Bacterial safety of cell-based therapeutic preparations, focusing on haematopoietic progenitor cells

Dual-Temperature Microbiological Control of Cellular Products: A Potential Impact for Bacterial Screening of Platelet Concentrates?

An experimental study by the Paul-Ehrlich Institute (PEI) demonstrated that temperatures between 35 and 37 °C are too high for the growth of some bacterial strains (e.g., Pseudomonas fluorescens), leading to false negative results. Thus, the question of whether it is necessary to adapt incubation temperatures for the microbiological control of blood products, especially platelet concentrates (PCs), to enhance safety and regulatory compliance has arisen. In order to further elucidate this issue, the growth capability of different bacterial strains of interest in PCs and the detection efficacy of cultivation of these at different incubation temperatures must be taken into account. Therefore, we inoculated PCs with 46 different strains (3-6 PCs from different donors per strain) from different origins (PC isolates, reference strains) and stored PCs at 20-22 °C under constant agitation. On day three of storage, the inoculated PCs were sampled; aerobic and anaerobic culture bottles (BacT/Alert AST/NST) were each inoculated with 5 mL of sample, and culture bottles were incubated at 25 and 35 °C using the automated BacT/Alert Dual-temperature system. Bacterial proliferation was enumerated using a colony-forming assay. All strains of Enterobacteriacae (n = 5), Staphy-lococcus spp. (n = 11), Streptococcus spp. (n = 5), and Bacillus spp. (n = 4) and most Pseudomonas aeruginosa strains (4 of 5) tested showed the capability to grow in most inoculated PCs, revealing a faster time to detection (TTD) at an incubation temperature of 35 °C. The tested Pseudomonas putida (n = 3) strains showed a noticeably reduced capability to grow in PCs. Nonetheless, those with a notable growth capability revealed a faster TTD at an incubation temperature of 35 °C. Only one of the four Pseudomonas fluorescens strains tested (strain ATCC 13525) was able to grow in PCs, showing a faster TTD at an incubation temperature of 25 °C but also detection at 35 °C. The commonly detected bacteria involved in the bacterial contamination of PCs showed a superior TTD at 35 °C incubation. Only one P. fluorescens strain showed superior growth at 25 °C; however, the microbiological control at 35 °C did not fail to identify this contamination. In conclusion, the use of PC screening using a dual-temperature setting for microbiological control is presently not justified according to the observed kinetics.

Engineered Magnetic Nanocomposites to Modulate Cellular Function

Magnetic nanoparticles (MNPs) have various applications in biomedicine, including imaging, drug delivery and release, genetic modification, cell guidance, and patterning. By combining MNPs with polymers, magnetic nanocomposites (MNCs) with diverse morphologies (core-shell particles, matrix-dispersed particles, microspheres, etc.) can be generated. These MNCs retain the ability of MNPs to be controlled remotely using external magnetic fields. While the effects of these biomaterials on the cell biology are still poorly understood, such information can help the biophysical modulation of various cellular functions, including proliferation, adhesion, and differentiation. After recalling the basic properties of MNPs and polymers, and describing their coassembly into nanocomposites, this review focuses on how polymeric MNCs can be used in several ways to affect cell behavior. A special emphasis is given to 3D cell culture models and transplantable grafts, which are used for regenerative medicine, underlining the impact of MNCs in regulating stem cell differentiation and engineering living tissues. Recent advances in the use of MNCs for tissue regeneration are critically discussed, particularly with regard to their prospective involvement in human therapy and in the construction of advanced functional materials such as magnetically operated biomedical robots.

Autologous hematopoietic stem cell product contaminated with Salmonella due to occult salmonellosis in an asymptomatic donor

Recent advancements in infectious disease testing methods and pathogen reduction technologies have greatly reduced the incidence of microbial contamination of allogeneic blood products. Despite this significant reduction, contamination of autologous cellular therapy products remains a challenging issue, as many of these mitigation strategies are not feasible for such products. Most microorganisms isolated from cellular therapy products are Gram-positive normal skin flora, and studies have demonstrated that adverse effects are infrequent when these contaminated products are infused. However, no prior report has documented an autologous hematopoietic stem cell (HSC) or other cellular therapy product contaminated with Salmonella bacteria-a pathogenic Gram-negative organism. We present the first known case of Salmonella contaminating an HSC product secondary to occult salmonellosis in the donor, and discuss the implications of this contaminating organism and the therapeutic dilemma posed by this scenario.

