Size and conformational stability of the hepatitis A virus used to prepare VAQTA, a highly purified inactivated vaccine

Calcium Chloride as a Novel Stabilizer for Foot-and-Mouth Disease Virus and Its Application in the Vaccine Formulation

The thermal stability of the in-house-developed foot-and-mouth disease (FMD) type O and A viruses was evaluated, and the O Jincheon virus was found to exhibit the lowest thermal stability. To overcome this instability, we proposed a novel stabilizer, calcium chloride. The thermal stability of FMDVs increased up to a CaCl2 concentration of 10 mM, and it had a decreasing trend at >30 mM. The O Jincheon virus showed a significant decrease in the amount of antigen over time at 4 °C. In contrast, the samples treated with CaCl2 showed stable preservation of the virus without significant antigen loss. After the CaCl2-formulated vaccine was administered twice to pigs, the virus neutralization titer reached approximately 1:1000, suggesting that the vaccine could protect pigs against the FMDV challenge. In summary, the O Jincheon virus is difficult to utilize as a vaccine given its low stability during storage after antigen production. However, following its treatment with CaCl2, it can be easily utilized as a vaccine. This study evaluated CaCl2 as a novel stabilizer in FMD vaccines and may contribute to the development of stable vaccine formulations, especially for inherently unstable FMDV strains.

Immunochemical and Biophysical Characterization of Inactivated Sabin Poliovirus Products: Insights into Rapid Quality Assessment Tools

The aim of this study was to demonstrate the strength of combining immunochemical and biophysical analysis tools for assessing the quality of Sabin inactivated poliovirus vaccine (Sabin-IPV) bulk products. We assessed Sabin-IPV serotypes 1, 2 and 3 from six different manufacturers and evaluated their comparability through biosensor analysis and biophysical characterization methods, including tryptophan fluorescence and asymmetrical flow field-flow fractionation - multi-angle light scattering analysis. These methods enabled us to assess antigenic as well as conformational and structural integrity profiles, respectively. Based on Sabin-IPV samples that were subjected to accelerated storage conditions, we revealed that existing immunochemical methods exhibit remarkably similar trends to the results obtained by the biophysical characterization methods. While the results underpin that the comparability of Sabin-IPV bulk products of different manufacturers is poor, information about their quality can rapidly be obtained by using both immunochemical and biophysical methods. Furthermore, the study highlights that quality assessment of Sabin-IPV can be obtained through biophysical techniques can complement the assessments performed with monoclonal antibodies and suggests that similar techniques could be employed to characterize other enteroviruses.

Thermal Inactivation of Hepatitis A Virus, Noroviruses, and Simian Rotavirus in Cows' Milk

Consumption of raw or unpasteurized milk is a risk for the consumers because indirect contaminations such as fecal-cross-contamination could occur and determine the presence of enteric viruses. In this study, milk was treated with several temperature and time combinations chosen by performing a preliminary experiment to evaluate the intervals needed to inactivate Hepatitis A virus (HAV) HM175 strain, noroviruses genogroups I and II (GI and GII), and simian rotavirus SA11 at different temperatures. Results were obtained by measuring the genome copies and infectious units by real-time PCR and plaque assays respectively. At 85 °C, one minute and two minutes were needed to achieve 6.6 log₁₀ ± 0.2 and 8 log₁₀ ± 0 reductions of genome copies of HAV respectively. Similar genome copies reduction was also observed for noroviruses (GI and GII) and simian rotavirus. At higher temperatures, 90 s (s) at 90 °C and 60 s at 95 °C were needed to achieve 8 log₁₀ ± 0 reductions of the genome copies of all studied viruses. Significant higher sensitivity of the infectious units of both HAV and simian rotavirus to heat treatment of milk than their genome copies was observed. At boiling point of milk (100.5 °C), 40 s were needed to achieve 8 log₁₀ ± 0 reductions of genome copies of all the studied viruses, while 10 s were needed to achieve 6 log₁₀ ± 0 reductions of the infectious units of HAV and simian rotavirus. Significant higher reduction of infectious units than genome copies was observed confirming that genome copies reduction does not correspond to infectious virus.

