In vitro infectivity of oncolytic Newcastle Disease Virus: Correlation between plaque and fluorescent focus assays

Vaccine process technology-A decade of progress

In the past decade, new approaches to the discovery and development of vaccines have transformed the field. Advances during the COVID-19 pandemic allowed the production of billions of vaccine doses per year using novel platforms such as messenger RNA and viral vectors. Improvements in the analytical toolbox, equipment, and bioprocess technology have made it possible to achieve both unprecedented speed in vaccine development and scale of vaccine manufacturing. Macromolecular structure-function characterization technologies, combined with improved modeling and data analysis, enable quantitative evaluation of vaccine formulations at single-particle resolution and guided design of vaccine drug substances and drug products. These advances play a major role in precise assessment of critical quality attributes of vaccines delivered by newer platforms. Innovations in label-free and immunoassay technologies aid in the characterization of antigenic sites and the development of robust in vitro potency assays. These methods, along with molecular techniques such as next-generation sequencing, will accelerate characterization and release of vaccines delivered by all platforms. Process analytical technologies for real-time monitoring and optimization of process steps enable the implementation of quality-by-design principles and faster release of vaccine products. In the next decade, the field of vaccine discovery and development will continue to advance, bringing together new technologies, methods, and platforms to improve human health.

Purification of a recombinant oncolytic virus from clarified cell culture media by anion exchange monolith chromatography

The use of viral vectors for vaccine, gene therapy, and oncolytic virotherapy applications has received increased attention in recent years. Large-scale purification of viral vector-based biotherapeutics still presents a significant technical challenge. Chromatography is the primary tool for the purification of biomolecules in the biotechnology industry; however, the majority of chromatography resins currently available have been designed for the purification of proteins. In contrast, convective interaction media monoliths are chromatographic supports that have been designed and successfully utilized for the purification of large biomolecules, including viruses, viruslike particles, and plasmids. We present a case study on the development of a purification method for recombinant Newcastle disease virus directly from clarified cell culture media using strong anion exchange monolith technology (CIMmultus QA, BIA Separations). Resin screening studies showed at least 10 times higher dynamic binding capacity of CIMmultus QA compared to traditional anion exchange chromatography resins. Design of experiments was used to demonstrate a robust operating window for the purification of recombinant virus directly from clarified cell culture without any further pH or conductivity adjustment of the load material. The capture step was successfully scaled up from 1 mL CIMmultus QA columns to the 8 L column scale and achieved a greater than 30-fold reduction in process volume. Compared to the load material, total host cell proteins were reduced by more than 76%, and residual host cell DNA by more than 57% in the elution pool, respectively. Direct loading of clarified cell culture onto a high-capacity monolith stationary phase makes convective flow chromatography an attractive alternative to centrifugation or TFF-based virus purification procedures.

Considerations for bioanalytical characterization and batch release of COVID-19 vaccines

The COVID-19 pandemic has prompted hundreds of laboratories around the world to employ traditional as well as novel technologies to develop vaccines against SARS-CoV-2. The hallmarks of a successful vaccine are safety and efficacy. Analytical evaluation methods, that can ensure the high quality of the products and that can be executed speedily, must be in place as an integral component of Chemistry, Manufacturing, and Control (CMC). These methods or assays are developed to quantitatively test for critical quality attributes (CQAs) of a vaccine product. While clinical (human) efficacy of a vaccine can never be predicted from pre-clinical evaluation of CQA, precise and accurate measurements of antigen content and a relevant biological activity (termed “potency”) elicited by the antigen allow selection of potentially safe and immunogenic doses for entry into clinical trials. All available vaccine technology platforms, novel and traditional, are being utilized by different developers to produce vaccines against SARS-CoV-2. It took less than a year from the publication of SARS-CoV-2 gene sequence to Emergency Use Authorization (EUA) of the first vaccine, setting a record for speed in the history of vaccine development. The largest ever global demand for vaccines has prompted some vaccine developers to enter multiple manufacturing partnerships in different countries in addition to implementing unprecedented scale-up plans. Quantitative, robust, and rapid analytical testing for CQA of a product is essential in ensuring smooth technology transfer between partners and allowing analytical bridging between vaccine batches used in different clinical phases leading up to regulatory approvals and commercialization. We discuss here opportunities to improve the speed and quality of the critical batch release and characterization assays.

