Hepatitis B nucleotide sequence analysis: linking an outbreak of acute hepatitis B to contamination of a cryopreservation tank

Risk assessment of hepatitis E transmission through tissue allografts

Hepatitis E virus (HEV) is a small non-enveloped single stranded RNA virus whose genotypes 3 and 4 have been associated with zoonotic transmission in industrialized countries. HEV infection is considered the main cause of acute hepatitis worldwide. In some cases, transfusion of blood components or organ transplantation have been reported as the source of infection. We have conducted a literature review on the risk of transmission through cell and tissue allografts. Although no case was found, measures to control this risk should be taken when donor profile (based upon geographical and behavioural data) recommended it. Issues to be considered in donor screening and tissue processing to assess and to reduce the risk of HEV transmission are approached.

The Impact of SARS-CoV-2 on Sperm Cryostorage, Theoretical or Real Risk?

Cryopreservation of human gametes and embryos as well as human reproductive tissues has been characterized as an essential process and aspect of assisted reproductive technology (ART). Notably, sperm cryopreservation is a fundamental aspect of cryopreservation in oncological patients or patients undergoing gonadotoxic treatment. Given that there is a risk of contamination or cross-contamination, either theoretical or real, during the procedures of cryopreservation and cryostorage, both the European Society for Human Reproduction and Embryology (ESHRE) and the American Society for Reproductive Medicine (ASRM) have provided updated guidelines for preventing or reducing the contamination risk of sexually transmitted viruses. Given the ongoing and worldwide COVID-19 pandemic, there is considerable interest in what measures should be taken to mitigate SARS-CoV-2 contamination during cryopreservation and cryostorage of semen samples. The SARS-CoV-2 virus is the virus that causes COVID-19, and whose transmission and infection is mainly aerosol-mediated. Several ART professional societies, including ESHRE and ASRM have proposed measures to mitigate the spread of the SARS-CoV-2 virus. Whether the proposed safety directives are enough to mitigate the possible SARS-CoV-2-contamination of sperm samples during cryopreservation or whether the policies should be re-evaluated will be discussed in this review. Additionally, insights regarding the possible impact of COVID-19 vaccination on the safety of sperm cryopreservation will be discussed.

Sperm cryostorage in a dry tank: An accurate alternative

This prospective study aimed to determine the effects of dry nitrogen cryostorage on human sperm characteristics in comparison with liquid nitrogen cryostorage. For this purpose, 42 men undergoing routine semen analysis (21 normozoospermia and 21 with altered semen parameters) were analyzed. After slow freezing, half of the straws of each sample were randomly stored in liquid and dry tanks, at the top and bottom levels of the latter. After 6 months storage, thawed samples were treated by density gradient centrifugation and sperm characteristics were compared. There was no difference in sperm progressive motility (15.1% ± 14.2% vs. 15.1% ± 12.7%; p = 0.76), sperm vitality (25.5% ± 17.7% vs. 26.2% ± 19%; p = 0.71), percentages of acrosome-reacted spermatozoa (38% ± 8.5% vs. 38.5% ± 7.4%; p = 0.53) and DNA fragmentation spermatozoa (27.3% ± 12.4% vs. 28.5% ± 12.9%, p = 0.47) after cryostorage in the dry or the liquid nitrogen tank. Moreover, we did not observe differences between either cryostorage system for normal and altered sperm samples. This lack of difference was also observed whatever the floor level of cryostorage in the dry tank. The temperature measurement of the dry tank showed a stable temperature at -194 °C throughout storage whatever the storage floor level, guaranteeing the stability of the low temperatures suitable for human sperm storage. Because of its greater safety, dry storage without contact with the liquid phase should be preferred and can be a useful alternative for the cryostorage of human sperm samples.

Technical Considerations in the Freezing, Low-Temperature Storage and Thawing of Stem Cells for Cellular Therapies

The commercial and clinical development of cellular therapy products will invariably require cryopreservation and frozen storage of cellular starting materials, intermediates and/or final product. Optimising cryopreservation is as important as optimisation of the cell culture process in obtaining maximum yield and a consistent end-product. Suboptimal cryopreservation can lead not only to batch-to-batch variation, lowered cellular functionality and reduced cell yield, but also to the potential selection of subpopulations with genetic or epigenetic characteristics divergent from the original cell line. Regulatory requirements also impact on cryopreservation as these will require a robust and reproducible approach to the freezing, storage and thawing of the product. This requires attention to all aspects of the application of low temperatures: from the choice of freezing container and cryoprotectant, the cooling rate employed and its mode of de-livery, the correct handling of the frozen material during storage and transportation, to the eventual thawing of the product by the end-user. Each of these influences all of the others to a greater or lesser extent and none should be ignored. This paper seeks to provide practical insights and alternative solutions to the technical challenges faced during cryopreservation of cells for use in cellular therapies.

Hepatitis B and C virus prevalence in couples attending an in vitro fertilization clinic in a tertiary care hospital in Saudi Arabia: comparison with ten years earlier

BACKGROUND

Viral hepatitis B (HBV) and C (HCV) are a major public health problem in Saudi Arabia. Recent data has indicated a major reduction in viral hepatitis prevalence in Saudi population. However, there is limited data for infertile Saudi couples.

OBJECTIVES

To determine the prevalence of HCV and HBV attending an in vitro fertilization (IVF) clinic in Saudi Arabia between 2012 and 2015 to compare with the prevalence 10 years earlier in the same center.

DESIGN

Retrospective prevalence study.

SETTING

Tertiary care center in Riyadh.

PATIENTS AND METHODS

Data on the prevalence of HBV and HCV was collected on all couples seen at the IVF unit between 2002-2005 and 2012-2015.

MAIN OUTCOME MEASURE(S)

Prevalence of HBV and HCV.

RESULTS

In 4442 patients during 2002-2005 and 5747 patients during 2012-2015, the prevalence of HBV was significantly less in 2012-2015 compared with 2002-2005 (1.67% [97 patients] vs 4.7% [210 patients], P < .0001), respectively, but HCV prevalence was similar for the two periods (0.7% for both periods) (P=.887). The hepatitis B seroprevalence rate was higher in males compared to females during 2002-2005 (6.3% vs 3.1%) (P < .0001) and 2012-2015 (2.4% vs 1.1% ) (P < .0001), respectively.

