The cytogenetic effects of mycoplasma in human leukocyte cultures

Effect of storage conditions on detection of mycoplasma in biopharmaceutical products

Mycoplasma contamination affects many different aspects of cell culturing, resulting in unreliable experimental results and potentially harmful biological products. Therefore, the specificity, sensitivity, and reliability of detecting mycoplasma contamination are important aspects of quality control in biotechnological products. In this study, Mycoplasma hyorhinis was adopted as a model strain to evaluate the effects of storage on the viability of Mycoplasma species in cell culture samples. Medium X was compared with conventional media 243 and 988 for the ability to detect M. hyorhinis. The 10(1) CFU/ml of M. hyorhinis was inoculated into medium X prepared using the same lots of components and preserved for 7 d, 1 mo, and 2 mo. M. hyorhinis grew readily and typically on agar plates prepared within 1 mo. The viable mycoplasmas in samples containing different initial titers (10(1) and 10(6) CFU/ml) after storage at 4 degrees C and -30 degrees C were analyzed. During storage, viable organisms were found with little or no reduction in titers after storage for 8 wk at -30 degrees C under aerobic and anaerobic conditions. A reduction in titers of 3 log10 occurred after 4 wk storage for high-dose cultures (10(6) CFU/ml) at 4 degrees C. The titers of viable organisms were diminished over 8 wk at 4 degrees C under aerobic and anaerobic conditions.

Mycoplasma fermentans infection promotes immortalization of human peripheral blood mononuclear cells in culture

Chronic infection or colonization by mycoplasma(s) could gradually and significantly alter many biologic properties of mammalian host cells in culture, including induction of malignant transformation. We examined effects of Mycoplasma fermentans infection on the continuing survival and immortality of human peripheral blood mononuclear cells (PBMCs) from healthy blood donors. Without specific supplemental growth factors, human PBMCs normally die rapidly, with few cells other than macrophages/monocytes surviving after 2 weeks in cultures. Only occasional Epstein-Barr virus (EBV)–positive B lymphocytes would continue to proliferate and undergo spontaneous immortalization. Our present study revealed that infection of human PBMCs in culture with the incognitus and PG18 strains of M fermentans, but surprisingly not with some other strains tested in parallel, markedly enhanced the rate of EBV-positive B lymphocytes to undergo immortalization (74% vs 17%). Compared with spontaneously immortalized PBMCs, the PBMCs immortalized in cultures infected with the mycoplasmas often had prominent karyotype changes with chromosomal loss, gain, or translocations. Furthermore, many of these immortalized B lymphocytes were found to be monoclonal in nature. The in vitro findings would be of relevance to lymphoproliferative disorders that occurred in patients with immune suppression. The mycoplasma-mediated promotional effect in cell immortalization and its potential clinical implications warrant further study.

Do mycoplasmas cause human cancer?

A linkage between mycoplasmas and malignancy was mainly proposed in the 1960s when human-associated mycoplasmas were becoming of interest given the novel characterization of the human respiratory pathogen Mycoplasma pneumoniae. Associations with leukemia and other malignancies, however, were largely ascribed to tissue-culture contamination, which is now recognized as a significant potential problem in molecular biology circles. A few epidemiological studies, however, continue to raise concern over such a linkage. As well, in vitro data have demonstrated the potential for some mycoplasmas to induce karyotypic changes and malignant transformation during chronic tissue-culture infestation. As cellular and molecular mechanisms for such transformation become studied, a resurgence of interest in this area is inevitable. A role for mycoplasmas in malignancy of any sort is conjectural, but there remains a need to continue with focussed epidemiological and laboratory investigations.Key words: mycoplasma, cancer, oncogenesis, leukemia.

Clastogenic effects of different Ureaplasma urealyticum serovars on human chromosomes

The possibility that Ureaplasma urealyticum might play an important role in human infertility was first raised more than 20 years ago, but this association remains speculative. Considering the hypothesis that the pathogenicity of Ureaplasma urealyticum may depend on its serotypes, the clastogenic effects of different strains of Ureaplasma urealyticum, at concentrations of 10(3) CCU (color changing units)/ml, 10(4) CCU/ml and 10(5) CCU/ml, were evaluated in vitro in short-term cultures of human lymphocytes. Total or partial mitotic inhibition was produced by Ureaplasma urealyticum serotypes 2, 3 and 10 independent of the concentration (10(3) CCU/ml, 10(4) CCU/ml or 10(5) CCU/ml) of the microorganisms employed. In contrast, the clastogenic effects observed with serotypes 1, 7 and 12 varied according to the concentration employed in the test. Mitotic alterations were observed in Ureaplasma urealyticum serotypes 5, 6, 7, 8, 9, 11 and 12. Chromatid gaps (53.0%) and chromatid breaks (13.9%) were the most frequent types of alterations observed. The results of this in vitro assay demonstrated that the clastogenic effects varied with the Ureaplasma urealyticum serotypes evaluated.

