Publications
2013
M. Li, Y. X. Qiu
Vaccine 31 (2013) 1264-1267
An effective downstream bio-processing of vaccine products requires complete chemical knowledge of the contaminants that may arise from a given vector expression system. Whether the vaccine is made from the traditional egg-based or the new cell-cultured process, it is the expression system that determines the types of impurities that need to be identified and removed from the vaccine product.
There are mechanical and chemical factors that can either reduce the yield or render a vaccine product to be irreversibly inactive. The choice of equipment and solvents is therefore important in minimizing product loss, and for maintaining an efficient and optimized manufacturing process.
The frequent out-of-specification, irreproducible data and inefficiency in the manufacturing of biologics were the basis for FDA to propose the “cGMP for the 21st Century” initiative in the year of 2000. Effective 2004, the concept of quality by design (QbD) has been imposed in the manufacturing of biologics. To facilitate the implementation of QbD FDA has encouraged the use of process analytical technology (PAT). Further, FDA believes that an optimized manufacturing scheme requires one to identify and to control the variables that can negatively affect the yield and quality of the desired product, and PAT can reveal wrongful data and alert the operator for immediate correction during processing.
E. Mota, A. Sousa, U. Černigoj, J. A. Queiroz, C. T. Tomaz, F. Sousa
Journal of Chromatography A (2013)
The demand for high-purity supercoiled plasmid DNA to be applied as a vector for new therapeutic strategies, such as gene therapy or DNA vaccination has increased in the last years. Thus, it is necessary to implement an analytical technique suitable to control the quality of the supercoiled plasmid as a pharmaceutical product during the manufacturing process. The present study describes a new methodology to quantify and monitor the purity of supercoiled plasmid DNA by using a monolithic column based on anion-exchange chromatography. This analytical method with UV detection allows the separation of the plasmid isoforms by combining a NaCl stepwise gradient. The specificity, linearity, accuracy, reproducibility and repeatability of the method have been evaluated, and the lower quantification and detection limits were also established. The validation was performed according to the guidelines, being demonstrated that the method is precise and accurate for a supercoiled plasmid concentration up to 200 μg/mL. The main advantage achieved by using this monolithic column is the possibility to quantify the supercoiled plasmid in a sample containing other plasmid topologies, in a 4 min experiment. This column also permits the assessment of the supercoiled plasmid DNA present in more complex samples, allowing to control its quality throughout the bioprocess. Therefore, these findings strengthen the possibility of using this monolithic column associated with a powerful analytical method to control the process development of supercoiled plasmid DNA production and purification for therapeutic applications.
S. Haberl, M. Jarc, A. Štrancar, M. Peterka, D. Hodžić, D. Miklavčič
J Membrane Biol, DOI 10.1007/s00232-013-9580-5
The use of plasmid DNA (pDNA) as a pharmaceutical tool has increased since it represents a safer vector for gene transfer compared to viral vectors. Different pDNA extraction methods have been described; among them is alkaline lysis, currently the most commonly used. Although alkaline lysis represents an established method for isolation of pDNA, some drawbacks are recognized, such as entrapment of pDNA in cell debris, leading to lower pDNA recovery; the time-consuming process; and increase of the volume due to the buffers used, all leading to increased cost of production. We compared the concentration of extracted pDNA when two methods for extracting pDNA from Escherichia coli were used: alkaline lysis and a method based on membrane electroporation, electroextraction. At the same time, we also studied the effect of different pulse protocols on bacterial inactivation. The concentration of pDNA was assayed with anion exchange chromatography. When alkaline lysis was used, two incubations of lysis time (5 and 10 min) were compared in terms of the amount of isolated pDNA. We did not observe any difference in pDNA concentration regardless of incubation time used. In electroextraction, different pulse protocols were used in order to exceed the pDNA concentration obtained by alkaline lysis. We show that electroextraction gives a higher concentration of extracted pDNA than alkaline lysis, suggesting the use of electroporation as a potentially superior method for extracting pDNA from E. coli. In addition, electroextraction represents a quicker alternative to alkaline lysis for extracting pDNA.
