Clostridium difficile infections (CDI) are a leading cause of nosocomial diarrhea in the developed world. The main virulence factors of the bacterium are the large clostridial toxins (LCTs), TcdA and ...TcdB, which are largely responsible for the symptoms of the disease. Recent outbreaks of CDI have been associated with the emergence of hypervirulent strains, such as NAP1/BI/027, many strains of which also produce a third toxin, binary toxin (CDTa and CDTb). These hypervirulent strains have been associated with increased morbidity and higher mortality. Here we present pre-clinical data describing a novel tetravalent vaccine composed of attenuated forms of TcdA, TcdB and binary toxin components CDTa and CDTb. We demonstrate, using the Syrian golden hamster model of CDI, that the inclusion of binary toxin components CDTa and CDTb significantly improves the efficacy of the vaccine against challenge with NAP1 strains in comparison to vaccines containing only TcdA and TcdB antigens, while providing comparable efficacy against challenge with the prototypic, non-epidemic strain VPI10463. This combination vaccine elicits high neutralizing antibody titers against TcdA, TcdB and binary toxin in both hamsters and rhesus macaques. Finally we present data that binary toxin alone can act as a virulence factor in animal models. Taken together, these data strongly support the inclusion of binary toxin in a vaccine against CDI to provide enhanced protection from epidemic strains of C. difficile.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
•Membrane chromatography for large viral particles purification.•Multi-membrane chromatography through periodic counter current method.•Continuous manufacturing for viral vaccines.
Continuous ...multi-column chromatography (CMCC) has been successfully implemented to address biopharmaceutical biomolecule instability, to improve process efficiency, and to reduce facility footprint and capital cost. This paper explores the implementation of a continuous multi-membrane chromatography (CMMC) process, using four membrane units, for a large viral particle in just few weeks. CMMC improves the efficiency of the chromatography step by enabling higher loads with smaller membranes for multiple cycles of column use and enables steady-state continuous bioprocessing. The separation performance of CMMC was compared to a conventional batch chromatographic capture step used at full manufacturing scale. The product step yield was 80% using CMMC versus 65% in batch mode while increasing slightly the relative purity. Furthermore, the total amount of membrane area required for the CMMC approach was approximately 10% of the area needed for batch operation, while realizing similar processing times. Since CMMC uses smaller membrane sizes, it can take advantage of the high flow rates achievable for membrane chromatography that are not typically possible at larger membrane scales due to skid flow rate limitations. As such, CMMC offers the potential for more efficient and cost-effective purification trains.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Sterile filtration is used to remove microorganisms in the processing of most recombinant proteins, but there are significant challenges in applying this technology to large biotherapeutics like ...Live-Attenuated Vaccines (LAV), lipid-nanoparticles, and gene therapy agents. Previous studies have reported highly variable fouling and product retention behavior of different sterile filters in these applications, but there has been no clear understanding of the origin of these differences. This study used fluorescently-labeled 200, 300, and 400 nm polystyrene latex spheres as model particle challenges for eight commercially available, 0.2/0.22 μm pore size sterile filters, all of which were characterized using mercury intrusion porosimetry, bubble point measurements, and scanning electron microscopy. All filters showed significant fouling, causing an increase in particle retention at high throughput. The maximum transmission of the 300 nm particles varied from only 0.01 for the highly asymmetric Millipore Express® to 0.9 for the dual-layer Sartobran® P. The transmission was well correlated with the ratio of the particle diameter to the maximum pore size (determined by bubble point), with even better agreement obtained using the mean pore size evaluated from mercury intrusion porosimetry. These results provide important insights into the effects of pore size and structure on the retention characteristics of sterile filter as well as guidance on how to select the best sterile filters for processing vaccines and viruses that are >100 nm in size.
