat shock protein expression in cells after prolonged exposure to cadmium at sublethal concentrations. Here, we assayed total cell protein, neutral red uptake, cell death, and levels of metallothionein and heat shock proteins Hsp27 and inducible Hsp70 in cultures of MDCK and LLC-PK1 renal epithelial cells treated with cadmium for 3 days. Treatment with cadmium at concentrations equal to or greater than 10 microM (LLC-PK1) or 25 microM (MDCK) reduced measures of cell vitality and induced cell death. However, a concentration-dependent increase in Hsp27 was detected in both cell types treated with as little as 5 microM cadmium. Accumulation of Hsp70 was correlated only with cadmium treatment at concentrations also causing cell death. Metallothionein was maximally detected in cells treated with cadmium at concentrations that did not reduce cell vitality, and further increases were not detected at greater concentrations. These results reveal that heat shock proteins accumulate in renal epithelial cells during prolonged cadmium exposure, that cadmium induces differential expression of heat shock protein in epithelial cells, and that protein expression patterns in epithelial cells are specific to the cadmium concentration and degree of cellular injury. A potential role for Hsp27 in the cellular response to sublethal cadmium-induced injury is also implicated by our results.

Diagnosis and treatment of mycoplasma-contaminated cell cultures

Mycoplasma contamination is a serious and frequent problem in the culture laboratory. Although mycoplasma contamination may be suspected by the failure of cells to thrive, the formal diagnosis rests on the detection of adenosine phosphorylase secretion by infected cell lines. This appendix describes how to test for mycoplasma contamination, and also presents methods for antibiotic treatment of infected cultures.

The failure of Daudi cells to express the cellular prion protein is caused by a lack of glycosyl-phosphatidylinositol anchor formation

The cellular prion protein (PrPc) is a glycosyl-phosphatidylinositol (GPI)-linked cell surface protein, which is expressed at high density on nervous tissues and at lower levels on most other solid-organ tissues. It is also expressed on peripheral blood mononuclear cells (PBMC) of all lineages. In lymphocytes, its level of expression is dependent upon the state of cell activation, and polyclonal anti-PrP antisera partially block lectin-induced T-cell activation, suggesting a functional role of the protein in this process. Using the monoclonal antibody (mAb) 3F4 we examined PrPc surface immunoreactivity on leukaemic cell lines of T- and B-cell origin, and unexpectedly observed a complete lack of PrPc cell-surface expression in Daudi cells, while all other cell lines displayed discernible reactivity. We demonstrated the intracellular presence of PrP-specific mRNA and PrP protein. The lack of surface PrPc is unrelated to the well-known defect of beta2-microglobulin (beta2m) expression in Daudi cells as other beta2m-deficient cells, such as the melanoma cell line F0-1 and spleen cells from beta2m gene-deleted mice, were not deficient in cell-surface PrPc. Daudi cells failed to bind antibodies directed against all GPI-linked cell surface proteins. In somatic hybridization experiments using murine spleen cells as partners, we observed de novo expression of human PrPc, CD55 and CD59, thus demonstrating in Daudi cells the availability of these gene products for GPI linkage and cell-surface expression.

Conservation of the amino-terminal epitope of elongation factor Tu in eubacteria and Archaea

An epitope of elongation factor Tu (EF-Tu), which is found in organisms in both the bacterial and archaeal domains, was recently defined by mAb 900. To localize the conserved epitope within the EF-Tu molecule and to determine its sequence, SPOTScan analysis of synthetic peptides, Western blot analysis of purified EF-Tu domains and site-directed mutagenesis studies were used. Analysis of mAb 900 binding to overlapping 15-mer peptides encompassing the complete sequence of EF-Tu of Escherichia coli was inconclusive, suggesting three distinct regions may be epitopes. Western blot analysis of EF-Tu domains 1-3 of Thermus thermophilus suggested that the epitope was located at the N terminus. This was confirmed by site-directed mutagenesis of EF-Tu domain 1 of Mycoplasma hominis. By C-terminal truncation of the N-terminal 15-mer peptide the epitope was mapped to EF-Tu residues 1-6. Replacement of each of the residues in the epitope peptide demonstrated that only positions 5 and 6 were indispensable for antibody binding. These data provide evidence that the highly conserved epitope recognized by mAb 900 in the bacterial and archaeal domains is located at the very end of the N terminus of the EF-Tu molecule.

