Quantification methods for viruses and virus-like particles applied in biopharmaceutical production processes

ABSTRACTABSTRACTIntroduction Effective cell-based production processes of virus particles are the foundation for the global availability of classical vaccines, gene therapeutic vectors, and viral oncolytic treatments. Their production is subject to regulatory standards ensuring the safety and efficacy of the pharmaceutical product. Process analytics must be fast and reliable to provide an efficient process development and a robust process control during production. Additionally, for the product release, the drug compound and the contaminants must be quantified by assays specified by regulatory authorities.Areas covered This review summarizes analytical methods suitable for the quantification of viruses or virus-like particles. The different techniques are grouped by the analytical question that may be addressed. Accordingly, methods focus on the infectivity of the drug component on the one hand, and on particle counting and the quantification of viral elements on the other hand. The different techniques are compared regarding their advantages, drawbacks, required assay time, and sample throughput.Expert opinion Among the technologies summarized, a tendency toward fast methods, allowing a high throughput and a wide applicability, can be foreseen. Driving forces for this progress are miniaturization and automation, and the continuous enhancement of process-relevant databases for a successful future process control.KEYWORDS: Vaccine productionviral vectorupstream processingdownstream processingchromatographylight scatteringvirus titrationELISAquality controlprocess control AcknowledgmentsThe authors want to thank Catharine Meckel-Oschmann for critical reading of the manuscript.Article highlights In this article, classical and modern approaches of virus and virus-particle quantification are reviewed.It is outlined that the choice of the analytical method depends on the product composition (live-attenuated, inactivated, split-vaccine, virus-like particle).Individual sections describe the quantification possibilities with regard to infectivity, viral antigens, nucleic acids, and the targeting of whole particles using light scattering or imaging procedures.The article shows that often not the fastest or most sensitive quantification method is applied, but that the decision is made according to costs and benefits. Whereas novel approaches are often applied on a research level, more established techniques are preferred or accepted for the actual pharmaceutical production or product release.Quantification methods for virus-based pharmaceuticals can be derived from existing methods for diagnostic purposes or environmental investigations. However, sample preparation and target quantification ranges might require adjustments.For future developments, automation and miniaturization will be highly important in order to increase throughput and to reduce assay errors.Author contributionsAll named authors meet the International Committee of Medical Journal Editors (ICMJE) criteria for authorship for this article. All authors contributed to conception and design of the review article, drafting and revising of the manuscript, and have given their approval for this manuscript version to be published.Declaration of interestThe authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.Reviewer disclosuresPeer reviewers on this manuscript have no relevant financial or other relationships to disclose.Websites201.Team VGCVT. Covid19 Vaccine Tracker 2022 [25.02.2022]. Available from: https://covid19.trackvaccines.org/agency/who/Additional informationFundingThe review was written within the framework of the industrial collective research program (IGF/Project no. 21631 BG/FE 2). It was supported by the Federal Ministry for Economic Affairs and Energy (BMWi) through the AiF (German Federation of Industrial Research Associations eV) based on a decision taken by the German Bundestag.