CONCLUSION

The significant drop in HBV prevalence was most likely due to the introduction of the vaccination program in 1989, while reasons for HCV prevalence remaining unchanged are unclear.

LIMITATION

No data on confounding factors that may have affected the prevalence.

Cryopreservation: Vitrification and Controlled Rate Cooling

Cryopreservation is the application of low temperatures to preserve the structural and functional integrity of cells and tissues. Conventional cooling protocols allow ice to form and solute concentrations to rise during the cryopreservation process. The damage caused by the rise in solute concentration can be mitigated by the use of compounds known as cryoprotectants. Such compounds protect cells from the consequences of slow cooling injury, allowing them to be cooled at cooling rates which avoid the lethal effects of intracellular ice. An alternative to conventional cooling is vitrification. Vitrification methods incorporate cryoprotectants at sufficiently high concentrations to prevent ice crystallization so that the system forms an amorphous glass thus avoiding the damaging effects caused by conventional slow cooling. However, vitrification too can impose damaging consequences on cells as the cryoprotectant concentrations required to vitrify cells at lower cooling rates are potentially, and often, harmful. While these concentrations can be lowered to nontoxic levels, if the cells are ultra-rapidly cooled, the resulting metastable system can lead to damage through devitrification and growth of ice during subsequent storage and rewarming if not appropriately handled.The commercial and clinical application of stem cells requires robust and reproducible cryopreservation protocols and appropriate long-term, low-temperature storage conditions to provide reliable master and working cell banks. Though current Good Manufacturing Practice (cGMP) compliant methods for the derivation and banking of clinical grade pluripotent stem cells exist and stem cell lines suitable for clinical applications are available, current cryopreservation protocols, whether for vitrification or conventional slow freezing, remain suboptimal. Apart from the resultant loss of valuable product that suboptimal cryopreservation engenders, there is a danger that such processes will impose a selective pressure on the cells selecting out a nonrepresentative, freeze-resistant subpopulation. Optimizing this process requires knowledge of the fundamental processes that occur during the freezing of cellular systems, the mechanisms of damage and methods for avoiding them. This chapter draws together the knowledge of cryopreservation gained in other systems with the current state-of-the-art for embryonic and induced pluripotent stem cell preservation in an attempt to provide the background for future attempts to optimize cryopreservation protocols.

Potential for Stem Cell-Based Periodontal Therapy

Periodontal diseases are highly prevalent and are linked to several systemic diseases. The goal of periodontal treatment is to halt the progression of the disease and regenerate the damaged tissue. However, achieving complete and functional periodontal regeneration is challenging because the periodontium is a complex apparatus composed of different tissues, including bone, cementum, and periodontal ligament. Stem cells may represent an effective therapeutic tool for periodontal regeneration due to their plasticity and their ability to regenerate different tissues. This review presents and critically analyzes the available information on stem cell-based therapy for the regeneration of periodontal tissues and suggests new avenues for the development of more effective therapeutic protocols.

Cryoprotectant-free vitrification of fish (Oncorhynchus mykiss) spermatozoa: first report

The aims of this investigation were to test a novel technology comprising cryoprotectant-free vitrification of the spermatozoa of rainbow trout and to study the ability of sucrose and components of seminal plasma to protect these cells from cryo-injuries. Spermatozoa were isolated and vitrified using three different media: Group 1: standard buffer for fish spermatozoa, Cortland(®) medium (CM, control); Group 2: CM + 1% BSA + 40% seminal plasma; and Group 3: CM + 1% BSA + 40% seminal plasma + 0.125 m sucrose. For cooling, 20-μl suspensions of cells from each group were dropped directly into liquid nitrogen. For warming, the spheres containing the cells were quickly submerged in CM + 1% BSA at 37 °C with gentle agitation. The quality of spermatozoa before and after vitrification was analysed by the evaluation of motility and cytoplasmic membrane integrity with SYBR-14/propidium iodide staining technique. Motility (86%, 81% and 82% for groups 1, 2 and 3, respectively) (P > 0.1) was not decreased significantly. At the same time, cytoplasmic membrane integrity of spermatozoa of Groups 1, 2 and 3 was changed significantly (30%, 87% and 76% respectively) (P < 0.05). All tested solutions can be used for vitrification of fish spermatozoa with good post-warming motility. However, cytoplasmic membrane integrity was maximal in Group 2 (CM + 1% BSA + 40% seminal plasma). In conclusion, this is the first report about successful cryoprotectant-free cryopreservation of fish spermatozoa by direct plunging into liquid nitrogen (vitrification). Vitrification of fish spermatozoa without permeable cryoprotectants is a prospective direction for investigations: these cells can be successfully vitrified with 1% BSA + 40% seminal plasma.

Benefit and risk of application of European tissue management regulation in ART

The application of the European Tissues and Cells Directive requires that a high standard of quality and safety be applied to all tissue establishments, including that of assisted reproductive centres. In the countries where the Directive has been implemented, changes in the ART clinic and laboratory procedures have been made. However, many requirements stipulated in the Directive are already in place in some European countries and are mandatory by the country specific laws, while some other requirements have been recently implemented. In this article the benefits and the potential risks of the Directive implementation on the efficacy, safety and cost of all the different assisted reproductive technologies performed, including cryopreservation techniques and storage policies have been widely analysed. The feasibility of the implementation of some of the specific requirements when considering the delicate issues of reproductive cells in contrast to other cells or tissues covered by the Directive has been evaluated.

