Concepts for the Production of Viruses and Viral Vectors in Cell Cultures

The industrial-scale manufacturing of viruses or virus-like particles in cell culture is necessary for gene therapy and the treatment of cancer with oncolytic viruses. Complex multistep processes are required in both cases, but the low virus titers in batch cultures and the temperature sensitivity of the virus particles limit the production scale. To meet commercial and regulatory requirements, each process must be scalable and reproducible and must yield high virus titers. These requirements are met by establishing a cell culture process that matches the properties of the virus/host-cell system and by using serum-free cell culture medium. This chapter focuses on two case studies to consider the different aspects of process design, such as the reactor configuration and operational mode: the continuous production of retroviral pseudotype vectors in a retroviral packaging cell line and the production of oncolytic measles virus vectors for cancer therapy

Dynamic oncolytic measles virus production

Oncolytic viruses can be effective weapons against cancer with few treatment options. For example the tissue culture–adapted Edmonston strains of measles virus (MV) have altered its receptor specificity and became selectively oncolytic with attenuated pathogenicity. Russel et al. showed in 2014 full remission in an advanced stage multiple myeloma patient after systemic application of genetically modified MV. In this clinical trial, the patient was treated by intravenous infusion of 1011 TCID50 (50% tissue culture infectious dose) - of an engineered MV encoding human sodium iodide symporter. Appropriate medical treatment with oncolytic viruses calls for high concentrations and absolute product purity. The main challenge in the field of viral bioprocess design is the low product stability. Although oncolytic MV production is feasible in a stirred tank bioreactor, the poor knowledge about the virus release and inactivation process hampers oncolytic MV production in industrial scale. As published by Weiss et al. already a simple transfer of the MV production process from a static cultivation system (e.g. T-Flask) into a dynamic system (e.g. STR) can dramatically reduce MV yield. As static systems are only suitable for small-scale processes, the process transfer into scalable dynamic systems is a bottleneck for a broad application of MV as cancer drugs. Beside their limited scalability, T-flasks or cell factories only allows the MV production in a batch mode. Through this process mode, the MV particles can be harvest only once and at an assumed time of harvest (TOH). In consideration of the short MV half-life of one and two hours at 37°C and 32°C respectively, the TOH is a critical point in bioprocessing. But measles viruses are known to be sensitive against the production temperature. Therefore an infection cycle adapted virus harvest with related synchronal purification is required. Virus membrane filtration represents a beneficial trade-off. Membrane-based filtration like cross flow filtration can process potentially large volumes and yielding high host cell concentration in the bioreactor. On the other hand, membrane based filtration processes are very unspecific. To remain the advantages of membrane filtration and increase the selectivity of the purification, membrane chromatography is a true alternative. Application of adsorptive membranes based on the electric interaction between charged components of the liquid phase including viruses and ionic groups immobilized on the solid membrane matrix, ion exchange membrane chromatography (IEMC) is a potentially simple and efficient method for MV concentration and purification. In present work, a continuous bioprocess concept for oncolytic MV production and purification for the use in cancer therapy will be presented

A tailor-made purification strategy for oncolytic measles viruses using membrane-based processes

Cancer patients can benefit from the Measles virus, since in the early 70s a relation between cancer remission and an infection with Measles was first mentioned (Bluming, Ziegler 1971). Further studies confirmed this oncolytic activity and therefore, the Measles virus became highly interesting for the application in cancer treatment. However, for the widespread application as a therapeutic agent several bottlenecks have to be overcome in context of quantity and quality. For one therapeutic dose of oncolytic Measles viruses (OMV) at least 1011 infectious particles are needed (one vaccination contains ~103 TCID50) (Russell et al. 2014). Besides that, the impurities, such as host cell proteins (HCP) and host cell DNA (hcDNA), must be reduced to appropriate limits set by regulatory authorities. The full recovery of OMV infectivity must also addressed. This underlines the need of a tailor-made downstream processing. After we established a high titer production process, achieving OMV titers of 1011 TCID50 mL-1 (Grein et al. 2017), we are now focused on the downstream processing of OMV. For this purpose we characterized the OMV regarding process parameters used in DSP, such as stability towards ionic strength, osmolality, agglomeration and shear stress. Based on this, a clarification step was conducted, followed by the further purification with tangential flow filtration (TFF). By using polyether sulfone flat sheet membranes in concentration mode, we were able to recover the infectious virus and lowered the impurities by ~70% for hcDNA and ~80% for protein content. In the next purification step, we applied a discontinuous diafiltration and could deplete the impurities by ~95% in total. These results showed that TFF is an appropriate tool for the purification and formulation of OMV. References Bluming, Avrum Z.; Ziegler, John L. (1971): Regression of Burkitt\u27s Lymphoma in association with Measles infection. In The Lancet 298 (7715), pp. 105–106. DOI: 10.1016/S0140-6736(71)92086-1. Grein, Tanja A.; Schwebel, Felix; Kress, Marco; Loewe, Daniel; Dieken, Hauke; Salzig, Denise et al. (2017): Screening different host cell lines for the dynamic production of measles virus. In Biotechnology progress. DOI: 10.1002/btpr.2432. Russell, Stephen J.; Federspiel, Mark J.; Peng, Kah-Whye; Tong, Caili; Dingli, David; Morice, William G. et al. (2014): Remission of disseminated cancer after systemic oncolytic virotherapy. In Mayo Clinic proceedings 89 (7), pp. 926–933. DOI: 10.1016/j.mayocp.2014.04.003