The monomeric G-proteins Rac1 and/or Cdc42 are required for the inhibition of voltage-dependent calcium current by bradykinin

Although regulation of voltage-dependent calcium current (ICa,V) by neurotransmitters is a ubiquitous mechanism among nerve cells, the signaling pathways involved are not well understood. We have determined previously that in a neuroblastoma-glioma hybrid cell line (NG108-15), the heterotrimeric G-protein G13 mediates the inhibition of ICa,V produced by bradykinin (BK) via an unknown mechanism. Various reports indicate that G13 can couple to RhoA, Rac1, and Cdc42, which are closely related members of the Rho family of monomeric G-proteins. We have investigated their role as signaling intermediates in the pathway used by BK to inhibit ICa,V. Using immunoblot analysis and the PCR, we found evidence that RhoA, Rac1, and Cdc42 all are expressed in NG108-15 cells. Intracellularly perfused recombinant Rho-GDI (an inhibitor of guanine nucleotide exchange specific for the Rho family) attenuated the inhibition of ICa,V by BK. These findings indicate that activation of RhoA, Rac1, or Cdc42 may be required for the response to BK. To determine whether any of these monomeric G-proteins mediate the response to BK, we have intracellularly applied blocking antibodies specific for each of the candidate proteins. Only the anti-Rac1 antibody blocked the response to BK. In parallel experiments, peptides corresponding to the C-terminal regions of Rac1 and Cdc42 blocked the same response. These data indicate a novel functional contribution of Rac1 and possibly also of Cdc42 to the inhibition of ICa,V by neurotransmitters.

The immunomodulatory effects of antibiotics: in vitro and ex vivo investigations of 21 substances by means of the lymphocyte transformation test

Besides their antimicrobial activity antibiotics can modulate immune response. The paper provides original data about in vitro and in vivo influence of antibiotics on lymphocyte transformation test (LTT) and gives a comprehensive overview of literature data. In the study presented here the influence of several antimicrobial substances on unstimulated and PHA-stimulated lymphocyte transformation was investigated. The proliferative response was measured as (3H) thymidine uptake by lymphocytes. For initial screening the lymphocyte transformation test was performed on murine lymphocytes in vitro. As a whole 21 antimicrobial substances were tested including representative substances of the most important main groups. As a second step experiments were done with selected substances on human lymphocytes that had shown a distinct influence on murine cells in vitro. At therapeutic concentrations a pronounced stimulation of murine lymphocyte transformation was caused by carbapenems, aminothiazole cephalosporins and imidazoles. Purine analogs had only suppressive effects. However, the increased (3H) thymidine uptake in murine cells could not be regularly reproduced in human lymphocytes and in ex vivo experiments.

Heparin inhibits the antiparasitic and immune modulatory effects of human recombinant interferon-gamma

Interferon-gamma (IFN-gamma) is a potent immune regulatory cytokine and is, in addition, involved in the induction of antiparasitic effector mechanisms in different cell types. The first step of IFN-gamma action is its binding to a specific receptor. Furthermore, it has been shown that IFN-gamma binds with a great affinity to the heparin-like structure of heparan sulfate, which is localized in basement membranes and on cell surfaces. In this study, we analyze the effect of heparin and heparan sulfate on three different IFN-gamma-mediated activities inducible in human glioblastoma cells (87HG31 and 86HG39). We find firstly that heparin is able to inhibit IFN-gamma-mediated induction of major histocompatibility complex (MHC) class II antigen expression on 87HG31 cells, an effect which can be abrogated by protamine. Secondly, we show that heparin inhibits the IFN-gamma-induced toxoplasmostasis within 86HG39 cells in a dose-dependent fashion, and thirdly that heparin inhibits the IFN-gamma-mediated induction of the tryptophan-degrading enzyme indoleamine 2,3-dioxygenase. In contrast to IFN-gamma-induced effects, the activity of other cytokines, such as interleukin (IL)-1, IL-2 and IL-6, is not influenced by heparin. The possible mechanism of heparin-induced inhibition of IFN-gamma is discussed.