An outbreak of hepatitis B with high mortality in India: association with precore, basal core promoter mutants and improperly sterilized syringes

In 2009, an outbreak of hepatitis B with high mortality was observed in Sabarkantha district, Gujarat state, India with 456 cases and 89 deaths. Hospitalized patients with self-limiting disease (152, AVH)) and fulminant hepatic failure (39, FHF including 27 fatal and 12 survivals) were investigated. These were screened for diagnostic markers for hepatitis viruses, hepatitis B virus (HBV) genotyping and mutant analysis. Complete HBV genomes from 22 FHF and 17 AVH cases were sequenced. Serosurveys were carried out in the most and least affected blocks for the prevalence of HBV and identification of mutants. History of injection from a physician was associated with FHF and AVH cases. Co-infection with other hepatitis viruses or higher HBV DNA load was not responsible for mortality. Four blocks contributed to 85.7% (391/456) of the cases and 95.5% (85/89) mortality while two adjacent blocks had negligible mortality. Sequence analysis showed the presence of pre-core and basal core promoter mutants and 4 amino acid substitutions exclusively among FHF cases. None of the self-limiting patients exhibited these dual mutations. Genotype D was predominant, D1 being present in all FHF cases while D2 was most prevalent in AVH cases. Probably due to violation of accepted infection control procedures by the qualified medical practitioners, HBV prevalence was higher in the affected blocks before the outbreak. Gross and continued use of HBV contaminated (mutant and wild viruses) injection devices led to an explosive outbreak with high mortality with a striking association with pre-C/BCP mutants and D1 genotype.

Packaging Considerations for Biopreservation

SUMMARY: The packaging system chosen for biopreservation is critical for many reasons. An ideal biopreservation container system must provide for closure integrity, sample stability and ready access to the preserved material. This means the system needs to be hermetically sealed to ensure integrity of the specimen is maintained throughout processing, storage and distribution; the system must remain stable over long periods of time as many biobanked samples may be stored indefinitely; and functionally closed access systems must be used to avoid contamination upon sample withdraw. This study reviews the suitability of a new commercially available vial configuration container utilizing blood bag style closure and access systems that can be hermetically sealed and remain stable through cryopreservation and biobanking procedures. This vial based systems allow for current good manufacturing/tissue practice (cGTP) requirements during processing of samples and may provide the benefit of ease of delivery by a care giver. In this study, the CellSeal® closed system cryovial was evaluated and compared to standard screw cap vials. The CellSeal system was evaluated for durability, closure integrity through transportation and maintenance of functional viability of a cryopreserved mesenchymal stem cell model. The results of this initial proof-of-concept study indicated that the CellSeal vials are highly suitable for biopreservation and biobanking, and provide a suitable container system for clinical and commercial cell therapy products frozen in small volumes.

Cryopreservation of Human Stem Cells for Clinical Application: A Review

SUMMARY: Stem cells have been used in a clinical setting for many years. Haematopoietic stem cells have been used for the treatment of both haematological and non-haematological disease; while more recently mesenchymal stem cells derived from bone marrow have been the subject of both laboratory and early clinical studies. Whilst these cells show both multipotency and expansion potential, they nonetheless do not form stable cell lines in culture which is likely to limit the breadth of their application in the field of regenerative medicine. Human embryonic stem cells are pluripotent cells, capable of forming stable cell lines which retain the capacity to differentiate into cells from all three germ layers. This makes them of special significance in both regenerative medicine and toxicology. Induced pluripotent stem (iPS) cells may also provide a similar breadth of utility without some of the confounding ethical issues surrounding embryonic stem cells. An essential pre-requisite to the commercial and clinical application of stem cells are suitable cryopreservation protocols for long-term storage. Whilst effective methods for cryopreservation and storage have been developed for haematopoietic and mesenchymal stem cells, embryonic cells and iPS cells have proved more refractory. This paper reviews the current state of cryopreservation as it pertains to stem cells and in particular the embryonic and iPS cell.

Fish (Oncorhynchus mykiss) spermatozoa cryoprotectant-free vitrification: stability of mitochondrion as criterion of effectiveness

The aim of the present investigations was to test a novel technology comprising cryoprotectant-free vitrification of the spermatozoa of rainbow trout and to study the ability of sucrose and components of seminal plasma to protect these cells from cryoinjuries. Spermatozoa were isolated and vitrified using five different mediums: Group 1: standard buffer for fish spermatozoa, Cortland(®)-medium (CM, control); Group 2: CM+1% bovine serum albumin (BSA); Group 3: CM+1% BSA+0.125 M sucrose; Group 4: CM+1% BSA+40% seminal plasma; and Group 5: CM+1% BSA+40% seminal plasma+0.125 M sucrose. For cooling, 20 μL suspensions of cells from each group were dropped directly into liquid nitrogen. For warming, the spheres containing the cells were quickly submerged in CM+1% BSA at 37 °C with gentle agitation. The quality of spermatozoa before and after vitrification was analysed by the evaluation of motility, cytoplasmic membrane integrity (SYBR-14/propidium iodide staining technique), and mitochondrial membrane integrity (JC-1 staining). Motility (86%, 71%, 80%, 81%, and 82%, for Groups 1, 2, 3, 4, and 5, respectively) and cytoplasmic membrane integrity (90%, 82%, 83%, 84%, and 87%, respectively) of spermatozoa in all the 5 groups were not decreased significantly. All tested solutions can be used for vitrification of fish spermatozoa with good post-warming motility and cytoplasmic membrane integrity. However, mitochondrial membrane potentials of the spermatozoa in Groups 1, 2, 3, 4, and 5 were changed significantly (6%, 50%, 37%, 55%, and 34%, respectively) (P(1,2,3,4,5)<0.001; P(2,3,4,5) <0.01)(P(3-5)>0.1). This rate was maximal in Group 4 (CM+1% BSA+40% seminal plasma). In conclusion, this is the first report about successful cryoprotectant-free cryopreservation of fish spermatozoa by direct plunging into liquid nitrogen (vitrification). Vitrification of fish spermatozoa without permeable cryoprotectants is a prospective direction for investigations: these cells can be successfully vitrified with 1% BSA+40% seminal plasma without significant loss of important physiological parameters.

Cell culture contamination

Microbial contamination is a major issue in cell culture, but there are a range of procedures which can be adopted to prevent or eliminate contamination. Contamination may arise from the operator and the laboratory environment, from other cells used in the laboratory, and from reagents. Some infections may present a risk to laboratory workers: containment and aseptic technique are the key defence against such risks. Remedial management of suspected infection may simply mean discarding a single potentially infected culture. However, if a more widespread problem is identified, then all contaminated cultures and associated unused media that have been opened during this period should be discarded, equipment should be inspected and cleaned, cell culture operations reviewed, and isolation from other laboratories instituted until the problem is solved. Attention to training of staff, laboratory layout, appropriate use of quarantine for new cultures or cell lines, cleaning and maintenance, and quality control are important factors in preventing contamination in cell culture laboratories.