B. Gabor, U. Černigoj, M. Barut, A. Štrancar
Journal of Chromatography A, 1311 (2013) 106-114
HPLC based analytical assay is a powerful technique that can be used to efficiently monitor plasmid DNA (pDNA) purity and quantity throughout the entire purification process. Anion exchange monolithic and non-porous particle based stationary phases were used to study the recovery of the different pDNA isoforms from the analytical column. Three differently sized pDNA molecules of 3.0 kbp, 5.2 kbp and 14.0 kbp were used. Plasmid DNA was injected onto columns under the binding conditions and the separation of the isoforms took place by increasing the ionic strength of the elution buffer. While there was no substantial decrease of the recovered supercoiled and linear isoforms of the pDNA with the increase of the plasmid size and with the increase of the flow rate (recoveries in all cases larger than 75%), a pronounced decrease of the oc isoform recovery was observed. The entrapment of the oc pDNA isoform occurred under non-binding conditions as well. The partial oc isoform elution from the column could be achieved by decreasing the flow rate of the elution mobile phase. The results suggested a reversible entrapment of the oc isoform in the restrictions within the pores of the monolithic material as well as within the intra-particle space of the non-porous particles. This phenomenon was observed on both types of the stationary phase morphologies and could only be connected to the size of a void space through which the pDNA needs to migrate. A prediction of reversible pDNA entrapment was successfully estimated with the calculation of Peclet numbers, Pe, which defines the ratio between a convective and diffusive mass transport.
M. Limonta, N. Lendero Krajnc, U. Vidic, L. Zumalacárregui
Biochemical Engineering Journal 80 (2013) 14-18
The pIDKE2 plasmid is the main component of the CIGB's candidate vaccine against Hepatitis C virus (HVC), which is being used in HCV chronically-infected individuals during clinical trials phase 1 and 2. The designed downstream process of pIDKE2 plasmid produces up to 179 g/year. In order to conduct further improvements, modelling of the downstream process was performed. A methodology based on process analysis tools, such as experimental design and modelling was established to identify factors with the highest influence on production cost and the amount of annual plasmid. Taking into account that the pIDKE2 downstream process designed is in its initial stages of development, CIM technology was evaluated as a new manufacturing process on lab scale. Purity and recovery of CIM technology was better than porous particle matrix, thus SuperPro Designer was used in order to simulate the purification process. Cost efficiency optimization of the pIDKE2 downstream process was done with the simulation model.
P. Fernandes, C. Peixoto, VM Santiago, EJ Kremer, AS Coroadinha and PM Alves
Gene Therapy (2012), 1–8
Canine adenovirus type 2 (CAV-2) vectors overcome many of the clinical immunogenic concerns related to vectors derived from human adenoviruses (AdVs). In addition, CAV-2 vectors preferentially transduce neurons with an efficient traffic via axons to afferent regions when injected into the brain. To meet the need for preclinical and possibly clinical uses, scalable and robust production processes are required. CAV-2 vectors are currently produced in E1-transcomplementing dog kidney (DK) cells, which might raise obstacles in regulatory approval for clinical grade material production. In this study, a GMP-compliant bioprocess was developed. An MDCK-E1 cell line, developed by our group, was grown in scalable stirred tank bioreactors, using serum-free medium, and used to produce CAV-2 vectors that were afterwards purified using column chromatographic steps. Vectors producedin MDCK-E1 cells were identical to those produced in DK cells as assessed by SDS-PAGE and dynamic light scatering measurements (diameter and Zeta potential). Productivities of ~109 infectious particles (IP) ml-1 and 2x103 IP per cell were possible. A downstream process using technologies transferable to process scales was developed, yielding 63% global recovery. The total particles to IP ratio in the purified product (<20:1) was within the limits specified by the regulatory authorities for AdV vectors. These results constitute a step toward a scalable process for CAV-2 vector production compliant with clinical material specifications.
Attachments
P. Gerster, E.-M. Kopecky, N. Hammerschmidt, M. Klausberger, F. Krammer, R. Grabherr, C. Mersich, L. Urbas, P. Kramberger, T. Paril, M. Schreiner, K. Nöbauer, E. Razzazi-Fazeli, A. Jungbauer
Journal of Chromatography A, 1290 (2013) 36-45(2013) 36-45
A chromatographic process based on monoliths for purification of infective baculovirus without prior concentration step has been established. Baculovirus produced in Spodoptera frugiperda cells (Sf-9) were harvested by centrifugation, filtered through 0.8 μm filters and directly loaded onto radial 1 mL anion exchange monoliths with a channel size of 1.5–2.0 μm operated at a volumetric flow rate of one bed volume per minute. Optional an epoxy monolith was used as pre-column to reduce interfering compounds and substances influencing the capacity of anion exchange monoliths for baculovirus infectious virus could be eluted with a step gradient at salt concentrations of 440 mM NaCl. Recovery of infectious virus was highly influenced by composition and age of supernatant and ranged from 20 to >99% active baculovirus. Total protein content could be reduced to 1–8% and DNA content to 38–48% in main virus fraction. Infective virus could be 52-fold concentrated within 20.5 h and simultaneously an 82-fold volume reduction was possible when loading 1150 mL (2.1 × 108 pfu/mL) onto 1 mL scale support.