Aeration and Shear Stress Are Critical Process Parameters for the Production of Oncolytic Measles Virus

Oncolytic Measles virus is a promising candidate for cancer treatment, but clinical studies have shown that extremely high doses (up to 1011 TCID50 per dose) are required to effect a cure. Very high titers of the virus must therefore be achieved during production to ensure an adequate supply. We have previously shown that Measles virus can be produced in Vero cells growing on a Cytodex 1 microcarrier in serum-containing medium using a stirred-tank reactor (STR). However, process optimization and further process transfer or scale up requires the identification of critical process parameters, particularly because the use of STRs increases the risk of cell damage and lower product yields due to shear stress. Using a small-scale STR (0.5 L working volume) we found that Measles virus titers are sensitive to agitator-dependent shear, with shear stress ≥0.25 N m−2 reducing the titer by more than four orders of magnitude. This effect was observed in both serum-containing and serum-free medium. At this scale, virus of titers up to 1010 TCID50 mL−1 could be achieved with an average shear stress of 0.1 N m−2. We also found that the aeration method affected the virus titer. Aeration was necessary to ensure a sufficient oxygen supply to the Vero cells, and CO2 was also needed to regulate the pH of the sodium bicarbonate buffer system. Continuous gassing with air and CO2 reduced the virus titer by four orders of magnitude compared to head-space aeration. The manufacture of oncolytic Measles virus in a STR can therefore be defined as a shear-sensitive process, but high titers can nevertheless be achieved by keeping shear stress levels below 0.25 N m−2 and by avoiding extensive gassing of the medium

Antimicrobial Potential of Bacteria Associated with Marine Sea Slugs from North Sulawesi, Indonesia

Nudibranchia, marine soft-bodied organisms, developed, due to the absence of a protective shell, different strategies to protect themselves against putative predators and fouling organisms. One strategy is to use chemical weapons to distract predators, as well as pathogenic microorganisms. Hence, these gastropods take advantage of the incorporation of chemical molecules. Thereby the original source of these natural products varies; it might be the food source, de novo synthesis from the sea slug, or biosynthesis by associated bacteria. These bioactive molecules applied by the slugs can become important drug leads for future medicinal drugs. To test the potential of the associated bacteria, the latter were isolated from their hosts, brought into culture and extracts were prepared and tested for antimicrobial activities. From 49 isolated bacterial strains 35 showed antibiotic activity. The most promising extracts were chosen for further testing against relevant pathogens. In that way three strains showing activity against methicillin resistant Staphylococcus aureus and one strain with activity against enterohemorrhagic Escherichia coli, respectively, were identified. The obtained results indicate that the sea slug associated microbiome is a promising source for bacterial strains, which hold the potential for the biotechnological production of antibiotics

Complications and Short-Term Explantation Rate Following Artificial Urinary Sphincter Implantation: Results from a Large Middle European Multi-Institutional Case Series

