Cross comparison of rapid mycoplasma detection platforms

Historical evaluation of the in vivo adventitious virus test and its potential for replacement with next generation sequencing (NGS)

The Consortium on Adventitious Agent Contamination in Biomanufacturing (CAACB) collected historical data from 20 biopharmaceutical industry members on their experience with the in vivo adventitious virus test, the in vitro virus test, and the use of next generation sequencing (NGS) for viral safety. Over the past 20 years, only three positive in vivo adventitious virus test results were reported, and all were also detected in another concurrent assay. In more than three cases, data collected as a part of this study also found that the in vivo adventitious virus test had given a negative result for a sample that was later found to contain virus. Additionally, the in vivo adventitious virus test had experienced at least 21 false positives and had to be repeated an additional 21 times all while using more than 84,000 animals. These data support the consideration and need for alternative broad spectrum viral detection tests that are faster, more sensitive, more accurate, more specific, and more humane. NGS is one technology that may meet this need. Eighty one percent of survey respondents are either already actively using or exploring the use of NGS for viral safety. The risks and challenges of replacing in vivo adventitious virus testing with NGS are discussed. It is proposed to update the overall virus safety program for new biopharmaceutical products by replacing in vivo adventitious virus testing approaches with modern methodologies, such as NGS, that maintain or even improve the final safety of the product.

Real-time PCR assay is superior to other methods for the detection of mycoplasma contamination in the cell lines of the National Cell Bank of Iran

Mycoplasmas are the most important contaminants of cell cultures throughout the world. They are considered as a major problem in biological studies and biopharmaceutical economic issues. In this study, our aim was to find the best standard technique as a rapid method with high sensitivity, specificity and accuracy for the detection of mycoplasma contamination in the cell lines of the National Cell Bank of Iran. Thirty cell lines suspected to mycoplasma contamination were evaluated by five different techniques including microbial culture, indirect DNA DAPI staining, enzymatic mycoalert(®) assay, conventional PCR and real-time PCR. Five mycoplasma-contaminated cell lines were assigned as positive controls and five mycoplasma-free cell lines as negative controls. The enzymatic method was performed using the mycoalert(®) mycoplasma detection kit. Real-time PCR technique was conducted by PromoKine diagnostic kits. In the conventional PCR method, mycoplasma genus-specific primers were designed to analyze the sequences based on a fixed and common region on 16S ribosomal RNA with PCR product size of 425 bp. Mycoplasma contamination was observed in 60, 56.66, 53.33, 46.66 and 33.33 % of 30 different cell cultures by real-time PCR, PCR, enzymatic mycoalert(®), indirect DNA DAPI staining and microbial culture methods, respectively. The analysis of the results of the different methods showed that the real-time PCR assay was superior the other methods with the sensitivity, specificity, accuracy, predictive value of positive and negative results of 100 %. These values were 94.44, 100, 96.77, 100 and 92.85 % for the conventional PCR method, respectively. Therefore, this study showed that real-time PCR and PCR assays based on the common sequences in the 16S ribosomal RNA are reliable methods with high sensitivity, specificity and accuracy for detection of mycoplasma contamination in cell cultures and other biological products.

Multi-primer qPCR assay capable of highly efficient and specific detection of the vast majority of all known Mycoplasma

Mycoplasma bacteria are able to pass through sterilizing grade filters due to their small size and lack of a cell wall, making them a common contaminant of biopharmaceutical productions. The classical method for detecting Mycoplasma is described in the European Pharmacopeia (Ph.Eur) 2.6.7. The method takes 28 days to perform, due to the slow growing nature of some Mycoplasma species. The Ph.Eur has described Nucleic Acid Testing (NAT) as a rapid alternative to the classical method. Here we present the development of a quantitative polymerase chain reaction (qPCR) assay capable of unambiguous detection of Mycoplasma with high sensitivity and specificity. The broadness of detection and the specificity towards Mycoplasma has been investigated by in silico analysis of the primer sequences followed by testing on purified Mycoplasma DNA as well as DNA from closely related genera. The assay will in all probability detect at least 356 species and strains of Mycoplasma, Spiroplasma and Acholeplasma with high sensitivity. To our knowledge this assay has the most uniform amplification efficiency over the broadest range of species and it is extremely specific towards Mycoplasma. With appropriate validation, the assay can be applied as a powerful tool for rapid Mycoplasma detection in the biopharmaceutical industry.