Epidemic history and evolutionary dynamics of hepatitis B virus infection in two remote communities in rural Nigeria

Background

In Nigeria, hepatitis B virus (HBV) infection has reached hyperendemic levels and its nature and origin have been described as a puzzle. In this study, we investigated the molecular epidemiology and epidemic history of HBV infection in two semi-isolated rural communities in North/Central Nigeria. It was expected that only a few, if any, HBV strains could have been introduced and effectively transmitted among these residents, reflecting limited contacts of these communities with the general population in the country.

Methods and Findings

Despite remoteness and isolation, ∼11% of the entire population in these communities was HBV-DNA seropositive. Analyses of the S-gene sequences obtained from 55 HBV-seropositive individuals showed the circulation of 37 distinct HBV variants. These HBV isolates belong predominantly to genotype E (HBV/E) (n = 53, 96.4%), with only 2 classified as sub-genotype A3 (HBV/A3). Phylogenetic analysis showed extensive intermixing between HBV/E variants identified in these communities and different countries in Africa. Quasispecies analysis of 22 HBV/E strains using end-point limiting-dilution real-time PCR, sequencing and median joining networks showed extensive intra-host heterogeneity and inter-host variant sharing. To investigate events that resulted in such remarkable HBV/E diversity, HBV full-size genome sequences were obtained from 47 HBV/E infected persons and P gene was subjected to Bayesian coalescent analysis. The time to the most recent common ancestor (tMRCA) for these HBV/E variants was estimated to be year 1952 (95% highest posterior density (95% HPD): 1927–1970). Using additional HBV/E sequences from other African countries, the tMRCA was estimated to be year 1948 (95% HPD: 1924–1966), indicating that HBV/E in these remote communities has a similar time of origin with multiple HBV/E variants broadly circulating in West/Central Africa. Phylogenetic analysis and statistical neutrality tests suggested rapid HBV/E population expansion. Additionally, skyline plot analysis showed an increase in the size of the HBV/E-infected population over the last ∼30–40 years.

Conclusions

Our data suggest a massive introduction and relatively recent HBV/E expansion in the human population in Africa. Collectively, these data show a significant shift in the HBV/E epidemic dynamics in Africa over the last century.

Epidemic history and evolutionary dynamics of hepatitis B virus infection in two remote communities in rural Nigeria

BACKGROUND

In Nigeria, hepatitis B virus (HBV) infection has reached hyperendemic levels and its nature and origin have been described as a puzzle. In this study, we investigated the molecular epidemiology and epidemic history of HBV infection in two semi-isolated rural communities in North/Central Nigeria. It was expected that only a few, if any, HBV strains could have been introduced and effectively transmitted among these residents, reflecting limited contacts of these communities with the general population in the country.

METHODS AND FINDINGS

Despite remoteness and isolation, approximately 11% of the entire population in these communities was HBV-DNA seropositive. Analyses of the S-gene sequences obtained from 55 HBV-seropositive individuals showed the circulation of 37 distinct HBV variants. These HBV isolates belong predominantly to genotype E (HBV/E) (n=53, 96.4%), with only 2 classified as sub-genotype A3 (HBV/A3). Phylogenetic analysis showed extensive intermixing between HBV/E variants identified in these communities and different countries in Africa. Quasispecies analysis of 22 HBV/E strains using end-point limiting-dilution real-time PCR, sequencing and median joining networks showed extensive intra-host heterogeneity and inter-host variant sharing. To investigate events that resulted in such remarkable HBV/E diversity, HBV full-size genome sequences were obtained from 47 HBV/E infected persons and P gene was subjected to Bayesian coalescent analysis. The time to the most recent common ancestor (tMRCA) for these HBV/E variants was estimated to be year 1952 (95% highest posterior density (95% HPD): 1927-1970). Using additional HBV/E sequences from other African countries, the tMRCA was estimated to be year 1948 (95% HPD: 1924-1966), indicating that HBV/E in these remote communities has a similar time of origin with multiple HBV/E variants broadly circulating in West/Central Africa. Phylogenetic analysis and statistical neutrality tests suggested rapid HBV/E population expansion. Additionally, skyline plot analysis showed an increase in the size of the HBV/E-infected population over the last approximately 30-40 years.

CONCLUSIONS

Our data suggest a massive introduction and relatively recent HBV/E expansion in the human population in Africa. Collectively, these data show a significant shift in the HBV/E epidemic dynamics in Africa over the last century.

Human ovarian tissue vitrification versus conventional freezing: morphological, endocrinological, and molecular biological evaluation

Cryopreservation as a process can be divided into two methods: conventional freezing and vitrification. The high effectiveness of vitrification in comparison with conventional freezing for human oocytes and embryos is shown, whereas data on human ovarian tissue are limited. The aim of this study was to compare the safety and effectiveness of conventional freezing and vitrification of human ovarian tissue. Ovarian tissue fragments from 15 patients were transported to the laboratory within 22–25 h in a special, isolated transport box that can maintain a stable temperature of between 5 and 8 °C for 36 h. Small pieces of ovarian tissue (0.3–1×1–1.5×0.7–1 mm) were randomly distributed into three groups: group 1, fresh pieces immediately after receiving transport box (control); group 2, pieces after vitrification; and group 3, pieces after conventional freezing. After thawing, all the pieces were culturedin vitro. The viability and proliferative capacity of the tissue byin vitroproduction of hormones, development of follicles, and glyceraldehyde 3-phosphate dehydrogenase (GAPDH) gene expression after culture were evaluated. A difference between freezing and vitrification was not found in respect to hormonal activity and follicle quality. The supernatants showed 17-β estradiol concentrations of 365, 285, and 300 pg/ml respectively, and progesterone concentrations of 3.82, 1.99, and 1.95 ng/ml respectively. It was detected that 95, 80, and 83% follicles respectively were morphologically normal. The molecular biological analysis, however, demonstrated that theGAPDHgene expression in ovarian tissue after vitrification was dramatically decreased in contrast to conventional freezing. For cryopreservation of human ovarian tissue, conventional freezing is more promising than vitrification, because of higher developmental potential.