A. Steyer, I. Gutierrez-Aguire, M. Kolenc, S. Koren, D. Kutnjak, M. Pokorn, M. Poljšak-Prijatelj, N. Rački, M. Ravnikar, M. Sagadin, A. Fratnik Steyer, N. Toplak
Journal of Clinical Microbiology, November 2013
Mammalian orthoreoviruses (MRV) are known to cause mild enteric and respiratory infections in humans. They are widespread and infect a broad spectrum of mammals. We report here the first case of MRV detected in a child with acute gastroenteritis, which showed the highest similarity to MRV reported recently in European bats. Stool sample examination of the child was negative for most common viral and bacterial pathogens. Reovirus particles were identified by electron microscopic examination of both stool suspension and cell culture supernatant. The whole genome sequence was obtained with the Ion Torrent next generation sequencing platform. Prior to sequencing, stool sample suspension and cell culture supernatant were pre-treated with nucleases and/or the convective interaction media (CIM) monolithic chromatographic method to purify and concentrate the target viral nucleic acid. Whole genome sequence analysis revealed that the Slovenian SI-MRV01 isolate was most similar to MRV found in bat in Germany. High similarity was shared in all genome segments, with nucleotide and amino acid identities between 93.8-99.0% and 98.4-99.7%, respectively. It was shown that CIM monolithic chromatography alone is an efficient method for enriching the sample in viral particles before nucleic acid isolation and next generation sequencing application.
E. Maksimova, E. Vlakh, E. Sinitsyna, T. Tennikova
J. Sep. Sci. 2013, 36, 3741–3749
Ultrashort monolithic columns (disks) were thoroughly studied as efficient stationary phases for precipitation–dissolution chromatography of synthetic polymers. Gradient elution mode was applied in all chromatographic runs. The mixtures of different flexible chain homopolymers, such as polystyrenes, poly(methyl methacrylates), and poly(tert-butylmethacrylates) were separated according to their molecular weights on both commercial poly(styrene-co divinylbenzene).
disks (12 id × 3 mm and 5 × 5 mm) and lab-made monolithic columns (4.6 id × 50 mm) filled with supports of different hydrophobicity. The experimental conditions were optimized to reach fast and highly efficient separation. It was observed that, similar to the separation of monoliths of other classes of (macro)molecules (proteins, DNA, oligonucleotides), the length of column did not affect the peak resolution.
A comparison of the retention properties of the poly(styrene-co-divinylbenzene) diskshaped monoliths with those based on poly(lauryl methacrylate-co-ethylene dimethacrylate), poly(butyl methacrylate-co-ethylene dimethacrylate), and poly(glycidyl methacrylate-co-ethylene dimethacrylate) supports demonstrated the obvious effect of surface chemistry on the resolution factor. Additionally, the results of the discussed chromatographic mode on the fast determination of the molecular weights of homopolymers used in this study were compared to those established by SEC on columns packed with sorbent beads of a similar nature to the monoliths.
Roy N D‘Souza, Ana M Azevedo, M Raquel Aires-Barros, Nika Lendero Krajnc, Petra Kramberger, Maria Laura Carbajal, Mariano Grasselli, Roland Meyer & Marcelo Fernández-Lahore
Vol. 1, No. 5, Pharmaceutical Bioprocessing (2013)
Downstream processing is currently the major bottleneck for bioproduct generation. In contrast to the advances in fermentation processes, the tools used for downstream processes have struggled to keep pace in the last 20 years. Purification bottlenecks are quite serious, as these processes can account for up to 80% of the total production cost. Coupled with the emergence of new classes of bioproducts, for example, virus-like particles or plasmidic DNA, this has created a great need for superior alternatives. In this review, improved downstream technologies, including aqueous two-phase systems, expanded bed adsorption chromatography, convective flow systems, and fibre-based adsorbent systems, have been discussed. These adaptive methods are more suited to the burgeoning downstream processing needs of the future, enabling the cost-efficient production of new classes biomaterials with a high degree of purity, and thereby hold the promise to become indispensable tools in the pharmaceutical and food industries.