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•Nanoparticle retention evaluated for range of commercial 0.2 μm sterile filters.•Transmission of 300 nm particles varied between 1% and >90%.•Filters characterized by bubble point and mercury porometry.•Differences in transmission directly related to small differences in pore size.•Particle fouling resulted in decrease in transmission at high throughput.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Prefilters are widely used to enhance the performance of normal flow filtration steps in bioprocessing; however little is known about the potential benefits of prefiltration in the sterile filtration ...of viral vaccines and other large particle biotherapeutics. Sterile filtration experiments were performed with a live-attenuated viral vaccine and model nanoparticle suspension, both of which have a size distribution of 100 – 400 nm. The results demonstrated that the outstanding performance of the Sartobran P sterile filter was directly due to the effective prefiltration provided by the 0.45 μm prefilter in this dual layer filter. The 0.45 μm prefilter dramatically improved particle transmission and capacity for other 0.2 μm sterile filters. The key foulants were removed primarily on the basis of size, which was confirmed using a nanoparticle tracking analyzer. Larger pore size prefilters were found to be much less effective in protecting the 0.2 μm sterile filter. The support structure of asymmetric sterile filters also provided significant prefiltration; however, some of these asymmetric membranes had size-selective pores that were too small to provide significant transmission of the viral particles. These results provided important insights into the role of the prefilter layer and membrane pore structure in enhancing the performance of the sterile filtration step for the processing of viruses and other large particle biotherapeutics.
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•Sterile filtration performed with Live Attenuated Viral vaccine (LAV).•Role of prefilter in Sartobran P dual-layer filter quantified.•Prefilter improves capacity and transmission by removing large particles.•Support structure of asymmetric membrane also provides effective prefiltration.•Combination of prefilter and sterile filter pore size determines performance.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Nanoparticle hydrophobicity is a key factor controlling the stability, adhesion, and transport of nanoparticle suspensions. Although a number of approaches have been presented for evaluating ...nanoparticle hydrophobicity, these methods are difficult to apply to larger nanoparticles and viruses (>100 nm in size) that are of increasing importance in drug delivery and gene therapy. This study investigated the use of a new analytical hydrophobic interaction chromatography method employing a 5.0 μm pore size polyvinylidene fluoride membrane as the stationary-phase in membrane hydrophobic interaction chromatography (MHIC). Experimental data obtained using a series of model proteins were in good agreement with literature values for the hydrophobicity (both experimental and computational). MHIC was then used to evaluate the hydrophobicity of a variety of nanoparticles, including a live attenuated viral vaccine, both in water and in the presence of different surfactants. This new method can be implemented on any liquid chromatography system, run times are typically <20 min, and the experiments avoid the use of organic solvents that could alter the structure of many biological nanoparticles.
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IJS, KILJ, NUK, PNG, UL, UM
There is growing interest in the development of new vaccines based on live‐attenuated viruses (LAVs) and virus‐like particles. The large size of these vaccines, typically 100–400 nm, significantly ...complicates the use of sterile filtration. The objectives of this study are to examine the performance of several commercial sterile filters for filtration of a cytomegalovirus vaccine candidate (referred to as the LAV) and to develop and evaluate the use of a model nanoparticle suspension to perform a more quantitative assessment. Data obtained with a mixture of 200‐ and 300‐nm fluorescent particles provided yield and pressure profiles that captured the behavior of the viral vaccine. This included the excellent performance of the Sartorius Sartobran P filter, which provided greater than 80% yield of both the vaccine and model particles even though the average particle size was more than 250 nm. The particle yield for the Sartobran P was independent of filtrate flux above 200 L/m2/h, but increased with increasing particle concentration, varying from less than 10% at concentrations around 107 particles/ml to more than 80% at concentrations above 1010 particles/ml due to saturation of particle capture/binding sites within the filter. These results provide important insights into the factors controlling transmission and fouling during sterile filtration of large vaccine products.
The authors developed a model nanoparticle suspension that mimics the filtration behavior of a live attenuated virus (LAV) vaccine during sterile filtration. Data were obtained for the effect of key process parameters on yield and capacity. The low yield observed at low feed concentrations was due to saturation of binding sites within the Sartobran P membrane.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
•Capillary western blotting is used to characterize glycoproteins in HCMV vaccine.•Triplet gH peaks in non-reduced western: pentameric gH, trimeric gH, monomeric gH.•Correlation between quantitative ...western with ELISA in measuring pentamer gH complex.