Contaminated liquid nitrogen vapour as a risk factor in pathogen transfer

Liquid nitrogen in storage containers will gather particulate matter from the atmosphere, or the surfaces of containers placed into it, with time. Some of these accumulating particles may be pathogenic organisms and it can be demonstrated that their viability may be conserved by immersion in the liquid nitrogen. This contamination constitutes a risk to the status of stored samples that can, largely, be avoided by the use of appropriate techniques for sealing sample containers and sterilizing their outer surfaces. The present study uses fungal spores and organic crystals to demonstrate that such particles contained in liquid nitrogen are released back into the environment when nitrogen vapour cools programmable freezers or dry shippers. This demonstrates that storage in the vapour phase above liquid nitrogen still carries a real risk of sample, or facility, contamination. Regardless of the safety of the stored sample, this is a potential source of cross-contamination between repositories or experimental sites, both locally and internationally, that could have serious consequences in clinical and agricultural situations. This study provides evidence to suggest that this possibility, as yet unquantified, should be included in risk analysis of storage protocols for reproductive materials. The risk becomes diverse when, for example, semen and embryos are frozen at an agricultural site and the dry shipper can co-transport spores of contaminating crop plant pathogens to the destination site.

Inhibition of the replication of hepatitis B virus in vitro by a novel 2,6-diaminopurine analog, beta-LPA

Antiviral therapy of chronic hepatitis B remains a major clinical problem worldwide. Like lamivudine, nucleoside analogs have become the focus of investigation of anti-hepatitis B virus (anti-HBV) drugs. Here, beta-LPA is a novel 2,6-diaminopurine analog found to possess potent anti-HBV activity. In HepG2.2.15 cell line, beta-LPA had a 50% effective concentration (EC(50)) of 0.01 microM against HBV, as determined by analysis of secreted and intracellular episomal HBV DNA. Levels of HBV surface antigen (HBsAg) and e antigen (HBeAg) in drug-treated cultures revealed that beta-LPA had no significant inhibitory effects on HBsAg and HBeAg. beta-LPA didn't show any cytotoxicity up to 0.4 microM with a 50% cytotoxic concentration (CC(50)) of 50 microM. Furthermore, treatment with beta-LPA resulted in no apparent inhibitory effects on mitochondrial DNA content. Considering the potent inhibition of HBV DNA synthesis and no obvious toxicity of beta-LPA, this compound should be further explored for development as an anti-HBV drug.

Transmission of hepatitis B virus (genotype E) in a haemodialysis unit

BACKGROUND

The Rosenheim report, published in 1972, was aimed at decreasing the transmission of hepatitis B virus (HBV) in the renal unit. A review in 1996, revealed the non-compliance of some centres with the guidance to vaccinate individuals against HBV.

OBJECTIVES

To describe two events of acute hepatitis B virus (HBV) infection within 9 weeks in individuals attending the renal unit and the steps taken to prevent further transmission.

STUDY DESIGN

Serological and molecular testing was carried out on the two individuals with acute HBV and other HBV carriers in the unit. Epidemiological information was collected along with information on HBV vaccination and HBsAg screening.

RESULTS

There were 15 known HBV carriers in the unit. HBV genotype E was transmitted from a carrier to patient 1 when they were in the same ward. Transmission to patient 2 occurred when he followed patient 1 on the theatre list. Breaks in infection control were identified and steps were taken to prevent further transmission events.

CONCLUSIONS

Breaks in infection control procedures were rectified. No further transmission of HBV was identified. This highlights the need for vigilance regarding infection control practices in the renal unit setting.

Cryopreservation of hematopoietic stem cells

Stem cell transplantation represents a critical approach for the treatment of many malignant and non-malignant diseases. The foundation for these approaches is the ability to cryopreserve marrow cells for future use. This technique is routinely employed in all autologous settings and is critical for cord blood transplantation. A variety of cryopreservatives have been used with multiple freezing and thawing techniques as outlined in the later chapters. Freezing efficiency has been proven repeatedly and the ability of long-term stored marrow to repopulate has been established. Standard approaches outlined here are used in many labs as the field continues to evolve.

High survival and hatching rates following vitrification of embryos at blastocyst stage: a bovine model study

Cryopreservation of embryos at the blastocyst stage may provide an effective method to increase the cumulative pregnancy rate for each treatment cycle of ovarian-stimulated IVF. The objective of this study was to evaluate the survival rate and hatching rate of bovine blastocysts following vitrification using a method designed for oocytes, with a view to introducing this methodology into human assisted reproduction technology and reproductive medicine. Bovine blastocysts were produced from abattoir materials subjected to in-vitro maturation and in-vitro fertilization. Survival rate of the bovine blastocysts was 100% (94/94) following vitrification using a method designed for oocyte cryopreservation. There was no difference in the hatching rate of the bovine blastocysts between control (62.5%: 60/96) and vitrified (61.7%: 58/94) groups. The number of dead cells in the blastocysts was not significantly different between control (5.0 +/- 2.9) and vitrified (9.5 +/- 4.0) groups. In conclusion, the results of this study indicate that bovine blastocysts can be vitrified successfully using a procedure designed for oocyte cryopreservation. It is possible that this method may also be successful for the cryopreservation of human embryos. A further study into this is currently being organized.

Bacterial infection transmitted by human tissue allograft transplantation

Bacterial contamination of tissue allografts obtained from cadaveric donors has been a serious cause of morbidity and mortality in recipients. Recent cases of fatal and nonfatal bacterial infections in recipients of contaminated articular cartilage (distal femur) and tendon allografts have called attention to the importance of avoiding tissue donors suspected of carrying infectious disease, of not processing donated tissue carrying virulent bacteria, the occurrence of falsely negative final sterility tests, and the need to sterilize tissues. These cases demonstrated that contamination can arise from an infected donor, during tissue removal from cadaveric donors, from the processing environment, and from contaminated supplies and reagents used during processing. Final sterility testing can be unreliable, especially when antibiotics remain on tissues. There is an increasing need for control of microbial contamination in tissue banks, and sterilization of tissue allografts should be recommended whenever possible.