Treatment of mycoplasma contamination in a large panel of cell cultures

Mycoplasmal contamination remains a significant impediment to the culture of eukaryotic cells. For certain cultures, attempts to eliminate the infection are feasible alternatives to the normally recommended disposal of the contaminated culture. Here, three antibiotic regimens for mycoplasmal decontamination were compared in a large panel of naturally infected cultures: a 1-wk treatment with the fluoroquinolone mycoplasma removal agent (MRA), a 2-wk treatment with the fluoroquinolone ciprofloxacin, and three rounds of a sequential 1-wk treatment with BM-Cyclin containing tiamulin and minocyclin. These antibiotic treatments had a high efficiency of permanent cure: MRA 69%, ciprofloxacin 75%, BM-Cyclin 87%. Resistance to mycoplasma eradication was observed in some cell cultures: BM-Cyclin 0%, MRA 20%, ciprofloxacin 20%. Nearly all resistant contaminants that could be identified belonged to the species Mycoplasma arginini and M. orale. Detrimental effects of the antibiotics were seen in the form of culture death caused by cytotoxicity (in 5 to 13% of the cultures). Alterations of the cellular phenotypic features or selective clonal outgrowth might represent further untoward side effects of exposure to these antibiotics. Overall, antibiotic decontamination of mycoplasmas is an efficient, inexpensive, reliable, and simple method: 150/200 (75%) chronically and heavily contaminated cultures were cured and 50/200 (25%) cultures could not be cleansed and were either lost or remained infected. It is concluded that eukaryotic cell cultures containing mycoplasmas are amenable to antibiotic treatment and that a cure rate of three-quarters is a reasonable expectation.

A new, simple, bioassay for human IFN-gamma

IFN-gamma induces the production of N-formyl-kynurenine from L-tryptophan in various cell types by the induction of the enzyme indoleamine 2,3-dioxygenase (IDO). The IFN-gamma induced IDO activity in the glioblastoma cell line 86HG39 and cells of clone 2D9 derived from this cell line was found to be greater than that in Hela cells and U373MG cells. Consequently 2D9 cells were used in all subsequent experiments. The determination of kynurenine in the supernatant of IFN-gamma activated cells was performed photometrically using a microplate reader. It was found that the amount of kynurenine produced was directly proportional to the amount of IFN-gamma used to activate cells. The detection limit for IFN-gamma of this assay was 20 U/ml. The induction of L-tryptophan degradation was specific for IFN-gamma since neither IFN-alpha, IFN-beta, IL-1, IL-2, IL-6, GM-CSF nor TNF alpha induced the production of detectable amounts of kynurenine by 86HG39 and 2D9 cells. Furthermore, a mab directed against IFN-gamma was able to completely block the IFN-gamma induced IDO activation. This bioassay was used to determine the IFN-gamma content of supernatants harvested from toxoplasma antigen specific human T cell lines and clones. This assay gave reproducible results which correlated well with the IFN-gamma content detected in the same samples using a commercially available ELISA kit. Furthermore in the case of T cell supernatant stimulated 2D9 cells a mab directed against IFN-gamma was able to completely block IDO induction. We conclude that the measurement of kynurenine production induced by IFN-gamma can be used to determinate IFN-gamma content. This is a simple bioassay which can be performed with standard laboratory equipment.

A simple method to eliminate mycoplasma from cell cultures

The efficacy of several antibiotic treatments to eliminate mycoplasma from Vero cells contaminated chronically with Mycoplasma orale II were tested. Minocyclin, Kanamycin, Tylosine and Roxitromycin, at non cytotoxic concentrations, were assayed alone or in different combinations. Mycoplasma contamination was effectively eradicated without recurrence once the following regimen was applied: Incubation of contaminated cells with Tylosine (250 micrograms/ml) for 12 days followed by incubation with Minocycline (5 micrograms/ml) for 10 days. This treatment was not deleterious for cell growth, it was effective after only one application and it was successful to eradicate mycoplasma from other contaminated eukaryotic continuous cell lines.

In vitro antibiotic susceptibility testing of different strains of Mycoplasma fermentans isolated from a variety of sources

The in vitro susceptibilities to antibiotics of 24 strains of Mycoplasma fermentans (isolated from human immunodeficiency virus type 1-infected AIDS patients, non-AIDS patients with acute respiratory disease, and tissue culture) were determined. MICs for 90% of the strains tested (micrograms per milliliter) were obtained for chloramphenicol (1.25), ciprofloxacin (0.078), clindamycin (0.078), doxycycline (0.625), erythromycin (> 10), gentamicin (> 10), levofloxacin (0.078), lincomycin (0.156), streptomycin (> 10), and tetracycline (0.625).