A Multifaceted Evaluation on the Penetration Resistance of Protective Clothing Fabrics against Viral Liquid Drops without Pressure

Healthcare workers should wear appropriate personal protective clothing (PPC) on assuming the risk of exposure to various pathogens. Therefore, it is important to understand PPC performance against pathogen penetration. Currently, standard methods to evaluate and classify the penetration resistance of PPC fabrics with pressure using synthetic blood or phi-X174 phage have been established by the International Organization for Standardization (ISO). However, the penetration of viral liquid drops (VLDrop) on the PPC without pressure is also a major exposure route and more realistic, necessitating further studies. Here, we evaluated the penetration resistance against VLDrop without pressure using phi-X174 phage on woven and nonwoven fabrics of commercially available PPC classified by the ISO, and analyzed in detail the penetration behaviors of VLDrop by quantifying the phage amounts in leak-through and migration into test fabrics. Our results showed that some nonwoven test fabrics had nearly the same penetration resistance against VLDrop, even if the ISO resistance class differed. Furthermore, the results revealed that the amount of leakage through the fabrics was correlated with the migration amount into the fabric, which was related to fluid-repellency of fabrics, suggesting the effectiveness for penetration resistance. Our study may facilitate more appropriate selection for PPC against pathogen penetration.

nanoDSF: In vitro Label-Free Method to Monitor Picornavirus Uncoating and Test Compounds Affecting Particle Stability

Thermal shift assays measure the stability of macromolecules and macromolecular assemblies as a function of temperature. The Particle Stability Thermal Release Assay (PaSTRy) of picornaviruses is based on probes becoming strongly fluorescent upon binding to hydrophobic patches of the protein capsid (e.g., SYPRO Orange) or to the viral RNA genome (e.g., SYTO-82) that become exposed upon heating virus particles. PaSTRy has been exploited for studying the stability of viral mutants, viral uncoating, and the effect of capsid-stabilizing compounds. While the results were usually robust, the thermal shift assay with SYPRO Orange is sensitive to surfactants and EDTA and failed at least to correctly report the effect of excipients on an inactivated poliovirus 3 vaccine. Furthermore, interactions between the probe and capsid-binding antivirals as well as mutual competition for binding sites cannot be excluded. To overcome these caveats, we assessed differential scanning fluorimetry with a nanoDSF device as a label-free alternative. NanoDSF monitors the changes in the intrinsic tryptophan fluorescence (ITF) resulting from alterations of the 3D-structure of proteins as a function of the temperature. Using rhinovirus A2 as a model, we demonstrate that nanoDFS is well suited for recording the temperature-dependence of conformational changes associated with viral uncoating with minute amounts of sample. We compare it with orthogonal methods and correlate the increase in viral RNA exposure with PaSTRy measurements. Importantly, nanoDSF correctly identified the thermal stabilization of RV-A2 by pleconaril, a prototypic pocket-binding antiviral compound. NanoDFS is thus a label-free, high throughput-customizable, attractive alternative for the discovery of capsid-binding compounds impacting on viral stability.

Structural Characterization and Physicochemical Stability Profile of a Double Mutant Heat Labile Toxin Protein Based Adjuvant

A novel protein adjuvant double-mutant Escherichia coli heat-labile toxin, LT (R192G/L211A) or dmLT, is in preclinical and early clinical development with various vaccine candidates. Structural characterization and formulation development of dmLT will play a key role in its successful process development, scale-up/transfer, and commercial manufacturing. This work describes extensive analytical characterization of structural integrity and physicochemical stability profile of dmLT from a lyophilized clinical formulation. Reconstituted dmLT contained a heterogeneous mixture of intact holotoxin (AB₅, ∼75%) and free B₅ subunit (∼25%) as assessed by analytical ultracentrifugation and hydrophobic interaction chromatography. Intact mass spectrometry (MS) analysis revealed presence of Lys⁸⁴ glycation near the native sugar-binding site in dmLT, and forced degradation studies using liquid chromatography-MS peptide mapping demonstrated specific Asn deamidation and Met oxidation sites. Using multiple biophysical measurements, dmLT was found most stable between pH 6.5 and 7.5 and at temperatures ≤50°C. In addition, soluble aggregates and particle formation were observed upon shaking stress. By identifying the physicochemical degradation pathways of dmLT using newly developed stability-indicating analytical methods from this study, we aim at developing more stable candidate formulations of dmLT that will minimize the formation of degradants and improve storage stability, as both a frozen bulk substance and eventually as a liquid final dosage form.