Background/Aims/Objectives: To analyze perioperative complication and short-term explantation rates after perineal or penoscrotal single-cuff and double-cuff artificial urinary sphincter (AUS) implantation in a large middle European multi-institutional patient cohort. Methods: 467 male patients with stress urinary incontinence underwent implantation of a perineal single-cuff (n = 152), penoscrotal single-cuff (n = 99), or perinea! double-cuff (n = 216) AUS between 2010 and 2012. Postoperative complications and 6-month explantation rates were assessed. For statistical analysis, Fisher's exact test and Kruskal Wallis rank sum test, and a multiple logistic regression model were used (p < 0.05). Results: Compared to perineal single-cuff AUS, penoscrotal single-cuff implantation led to significantly increased short-term explantation rates (8.6% (perinea)) vs. 19.2% (penoscrotal), p = 0.019). The postoperative infection rate was significantly higher after double-cuff compared to single cuff implantation (6.0% (single-cuff) vs. 13.9% (double-cuff), p = 0.019). The short-term explantation rate after primary double-cuff placement was 6.5% (p = 0.543 vs. perineal single -cuff). In multivariate analysis, the penoscrotal approach (p = 0.004), intraoperative complications (p = 0.005), postoperative bleeding (p = 0.011), and perioperative infection (p < 0.001) were independent risk factors for short-term explantation. Conclusions: Providing data from a large contemporary multi-institutional patient cohortfrom high-volume and low-volume institutions, our results reflect the current standard of care in middle Europe. We indicate that the penoscrotal approach is an independent risk factor for increased short-term explantation rates. (C) 2016 S. Karger AG, Base

An antibiotic from an uncultured bacterium binds to an immutable target

Antimicrobial resistance is a leading mortality factor worldwide. Here, we report the discovery of clovibactin, an antibiotic isolated from uncultured soil bacteria. Clovibactin efficiently kills drug-resistant Gram-positive bacterial pathogens without detectable resistance. Using biochemical assays, solid-state nuclear magnetic resonance, and atomic force microscopy, we dissect its mode of action. Clovibactin blocks cell wall synthesis by targeting pyrophosphate of multiple essential peptidoglycan precursors (C 55PP, lipid II, and lipid III WTA). Clovibactin uses an unusual hydrophobic interface to tightly wrap around pyrophosphate but bypasses the variable structural elements of precursors, accounting for the lack of resistance. Selective and efficient target binding is achieved by the sequestration of precursors into supramolecular fibrils that only form on bacterial membranes that contain lipid-anchored pyrophosphate groups. This potent antibiotic holds the promise of enabling the design of improved therapeutics that kill bacterial pathogens without resistance development. </p

Coulomb dissociation of O-16 into He-4 and C-12

We measured the Coulomb dissociation of O-16 into He-4 and C-12 within the FAIR Phase-0 program at GSI Helmholtzzentrum fur Schwerionenforschung Darmstadt, Germany. From this we will extract the photon dissociation cross section O-16(alpha,gamma)C-12, which is the time reversed reaction to C-12(alpha,gamma)O-16. With this indirect method, we aim to improve on the accuracy of the experimental data at lower energies than measured so far. The expected low cross section for the Coulomb dissociation reaction and close magnetic rigidity of beam and fragments demand a high precision measurement. Hence, new detector systems were built and radical changes to the (RB)-B-3 setup were necessary to cope with the high-intensity O-16 beam. All tracking detectors were designed to let the unreacted O-16 ions pass, while detecting the C-12 and He-4

Coulomb dissociation of 16O into 4He and 12C

We measured the Coulomb dissociation of 16O into 4He and 12C at the R3B setup in a first campaign within FAIR Phase 0 at GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt. The goal was to improve the accuracy of the experimental data for the 12C(a,?)16O fusion reaction and to reach lower center-ofmass energies than measured so far. The experiment required beam intensities of 109 16O ions per second at an energy of 500 MeV/nucleon. The rare case of Coulomb breakup into 12C and 4He posed another challenge: The magnetic rigidities of the particles are so close because of the same mass-To-charge-number ratio A/Z = 2 for 16O, 12C and 4He. Hence, radical changes of the R3B setup were necessary. All detectors had slits to allow the passage of the unreacted 16O ions, while 4He and 12C would hit the detectors' active areas depending on the scattering angle and their relative energies. We developed and built detectors based on organic scintillators to track and identify the reaction products with sufficient precision

A Combined Ultrafiltration/Diafiltration Process for the Purification of Oncolytic Measles Virus

Measles virus (MV) is an important representative of a new class of cancer therapeutics known as oncolytic viruses. However, process intensification for the downstream purification of this fragile product is challenging. We previously found that a mid-range molecular weight cut-off (300 kDa) is optimal for the concentration of MV. Here, we tested continuous and discontinuous diafiltration for the purification of MV prepared in two different media to determine the influence of high and low protein loads. We found that a concentration step before diafiltration improved process economy and MV yield when using either serum-containing or serum-free medium. We also found that discontinuous diafiltration conferred a slight benefit in terms of the permeate flow, reflecting the repetitive dilution steps and the ability to break down parts of the fouling layer on the membrane. In summary, the combined ultrafiltration/diafiltration process is suitable for the purification of MV, resulting in the recovery of ~50% infectious virus particles with a total concentration factor of 8 when using 5 diavolumes of buffer