Detection of Mycoplasma pneumoniae by polymerase chain reaction and nonradioactive hybridization in microtiter plates

In order to improve the diagnosis of a Mycoplasma pneumoniae infection, we developed a polymerase chain reaction (PCR)-based assay. The gene encoding elongation factor Tu (tuf) was selected as the target sequence. Oligonucleotides derived from variable stretches of the tuf gene were able to prime the amplification of a 950-bp fragment exclusively when M. pneumoniae DNA was used as the template. The sensitivity of the assay was increased 10-fold when the amplification products were hybridized with an internal M. pneumoniae-specific oligonucleotide. The use of three to four genome copies for PCR was sufficient for obtaining a hybridization signal. In addition, we substituted radioactive filter hybridization with a microtiter plate assay. Via a biotin moiety of one PCR primer, the amplification products were immobilized on streptavidin-coated microtiter plates. Subsequent hybridization with a digoxigenin-labeled oligonucleotide resulted in the same sensitivity and specificity as those obtained by filter hybridization. Clinical application of the assay was performed on 102 throat swab specimens from patients with respiratory tract infections. Of 21 culture-positive samples, 19 were confirmed to be positive in the PCR-based assay (sensitivity, 90%). Furthermore, 14 of 19 seropositive but culture-negative samples gave a positive hybridization signal. Of 62 culture-negative and seronegative specimens, 60 gave a negative result in our assay (specificity, 97%). Of the 33 samples that were positive in our PCR-based assay, 5 samples initially gave false-negative results because of the presence of inhibitory substances in those specimens. Inhibition of Taq polymerase in these five cases was prevented by an additional step of phenol extraction and subsequent ethanol precipitation.

Human glioblastoma cell line 86HG39 activates T cells in an antigen specific major histocompatibility complex class II-dependent manner

The capacity of three different human glioblastoma cell lines to activate human T cells was analysed by measuring major histocompatibility complex (MHC) antigen expression, monokine secretion and lectin, mAb OKT3 and antigen-driven T cell proliferation. All glioblastoma cells tested were able to induce PHA and concanavalin A (ConA)-driven T cell proliferation in a dose-dependent fashion, while all failed to induce T cell activation with mAb OKT3. In addition, the glioblastoma cell line 86HG39 was able to induce tetanus toxoid and toxoplasma lysate antigen-specific T cell proliferation. The responding T cell lines originated from only one out of five different donors. This foreign antigen-specific T cell proliferation induced by 86HG39 cells could be inhibited with mAb L243 directed against HLA-DR molecules. The study of monokine secretion by 86HG39 cells showed a strong interleukin (IL)-6 secretion after lipopolysaccharide (LPS) treatment, whilst no IL-1 secretion was observed. Furthermore, only 86HG39 cells were positive for HLA-DR molecules, whereas interferon (IFN) gamma treatment of 87HG28 and 87HG31 cells was necessary for the induction of class II antigen expression. Thus, cell line 86HG39 shows many features of an antigen presenting cell and the interaction of these cells with MHC compatible human T cells might be a useful model to study cellular immune reactions within the central nervous system.

Treatment of mycoplasma-contaminated continuous cell lines with mycoplasma removal agent (MRA)

Thirty-nine continuous adherent or suspension cell lines were treated with a quinolone antibiotic, Mycoplasma Removal Agent (MRA), for the elimination of chronic mycoplasma contamination. In preliminary experiments MRA did not show any cytostatic or cytotoxic effects on mycoplasma-free cell cultures in concentrations up to ten-fold the concentration used for mycoplasma eradication. Twenty-eight cell lines (72%) were effectively cleansed of the mycoplasma contaminants by MRA treatment. The persistent removal of the mycoplasma infection was monitored by three mycoplasma detection assays. In seven cell lines (18%) the mycoplasmas were resistant to treatment with MRA. The resistant species was mainly M. arginini followed by M. orale and A. laidlawii; however, other cell lines harboring these species were cured. Four cell lines (10%) which prior to treatment presented with decreased viability and poor or no cell growth were lost during or shortly after the exposure to the antibiotic. If an antibiotic elimination is attempted it is imperative to closely examine the effectiveness of treatment and possible eukaryotic cytotoxicity. The treated mycoplasma-free cells may also no longer express the original features as a result of treatment or the absence of mycoplasma.