Human cytomegalovirus (HCMV) is currently a major cause of congenital disease in newborns and organ failure in transplant recipients. Despite decades of efforts, an effective vaccine against HCMV has yet to be developed. However, the discovery of pentameric gH complex on viral surface which contains potent neutralizing epitopes may help enable development of an effective vaccine. In our company ongoing Phase II clinical trial of whole-live virus HCMV vaccine (V160), the pentameric gH complex has been restored on the surface of live attenuated AD169 virus strain. The reconstructed HCMV virus contains a variety of surface glycoproteins including pentameric gH/gL/gUL128-131 complex, trimeric gH/gL/gO complex, gB glycoprotein, and gM/gN heterodimer complex. To further characterize this virus and enable the monitoring of multiple viral antigens during vaccine process development an effective and efficient analytical strategy was required to detect and quantify several viral surface proteins. In this paper, we present an innovative approach based on capillary western blot technology that allows fast and accurate quantitation of pentameric gH/gL/gUL128-131 complex, trimeric gH/gL/gO complex, and gB glycoprotein. This method is suitable for analyzing target proteins in multiple sample types including supernatants from infected cell culture, purification intermediates, concentration bulk, and the final vaccine product. In addition, the capillary western blot-based technology identified a previously unknown biochemical profile present in some HCMV viruses: triplet gH peaks of viral surface proteins in non-reducing environment, which could potentially present a new strategy for specificity and identity testing.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Live virus vaccine (LVV) purification, employing chromatography, can be challenged by low binding capacities and elution yields. Alternatively, processes relying solely on enzymatic digestion steps ...and size-based membrane separations can be limited by suboptimal reduction of process related impurities and poorly scalable unit operations. Here, we demonstrate that the combination of flowthrough mode chromatography and an ultrafiltration/diafiltration (UF/DF) unit operation delivers a purification process for two different LVV candidates, V590 and Measles, expressed in adherent Vero cells. For V590, chromatography with mixed mode cation exchange resins returned final product yields of ∼50% and logarithmic reduction values (LRVs) of 1.7->3.4 and 2.5-3.0 for host cell DNA (hcDNA) and host cell proteins (HCPs), respectively. For Measles, chromatography with mixed mode anion exchange resins returned final product yields of ∼50% and LRVs of 1.6 and 2.2 for hcDNA and HCPs, respectively. For both V590 and Measles processing, the employed resins cleared a key HCP, fibronectin, which could foul the UF/DF unit operation, and thusly enabling it to further reduce HCPs and to formulate the final LVV products. This integrated purification process utilizes the complementary action of the two unit operations and its applicability across LVVs supports its consideration for their processing.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Targeting Clostridium difficile infection is challenging because treatment options are limited, and high recurrence rates are common. One reason for this is that hypervirulent C. difficile strains ...often have a binary toxin termed the C. difficile toxin, in addition to the enterotoxins TsdA and TsdB. The C. difficile toxin has an enzymatic component, termed CDTa, and a pore-forming or delivery subunit termed CDTb. CDTb was characterized here using a combination of single-particle cryoelectron microscopy, X-ray crystallography, NMR, and other biophysical methods. In the absence of CDTa, 2 di-heptamer structures for activated CDTb (1.0 MDa) were solved at atomic resolution, including a symmetric (SymCDTb; 3.14 Å) and an asymmetric form (AsymCDTb; 2.84 Å). Roles played by 2 receptor-binding domains of activated CDTb were of particular interest since the receptor-binding domain 1 lacks sequence homology to any other known toxin, and the receptor-binding domain 2 is completely absent in other well-studied heptameric toxins (i.e., anthrax). For AsymCDTb, a Ca2+ binding site was discovered in the first receptor-binding domain that is important for its stability, and the second receptor-binding domain was found to be critical for host cell toxicity and the di-heptamer fold for both forms of activated CDTb. Together, these studies represent a starting point for developing structure-based drug-design strategies to target the most severe strains of C. difficile.
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BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
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