Use of 27G needles improves sensitivity and performance of ATCC anaerobe reference microorganism detection in BacT/Alert system

Effective detection of microbiological contaminations present in medicinal cellular products is a crucial step to ensure patients' safety. In recent decades, several rapid microbiological methods have been developed and validated, but variabilities linked to the use of different resources have led to discordant validation of methods and performance results. Considering this, while developing an in-house BacT/Alert-based method, we evaluated all of the materials used in its validation. Of particular importance, we noticed that the syringe gauge used to inject the samples into the bottles was crucial to obtain robust results. We chose to conduct a comparative test between the BacT/Alert system and the compendial method described in the European Pharmacopoeia, using five dilutions of nine reference microorganism strains and 21G or 27G needles. Our results confirmed that the BacT/Alert system is a valid and faster alternative method to assess sterility of clinical cell therapy products, and that the use of 27G needles increases its sensitivity to detect reference anaerobe microorganisms.

Guidelines for establishing a 3-D printing biofabrication laboratory

Advanced manufacturing and 3D printing are transformative technologies currently undergoing rapid adoption in healthcare, a traditionally non-manufacturing sector. Recent development in this field, largely enabled by merging different disciplines, has led to important clinical applications from anatomical models to regenerative bioscaffolding and devices. Although much research to-date has focussed on materials, designs, processes, and products, little attention has been given to the design and requirements of facilities for enabling clinically relevant biofabrication solutions. These facilities are critical to overcoming the major hurdles to clinical translation, including solving important issues such as reproducibility, quality control, regulations, and commercialization. To improve process uniformity and ensure consistent development and production, large-scale manufacturing of engineered tissues and organs will require standardized facilities, equipment, qualification processes, automation, and information systems. This review presents current and forward-thinking guidelines to help design biofabrication laboratories engaged in engineering model and tissue constructs for therapeutic and non-therapeutic applications.

The quality evaluation system establishment of mesenchymal stromal cells for cell-based therapy products

BACKGROUND

Cell-based therapy products are supposed to be the most complex medicine products in the history of human medical care. In this study, we established a safety evaluation system for therapeutic stromal cells based on the existing regulations and current testing techniques to provide general quality requirements for human umbilical cord mesenchymal stromal cell (HUCMSC) therapy product.

METHODS

In this system, we comprehensively evaluate the environmental monitoring program, quality control of critical raw materials and reagents, donor screening criteria, cell safety, quality, and biological effects, not only in line with the basic criteria of biological products, but also following the general requirements of drugs.

RESULTS

The qualified HUCMSCs were tested for various clinical researches in our hospital, and no severe adverse reaction was observed in 225 patients during a 1-year follow-up period.

CONCLUSION

In this study, we establish a systemic quality control and potent assays to guarantee the safety and effectiveness of HUCMSCs based on a minimum set of standards in MSC-based product.

Bacterial contamination rates in extracorporeal photopheresis

BACKGROUND

Extracorporeal photopheresis (ECP) is an immunosuppressive treatment that involves leukocyte apheresis, psoralen and UV light treatment, and subsequent reinfusion. Patients treated with ECP are usually immunosuppressed. Bacterial contamination therefore poses a much unwanted risk, but incidence data are lacking.

PATIENTS AND METHODS

We screened all 1922 consecutive ECP procedures scheduled within a roughly 3-year period for eligibility. Those with missing data on ECP method (inline or offline) or type of venous access (peripheral or central) were excluded. ECPs with complete aerobic and anaerobic microbial testing of baseline patient blood samples (n = 1637) and of ECP cell concentrates (n = 1814) were included in the analysis.

RESULTS

A test for microbial contamination was positive for 1.82% of the cell concentrates, with central venous access was the most significant risk factor for the contamination (odds ratio = 19). Patient blood samples were positive in 3.85% of cases, but no patients became septic. Staphylococcus spp. were most abundant, and products with bacterial contamination did not cause side effects after reinfusion. There were no significant differences in contamination rates between inline and offline ECP.

CONCLUSION

These findings stress the importance of sterile procedures and the benefits of using peripheral over central venous access for reducing the risk of bacterial contamination in ECP.

Microbial contamination risk in hematopoietic stem cell products: retrospective analysis of 1996–2016 data

Quality assurance and safety of hematopoietic stem cells (HSC) with special emphasis on bacterial and fungal contamination is the prerequisite for any transplantation procedure. The aim was to determine the incidence rate of such contamination during processing of transplantation material with regard to HSC source: peripheral blood stem cell (PBSC), bone marrow (BM), or cord blood (CB). Analysis involved autologous and allogenic products dedicated for patients and comprised in all 4135 donations, including 112 BM (2.70%), 3787 PBSC (91.60%), and 236 CB (5.70%) processed in cell bank over the period 1996–2016. Aerobic and anaerobic contamination was determined.