A. Ghanem, R. Healey, F. G. Adly
Analytica Chimica Acta 760 (2013) 1-15
Abstract
Plasmid DNA (pDNA)-based vaccines offer more rapid avenues for development and production if compared to those of conventional virus-based vaccines. They do not rely on time- or labour-intensive cell culture processes and allow greater flexibility in shipping and storage. Stimulating antibodies and cellmediated components of the immune system are considered as some of the major advantages associated with the use of pDNA vaccines. This review summarizes the current trends in the purification of pDNA vaccines for practical and analytical applications. Special attention is paid to chromatographic techniques aimed at reducing the steps of final purification, post primary isolation and intermediate recovery, in order to reduce the number of steps necessary to reach a purified end product from the crude plasmid.
A. Romanovskaya, L. P. Sarina, D. H. Bamford, M. M. Poranen
Journal of Chromatography A (2013)
Recent advances in the field of RNA interference and new cost-effective approaches for large-scale double-stranded RNA (dsRNA) synthesis have fuelled the demand for robust high-performance purification techniques suitable for dsRNA molecules of various lengths. To address this issue, we developed an improved dsRNA purification method based on anion exchange chromatography utilizing convective interaction media (CIM) monolithic columns. To evaluate column performance we synthesized a selection of dsRNA molecules (58–1810 bp) in a one-step enzymatic reaction involving bacteriophage T7 DNA-dependent RNA polymerase and phi6 RNA-dependent RNA polymerase. In addition, small interfering RNAs (siRNAs) of 25–27 bp were generated by Dicer digestion of the genomic dsRNA of bacteriophage phi6. We demonstrated that linearly scalable CIM monolithic quaternary amine (QA) columns can be used as a fast and superior alternative to standard purification methods (e.g. LiCl precipitation) to obtain highly pure dsRNA preparations. The impurities following Dicer treatment were quickly and efficiently removed with the QA CIM monolithic column, yielding siRNA molecules of high purity suitable for potential therapeutic applications. Moreover, baseline separation of dsRNA molecules up to 1 kb in non-denaturing conditions was achieved.
2012
J. Lee, H. T. Gan, S. M. Abdul Latiff , C. Chuah, W. Y. Lee, Y.-S. Yang, B. Loo, S. K. Ng, P. Gagnon
Journal of Chromatography A, 1270 (2012) 162-170
We introduce a chromatography method for purification of large proteins and viruses that works by capturing them at a non-reactive hydrophilic surface by their mutual steric exclusion of polyethylene glycol (PEG). No direct chemical interaction between the surface and the target species is required. We refer to the technique as steric exclusion chromatography. Hydroxyl-substituted polymethacrylate monoliths provide a hydrophilic surface and support convective mass transport that is unaffected by the viscosity of the PEG. Elution is achieved by reducing PEG concentration. Selectivity correlates with molecular size, with larger species retained more strongly than smaller species. Retention increases with PEG size and concentration. Salts weaken retention in proportion to their concentration and Hofmeister ranking. Retention is enhanced near the isoelectric point of the target species. Virus binding capacity was measured at 9.9 × 1012 plaque forming units per mL of monolith. 99.8% of host cell proteins and 93% of DNA were eliminated. Mass recovery exceeded 90%. IgM capacity was greater than 60 mg/mL. 95% of host cell proteins were eliminated from IgM produced in protein-free media, and mass recovery was up to 90%. Bioactivity was fully conserved by both viruses and antibodies. Process time ranged from less than 30 min to 2 h depending on the product concentration in the feed stream.
H. M. Oksanen, A. Domanska, D. H. Bamford
Virology Volume 434, Issue 2, 20 December 2012
We report anion exchange chromatographic purification method powerful for preparation of virus particles with ultra pure quality. The technology is based on large pore size monolithic anion exchangers, quaternary amine (QA) and diethylaminoethyl (DEAE). These were applied to membrane-containing icosahedral bacteriophage PRD1, which bound specifically to both matrices. Virus particles eluted from the columns retained the ir infectivity, and were homogenous with high specific infectivity. The yields of infectious particles were up to 80%. Purified particles were recovered at high concentrations, approximately 5mg/ml, sufficient for virological, biochemical and structural analyses. We also tested the applicability of the monolithic anion exchange purification on a filamentous bacteriophage phi 05_2302. Monolithic ion exchange chromatography is easily scalable and can be combined with other preparative virus purification methods.
