sIPV process development for costs reduction

Development of an animal component free production process for Sabin inactivated polio vaccine

Inactivated polio vaccine production using attenuated Sabin strains (sIPV) instead of wild type polio viruses (cIPV) is an initiative encouraged by the World Health Organization. This use of attenuated viruses is preferred as it reduces risks related to potential outbreaks during IPV production. Previously, an sIPV production process was set up based on the cIPV production process. Optimizing this process while using only animal component free (ACF) substances allows reduction of operational costs and mitigates risks of adverse effects related with animal derived compounds. Here, development of a process for production of sIPV using only ACF compounds, is described.

The upstream process required a change in cell growth medium from serum-containing medium to ACF medium, while virus production media remained the same as the already used M199 medium was free of animal components. In the downstream process multiple modifications in existing unit operations were made including addition of a diafiltration step prior to inactivation. After optimizing each unit operation, robustness of the whole process was demonstrated using design of experiments (DoE) methodology. By using DoE we were able to vary different process parameters across unit operations to assess the impact on our quality attributes. The developed process was robust as the observed variation for quality attributes due to differences in process parameters remained within specification.

The resulting pilot process showed not only to be robust, but also to have a considerable higher product yield when compared to the serum containing sIPV process. Product yields are now comparable to the cIPV process based on using wild type polio viruses. Moreover, the potency of the produced vaccine was comparable that of cIPV vaccine. The developed ACF sIPV process can be transferred to vaccine manufacturers at the end-of pre-clinical development phase, at lab- or pilot scale, before production of clinical trial material.

VaxArray immunoassay for the multiplexed quantification of poliovirus D-antigen

Next generation poliovirus vaccines are critical to reaching global poliovirus eradication goals. Recent efforts have focused on creating inactivated vaccines using attenuated Sabin strains that maintain patient safety benefits and immunogenicity of conventional inactivated vaccines while increasing manufacturing safety and lowering production costs, and on developing novel oral vaccines using modified Sabin strains that provide critical mucosal immunity but are further attenuated to minimize risk of reversion to neurovirulence. In addition, there is a push to improve the analytical tools for poliovirus vaccine characterization. Conventional and Sabin inactivated poliovirus vaccines typically rely on standard plate-based ELISA as in vitro D-antigen potency assays in combination with WHO international standards as calibrants. While widely utilized, the current D-antigen ELISA assays have a long time to result (up to 72 h), can suffer from lab-to-lab inconsistency due to non-standardized protocols and reagents, and are inherently singleplex. For D-antigen quantitation, we have developed the VaxArray Polio Assay Kit, a multiplexed, microarray-based immunoassay that uses poliovirus-specific human monoclonal antibodies currently under consideration as standardized reagents for characterizing inactivated Sabin and Salk vaccines. The VaxArray assay can simultaneously quantify all 3 poliovirus serotypes with a time to result of less than 3 h. Here we demonstrate that the assay has limits of quantification suitable for both bioprocess samples and final vaccines, excellent reproducibility and precision, and improved accuracy over an analogous plate-based ELISA. The assay is suitable for adjuvanted combination vaccines, as common vaccine additives and crude matrices do not interfere with quantification, and is intended as a high throughput, standardized quantitation tool to aid inactivated poliovirus vaccine manufacturers in streamlining vaccine development and manufacturing, aiding the global polio eradication effort.

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Multiplexed D-antigen immunoassay for all 3 poliovirus serotypes

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Has <3 h time to result and compares well to 3-day plate-based ELISA

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Assay shows high specificity and is reactive to sIPV, cIPV, and OPV

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Applicable to in-process samples, final IPV and combination vaccine formulations

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High accuracy and precision for both sIPV and cIPV over multiple users and days

Physicochemical Characterization of Sabin Inactivated Poliovirus Vaccine for Process Development

Upscaling the production capacity of inactivated poliovirus vaccines (IPV) is urgently needed to eradicate polio worldwide. For the development of a robust manufacturing process for IPV, the impact of stresses on the properties of the poliovirus during manufacturing needs to be carefully evaluated. In this study, the physicochemical properties of Sabin poliovirus after low pH exposure were analyzed by asymmetrical flow field-flow fractionation coupled to multi-angle laser light scattering (AF4-MALS), sedimentation velocity analytical ultracentrifugation (SV-AUC), transmission electron microscopy (TEM), dynamic light scattering (DLS) and surface plasmon resonance (SPR). Low pH stress caused structural changes and aggregation of inactivated poliovirus virions, whereas degraded virion particles would not revert to native virions even after neutralization. Importantly, a complete loss of the D-antigenicity of IPV by low pH stress, followed by neutralization, was observed in SPR. These results suggest that the exposure of poliovirus particle to low pH stress would induce irreversible denaturation and aggregation of virus particles and lead to the loss of D-antigenicity; thus, low pH stress during the manufacturing of poliovirus vaccine should be minimized. The analytical methods above can be efficiently utilized in the development of high-integrity manufacturing processes and high-quality vaccines.

