Elimination of mycoplasma, bacteria, and fungi contaminants of hybridoma cultures by intraperitoneal passage in the mouse

Elimination of Mycoplasma Contamination from Infected Human Hepatocyte C3A Cells by Intraperitoneal Injection in BALB/c Mice

Background/Aims: The use of antibiotics to eliminate Mycoplasma contamination has some serious limitations. Mycoplasma contamination can be eliminated by intraperitoneal injection of BALB/c mice with contaminated cells combined with screening monoclonal cells. However, in vivo passage in mice after injection with contaminated cells requires a long duration (20-54 days). Furthermore, it is important to monitor for cross-contamination of mouse and human cells, xenotropic murine leukemia virus-related virus (XMRV) infection, and altered cell function after the in vivo treatment. The present study aimed to validate a reliable and simplified method to eliminate mycoplasma contamination from human hepatocytes. BALB/c mice were injected with paraffin oil prior to injection with cells, in order to shorten duration of intraperitoneal passage. Cross-contamination of mouse and human cells, XMRV infection and cell function-related genes and proteins were also evaluated. Methods: PCR and DNA sequencing were used to confirm Mycoplasma hyorhinis (M. hyorhinis) contamination in human hepatocyte C3A cells. Five BALB/c mice were intraperitoneally injected with 0.5 ml paraffin oil 1 week before injection of the cells. The mice were then intraperitoneally injected with C3A hepatocytes (5.0 × 10⁶/ml) contaminated with M. hyorhinis (6.2 ± 2.2 × 10⁸ CFU/ml). Ascites were collected for monoclonal cell screening on the 14th day after injection of contaminated cells. Elimination of mycoplasma from cells was determined by PCR and Transmission Electron Microscopy (TEM). Human-mouse cell and XMRV contamination were also detected by PCR. Quantitative reverse transcription PCR and western blotting were used to compare the expression of genes and proteins among treated cells, non-treated infected cells, and uninfected cells. Results: Fourteen days after injection with cells, 4 of the 5 mice had ascites. Hepatocyte colonies extracted from the ascites of four mice were all mycoplasma-free. There was no cell cross-contamination or XMRV infection in treated cell cultures. Elimination of Mycoplasma resulted in partial or complete recovery in the expression of ALB, TF, and CYP3A4 genes as well as proteins. Proliferation of the treated cells was not significantly affected by this management. Conclusion: The method of elimination of Mycoplasma contamination in this study was validated and reproducible. Success was achieved in four of five cases examined. Compared to the previous studies, the duration of intraperitoneal passage in this study was significantly shorter.

Of mice and microflora: considerations for genetically engineered mice

The phenotype of genetically engineered mice is a combination of both genetic and environmental factors that include the microflora of the mouse. The impact a particular microbe has on a mouse reflects the host-microbe interaction within the context of the mouse genotype and environment. Although often considered a confounding variable, many host-microbe interactions have resulted in the generation of novel model systems and characterization of new microbial agents. Microbes associated with overt disease in mice have been the historical focus of the laboratory animal medical and pathology community and literature. The advent of genetic engineering and the complex of mouse models have revealed previously unknown or disregarded agents that now oblige the attention of the biomedical research community. The purpose of this article is to describe and illustrate how phenotypes can be affected by microflora by focusing on the infectious diseases present in genetically engineered mouse (GEM) colonies of our collective institutions and by reviewing important agents that are rarely seen in most research facilities today. The goal is to introduce the concept of the role of microflora on phenotypes and in translational research using GEM models.

From bench to cageside: Risk assessment for rodent pathogen contamination of cells and biologics

Many newly developed animal models involve the transfer of cells, serum, or other tissue-derived products into live rodents. These biologics can serve as repositories for adventitious rodent pathogens that, when used in animal studies, can alter research outcomes and result in endemic outbreaks. This review includes a description of some of the biologics that have inadvertently introduced infectious agents into in vivo studies and/or resulted in endemic outbreaks. I also discuss the points of potential exposure of specific biologics to adventitious rodent pathogens as well as the importance of acquiring a complete developmental and testing history of each biologic introduced into a barrier facility. There are descriptions of specific cases of mycoplasma and lactate dehydrogenase–elevating virus (LDHV), two of the most common organisms that contaminate cells and cell byproducts. The information in this article should help investigators and animal resource program personnel to perform an appropriate risk assessment of biologics before their use in in vivo studies that involve rodents.

Evaluation of three methods for curing hybridomas from mycoplasma contamination

Hybridomas are as susceptible to mycoplasma contamination as animal cell cultures. Two in vitro methods and one in vivo passage into mice were compared for efficiency of curing hybridomas from mycoplasma contaminations. Four contaminated clones were treated with the combined action of 5-bromouracil (5-BrUra) and the Hoechst 33258 followed by photosensitization. The other in vitro method involved the use of BM-cycline. The success of overcoming the mycoplasma contamination was dependent on the level of the initial contamination of the individual hybridoma. BM-cycline was more efficient than the photosensitization method. For the most contaminated hybridomas, 10 successive treatments with 5-BrUra were necessary as compared to six treatments with BM-cycline. Moreover, the use of BM-cycline reduced the contamination by as much as 50% after the first treatment. After twenty passages following the curing of hybridomas with BM-cycline, cells were stable and retained their specificity and secretion of their respective immunoglobulins. Whereas, treatment with 5-bromouracil, recurrence of contamination was observed in one of the four hybridomas after 10 passages following treatment. Decontamination after one passage in peritoneal cavity in mice was not always sufficient since one of four hybridomas remained contaminated. BM-cycline appears to be the method of choice since it is more efficient, less time consuming, simpler and less expensive. Mycoplasma strains that could be identified were of bovine origin: Mycoplasma arginini and Acholeplasma laidlawii.

Rapid removal of mycoplasma from cell lines mediated by a direct effect of complement

Mycoplasma can be removed from the surface of contaminated human and murine cell lines by incubation for 4 h with human, rabbit, guinea pig, or mouse sera. Several lines of evidence suggest the involvement of complement in this process: (1) The activity can be abrogated by heat treatment (56 degrees C for 45 min). (2) Using monoclonal antibodies directed against C3a and C3b, the deposition of C3b fragments on the surface of mycoplasma-positive cells can be demonstrated after 1 h incubation with human serum. (3) Ca2+ depletion ablates the ability of serum to remove the activity. (4) C2def' sera are inactive while addition of purified C2 reconstitutes the activity. The latter two findings implicate that activation of the classical pathway of complement is responsible for the effect. Antibody, however, is not required as demonstrated by the uncompromised activity of Ig-deficient sera from bursectomized chicken. Treatment with human serum or rabbit serum was used successfully to permanently cleanse 10/10 tumor cell lines of human and of murine origin. The complete removal of mycoplasma was monitored over at least 8 weeks by direct DNA staining and confirmed by agar culture and transfer of supernatants to mycoplasma-free Vero cells followed by DNA staining. Thus the direct interaction of mycoplasma and complement appears to be an effective and rapid means of curing cell lines from mycoplasma.