P. Gagnon
Journal of Chromatography A, 1221 (2012) 57-70(2012) 57-70
This article reviews technology trends in antibody purification. Section 1 discusses non-chromatography methods, including precipitation, liquid–liquid extraction, and high performance tangential flow filtration. The second addresses chromatography methods. It begins with discussion of fluidized and fixed bed formats. It continues with stationary phase architecture: diffusive particles, perfusive particles, membranes and monoliths. The remainder of the section reviews recent innovations in size exclusion, anion exchange, cation exchange, hydrophobic interaction, immobilized metal affinity, mixed-mode, and bioaffinity chromatography. Section 3 addresses an emerging trend of formulating process buffers to prevent or correct anomalies in the antibodies being purified. Methods are discussed for preventing aggregate formation, dissociating antibody-contaminant complexes, restoring native antibody from aggregates, and conserving or restoring native disulfide pairing.
M. Žorž
ChemieXtra 3/2012 pp 30-33
Sartorius BIA Separations produziert und vertreibt kurze monolithischen Chromatografiesäulen, die auf der CIM-Convective Interaction Media-Technologie basieren. CIM-Säulen eignen sich vor allem für die Reinigung von grossen Biomolekülen wie etwa Viren (virale Vektoren und Impfstoffe), DNA (Plasmid-DNA) und grössere Proteine (Immunglobuline G und M, pegylierte Proteine). Sie weisen einzigartige Eigenschaften in Bezug auf operative Flussraten, Adsorptionsfähigkeit und Trennung grosser Biomoleküle auf. Die Säulen werden in Forschung, Labor, Pilot- und industriellen Produktionsstufen eingesetzt und sind extrem einfach zu handhaben.
R. Milačič, D. Ajlec, T. Zuliani, D. Žigon, J. Ščančar
Talanta 101 (2012) 203-210
In human milk zinc (Zn) is bound to proteins and low molecular mass (LMM) ligands. Numerous investigations demonstrated that Zn bioavailability in human milk is for infant much higher than in cow's milk. It was presumed that in the LMM human milk fraction highly bioavailable Zn-citrate prevails. However, literature data are controversial regarding the amount of Zn-citrate in human milk since analytical procedures reported were not quantitative. So, complex investigation was carried out to develop analytical method for quantitative determination of this biologically important molecule. Studies were performed within the pH range 5–7 by the use of synthetic solutions of Zn-citrate prepared in HEPES, MOPS and MES buffers. Zn-citrate was separated on weak anion-exchange convective interaction media (CIM) diethylaminoethyl (DEAE) monolithic chromatographic column using NH4NO3 as an eluent. Separated Zn species were determined by flame atomic absorption spectrometry (FAAS) or inductively coupled plasma mass spectrometry (ICP-MS). Quantitative separation of Zn-citrate complexes ([Zn(Cit)]- and [Zn(Cit)2]4-; column recoveries 94–102%) and good repeatability and reproducibility of results with relative standard deviation (RSD±3.0%) were obtained. In fractions under the chromatographic peaks Zn-binding ligand was identified by electrospray ionization tandem mass spectrometry (ESI-MS-MS). Limits of detection (LOD) for determination of Zn-citrate species by CIM DEAE-FAAS and CIM DEAE-ICP-MS were 0.01 μg Zn mL-1 and 0.0005 μg Zn mL-1, respectively. Both techniques were sensitive enough for quantification of Zn-citrate in human milk. Results demonstrated that about 23% of total Zn was present in the LMM milk fraction and that LMM-Zn corresponded to Zn-citrate. The developed speciation method represents a reliable analytical tool for investigation of the percentage and the amount of Zn-citrate in human milk.