Performance of PCR-based and Bioluminescent assays for mycoplasma detection

Contaminated eukaryotic cell cultures are frequently responsible for unreliable results. Regulatory entities request that cell cultures must be mycoplasma-free. Mycoplasma contamination remains a significant problem for cell cultures and may have an impact on biological analysis since they affect many cell parameters. The gold standard microbiological assay for mycoplasma detection involves laborious and time-consuming protocols. PCR-based and Bioluminescent assays have been considered for routine cell culture screening in research laboratories since they are fast, easy and sensitive. Thus, the aim of this work is to compare the performance of two popular commercial assays, PCR-based and Bioluminescent assays, by assessing the level of mycoplasma contamination in cell cultures from Rio de Janeiro Cell Bank (RJCB) and also from customers' laboratories. The results obtained by both performed assays were confirmed by scanning electron microscopy. In addition, we evaluated the limit of detection of the PCR kit under our laboratory conditions and the storage effects on mycoplasma detection in frozen cell culture supernatants. The performance of both assays for mycoplasma detection was not significantly different and they showed very good agreement. The Bioluminescent assay for mycoplasma detection was slightly more dependable than PCR-based due to the lack of inconclusive results produced by the first technique, especially considering the ability to detect mycoplasma contamination in frozen cell culture supernatants. However, cell lines should be precultured for four days or more without antibiotics to obtain safe results. On the other hand, a false negative result was obtained by using this biochemical approach. The implementation of fast and reliable mycoplasma testing methods is an important technical and regulatory issue and PCR-based and Bioluminescent assays may be good candidates. However, validation studies are needed.

World Health Organization International Standard To Harmonize Assays for Detection of Mycoplasma DNA

Nucleic acid amplification technique (NAT)-based assays (referred to here as NAT assays) are increasingly used as an alternative to culture-based approaches for the detection of mycoplasma contamination of cell cultures. Assay features, like the limit of detection or quantification, vary widely between different mycoplasma NAT assays. Biological reference materials may be useful for harmonization of mycoplasma NAT assays. An international feasibility study included lyophilized preparations of four distantly related mycoplasma species (Acholeplasma laidlawii, Mycoplasma fermentans, M. orale, M. pneumoniae) at different concentrations which were analyzed by 21 laboratories using 26 NAT assays with a qualitative, semiquantitative, or quantitative design. An M. fermentans preparation was shown to decrease the interassay variation when used as a common reference material. The preparation was remanufactured and characterized in a comparability study, and its potency (in NAT-detectable units) across different NATs was determined. The World Health Organization (WHO) Expert Committee on Biological Standardization (ECBS) established this preparation to be the "1st World Health Organization international standard for mycoplasma DNA for nucleic acid amplification technique-based assays designed for generic mycoplasma detection" (WHO Tech Rep Ser 987:42, 2014) with a potency of 200,000 IU/ml. This WHO international standard is now available as a reference preparation for characterization of NAT assays, e.g., for determination of analytic sensitivity, for calibration of quantitative assays in a common unitage, and for defining regulatory requirements in the field of mycoplasma testing.

Role of Analytics in Viral Safety

In summary, this chapter reviews the principles of how the current and routine tests detect adventitious agents, and reviews how novel and emerging methods differ in their detection principles. These facets may permit novel methods to emerge to supplement, refine, or replace the routine methods. We have suggested a framework for risk assessment to assure biosafety in vaccines and suggested quantitative modeling to help crystallize thinking about the place of testing, either routine or novel, in this assurance. We assert that testing for adventitious agents should not be the sole basis on which product biosafety is assured. Appropriate sourcing and quality control of raw and starting materials, adherence to principles of Good Manufacturing Practices, including environmental and personnel monitoring and process validation, and finally, testing as verification are the package needed for maximal assurance of biosafety. Thus, a pathway forward to a new paradigm for adventitious agent testing exists in which detection of a broader array of potential adventitious agents might be included in the testing, with adequate sensitivity to provide the needed assurance of verification that there has been no catastrophic breach, in the context of the overall process, design, and adherence to cGMP. Furthermore, it is our hope that we may be able to implement the 3 Rs policy to reduce, replace, and/or refine the use of animals in product safety testing, at the same time that we provide greater assurance of the biosafety of vaccines.

Sensitivity of biochemical test in comparison with other methods for the detection of mycoplasma contamination in human and animal cell lines stored in the National Cell Bank of Iran

Mycoplasma contamination in cell culture is considered as serious problem in the manufacturing of biological products. Our goal in this research is to find the best standard and rapid method with high sensitivity, specificity, accuracy and predictive values of positive and negative results for detection of mycoplasma contamination in cell cultures of the National Cell Bank of Iran. In this study, 40 cell lines suspected to mycoplasma contamination were evaluated by three different methods: microbial culture, enzymatic mycoalert(®) and molecular. Enzymatic evaluation was performed using the mycoalert(®) kit while in the molecular technique, a universal primer pair was designed based on the common and fixed 16SrRNA ribosomal sequences used. Mycoplasma contaminations in cell cultures with molecular, enzymatic and microbial culture methods were determined as 57.5, 52.5 and 40 %, respectively. These results confirmed the higher rate of sensitivity, specificity and accuracy for the molecular method in comparison with enzymatic and microbial methods. Polymerase chain reaction (PCR) assay based on fixed and common sequences in the 16SrRNA, is a useful valuable and reliable technique with high sensitivity, specificity and accuracy for detection of mycoplasma contamination in cell cultures and other biological products. The enzymatic mycoalert(®) method can be considered as a substitution for conventional microbial culture and DNA staining fluorochrome methods due to its higher sensitivity, specificity and speed of detection (<20 min).