Cytokines in oncolytic virotherapy

Tumors represent a hostile environment for the effector cells of cancer immunosurveillance. Immunosuppressive receptors and soluble or membrane-bound ligands are abundantly exposed and released by malignant entities and their stromal accomplices. As a consequence, executioners of antitumor immunity inefficiently navigate across cancer tissues and fail to eliminate malignant targets. By inducing immunogenic cancer cell death, oncolytic viruses profoundly reshape the tumor microenvironment. They trigger the local spread of danger signals and tumor-associated (as well as viral) antigens, thus attracting antigen-presenting cells, promoting the activation and expansion of lymphocytic populations, facilitating their infiltration in the tumor bed, and reinvigorating cytotoxic immune activity. The present review recapitulates key chemokines, growth factors and other cytokines that orchestrate this ballet of antitumoral leukocytes upon oncolytic virotherapy.

Ionic Strength-Dependent, Reversible Pleomorphism of Recombinant Newcastle Disease Virus

A genetically modified, recombinant form of Newcastle disease virus (rNDV) undergoes ionic strength-dependent changes in morphology, as observed by cryo-electron microscopy (cEM). In hypotonic solutions with ionic strengths ranging from < 0.01 to 0.02 M, rNDV virions are spherical or predominantly spherical. In isotonic and hypertonic solutions, rNDV displays pleomorphism and contains a mixed population of spherical and elongated particles, indicating that a change from spherical to elongated shape is induced with increasing salt concentration. This ionic strength-dependent transition is largely reversible, as determined by cEM. Concomitantly, we measured infectious titers of these same rNDV samples at different ionic strengths using a fluorescent focus assay (FFA). The infectivity of oncolytic rNDV was found to be independent of ionic strength, ranging from 0.01 M to approximately 0.5 M. These structural and functional observations, in combination, suggest that infectivity (and, by inference, oncolytic activity) of rNDV virions is fully maintained in their pleomorphic forms.IMPORTANCE Oncolytic viruses are being developed for cancer therapy, as they selectively target, infect, and kill cancer cells. NDV is particularly attractive because while it is pathogenic to avians (e.g., chickens), it does not cause significant viremia in humans. We have developed a genetically modified recombinant NDV (rNDV) that has much reduced pathogenicity in chickens but is highly oncolytic. The morphology of rNDV transitions from spherical at very low salt concentrations to a heterogeneous population of spherical and elongated virions in isotonic (physiologic salt concentration) and hypertonic solutions. The infectivity (cell-killing activity by infecting cells) of rNDV is unaltered by changes in salt concentration despite morphological changes. These observations are significant for purification and formulation of rNDV, as exposure to different salt concentrations may be needed. Importantly, at physiological salt concentration, relevant to clinical testing, infectivity and, therefore, oncolytic activity will not be compromised despite morphological heterogeneity.

Upstream and Downstream Processes for Viral Nanoplexes as Vaccines

The increasing medical interest in viral nanoplexes, such as viruses or virus-like particles used for vaccines, gene therapy products, or oncolytic agents, raises the need for fast and efficient production processes. In general, these processes comprise upstream and downstream processing. For the upstream process, efficiency is mainly characterized by robustly achieving high titer yields, while reducing process times and costs with regard to the cell culture medium, the host cell selection, and the applied process conditions. The downstream part, on the other hand, should effectively remove process-related contaminants, such as host cells/cell debris as well as host cell DNA and proteins, while maintaining product stability and reducing product losses. This chapter outlines a combination of process steps to successfully produce virus particles in the controlled environment of a stirred tank bioreactor, combined with a platform-based purification approach using filtration-based clarification and steric exclusion chromatography. Additionally, suggestions for off-line analytics in terms of virus characterization and quantification as well as for contaminant estimation are provided.

Recent advances in oncolytic virus-based cancer therapy

Administration of oncolytic viruses (OVs) is an emerging anticancer strategy that exploits the lytic nature of viral replication to enhance the killing of malignant cells. OVs can be used as tools to directly induce cancer cell death and to trigger local and/or systemic immune responses to metastatic cancer in vivo. The effectiveness of OV therapy was initially highlighted by the clinical use of the genetically modified herpes virus, talimogene laherparepvec, for melanoma therapy. A number of OVs are now being evaluated as potential treatments for cancer in clinical trials. In spite of being engineered to specifically target tumor cells, the safety and off-target effects of OV therapy are a concern. The potential safety concerns of OVs are highlighted by current clinical trial criteria, which exclude individuals harbouring other viral infections and people who are immunocompromised. Despite the potential for adverse effects, clinical trials to date revealed relatively minimal adverse immune-related effects, such as fever. With advances in our understanding of virus replication cycles, several novel OVs have emerged. Reverse genetic systems have facilitated the insertion of anticancer genes into a range of OVs to further enhance their tumor-killing capacity. In this review, we highlight the recent advances in OV therapy for a range of human cancers in in vitro and in in vivo animal studies. We further discuss the future of OVs as a therapeutic strategy for a range of life-threatening cancers.