Thermal Inactivation of Foodborne Enteric Viruses and Their Viral Surrogates in Foods

Foodborne viruses, in particular human norovirus and hepatitis A virus, are the most common causes of food-associated infections and foodborne illness outbreaks around the world. Since it is currently not possible to cultivate human noroviruses and the wild-type strain of hepatitis A virus in vitro, the use of a variety of viral surrogates is essential to determine appropriate thermal processing conditions to reduce the risk associated with their contamination of food. Therefore, the objectives of this review are to (i) present pertinent characteristics of enteric foodborne viruses and their viral surrogates, (ii) discuss the viral surrogates currently used in thermal inactivation studies and their significance and value, (iii) summarize available data on thermal inactivation kinetics of enteric viruses, (iv) discuss factors affecting the efficacy of thermal treatment, (v) discuss suggested mechanisms of thermal inactivation, and (vi) provide insights on foodborne enteric viruses and viral surrogates for future studies and industrial applications. The overall goal of this review is to contribute to the development of appropriate thermal processing protocols to ensure safe food for human consumption.

Physicochemical stability profile of Tulane virus: a human norovirus surrogate

AIMS

Human norovirus (HuNoV) is estimated to cause 19-21 million illnesses each year in the US. A major limitation in HuNoV research is the lack of an in vitro culture system; therefore, surrogate viruses including murine norovirus (MNV) and feline calicivirus (FCV) are used to study HuNoV. Here, we aim to establish the physiochemical properties of Tulane virus (TV)—a newer HuNoV surrogate.

METHODS AND RESULTS

For thermal inactivation, TV was exposed to 37°C for 2 h, and 56, 63 and 72°C for 30 min. For ethanol tolerance, TV was treated with 60, 70 and 90% ethanol at room temperature (RT) for 5 min. Tulane virus pH stability at pH 2, 3, 7, 9 and 10 was performed at RT for 90 min. At 37°C, there was no significant reduction in TV after 2 h. However, at 56, 63 and 72°C, D-values of 4·03, 1·18, and 0·24 min, were calculated respectively. The D-values obtained for TV ethanol tolerance were 1·46, 1·93, and 0·35 min at 60, 70 and 90% respectively. Less than 1 log10 plaque forming units (PFU) reduction was observed for TV at all pH levels except pH 10 where about a 2-log10 PFU reduction was observed. Tulane virus was also tolerant to chlorine disinfection on a solid surface with D-values of 15·82 and 5·42 min at 200 and 1000 ppm respectively.

CONCLUSIONS

Tulane virus is likely a suitable surrogate to study HuNoV thermal stability as well as ethanol tolerance below 90%. Tulane virus also is a promising surrogate to study HuNoV pH stability and chlorine tolerance.

SIGNIFICANCE AND IMPACT OF THE STUDY

Based on current work, in vitro studies demonstrate that TV is an overall more conservative and suitable surrogate for the study of HuNoV physicochemical properties.

Stabilizing effects of excipients on dissociation of intact (146S) foot-and-mouth disease virions into 12S particles during storage as oil-emulsion vaccine

Most conventional foot-and-mouth disease virus (FMDV) vaccines contain oil-adjuvant. Their potency decreases upon prolonged storage. Intact (146S) FMDV particles can dissociate into 12S degradation products with a concomitant decrease in immunogenicity. We therefore measured virion stability in vaccines using two previously developed ELISAs to separately quantify 12S and 146S particles. Virions completely dissociated into 12S particles within 3 months after oil-emulsification. Dissociation occurred at a much lower rate in a comparable aqueous solution that was not oil-emulsified. Thus, oil-emulsification stimulates virion dissociation, presumably due to the protein denaturing effect of the oil-water interface. In real-time stability studies the stability of oil-adjuvanted virions of four different FMDV strains was significantly increased by addition of sucrose and BSA in a synergistic manner. Contrary to BSA addition, the effect of sucrose addition was concentration dependent. This study illustrates the importance of analysing antigen integrity after oil-emulsification and provides methods for FMDV vaccine stabilization.

Comparison of methods for evaluating the thermal stability of human enteric viruses

Human enteric viruses have been identified as one of the predominant causative agents of food-borne illnesses in developed countries, and it is estimated that human norovirus accounts for a majority of these illnesses each year. Not all of these viruses can be cultured and hence relatively little is known about their pathogenesis and physicochemical properties. To overcome this, researchers have utilized different virus surrogates for the study of non-cultivable human enteric viruses. In this review, we discuss various methods utilized for the evaluation of the thermal stability of human enteric viruses, compare the results of these methods, and examine how researchers may move toward a single standard approach (i.e., temperatures, virus concentrations, volume/weight of matrices, etc.) for determining thermal inactivation profiles of human enteric viruses and their surrogates. Based on our review, we found that temperature, time of exposure, type of matrix, analysis type, type of heat application, and the concentration and volume of virus used in the experiments were highly variable across virus surrogates even for the same surrogates. Because of these differences-along with the inherent limitations of using surrogate viruses-comparison of these methods and how the results may be extrapolated to human enteric viruses is quite challenging. As a result, we discuss how researchers may move toward a single standard approach for determining thermal inactivation profiles of human enteric viruses and their surrogates.