T. Koho, T. Mantyla, P. Laurinmaki, L. Huhti, S. J. Butcher, T. Vesikari, M. S. Kulomaa, V. P. Hytonen
Journal of Virological Methods 181 (2012) 6-11
Recombinant expression of the norovirus capsid protein VP1 leads to self-assembly of non-infectious virus-like particles (VLPs), which are recognized as promising vaccine candidates against norovirus infections. To overcome the scalability issues connected to the ultracentrifugation-based purification strategies used in previous studies, an anion exchange-based purification method for norovirus VLPs was developed in this study. The method consists of precipitation by polyethylene glycol (PEG) and a single anion exchange chromatography step for purifying baculovirus-expressed GII.4 norovirus VLPs, which can be performed within one day. High product purity was obtained using chromatography. The purified material also contained fully assembled monodispersed VLPs, which were recognized by human sera containing polyclonal antibodies against norovirus GII.4.
M. Rupar, M. Ravnikar, M. Tušek-Žnidarič, P. Kramberger, L. Glais, I. Gutiérrez-Aguirre
Journal of Chromatography A, 1272 (2013) 33-40(2013) 33-40
Obtaining pure virus suspensions is an essential step in many applications, such as vaccine production, antibody production, sample preparation for procedures requiring enrichment in viruses and other in vitro characterizations. Purification procedures usually consist of complex, long lasting and tedious protocols involving several ultracentrifugation steps. Such complexity is particularly evident in the case of plant viruses, where the virus needs to be isolated from the complex plant tissue matrix. Convective Interaction Media (CIM) monoliths are chromatographic supports that have been successfully utilized for the purification of large bio-molecules such as viruses, virus like particles and plasmids from various matrixes. In this study a CIM monolith based procedure was developed for the fast purification from plant tissue of the filamentous Potato virus Y (PVY) (virion size, 740 nm × 11 nm), which is one of the most important plant viruses causing great economical losses in potato production. Different mobile phases, chemistries and sample preparation strategies were tested. The presence of the virus in the chromatographic fraction was monitored with viral RNA quantification (RT-qPCR), viral protein purity estimation (SDS-PAGE) and viral particle integrity observation (transmission electron microscopy). The optimized procedure involves initial clarification steps, followed by chromatography using CIM quaternary amine (QA) monolithic disk column. In comparison to classical purification procedure involving ultracentrifugation through sucrose and caesium chloride, the developed CIM-QA purification achieved comparable yield, concentration and purity. Plant nucleic acids were successfully removed. Purification showed good reproducibility and moreover it reduced the purification time from four working days required for classic purification to a day and a half. This is the first study where a filamentous virus was purified using CIM monolithic supports. The advantages of this new purification procedure make it an attractive method in serological diagnostic tool production, which requires purified viruses for the immunization step. Moreover, the outcome of this study could serve as starting point for the improvement of the purification methods of other important filamentous viruses.
Call
Send SMS
Add to Skype
You'll need Skype CreditFree via Skype
M. M. Segura, M. Puig, M. Monfar, M. Chillon
HUMAN GENE THERAPY METHODS 23:182–197 (June 2012)
Canine adenovirus vectors (CAV2) are currently being evaluated for gene therapy, oncolytic virotherapy, and as vectors for recombinant vaccines. Despite the need for increasing volumes of purified CAV2 preparations for preclinical and clinical testing, their purification still relies on the use of conventional, scale-limited CsCl ul- tracentrifugation techniques. A complete downstream processing strategy for CAV2 vectors based on membrane filtration and chromatography is reported here. Microfiltration and ultra/diafiltration are selected for clarifi- cation and concentration of crude viral stocks containing both intracellular and extracellular CAV2 particles. A DNase digestion step is introduced between ultrafiltration and diafiltration operations. At these early stages, concentration of vector stocks with good recovery of viral particles (above 80%) and removal of a substantial amount of protein and nucleic acid contaminants is achieved. The ability of various chromatography techniques to isolate CAV2 particles was evaluated. Hydrophobic interaction chromatography using a Fractogel propyl tentacle resin was selected as a first chromatography step, because it allows removal of the bulk of contami- nating proteins with high CAV2 yields (88%). An anion-exchange chromatography step using monolithic supports is further introduced to remove the remaining contaminants with good recovery of CAV2 particles (58– 69%). The main CAV2 viral structural components are visualized in purified preparations by electrophoresis analyses. Purified vector stocks contained intact icosahedral viral particles, low contamination with empty viral capsids (10%), and an acceptable total-to-infectious particle ratio (below 30). The downstream processing strategy that was developed allows preparation of large volumes of high-quality CAV2 stocks.