Preparation of reference stocks suitable for evaluation of alternative NAT-based mycoplasma detection methods

AIMS

The aim of this study was to optimize conditions for preparation and cryopreservation of mycoplasma reference materials suitable to evaluate alternative nucleic acid testing (NAT)-based assays and to compare their limits of detection (LODs) with those of conventional culture-based methods.

METHODS AND RESULTS

Acholeplasma laidlawii, Mycoplasma gallisepticum and Mycoplasma arginini stocks with low ratios of genomic copies to colony forming units (12, 8 and 4, respectively) harvested in early stationary phases of growth were preserved with different cryoprotective agents (CPAs) under slow (1°C min(-1)), moderate (8°C min(-1)), fast (13°C min(-1)) and 'snapshot' (60°C min(-1)) cooling rates. Depending on mycoplasma species, increasing the cooling rate from slow to snapshot enhanced cell survival up to 5-fold. The addition of 10% (v/v) dimethyl sulfoxide (DMSO) and 15% (v/v) glycerol significantly improved cell survival of all tested strains. Cryoprotected stocks maintained high and stable titres for at least 1 year during storage at -80°C. Sonication of cell cultures prior to cryopreservation enhanced cell dispersion and reduced of GC/CFU ratios.

CONCLUSIONS

It is feasible to prepare stable reference stocks of cryopreserved mycoplasma cells suitable to reliably compare NAT- and culture-based mycoplasma testing methods.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study describes experimental results demonstrating the preparation and storage of highly viable and dispersed mycoplasma reference stocks suitable for comparing alternative NAT-and conventional culture-based mycoplasma detection methods.

Collaborative study report: evaluation of the ATCC experimental mycoplasma reference strains panel prepared for comparison of NAT-based and conventional mycoplasma detection methods

The main goal of this collaborative study was to evaluate the experimental panel of cryopreserved mycoplasma reference strains recently prepared by the American Type Culture Collection (ATCC(®)) in order to assess the viability and dispersion of cells in the mycoplasma stocks by measuring the ratio between the number of genomic copies (GC) and the number of colony forming units (CFU) in the reference preparations. The employment of microbial reference cultures with low GC/CFU ratios is critical for unbiased and reliable comparison of mycoplasma testing methods based on different methodological approaches, i.e., Nucleic Acid Testing (NAT) and compendial culture-based techniques. The experimental panel included ten different mycoplasma species known to represent potential human and animal pathogens as well as common contaminants of mammalian and avian cell substrates used in research, development, and manufacture of biological products. Fifteen laboratories with expertise in field of mycoplasma titration and quantification of mycoplasmal genomic DNA participated in the study conducted from February to October of 2012. The results of this study demonstrated the feasibility of preparing highly viable and dispersed (possessing low GC/CFU ratios) frozen stocks of mycoplasma reference materials, required for reliable comparison of NAT-based and conventional mycoplasma detection methods.

Look back in anger - what clinical studies tell us about preclinical work

Misled by animal studies and basic research? Whenever we take a closer look at the outcome of clinical trials in a field such as, most recently, stroke or septic shock, we see how limited the value of our preclinical models was. For all indications, 95% of drugs that enter clinical trials do not make it to the market, despite all promise of the (animal) models used to develop them. Drug development has started already to decrease its reliance on animal models: In Europe, for example, despite increasing R&D expenditure, animal use by pharmaceutical companies dropped by more than 25% from 2005 to 2008. In vitro studies are likewise limited: questionable cell authenticity, over-passaging, mycoplasma infections, and lack of differentiation as well as non-homeostatic and non-physiologic culture conditions endanger the relevance of these models. The standards of statistics and reporting often are poor, further impairing reliability. Alarming studies from industry show miserable reproducibility of landmark studies. This paper discusses factors contributing to the lack of reproducibility and relevance of pre-clinical research.

THE CONCLUSION

Publish less but of better quality and do not rely on the face value of animal studies.

Mycoplasma removal: simple curative methods for viral supernatants

As a partner of the European Virus Archive (EVA) FP7 infrastructure, our research group is maintaining and developing a large virus collection. To meet the standards of the quality management system adopted by all European Virus Archive partners, the detection and eradication of mycoplasma in cell culture supernatants (stored at -80°C or freeze-dried) has to be improved. Although the methods for mycoplasma elimination from infected cell lines were largely described, the decontamination procedures of precious cell culture supernatants was poorly documented. In this study, a large panel of mycoplasma-contaminated virus stocks (enveloped and non enveloped, RNA and DNA viruses) was tested successfully for mycoplasma removal using two simple optimized methods. These easy-to-perform protocols, using respectively Plasmocin™ (InvivoGen, Cayla, France) and chloroform, were shown to remove mycoplasma completely from cell supernatant without incidence in viral infectivity.