Vaccine instability in the cold chain: mechanisms, analysis and formulation strategies

Instability of vaccines often emerges as a key challenge during clinical development (lab to clinic) as well as commercial distribution (factory to patient). To yield stable, efficacious vaccine dosage forms for human use, successful formulation strategies must address a combination of interrelated topics including stabilization of antigens, selection of appropriate adjuvants, and development of stability-indicating analytical methods. This review covers key concepts in understanding the causes and mechanisms of vaccine instability including (1) the complex and delicate nature of antigen structures (e.g., viruses, proteins, carbohydrates, protein-carbohydrate conjugates, etc.), (2) use of adjuvants to further enhance immune responses, (3) development of physicochemical and biological assays to assess vaccine integrity and potency, and (4) stabilization strategies to protect vaccine antigens and adjuvants (and their interactions) during storage. Despite these challenges, vaccines can usually be sufficiently stabilized for use as medicines through a combination of formulation approaches combined with maintenance of an efficient cold chain (manufacturing, distribution, storage and administration). Several illustrative case studies are described regarding mechanisms of vaccine instability along with formulation approaches for stabilization within the vaccine cold chain. These include live, attenuated (measles, polio) and inactivated (influenza, polio) viral vaccines as well as recombinant protein (hepatitis B) vaccines.

Determination of thermal inactivation kinetics of hepatitis A virus in blue mussel (Mytilus edulis) homogenate

Hepatitis A virus (HAV) is a food-borne enteric virus responsible for outbreaks of hepatitis associated with shellfish consumption. The objectives of this study were to determine the thermal inactivation behavior of HAV in blue mussels, to compare the first-order and Weibull models to describe the data, to calculate Arrhenius activation energy for each model, and to evaluate model efficiency by using selected statistical criteria. The times required to reduce the population by 1 log cycle (D-values) calculated from the first-order model (50 to 72°C) ranged from 1.07 to 54.17 min for HAV. Using the Weibull model, the times required to destroy 1 log unit (tD = 1) of HAV at the same temperatures were 1.57 to 37.91 min. At 72°C, the treatment times required to achieve a 6-log reduction were 7.49 min for the first-order model and 8.47 min for the Weibull model. The z-values (changes in temperature required for a 90% change in the log D-values) calculated for HAV were 15.88 ± 3.97°C (R(2), 0.94) with the Weibull model and 12.97 ± 0.59°C (R(2), 0.93) with the first-order model. The calculated activation energies for the first-order model and the Weibull model were 165 and 153 kJ/mol, respectively. The results revealed that the Weibull model was more appropriate for representing the thermal inactivation behavior of HAV in blue mussels. Correct understanding of the thermal inactivation behavior of HAV could allow precise determination of the thermal process conditions to prevent food-borne viral outbreaks associated with the consumption of contaminated mussels.

Thermal inactivation kinetic modeling of human norovirus surrogates in blue mussel (Mytilus edulis) homogenate

Control of seafood-associated norovirus outbreaks has become an important priority for public health authorities. Due to the absence of human norovirus infectivity assays, cultivable surrogates such as feline calicivirus (FCV-F9) and murine norovirus (MNV-1) have been used to begin to understand their thermal inactivation behavior. In this study, the effect of thermal treatment on inactivation of human norovirus surrogates in blue mussels was investigated at 50, 56, 60, 65, and 72 °C for various times (0-6 min). The results obtained were analyzed using the Weibull and first-order models. The Theil error splitting method was used for model comparison. This method splits the error in the predicted data into fixed and random error. This method was applied to select satisfactory models for determination of thermal inactivation of norovirus surrogates and kinetic modeling. The D-values calculated from the first-order model (50-72 °C) were in the range of 0.07 to 5.20 min for FCV-F9 and 0.18 to 20.19 min for MNV-1. Using the Weibull model, the t(D=1) for FCV-F9 and MNV-1 to destroy 1 log (D=1) at the same temperatures were in the range of 0.08 to 4.03 min and 0.15 to 19.80 min, respectively. The z-values determined for MNV-1 were 9.91±0.71 °C (R²=0.95) using the Weibull model and 11.62±0.59 °C (R²=0.93) for the first-order model. For FCV-F9 the z-values were 12.38±0.68 °C (R²=0.94) and 11.39±0.41 °C (R²=0.97) for the Weibull and first-order models, respectively. The Theil method revealed that the Weibull model was satisfactory to represent thermal inactivation data of norovirus surrogates and that the model chosen for calculation of thermal inactivation parameters is important. Knowledge of the thermal inactivation kinetics of norovirus surrogates will allow development of processes that produce safer shellfish products and improve consumer safety.