The quality control of cell banks using DNA fingerprinting

Reproducibility in animal cell culture technology requires careful preparation and characterisation of banks of cell cultures. The two standard techniques used in the quality control of such banks are isoenzyme analysis and cytogenetics which require complex and time-consuming procedures to enable cell line identification. However, DNA fingerprinting is potentially a more powerful method of analysis which can detect mutation and intra-species cross-contamination. At the European Collection of Animal Cell Cultures (ECACC) multilocus fingerprint analysis using probes 33.6 and 33.15 has been assessed in the quality control of cell banks. This method has confirmed consistency between master and working banks, has proven useful over a wide species range and can differentiate closely related cell lines. The key advantage of this method is its ability to detect cross-contamination by cell lines from a wide range of species using a straightforward and economical test. In addition the reproducibility of DNA fingerprints indicates their possible role in cell line authentication procedures which are important for patent and product licence applications.

Differential sensitivity of peripheral blood lymphocytes of untreated leprosy patients to mitomycin C

The effects of a bifunctional alkylating agent mitomycin C (MMC), an effective inducer of chromosome aberrations and sister-chromatid exchanges (SCEs), have been studied in untreated leprosy patients. This was done to study the mutagen sensitivity of the leprosy patients. The frequency of chromosomal aberrations induced by MMC (conc. 0.01 microgram/ml) was 2.5% in controls, 3.6% in paucibacillary (PB), and 6.8% in multibacillary (MB) patients. The difference in the frequency of MMC-induced chromosome aberrations between the 3 groups studied was highly significant (p less than 0.01). Cultures grown with MMC showed the frequency of SCEs/cell to be 12.70 +/- 1.19 in controls, 19.97 +/- 3.51 in PB, and 29.66 +/- 5.92 in MB patients. The differences in the frequency of MMC-induced SCEs between the 3 groups were found to be highly significant (p less than 0.01). The enhanced frequencies of spontaneous and MMC-induced chromosome aberrations and SCEs observed in PB and MB patients indicate a clear differential mutagen sensitivity between PB and MB patients who are known to have different immunological status and thereby differ in the severity of the disease.

SCE induction and harlequin staining in mycoplasma-contaminated Chinese hamster cells

Chinese hamster V79 and CHO cells infected with Mycoplasma hyorhinis show elevated sister-chromatid exchange (SCE) levels but normal cell proliferation and levels of chromosomal aberrations when compared with uninfected cells. Harlequin staining patterns differ from those seen with uninfected cells at similar levels of bromodeoxyuridine (BrdUrd), indicating that BrdUrd is rapidly depleted from the medium by the mycoplasmal uridine phosphorylase and therefore becomes unavailable over the two cell cycles necessary for harlequin staining. Continuous treatment with the antibiotic minocycline restores the SCE level and harlequin staining to that seen in uncontaminated cells. The results suggest that mycoplasma infection should be suspected if harlequin staining patterns indicate a sudden decrease in incorporation of BrdUrd in cells grown in normal levels of BrdUrd.

Increased sister chromatid exchange in human lymphocyte cultures infected with mycoplasma

The effects of fermenting, poorly arginine-utilizing Mycoplasma fermentans and arginine-utilizing Mycoplasma salivarium on the frequency of sister chromatid exchange (SCE) in cultured human lymphocytes were examined. M. fermentans caused no apparent mitosis inhibition of lymphocytes and the increase in SCE frequency was dependent on the inoculum size of the mycoplasma. An evident increase in SCE frequency was observed in lymphocytes infected with smaller inoculum sizes of M. salivarium whereas there was mitosis inhibition of lymphocytes infected with larger inoculum sizes of the mycoplasma. In lymphocyte cultures infected with M. salivarium, the addition of arginine to the culture medium reduced mitosis inhibition but did not diminish the increase in SCE frequency, indicating that arginine depletion was not involved in causing the induction of SCEs in mycoplasma-infected lymphocytes. With regard to the genetic effectiveness of SCE, these results suggested that mycoplasmas are capable of inducing cytogenetic changes in infected host cells.

Effect of mycoplasma infection on pyruvate dehydrogenase complex activity of normal and pyruvate dehydrogenase complex-deficient fibroblasts

The fermentative mycoplasmas A. laidlawii JS, M. hyorhinis DBS-50, M. hyorhinis GDL and M. pneumoniae FH have very high apparent activities of pyruvate dehydrogenase (PDH) (EC 1.2.4.1) and pyruvate dehydrogenase complex (PDHC). Infection of normal and PDHC-deficient fibroblasts with these mycoplasma species resulted in a marked increase of the specific activity of these two enzymes, and under certain conditions could conceal the enzymatic defect. The non-fermentative mycoplasmas M. salivarium VV and M. arthritidis PG-6 have very low apparent activities of these two enzymes. Normal fibroblasts infected with non-fermentative mycoplasmas could appear as deficient in these two enzymes. The degree of interference depends on the number of mycoplasmas associated with the harvested cells. Besides the mycoplasma species, this depends (1) on the duration of infection which determines mycoplasmal titers and also can have a killing effect on both host cells and/or mycoplasmas; (2) harvest of the cells by scraping or trypsinization; (3) centrifugal force used in the collection of the cells; (4) washing and the inherent mechanical treatment; and (5) other possibilities.