Prevention of infection transmission during stem cell transplantation

Group of 152 patients (investigated before autologous transplantation) and 35 healthy donors for allogeneic transplantation was examined for the risk of infection transmission that can be associated with the infusion of cryopreserved peripheral blood progenitor cells to the patient and/or cross-contamination of stored grafts. No laboratory signs of active infection were found in 22 donors (63 %) and in 91 patients (60%). The most common was active infection by herpes viruses--50 cases in patients, 21 cases in donors; hepatitis B was found in only two cases. The rate of clinically unsuspected (but dangerous) infections in donors and patients thus remains relatively high in spite of the fact that the system of donor search and the whole transplantation procedure have improved in the last years. The system of safety assurance is extremely important and the whole palette of preventive tests according to EBMT (European Blood and Marrow Transplantation Group) and ISHAGE (International Society for Hemotherapy and Graft Engineering) is fully justified.

Hepatitis and reproduction

This bulletin will review the various viral etiologies of hepatitis, their mode of transmission, and implications for infertile couples, pregnant women, and health care workers.

Cryovial with partial membrane sealing can prevent liquid nitrogen penetration in submerged storage

Cryopreservation is one of the fundamental techniques in life science. To preserve the viability of cells and tissues, many researchers use plastic cryogenic vials and immerse them into liquid nitrogen for long-term storage. However, the non-sterile liquid nitrogen usually infiltrates into the vials and may cause a high rate of microbial contamination, and even some explosive incidents upon retrieval. To prevent these drawbacks while retaining the benefit of constant ultra-low temperature in submerged liquid nitrogen, we used a heat-sealable membrane to cover the upper portion of vials. After heat-sealing, the vials were completely free of liquid nitrogen penetration in the submerging test. Moreover, the sealing process did not affect the cell viability. This modified protocol provides an easy and efficient tool to ensure the integrity of biospecimens in long-term storage without interfering with existing cryobox storage systems.

Aseptic vitrification of human germinal vesicle oocytes using dimethyl sulfoxide as a cryoprotectant

OBJECTIVE

To evaluate the viability of vitrified human germinal vesicle (GV)-oocytes to mature to metaphase II (MII) stage after "rapid" cooling directly in liquid nitrogen in comparison with "slow" cooling in a closed 0.5-mL straw (aseptic system), with or without dimethyl sulfoxide (DMSO) in vitrification solution. The possibility of avoiding parthenogenesis of the oocytes after vitrification using DMSO was investigated.

DESIGN

In vitro maturation after vitrification.

SETTING

Assisted reproduction centers.

PATIENT(S)

Patients undergoing standard superovulation treatment and having GV-oocytes after follicular puncture.

INTERVENTION(S)

The GV-oocytes were vitrified with long/short exposure to DMSO using slow or rapid cooling, then warmed and matured in vitro.

MAIN OUTCOME MEASURE(S)

Maturation after warming.

RESULT(S)

Oocyte development up to MII stage after vitrification with DMSO was 71% in the group with "rapid" cooling, and in groups with "slow" cooling, 68% and 72% for long and short exposure to DMSO, respectively. The maturation rate of GV-oocytes after slow cooling without DMSO was 51%. In the vitrification with long-term contact of oocytes with DMSO group, a high rate of parthenogenesis was observed. When vitrification with short-term contact of oocytes with DMSO at room temperature was used, no parthenogenesis was observed.

CONCLUSION(S)

Cryopreservation of human GV-oocytes in open-pulled straws OPS) using an aseptic slow cooling method gives high maturation rates but only in combination with DMSO. To avoid spontaneous parthenogenesis, the exposure to DMSO must occur for a reduced time and at room temperature.

Vitrification of mouse pronuclear oocytes with no direct liquid nitrogen contact

The ability to routinely cryopreserve human oocytes and embryos represents a significant advancement in the field of assisted reproductive technology. Although the method of slow freezing is commonly employed, research on the alternative technique of vitrification is promising. Vitrification involves incubation of the cell in a cryoprotectant rich solution, which permits a glass-like state to occur almost instantaneously in liquid nitrogen. A number of different techniques have been invented for holding oocytes and embryos in the cryoprotectant solution during rapid vitrification and subsequent storage. Most of these involve direct contact with liquid nitrogen. Recently, concerns have been raised regarding the sterility of such a method and the potential of viral contamination from the liquid nitrogen. The present study shows that the previously reported Cryoloop method can be used to vitrify and store embryos without direct liquid nitrogen contact (during vitrification and storage). When such vitrified embryos are warmed, they are capable of subsequent development comparable with non-vitrified embryos.

Vitrification of mouse pronuclear embryos after polar body biopsy without direct contact with liquid nitrogen

OBJECTIVE

To evaluate the viability of vitrified mouse pronuclear embryos after polar body biopsy by cooling directly in liquid nitrogen in comparison with cooling in closed 0.5 mL straw (aseptic system).

DESIGN

In vitro culture after vitrification.

SETTING

Department of Gynecological Endocrinology and Reproductive Medicine, University of Bonn, Germany.

PATIENT(S)

Superovulated mice.

INTERVENTION(S)

Biopsied embryos were vitrified, warmed, and cultured in vitro.

MAIN OUTCOME MEASURE(S)

Development after warming.

RESULT(S)

Development rates up to expanded blastocyst stage after in vitro culture were 25% in group with "direct" vitrification and 23% in group with "straw in straw" vitrification.

CONCLUSION(S)

Cryopreservation of biopsied mouse pronuclear embryos in open-pulled straws, which are placed inside a hermetically closed container, guarantees a complete isolation of embryos from liquid nitrogen and avoids potential contamination by pathogenic microorganisms. The combination of plunging this container into liquid nitrogen and rapid warming makes this process as efficient as conventional vitrification.

Archiving mouse strains by cryopreservation

A great deal of time and energy goes into the creation of each new line of transgenic mice; established lines are expensive and labor-intensive to maintain. Archiving of mice by cryopreservation of germ cells or embryos represents a means to free up facility space, while protecting the line from loss due to environmental disasters, genetic drift, or infectious disease. The author reviews the available cryopreservation techniques and presents considerations for setting up a cryopreservation facility.