Universal ELISA for quantification of D-antigen in inactivated poliovirus vaccines

To address the biosafety and biosecurity concerns related to the manufacture of inactivated polio vaccine (IPV), several manufacturers started producing it from attenuated Sabin strains. Slight immunological differences between wild and attenuated strains create a challenge for testing IPV potency, which is defined as the content of protective D-antigen determined in an ELISA test. Some ELISA reagents selected for testing conventional IPV made from wild strains (cIPV) may not be suitable for testing Sabin IPV (sIPV). This paper describes an ELISA procedure using human monoclonal antibodies selected to capture equally well both wild and attenuated strains of poliovirus. A unique monoclonal antibody neutralizing all three serotypes of poliovirus was used as the detection antibody. The method was shown to detect only D-antigen of both conventional and Sabin IPV and to be strictly serotype-specific. The method is highly sensitive and robust and produces linear results in a wide range of concentrations. We have also found that reference standards used for measuring potency of cIPV and sIPV must be made from respective vaccines. This makes it impossible to cross-calibrate potency reagents made from heterologous vaccine and requires the establishment of a new unit to measure potency of sIPV that is different from conventional D-antigen unit.

Accelerating bioprocess development by analysis of all available data: A USP case study

Bioprocess development generates extensive datasets from different unit operations and sources (e.g. time series, quality measurements). The development of such processes can be accelerated by evaluating all data generated during the experimental design. This can only be achieved by having a clearly defined data logging and analysis strategy. The latter is described in this manuscript. It consists in a combination of a feature based approach along with principal component analysis and partial least square regression. Application of this combined strategy is illustrated by applying it in an upstream processing (USP) case study. Data from the development and optimization of an animal component free USP of Sabin inactivated poliovirus vaccine (sIPV) was evaluated. During process development, 26 bioreactor runs at scales ranging from 2.3 to 16 L were performed. Several operational parameters were varied, and data was routinely analyzed following a design of experiments (DoE) methodology. With the strategy described here, it became possible to scrutinize all data from the 26 runs in a single data study. This included the DoE response parameters, all data generated by the bioreactor control systems, all offline data, and its derived calculations. This resulted in a more detailed, reliable and exact view on the most important parameters affecting bioreactor performance. In this case study, the strategy was applied for the analysis of previously produced data. Further development will use this data analysis methodology for continuous enhancing and accelerating process development, intensified DoE and integrated process modelling.

Sailing in Uncharted Waters: Carefully Navigating the Polio Endgame

In a Perspective linked to the research article by Isobel Blake and colleagues, Elizabeth Miller and T. Jacob John discuss the path towards global polio eradication and the challenges, strategies, and necessary precautions around oral polio vaccine cessation.

Cold-Adapted Viral Attenuation (CAVA): Highly Temperature Sensitive Polioviruses as Novel Vaccine Strains for a Next Generation Inactivated Poliovirus Vaccine

The poliovirus vaccine field is moving towards novel vaccination strategies. Withdrawal of the Oral Poliovirus Vaccine and implementation of the conventional Inactivated Poliovirus Vaccine (cIPV) is imminent. Moreover, replacement of the virulent poliovirus strains currently used for cIPV with attenuated strains is preferred. We generated Cold-Adapted Viral Attenuation (CAVA) poliovirus strains by serial passage at low temperature and subsequent genetic engineering, which contain the capsid sequences of cIPV strains combined with a set of mutations identified during cold-adaptation. These viruses displayed a highly temperature sensitive phenotype with no signs of productive infection at 37°C as visualized by electron microscopy. Furthermore, decreases in infectious titers, viral RNA, and protein levels were measured during infection at 37°C, suggesting a block in the viral replication cycle at RNA replication, protein translation, or earlier. However, at 30°C, they could be propagated to high titers (9.4-9.9 Log10TCID50/ml) on the PER.C6 cell culture platform. We identified 14 mutations in the IRES and non-structural regions, which in combination induced the temperature sensitive phenotype, also when transferred to the genomes of other wild-type and attenuated polioviruses. The temperature sensitivity translated to complete absence of neurovirulence in CD155 transgenic mice. Attenuation was also confirmed after extended in vitro passage at small scale using conditions (MOI, cell density, temperature) anticipated for vaccine production. The inability of CAVA strains to replicate at 37°C makes reversion to a neurovirulent phenotype in vivo highly unlikely, therefore, these strains can be considered safe for the manufacture of IPV. The CAVA strains were immunogenic in the Wistar rat potency model for cIPV, inducing high neutralizing antibody titers in a dose-dependent manner in response to D-antigen doses used for cIPV. In combination with the highly productive PER.C6 cell culture platform, the stably attenuated CAVA strains may serve as an attractive low-cost and (bio)safe option for the production of a novel next generation IPV.