Mycoplasma contamination in human leukemia cell lines. II. Elimination with various antibiotics

19 suspension cell lines were treated with antibiotics for elimination of chronic contamination with mycoplasma. We compared the efficiency, cytotoxicity and cross-resistance of the commercially available antibiotics MRA (Mycoplasma Removal Agent, a quinolone derivative and DNA gyrase inhibitor), Ciprobay (ciprofloxacin, also a quinolone derivative and DNA gyrase inhibitor), and BM-cyclin (a combination of tiamulin, a pleuromutilin derivative, and minocycline, a tetracycline derivative, both inhibitors of protein synthesis on ribosomes). Contaminants were eliminated in all 19 cell lines by BM-Cyclin. Only 74% of the cell lines were cleared of contamination by both MRA and Ciprobay. Successful treatment was monitored by three mycoplasma detection assays. Cross-resistance was noted between MRA and Ciprobay in four of the five cell lines not cleared by either reagent. This resistance could, however, be overcome by consecutive exposure to BM-cyclin. Employed at the recommended concentrations, the antibiotics did not cause marked cytotoxicity, but the growth of the cells was affected to various degrees by some antibiotics. The elimination of mycoplasma from chronically contaminated cell lines is an effective alternative to other treatment protocols, but is cost-intensive and time-consuming; lasting damaging effects of the treatments on the eukaryotic cells cannot be excluded. Long-term post-treatment monitoring is mandatory, since contaminants may only be suppressed and then recur.

Decreased metabolism and viability of Mycoplasma hominis induced by monoclonal antibody-mediated agglutination

Monoclonal antibodies (MAbs) were generated against lysates of clinical Mycoplasma hominis isolates. Three of these, designated BG2, BA10, and FE6, recognized an integral membrane protein of M. hominis with an apparent molecular weight of 50,000 (p50). Electron microscopy studies demonstrated that this protein is distributed evenly over the cell surface. These anti-p50 MAbs were species specific for M. hominis; they reacted with 42% of 126 tested clinical M. hominis isolates and showed no reactivity to heterologous mycoplasma species. Immunoblot analysis after limited proteolysis of purified p50 demonstrated that the three MAbs reacted with different epitopes of the protein. Unlike BA10 and FE6, MAb BG2 induced a decrease in arginine metabolism and a reduction of CFU in metabolic inhibition tests. F(ab)2 fragments of MAb BG2 showed the same inhibitory effect as the intact MAb molecule, while Fab and Fc fragments had no influence on vital functions. Preincubation of the mycoplasmas with MAb BG2 followed by trypsin treatment yielded the same amount of CFU as the control without antibodies. In conclusion, the cell aggregates were resolved by the trypsin treatment. These experiments and tests with the antibody fragments led to the conclusion that only the intact MAb structure or the F(ab)2 structure had metabolic inhibition potential and that the observed metabolism inhibition as well as the apparent decrease in viability were a result of agglutination by MAb BG2.

Sequence and expression in Escherichia coli of a Mycoplasma hominis gene encoding elongation factor Tu

We describe the molecular cloning and the complete nucleotide (nt) sequence of a Mycoplasma hominis gene common to a broad range of Mycoplasma species, as defined by hybridization analysis with the cloned gene. Production of M. hominis protein in Escherichia coli was assayed by use of a monoclonal antibody. The nt sequence analysis revealed a 1194-bp open reading frame that could encode a 43 516-Da protein. Computer-aided sequence comparison indicated that the gene codes for elongation factor Tu.

Elimination of mycoplasmas from cell cultures by a novel soft agar technique

Mycoplasmal infection of cell cultures remains a significant threat to diagnostic and research procedures. In certain defined situations, curing of mycoplasmal infected cultures is a reasonable exercise. Four methods of curing were compared: treatment with BM-cycline, 5 bromouracil, use of specific antisera and treatment of infected cells suspended in soft agar with antibiotics. Antisera treatments were of low efficiency of curing: 50%. None of nine infected cell lines treated with 5-bromouracil were consistently cured of mycoplasmas. The use of BM-cycline was effective for some, but not all lines and required long periods of treatment, 12-21 days. 35 naturally or deliberately infected cultures were treated in soft agar a total of 119 times. This procedure which consisted of suspending infected cultures in soft agar containing appropriate antibiotics resulted in successful mycoplasmal elimination 118/119 times. This soft agar technique took 1-3 days. In separate studies, it was shown that certain Mycoplasma fermentans strains were resisted to this and other curing methods. This may be due to their intracellular location. Such strains may be more amenable to antibiotics that penetrate mammalian cells. It is concluded that the soft agar technique is a rapid, efficient and reliable method to eliminate cell culture mycoplasmas.

