{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,27]],"date-time":"2026-09-27T12:17:04Z","timestamp":1790511424909,"version":"4.1.0"},"reference-count":36,"publisher":"MDPI AG","issue":"15","license":[{"start":{"date-parts":[[2024,7,24]],"date-time":"2024-07-24T00:00:00Z","timestamp":1721779200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["IJMS"],"abstract":"<jats:p>Infectivity assays are the key analytical technology for the development and manufacturing of virus-based therapeutics. Here, we introduce a novel assay format that utilizes label-free bright-field images to determine the kinetics of infection-dependent changes in cell morphology. In particular, cell rounding is directly proportional to the amount of infectious virus applied, enabling rapid determination of viral titers in relation to a standard curve. Our kinetic infectious virus titer (KIT) assay is stability-indicating and, due to its sensitive readout method, provides results within 24 h post-infection. Compared to traditional infectivity assays, which depend on a single readout of an infection endpoint, cumulated analysis of kinetic data by a fit model results in precise results (CV &lt; 20%) based on only three wells per sample. This approach allows for a high throughput with ~400 samples processed by a single operator per week. We demonstrate the applicability of the KIT assay for the genetically engineered oncolytic VSV-GP, Newcastle disease virus (NDV), and parapoxvirus ovis (ORFV), but it can potentially be extended to a wide range of viruses that induce morphological changes upon infection. The versatility of this assay, combined with its independence from specific instruments or software, makes it a promising solution to overcome the analytical bottleneck in infectivity assays within the pharmaceutical industry and as a routine method in academic research.<\/jats:p>","DOI":"10.3390\/ijms25158076","type":"journal-article","created":{"date-parts":[[2024,7,24]],"date-time":"2024-07-24T15:47:32Z","timestamp":1721836052000},"page":"8076","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":5,"title":["High-Throughput Determination of Infectious Virus Titers by Kinetic Measurement of Infection-Induced Changes in Cell Morphology"],"prefix":"10.3390","volume":"25","author":[{"given":"Dominik","family":"Hotter","sequence":"first","affiliation":[{"name":"Boehringer Ingelheim Pharma GmbH & Co. KG, Viral Therapeutics Center, 88397 Biberach an der Riss, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3005-5718","authenticated-orcid":false,"given":"Marco","family":"Kunzelmann","sequence":"additional","affiliation":[{"name":"Boehringer Ingelheim Pharma GmbH & Co. KG, Development Biologicals, 88397 Biberach an der Riss, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Franziska","family":"Kiefer","sequence":"additional","affiliation":[{"name":"Boehringer Ingelheim Pharma GmbH & Co. KG, Viral Therapeutics Center, 88397 Biberach an der Riss, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Chiara","family":"Leukhardt","sequence":"additional","affiliation":[{"name":"Boehringer Ingelheim Pharma GmbH & Co. KG, Viral Therapeutics Center, 88397 Biberach an der Riss, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Carolin","family":"Fackler","sequence":"additional","affiliation":[{"name":"Boehringer Ingelheim Pharma GmbH & Co. KG, Viral Therapeutics Center, 88397 Biberach an der Riss, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Stefan","family":"J\u00e4ger","sequence":"additional","affiliation":[{"name":"Boehringer Ingelheim Pharma GmbH & Co. KG, Central Nervous System Diseases Research, 88397 Biberach an der Riss, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9224-4296","authenticated-orcid":false,"given":"Johannes","family":"Solzin","sequence":"additional","affiliation":[{"name":"Boehringer Ingelheim Pharma GmbH & Co. KG, Viral Therapeutics Center, 88397 Biberach an der Riss, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2024,7,24]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Zhao, Z., Anselmo, A.C., and Mitragotri, S. (2021). Viral Vector-based Gene Therapies in the Clinic. Bioeng. Transl. Med., 7.","DOI":"10.1002\/btm2.10258"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"308","DOI":"10.1038\/nnano.2011.24","article-title":"A High-Throughput Label-Free Nanoparticle Analyser","volume":"6","author":"Fraikin","year":"2011","journal-title":"Nat. Nanotechnol."},{"key":"ref_3","unstructured":"Businger, R., Hochdorfer, D., Hotter, D., and Solzin, J. (2023). 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