Analysis of the 20-year data revealed 42 contaminated products: 25 PBSC (0.66% of tested units) and 17 CB (7.20% of tested units). No microbial contamination of BM products was detected. Overall percentage of contaminated products was 1.01%, mostly with Staphylococcus epidermidis (61.36%). Bacterial contamination rate at cell bank is relatively low and processing in a closed system does not seem as crucial as might be expected. This is particularly true for BM components. Equally important are evaluation of donor’s medical status and condition of the puncture site for collection of source material. Implementation of appropriate sample collection procedures should help minimize the risk of false-positive results due to environmental contamination.

Sterility release testing of peripheral blood stem cells for transplantation: impact of culture bottles and incubation temperature

BACKGROUND

Sterility testing of peripheral blood stem cells (PBSCs) is mandatory before release. As antibiotic treatment of the PBSC donor may result in false-negative results, PBSC matrix validation must be carried out.

STUDY DESIGN AND METHODS

Three spiked PBSCs and a buffy coat (BC; control matrix) were analyzed using the blood culture device BacT/ALERT 3D with the low-temperature module. Samples were spiked with Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa, Candida albicans, Aspergillus brasiliensis, Clostridium sporogenes, and Propionibacterium acnes. Standard iAST/iNST culture bottles and iFA/iFN Plus bottles, which include resorbing polymers, were incubated for 14 days. All aerobic bottles were incubated at 22.5°C and for a direct comparison also at 35°C while all anaerobic bottles were incubated at 35°C.

RESULTS

The BacT/ALERT 3D system detected all microbes in iAST/iNST culture bottles according to their growth behavior in the BC matrix. Detection of microbes differed significantly in PBSC products using standard iAST/iNST culture bottles and iFA/iFN Plus bottles with resorbing polymers: In Graft 1 no growth was detected in spiked bottles with S. aureus (iAST), B. subtilis (iAST/iNST), C. sporogenes (iNST), and P. acnes (iNST) compared to iFA Plus and iFN Plus bottles wherein growth of spiked microbes was confirmed. Graft 2, with another antibiotic treatment, showed no growth in iAST/iNST bottles spiked with P. aeruginosa, B. subtilis, and C. sporogenes. However, using iFA/iFN Plus bottles all spiked microbes were detectable. The comparison of incubation temperature showed an expected slower growth at 22.5°C.

CONCLUSION

The use of iFA/iFN Plus culture bottles incubated at different temperatures safely detected microbes in spiked PBSCs.

Prospective Evaluation of a Practical Guideline for Managing Positive Sterility Test Results in Cell Therapy Products

Product safety assurance is crucial for the clinical use of manufactured cellular therapies. A rational approach for delivering products that fail release criteria (because of potentially false-positive sterility results) is important to avoid unwarranted wastage of highly personalized and costly therapies in critically ill patients where benefits may outweigh risk. Accurate and timely interpretation of microbial sterility assays represents a major challenge in cell therapies. We developed a systematic protocol for the assessment of positive microbial sterility test results using retrospective data from 2007 to 2016. This protocol was validated and applied prospectively between October 2016 and September 2017 to 13 products from which positive sterility results had been reported. Viable and nonviable environmental monitoring (EM) data were collected concurrently as part of a facility control assessment. Three of 13 (23%) positive sterility results were attributable to bone marrow collections that had been contaminated with skin flora during harvest; all were infused without pertinent infectious sequelae. Of the remaining 10, 1 was deemed a true positive and was discarded before infusion, whereas 9 were classified as false positives attributed to laboratory sampling and/or culturing processes. Three products deemed false positive were infused and 6 were withheld because of patient issues unrelated to microbial sterility results. No postinfusion-associated infectious complications were documented. Almost half of the positive EM findings were skin flora. Paired detection of an organism in both product and associated EM was identified in 1 case. Application of our validated protocol to positive product sterility test results allowed for systematic data compilation for regulatory evaluation and provided comprehensive information to clinical investigators to ensure timely and strategic management for product recipients.

Detection of the relatively slow-growing Propionibacterium acnes in seven matrices of blood components and advanced therapeutical medicinal products

BACKGROUND

Relatively slow-growing bacteria like Propionibacterium acnes represent a challenge for quality control investigations in sterility release testing of blood components and advanced therapeutic medicinal products (ATMPs).

METHODS

A convenient validation with 7 matrices was performed using buffy coat, stem cells, islet cells, natural killer cells, red blood cells, platelets and plasma in the microbial detection system Bact/Alert^®3D incubator. All matrix samples were spiked twofold with Propionibacterium acnes with approximately 50 colony forming units (CFUs) per bottle in iAST and iNST culture bottles for 14days using a multishot bioball. Additionally, the stem cell preparations were also incubated in iFAplus and iFNplus culture bottles, which include neutralizing polymers.