Aseptic technology of vitrification of human pronuclear oocytes using open-pulled straws

BACKGROUND

The aim of this study was to compare the viability of human pronuclear oocytes subjected to vitrification using cooling by direct submerging of open-pulled straws in liquid nitrogen versus vitrification by cooling of open-pulled straws located inside a closed 0.5 ml straw (aseptic system).

METHODS

Two- and three-pronuclei stage oocytes (n=114) were cryopreserved in super-open-pulled straws by vitrification in 20% ethylene glycol +20% dimethylsulphoxide (DMSO) + osmotic active and neutral non-permeable cryoprotectants with a four-step exposure in 20, 33, 50 and 100% vitrification solution for 2, 1 and 1 min, and 30-50 s, respectively at room temperature, and plunging into liquid nitrogen. Oocytes of group 1 (n=42) were rapidly cooled at a speed of 20,000 degrees C/min by direct plunging of open-pulled straws into liquid nitrogen. Oocytes of group 2 (n=44) were first located in 0.5 ml straws, which were closed at both sides by metal balls, and then plunged into liquid nitrogen. This method resulted in a cooling speed of 200 degrees C/min. For both groups, oocytes were thawed rapidly at a speed of 20 000 degrees C/min using an identical protocol. Oocytes subsequently were expelled into a graded series of sucrose solutions (1.0, 0.75, 0.5, 0.25 and 0.12 mol/l) at 2.5 min intervals.

RESULTS

Oocyte development up to expanded blastocyst stage after in vitro culture was 15% in group 1, 14% in group 2 and 29% in an untreated control group.

CONCLUSION

The deposition of human pronuclear oocytes in open-pulled straws which are placed inside a hermetically closed container guarantees a complete isolation of oocytes from liquid nitrogen and avoids potential contamination by pathogenic microorganisms. The combination of direct plunging of this container into liquid nitrogen and rapid warming makes this process as efficient as conventional vitrification.

Effects of Type IV Collagen and Laminin on the Cryopreservation of Human Embryonic Stem Cells

Previous reports have indicated that extracellular matrices (ECMs) affect the developmental fate of human embryonic stem cells (hESCs). Specially, type IV collagen and laminin, which belong to a group of macromolecular proteins with a substantial proportion of ECMs, are known to influence the proliferation and differentiation of hES cells. In this study, we evaluated the effects of type IV collagen and laminin in freezing medium on the survival and differentiation rates of hES cells after slow freezing and rapid thawing. The addition of type IV collagen (1 microg/ml) to the freezing medium significantly increased the survival rate of hES cells after thawing compared with that of a control group. The spontaneous differentiation rates of groups treated with type IV collagen (1 microg/ml) or laminin (1 microg/ml) were significantly lower than those of the control group. Frozen-thawed hES cells have currently been cultured for more than 70 passages and retain key properties of hES cells such as morphological characteristics, normal karyotype, marker expression (alkaline phosphatase, SSEA-1, SSEA-3, SSEA-4, TRA-1-60, TRA-1-81, Rex-1, and Oct-4), basement membrane-related gene expression, and the potential to differentiate into derivatives of all three germ layers. This new slow freezing method by ECM treatment is a reliable and effective cryopreservation method for pluripotent hES cells.

Current and future concepts and practices in human sperm cryobanking

This article focuses on a range of issues that are of current concern to those working in human sperm cryobanking and considers them within a general framework of risk analysis and management, taking into account the available evidence and perceptions of 'best practice' from both the medical and legal perspectives. In particular, issues arising from concerns over the risk of cross-contamination between samples during storage immersed in liquid nitrogen have been analysed in detail. Even though such an occurrence has never been reported for spermatozoa or embryos, and the risk is generally accepted to be vanishingly small, it does represent a finite risk and all reasonable measures should be taken to reduce the chance of its occurring. It is concluded that all methods used to collect, cryopreserve, store, thaw and use cryobanked human spermatozoa must address the risk of contamination from any source throughout the entire process. To assist workers in this area, a series of recommendations as to current best practice are made, based upon conclusions from risk analyses using currently available information.

Potential risk of infection transmission during storage and transplantation of hematological progenitor cells. Safety assurance

In a group of 71 patients and 22 donors the danger of infection transmission by infusion of cryopreserved peripheral blood progenitor cells to the patient and/or cross contamination of stored grafts was evaluated. No laboratory signs of active infection were found in 15 donors (13 related, 2 unrelated; 68%) and in 55 patients (77%). Active infection by herpesviruses was the most common (in 13 patients and 7 donors), hepatitis B being found in only one case. The cytomegalovirus IgG test was the most common marker of previous infection; it was found in 14 donors and 55 patients. The rate of clinically unsuspected infections in donors and patients including cases requiring immediate treatment among the patients group is relatively high and fully justifies the practice of prophylactic serological testing in the whole range of tests according to the European Blood and Marrow Transplantation Group and International Society for Hematotherapy and Graft Engineering in both autologous and allogeneic transplantations of hematopoietic stem cells.

Inhibition of hepatitis B virus by a novel L-nucleoside, β-L-D4A and related analogues

AIM: To explore the inhibition of β-L-D4A on hepatitis B virus (HBV) in 2.2.15 cells derived from HepG2 cells transfected with HBV genome.

METHODS: 2.2.15 cells were plated at a density of 5 × 10⁴ per well in 12-well tissue culture plates, and treated with various concentrations of β-L-D4A for 6 days. In the end, 5 μl of medium was used for the estimation of HBsAg and HBeAg, the other medium was processed to obtain virions by a polyethlene glycol precipitation method. At the same time, intracellular DNA was also extracted and digested with HindIII. Both DNAs were subjected to Southern blot, hybridized with a ³²P-labeled HBV probe and autoradiographed. Intensity of the autoradiographic bands was quantitated by densitometric scans of computer and ED₅₀ was calculated. Then Hybond-N membrane was washed and rehybridized with a ³²P-labeled mtDNA-specific probe, and effect of β-L-D4A on mitochondrial DNA was studied. 2. 2.15 cells were also seeded in 24-well tissue culture plates, and cytotoxicity with different concentrations was examined by MTT method. ID₅₀ was calculated. Structure-activity relationships between D2A and D4A were also studied as above.