Fast and simple procedure for the detection of cell culture mycoplasmas using a single monoclonal antibody

The detection of mycoplasmas in cell cultures is still a problem, especially in those laboratories in which the detection and identification of microorganisms is not established as a routine procedure. In our laboratory, monoclonal antibodies (mAbs) have been prepared to Acholeplasma laidlawii, Mycoplasma hyorhinis, Mycoplasma orale, Mycoplasma arginini and Mycoplasma salivarium. 30 mAbs were obtained and one of these, designated CCM-2, was shown to bind to all five mycoplasma species. It also bound to Mycoplasma fermentans, Mycoplasma hominis and to all wild types (n = 54), isolated from cell cultures submitted to our laboratory. The mAb was used in a immunofluorescent assay (IF) and the method correlated with the microbiological assay. Using this mAb immunofluorescent staining of cells is a fast and simple procedure for mycoplasma detection in cell cultures.

Interactions between mycoplasmas and the immune system

Mycoplasmas are a heterogenous group of prokaryotic organisms causing a wide variety of diseases, including autoimmune disorders. Thus, it is not surprising that various mycoplasmas strains, including Mycoplasma arginini, M. arthritidis, M. neurolyticum and M. pulmonis, are able to regulate the immune response. Though some of the studies of the immunomodulatory action of mycoplasmas have been done in vivo, the majority of the investigations have been conducted in vitro. This has led to the recognition that mycoplasmas are polyclonal activators of both B and T cells from several species, acting through MHC-restricted or -unrestricted pathways. Mycoplasma activation not only induces T-cell proliferation but also leads but to the formation of cytotoxic T cells. We, as well as others, have shown that mycoplasma-mediated B-cell activation induces proliferation as well as Ig secretion, and also that mycoplasma stimulation of lymphocytes may result in the production of cytokines. We communicate here our investigations into the effects of an M. arginini strain on the growth and maturation of preactivated B cells. After an initial biological characterization of the M. arginini effects in vitro, we established the protein nature of the growth-supporting activity and proceeded further on to isolate and identify the responsible proteins. The use of lipid- and lipoglycan-free extracts has allowed us to further extend our studies on the biological activities of the proteins from M. arginini and to compare these results with the effects obtained using live organisms. Furthermore, the study was extended to include a characterization of the in vivo-induced effects of live M. arginini. Altogether, the results from these experiments allow us to conclude that M. arginini is a T-cell independent polyclonal B-cell mitogen, mediated by five identified proteins, inducing growth and Ig secretion of both resting and preactivated B cells.

Secretion and cell surface expression of IgG1 are impaired in human B lymphoblasts that lack HLA-A, -B, and -C antigens

B-lymphoblastoid cell line (LCL) 721.221 lacks HLA-A, -B, and -C class I antigens and transcripts as a result of gamma-ray-induced mutations. LCL 721, from which mutant .221 was derived, produces membrane and secreted forms of IgG1(kappa). In contrast, IgG expression in .221 had these characteristics: (i) gamma 1 heavy chains were diminished by 98% but were detectable with chain-specific antibodies in cell lysates; (ii) kappa light chains were present at normal levels in cell lysates and free kappa chains were secreted; (iii) cell-surface-associated IgG and secreted IgG were absent. Mutants that had partially reduced amounts of class I antigens continued to secrete IgG; however, both the absolute amount of IgG secreted and the relative amount of kappa vs. intact IgG secreted were abnormal in such partially class I-deficient cells. The failure to export IgG and the deficiency of HLA-A, -B, and -C were not merely coincidental in mutant .221, since production of IgG was restored by transferring a functional HLA-A, -B, or -C gene into .221. Cell surface antigen expression of cloned HLA-A, -B, and -C transgenes introduced into .221 was comparable to that of the same genes in their normal chromosomal locations. These observations reveal a relation between production of HLA class I gene products and production of IgG.