Impact of Sodium Chloride, Sucrose and Milk on Heat Stability of the Murine Norovirus and the MS2 Phage

Until now, little is known about the influence of food additives on heat inactivation of noroviruses. Only a few studies have shown a protective or inhibiting effect on virus infectivity caused by the food matrix. Therefore, the aim of this study was to examine the influence of sodium chloride, sucrose and milk on heat stability of the surrogates murine norovirus (MNV) and MS2 phage at 60 °C for 1-5 min in PBS for MNV and for 5-120 min in suspension medium buffer for MS2 phage. Different concentrations of sodium chloride (5, 10 %) and sucrose (5, 50 %) were added to the respective buffers. In addition, commercially available milk with different fat concentrations (0.3, 1.5, 3.5 %) was investigated in this study. In general, a linear titre reduction for MNV and MS2 phage could be observed, except for the heat treatment of MNV in PBS with 50 % sucrose. A protective effect of PBS with 50 % sucrose and of the matrix milk on MNV could be concluded. All other tested conditions did not show any influence on virus inactivation. However, MS2 phage did show a higher heat resistance throughout the experiments compared to MNV. In future investigations, it should be tested, whether the achieved data may be considered in risk assessments of heat-treated food products with high concentrations of sugar. Furthermore, it should be clarified, whether these results can also be referred to complex food matrices.

Protein-excipient interactions: mechanisms and biophysical characterization applied to protein formulation development

The purpose of this review is to demonstrate the critical importance of understanding protein-excipient interactions as a key step in the rational design of formulations to stabilize and deliver protein-based therapeutic drugs and vaccines. Biophysical methods used to examine various molecular interactions between solutes and protein molecules are discussed with an emphasis on applications to pharmaceutical excipients in terms of their effects on protein stability. Key mechanisms of protein-excipient interactions such as electrostatic and cation-pi interactions, preferential hydration, dispersive forces, and hydrogen bonding are presented in the context of different physical states of the formulation such as frozen liquids, solutions, gels, freeze-dried solids and interfacial phenomenon. An overview of the different classes of pharmaceutical excipients used to formulate and stabilize protein therapeutic drugs is also presented along with the rationale for use in different dosage forms including practical pharmaceutical considerations. The utility of high throughput analytical methodologies to examine protein-excipient interactions is presented in terms of expanding formulation design space and accelerating experimental timelines.

A predictive microbiology approach for thermal inactivation of Hepatitis A virus in acidified berries

Hepatitis A virus (HAV) is a food-borne enteric virus responsible for outbreaks of hepatitis associated with consumption of raw vegetables. Soft fruits, such as red berries, exposed to faecal contamination are increasingly responsible for collective food-borne illnesses associated with HAV, when eaten raw or used in unprocessed foods. Heat is the most effective measure for the inactivation of HAV. Thermal treatments are used on fruits as a decontamination method, but they have to be adapted to product characteristics; indeed, factors such as sugar or pH may have an impact on the viral sensitivity to thermal treatments. A model was developed for the inactivation of HAV in red berries without supplemented sugar and with different pH values. Nonlinear inactivation curves in acidified raspberries were modelled using an integrated model, with a single equation nesting secondary models of temperature and pH in the primary model. Model predictions were then confronted to experimental results obtained in another laboratory on other berries with different pH values. Excellent predictions were obtained in most cases, while failed predictions provided safe results, with the model predicting higher residual virus titres than what was observed.