Arginase as an inhibitory principle in liver plasma membranes arresting the growth of various mammalian cells in vitro

Plasma membranes prepared from rat livers inhibited the in vitro growth of various mammalian cells including hepatoma cells in a concentration-dependent manner, showing almost complete arrest of cell growth at 0.1 mg protein/ml. Some of these cells tested, i.e., leukemia (L1210 and P388) and myeloma (P3-NS-1/1-Ag4-1) cells, were labile in the presence of plasma membranes (losing the viability), and CHO (Chinese hamster ovary) cells became round without detaching from the substratum. The culture medium preincubated with liver plasma membranes no longer supported the growth of hepatoma cells (AHI3 and AH66F). However, the 'conditioned' medium supplemented with L-arginine, supported the growth of the cells. Moreover, the addition of L-ornithine to the cultures containing plasma membranes markedly reduced the inhibitory effect of plasma membranes. The plasma membrane preparations were found to possess considerable arginase activity. There results seem to indicate the possible involvement of arginase in the inhibition of cell growth by liver plasma membranes.

Mycoplasmal infection of lymphocyte cell cultures: infection with M. salivarium

Many conclusions concerning cell culture mycoplasmas are based on data from studies in fibroblast cultures. Some conclusions may not be valid in other types of differentiated cell cultures. M. salivarium was isolated from 35 human lymphocyte cultures (HLC), 34 from the same laboratory. The organism grew to more than 10(8) colony forming units (CFU) per ml of lymphocyte suspensions and was readily detectable by microbiological culture, uridine phosphorylase, and uridine/uracil assays. Direct mycoplasmal assays on HLC by DNA fluorochrome staining and scanning electron microscopy (SEM) yielded artifacts that interfered with diagnosis. For DNA and SEM of HLC, inoculation into indicator cell cultures is recommended. M. salivarium infection of HLC did not produce any immediate difference in growth rates; however, infected cultures eventually died 14 to 29 passages after infection in contrast to uninfected controls. The same organism in 3T6 fibroblasts effected a 60% decrease in growth rate. Although M. salivarium is a frequent isolate from the oral cavity, it is a rare cell culture isolate. M. salivarium was able to initiate growth over a wide pH range, grew as well in cell cultures as in cell-free media, and was resistant to 50 microgram per ml of gentamycin, tylocine, kanamycin, and erythromycin. By Cot1/2 analysis, M. salivarium had a genomic molecular weight of 4.2 X 10(6) daltons. M. salivarium did not increase chromosome aberrations in one HLC. Some of these results have application to infection of HLC by other mycoplasmal species.

The effect of Mycoplasma contamination on the in vitro assay of pyruvate dehydrogenase activity in cultured fibroblasts

Cultured fibroblasts contaminated with mycoplasma were shown to have increased in levels of apparent pyruvate dehydrogenase and pyruvate dehydrogenase complex enzyme activity. The apparent pyruvate dehydrogenase specific activity was about 1000-fold greater in cultured Mycoplasma pneumoniae than in cultured fibroblasts. Several acid hydrolytic enzyme activities were also shown to be present in M. pneumoniae though a lower apparent specific activity than in cultured fibroblasts.

Arginine deprivation in KB cells. II. Characterization of the DNA synthesized during starvation

DNA synthesis in cells deprived of arginine was examined. Three lines of evidence indicated that tritiated thymidine ([3H]TdR) incorporation in arginine-starved cells was due to replicative rather than repair DNA synthesis. (a) When made in the presence of bromodeoxyuridine, the [3H]TdR-labeled DNA sedimented at hybrid density in isopycnic gradients. (b) As determined by the diphenylamine reaction, there was a 15% increase in the chemical amount of DNA per culture 30 h after arginine deprivation. (c) [3H]TdR incorporation was hydroxyurea-sensitive. Alkaline velocity sedimentation of the total DNA made during starvation revealed the existence of two distinct size classes: most of the DNA sedimented at a position analogous to that of control DNA, but 40% migrated one-third the distance of the bulk. After arginine restoration, these shorter pieces appeared to be chased into DNA of normal length; thus, one lesion in deprived cultures may cause an arrest in completion of DNA stretches to mature size. These findings, together with results of morphological studies of starved cells, suggest that changes induced by arginine deficiency effect the organization of nucleoproteins. These changes are reversible upon arginine restoration.