RESULTS: Autoradiographic bands were similar between supernatant and intracellular HBV DNA. Episomal HBV DNA was inhibited in a dose-dependent manner. ED₅₀ was 0.2 μM. HBsAg or HBeAg was not apparently decreased, and inhibition of mitochondrial DNA was not obvious. The experiment of cytotoxicity gained ID₅₀ at 200 μM.

CONCLUSION: β-L-D4A possesses potent inhibitory effects on the replication of HBV in vitro with little cytotoxicity and mitochondrial toxicity, TI value is 1000. It is expected to be developed as a new clinically anti-HBV drug.

The risk of infection transmission from blood progenitor cell concentrates

The possibility of infection transmission by infusion of cryopreserved peripheral blood stem cells concentrates or bone marrow is well known. For this reason the European Blood and Marrow Transplantation Group (EBMT) and International Society for Haemotherapy and Graft Engineering (ISHAGE) standards include a panel of serological tests to be performed in donors and patients with the aim to lower the likelihood of infection transmission. The study was performed on a group of 71 patients and 22 donors. No laboratory signs of active infection were found in 15 donors (13 related, 2 unrelated), i.e., in 68.2% and in 55 patients (77.5%). The active infection from herpes viruses was the most common (in patients 13, in donors 7). Hepatitis B was found in only one case. The cytomegalovirus (CMV) immunoglobulin G (IgG) test was the most common marker of previous infection, and it was found in 14 donors and 55 patients. We can conclude that the rate of clinically unsuspected infections in donors and patients, including cases requiring immediate treatment among the patient groups, is relatively high and fully justifies the practice of prophylactic serological testing using the whole palette of tests according to EBMT and ISHGE in both autologous and allogenous transplantations of hematopoietic stem cells.

Experimental evaluation of cross-contamination between cryotubes containing mouse 2-cell embryos and murine pathogens in liquid nitrogen tanks

It has been suspected that embryos stored in liquid nitrogen tanks may become contaminated with murine pathogens, if some pathogens had been introduced to the tanks accidentally. To examine this, we stored tubes containing embryos with tubes containing mouse hepatitis virus (MHV) or Pasteurella pneumotropica in liquid nitrogen tanks and examined whether progeny mice derived from the embryos were contaminated with the pathogens or not. After storing for 6 months or 1 year the frozen embryos were thawed and implanted into the oviducts of pseudopregnant female mice, and the mice were bred in vinyl isolators. We could not detect serum antibodies to MHV and isolate Pasteurella pneumotropica in the progeny mice, suggesting that cross-contamination between tubes in a liquid nitrogen tank scarcely occurs.

Genetic variability in hepatitis B viruses

In 1988, it was reported that the full nucleotide sequences of 18 hepatitis B virus (HBV) strains clustered into four genetic groups (A to D) with more than 8% divergence between the groups. This classification of strains in terms of genome sequence has since proven to be an important tool in the understanding of HBV epidemiology and evolution and has been expanded to include three more genotypes. In parallel with the HBV genotypes described in humans, HBV strains isolated from different primates and hepadnaviruses found in woodchucks, ground squirrels, ducks and herons have been studied. Sequence differences between HBV genotypes can lead to structural differences at the level of the pregenome and can also lead to dramatic differences at the translational level when specific and commonly occurring mutations occur. There is increasing evidence that the clinical picture, the response to treatment and the long-term prognosis may differ depending on which genotype has infected the patient. The consideration of traditional serological patterns in a patient must therefore take the genotype of the infecting strain into account. Nucleotide variability between HBV strains has been used in several studies to trace routes of transmission and, since it is becoming increasingly clear that the differences between HBV genotypes are important, the need for reliable and easy methods of differentiating HBV genotypes has arisen. This review summarizes the knowledge of HBV genotypes with regard to their genetic, structural and clinically significant differences and their origin and evolution in the context of the hepadnaviruses in general.

Cryopreservation, screening and storage of sperm the challenges for the twenty-first century

The advent of HIV and the serious nature of the sequelae resulted in a major reassessment of artificial insemination practices in the UK. The development of human semen cryopreservation had enormous impact on reproductive medicine and the availability of cryopreserved quarantined donor semen became a mainstay for the treatment of male infertility in the UK. The regulation and accreditation of assisted reproductive technologies and the introduction of peer-reviewed guidelines have largely standardized clinical and laboratory practice. The introduction of assisted fertilization techniques such as intracytoplasmic sperm injection, testicular sperm retrieval and improved oncology treatments have placed pressure on reproductive biologists and cryobiologists to design and use cryopreservation protocols for the optimum survival of sperm.

A strategy for rapid cooling of mouse embryos within a double straw to eliminate the risk of contamination during storage in liquid nitrogen

Double packaging, in which an inner straw containing the specimen is inserted into an outer, larger straw (here termed 'straw-in-straw') to prevent the inner straw from coming into direct contact with liquid nitrogen provides a simple strategy for reducing or eliminating the potential contamination risk associated with storage in liquid nitrogen. This approach has in the past been used in conjunction with cryopreservation by slow cooling, but has not previously been tested for use throughout an entire rapid cooling and warming procedure. This study determined whether keeping the straw containing the embryos inside a second protecting container throughout the cryopreservation and storage protocol would compromise embryo viability. We established that a cryoprotectant containing a high polymer concentration (35% dextran or Ficoll) together with 25% ethylene glycol (as the penetrating cryoprotectant) was highly effective for day 2 and day 3 mouse embryos in both single and double straws. The survival and development of all cryopreserved embryos, as assessed both in vitro and in vivo, was not statistically different to their untreated controls. This established that a protein/serum-free cryoprotectant solution supplemented with polymers could provide complete protection of mouse embryos. It also shows, for the first time, that embryos can be cooled by direct immersion in liquid nitrogen and warmed by direct immersion into a waterbath within a double straw arrangement to reduce the likelihood of contamination.