Development of a fluorescent in situ method for visualization of enteric viruses

Studying the interactions between enteric pathogens and their environment is important to improving our understanding of their persistence and transmission. However, this remains challenging in large part because of difficulties associated with tracking pathogens in their natural environment(s). In this study, we report a fluorescent labeling strategy which was applied to murine norovirus (MNV-1), a human norovirus surrogate, and hepatitis A virus (HAV). Specifically, streptavidin-labeled Quantum dots (Q-Dots) were bound to biotinylated capsids of MNV-1 and HAV (bio-MNV-1 and bio-HAV); the process was confirmed by using a sandwich-type approach in which streptavidin-bound plates were reacted with biotinylated virus followed by a secondary binding to Q-Dots with an emission range of 635 to 675 nm (Q-Dots 655). The assay demonstrated a relative fluorescence of 528 +/- 48.1 and 112 +/- 8.6 for bio-MNV-1 and control MNV-1, respectively. The biotinylation process did not impact virus infectivity, nor did it interfere with the interactions between the virus and host cells or model produce items. Using fluorescent microscopy, it was possible to visualize both bio-HAV and bio-MNV-1 attached to the surfaces of permissive mammalian cells and green onion tissue. The method provides a powerful tool for the labeling and detection of enteric viruses (and their surrogates) which can be used to track virus behavior in situ.

Modelling effect of physical and chemical parameters on heat inactivation kinetics of hepatitis A virus in a fruit model system

While thermal destruction of pathogenic bacteria has been thoroughly studied in food industry, heat inactivation of viruses in food has been poorly investigated. Experiments were carried out to characterize the effects of controlled physical and chemical characteristics of a food matrix upon heat resistance parameters (D and z values) of hepatitis A virus (HAV), taken as model because of its reported heat resistance. Sucrose content (28-52 degrees Brix), calcium concentration (90-1700 mg kg(-1)) and pH (3.3-4.3) were selected for possible influence on thermal inactivation of HAV in strawberry mashes and thus included in an experimental design according to a Doehlert matrix. Use of this design not only allowed to detect and quantify the direct influence of sucrose concentration upon the D85 degrees C value to be higher than the one of pH, but also to reveal a sucrose concentration/pH specific interaction, while no effect of calcium concentration was evidenced. Although the model cannot be directly used to predict heat resistance in real fruit systems, because of differences observed between predicted and measured D85 degrees C values, it is useful for predicting the trends and relative changes in D values due to sucrose concentration and pH variations. Results suggested possible effects of other constituents of strawberry products on heat resistance of HAV and confirmed the importance of experimental validation of any model-derived process. Nevertheless, such a modelling approach using response surface methodology provides a rapid answer to heat resistance evaluation of a food-borne virus as a function of specific physical and chemical parameters of specific food products.

Thermal stability of vaccines

Worldwide vaccination programs against infectious diseases and toxins are estimated to save approximately 3 million lives yearly. Tragically, however, another 3 million individuals (primarily children) die of vaccine-preventable diseases. A significant portion of this problem results from the thermal instability of many of the currently used vaccines. This review argues that modern methods of physical and chemical analysis permit for the first time characterization of the degradative pathways of thermally labile vaccines. A rigorous description of these pathways permit a more rational and systematic approach to the stabilization of vaccines. A direct result of the replacement of currently employed, primarily empirical, approaches to vaccine stabilization with a more molecular-based methodology should be the development of more universally available vaccinations against life-threatening diseases. This has the potential to have a dramatic impact on world health.

Reduction of animal use in human vaccine quality control: opportunities and problems

In vivo assays play a crucial role in the assessment of the potency and safety of human vaccines. Robust vaccine production procedures, improved characterisation methods and development of well-characterised vaccines create possibilities to reduce animal use. In this paper the current status in this field is reviewed. Achievements with regard to in vivo and in vitro potency and safety testing are discussed as well as new developments and possibilities in the field of in vitro characterisation of vaccine components. Finally, validation and implementation issues will be dealt with. Although replacement of in vivo tests for batch release of existing vaccines is difficult, emerging technologies allow well-considered reduction of in vivo experiments during product and process development and improvement. Inextricably bound up with this approach is good manufacturing practice (GMP), resulting in robust, validated production processes.

Analysis of plasmid DNA from a pharmaceutical perspective

The advent of gene therapy and polynucleotide-based vaccines has resulted in the use of plasmid DNA as a drug substance. Although biologically (cell or animal) based assays must currently be employed to establish the identity and potency of such drugs, we argue that in the future, a combination of microchip-based mutation detection devices combined with an array of chromatographic, electrophoretic, hydrodynamic, and spectroscopic methods can be employed to rigorously establish these properties. We review a variety of such methods in this context and also consider the issue of the chemical stability of plasmids. Extensive comparison is made to protein-based pharmaceuticals with the unique importance of polynucleotide sequence emphasized in comparison to protein tertiary structure.