Infrequent chromosome aberrations in Syrian hamster cells following partial synchrony by amino-acid deprivation

Incubation of Syrian hamster embryo secondary cell cultures in isoleucine or arginine deficient medium inhibited cell multiplication; 4-7% of the cells were synthesizing DNA compared to approximately 40% for cells in complete medium. After the deficient medium was replaced with complete medium, cells resumed multiplication and within 12 hours 65--70% of the cells entered into the S phase. A second peak of labeled cells, approximately 55%, occurred 24 hours after addition of complete medium. Chromosomal damage characteristic for cell lines grown in amino acid deficient medium did not occur with these Syrian hamster cells. Isoleucine or arginine deprivation resulted in chromosomal or chromatid aberrations in only 2-5% of the cells, whereas chromosomes of control cells in complete medium occasionally exhibit chromatid gaps (less than 1% of the cells).

Comparison of methods for the detection of Mycoplasmal contamination of cell cultures: a review

Several reviews in recent years have emphasized the problems created by mycoplasmal contamination of cultured cells (1-5). Because of the hazards of interpreting data derived from mycoplasma contaminated cells, most cell biologists routinely screen their cultures for the presence of these organisms. In recent years, the limitations of standard microbiological testing for mycoplasmas have become increasingly apparent and have led to the development of several new biochemical techniques for detection of these organisms. The aim of this review is to describe and compare available detection techniques and to evaluate their relative efficacy. Those properties of mycoplasmas that are relevant to their role as cell culture contaminants will be briefly discussed.

Mycoplasma contamination of cultured amniotic fluid cells: potential hazard to prenatal chromosomal diagnosis

Amniotic fluid cell cultures were screened for mycoplasma contamination. Mycoplasma RNA's were observed in more than half the cultures examined. Karyotypic analyses of these contaminated cell cultures revealed a significant increase in chromosomal aberrations. These studies emphasize the need for screening for mycoplasma in cultured amniotic cells.

Chromosomal aberrations induced by T strains mycoplasmas

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Mycoplasmas and cell cultures

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Relationship between nucleic acids, histone and non-histone protein synthesis in human lymphocytes stimulated with phytohemagglutinin

The temporal relationship between the synthesis of histone and non-histone proteins and nucleic acids has been investigated by autoradiography in PHA stimulated human lymphocytes throughout the 72-hour culture period. It was found that a significant amount of3H-arginine and3H-lysine incorporation took place at a time when the cells were actively synthesizing DNA. Non-histone protein synthesis, as evidenced by3H-tryptophan incorporation, was found to be dependent on PHA stimulation in human lymphocytes. Inhibition of histone and/or non-histone protein synthesis leads to the inhibition of nucleic acid synthesis.

Studies of PPLO infection. V. Inhibition of lymphocyte mitosis and antibody formation by mycoplasmal extracts

Extracts of five arginine-utilizing mycoplasmas inhibit PHA-induced lymphocyte mitosis, while extracts of five glucose-utilizing mycoplasmas do not. Evidence is presented supporting the view that the inhibitory factor is the enzyme arginine deiminase. This enzyme inhibits the reactions of human lymphocytes to antigens as well as PHA, and the secondary production of antibody by rabbit lymph node fragments in vitro. Addition of enzyme to the cells several days after the initial mitotic or antigenic stimulus reduces, but does not abolish, further cellular activity. The production of serum proteins by hepatoma cells is totally unaffected by the mycoplasmal extract. It is concluded that arginine is an essential amino acid for the small lymphocyte, but not for the transformed cell nor for a number of other cell types. Suggestive evidence has been obtained that other enzymes similarly affect lymphocyte reactions.

Mycoplasmal deoxyribonuclease activity in virus-infected L-cell cultures

Cell-free extracts of Mycoplasma hominis and medium from 72-hr broth cultures had deoxyribonuclease activity like that of deoxyribonuclease I. Mg(++) stimulated activity, and the pH optimum was between 8.0 and 9.0. Double-stranded or heatdenatured deoxyribonucleic acid (DNA) served as a substrate, and oligonucleotides were produced. Cell-free extracts of L cells infected with M. hominis or M. hominis plus equine abortion virus (equine herpes virus, EAV) had greatly increased activity over that of extracts of L cells or of L cells infected with EAV alone. In the absence of M. hominis, however, extracts had little activity, most of which was in virus-infected cell cultures. Activity was found in the culture medium only in those systems in which M. hominis was present. It is concluded that M. hominis can contribute significant deoxyribonuclease activity to virus-infected as well as virusfree cell cultures. Perhaps the most interesting question arising concerns the ability of EAV, a DNA virus, to replicate successfully despite the presence of deoxyribonuclease activity at the site of replication (the nucleus).