RESULTS

The Bact/Alert^®3D-System detected Propionibacterium acnes in anaerobic culture bottles in buffy coat [3.3 d (=positive signal day to detection as mean value)], red blood cells [3.2 d], platelets [3.3], plasma [3.7 d], natural killer cells [3.3 d] and islet cells [4.9 d], resp. No growth of Propionibacterium was found in autologous stem cells using iAST and iNST culture bottles. However, Propionibacterium was safely detected in the iFNplus culture bottle with polymers in the stem cell matrix. A successful validation of media was performed.

CONCLUSIONS

Our study shows that Bact/Alert^®3D-System safely detects the relatively slow-growing bacterium Propionibacterium acnes in different matrices in a practical way except stem cells. Using the iFNplus culture bottle for stem cell products positive signals were observed.

Evaluating the Safety of Somatic Periosteal Cells by Flow-Cytometric Analysis Monitoring the History of DNA Damage

In preparing cell-based products for regenerative therapy, cell quality should be strictly controlled. Methodologies for evaluating cell viability, identity, and purity are established and used routinely, whereas current methodologies for evaluating cell safety, particularly genetic integrity or tumorigenicity, are time-consuming and relatively insensitive. As part of developing a more practical screening system, the authors previously demonstrated that γ-H2AX and p53 were useful markers for evaluating the history of DNA damage. To validate these markers further and develop a more quantitative methodology, single cell-based expression of these markers and two additional candidates have now been examined using flow cytometry (FCM). FCM analysis and immunofluorescent staining demonstrated that γ-ray-irradiation suppressed proliferation, enlarged cells, and cell nuclei, and immediately upregulated γ-H2AX and p21(waf1) in large numbers of cells for up to 12 days. Gamma-H2AX foci were formed in the nuclei of many affected cells. An initial sharp increase in p53 expression declined slowly over 12 days, while Rb expression increased linearly. The present findings suggest that this high-throughput, cell-based, combinational evaluation of protein markers and cell size enables a small number of cells with a history of DNA damage to be detected quickly and routinely from within a very large cell population. Using this screening methodology will improve the ability to verify the quality of cell-based products used in regenerative therapy.

[Current concept for the microbiological safety of cell-based medicinal products]

Ensuring microbiological safety in advanced-therapy medicinal products is still a big challenge for manufacturers. There are fundamental problems, especially in cell-based medicinal products, regarding sterility of source materials, short shelf-life of final products, and the selection of suitable microbiological methods. Different from classical medicinal products, there is the need to evaluate a large number of possible risks and to calculate the risk-benefit balance. Depending on the source material, the presence of micro-organisms with specific growth requirements has to be considered. They cannot be detected by conventional testing methods, but may replicate after the application of the preparation in the recipient. Mycoplasmas are the primary representatives of these contaminants and specific testing procedures are required. Additionally, depending on the source and processing of the biological material, specific testing methods for mycobacteria and other contaminants should be included. Alternative microbiological methods (e.g. NAT, flow cytometry) should be applied in order to reduce the time to detection and to provide reliable results before application of a preparation, but should be also assessed for their possible use for the detection of conventionally undetectable micro-organisms.

Biomedical Applications of Untethered Mobile Milli/Microrobots

Untethered robots miniaturized to the length scale of millimeter and below attract growing attention for the prospect of transforming many aspects of health care and bioengineering. As the robot size goes down to the order of a single cell, previously inaccessible body sites would become available for high-resolution in situ and in vivo manipulations. This unprecedented direct access would enable an extensive range of minimally invasive medical operations. Here, we provide a comprehensive review of the current advances in biome dical untethered mobile milli/microrobots. We put a special emphasis on the potential impacts of biomedical microrobots in the near future. Finally, we discuss the existing challenges and emerging concepts associated with designing such a miniaturized robot for operation inside a biological environment for biomedical applications.

A validation protocol and evaluation algorithms to determine compatibility of cell therapy product matrices in microbiological testing

As part of product release testing, "sterility" of cellular therapy products, using formally validated methods, must be demonstrated, irrespective of whether products are released and administered while microbiological results are pending or whether these can be awaited. Components of the matrix, i.e. the carrier fluid and the therapeutic cells, could potentially inhibit bacterial growth and may thus obscure their presence, resulting in false-negative data. The European Pharmacopoeia and equivalent guidelines therefore specify that for each cell therapy product the specific matrix' compatibility with validated detection methods is formally established. There for, matrix is spiked with known numbers of representative aerobic and anaerobic agents, cultured in automated systems such as BacT/ALERT, followed by microbiological species identification from culture-positive bottles. We here propose an easy-to-follow protocol for matrix validation and demonstrate its successful execution with a panel of novel advanced therapy medicinal products and standard cell therapy products, as well as algorithms for interpretation of conflicting results between BacT/Alert and culture methods. This protocol can serve as a basis for microbiological method (matrix) validations for cellular preparations.