{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,29]],"date-time":"2026-09-29T13:08:10Z","timestamp":1790687290435,"version":"4.1.0"},"reference-count":29,"publisher":"MDPI AG","issue":"12","license":[{"start":{"date-parts":[[2021,12,4]],"date-time":"2021-12-04T00:00:00Z","timestamp":1638576000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"National Institute of Health","award":["P51OD011106"],"award-info":[{"award-number":["P51OD011106"]}]},{"DOI":"10.13039\/100000060","name":"National Institute of Allergy and Infectious Diseases","doi-asserted-by":"publisher","award":["HHSN272201600013C"],"award-info":[{"award-number":["HHSN272201600013C"]}],"id":[{"id":"10.13039\/100000060","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Viruses"],"abstract":"<jats:p>SARS-CoV-2 pathogenesis, vaccine, and therapeutic studies rely on the use of animals challenged with highly pathogenic virus stocks produced in cell cultures. Ideally, these virus stocks should be genetically and functionally similar to the original clinical isolate, retaining wild-type properties to be reliably used in animal model studies. It is well-established that SARS-CoV-2 isolates serially passaged on Vero cell lines accumulate mutations and deletions in the furin cleavage site; however, these can be eliminated when passaged on Calu-3 lung epithelial cell lines, as presented in this study. As numerous stocks of SARS-CoV-2 variants of concern are being grown in cell cultures with the intent for use in animal models, it is essential that propagation methods generate virus stocks that are pathogenic in vivo. Here, we found that the propagation of a B.1.351 SARS-CoV-2 stock on Calu-3 cells eliminated viruses that previously accumulated mutations in the furin cleavage site. Notably, there were alternative variants that accumulated at the same nucleotide positions in virus populations grown on Calu-3 cells at multiple independent facilities. When a Calu-3-derived B.1.351 virus stock was used to infect hamsters, the virus remained pathogenic and the Calu-3-specific variants persisted in the population. These results suggest that Calu-3-derived virus stocks are pathogenic but care should still be taken to evaluate virus stocks for newly arising mutations during propagation.<\/jats:p>","DOI":"10.3390\/v13122434","type":"journal-article","created":{"date-parts":[[2021,12,7]],"date-time":"2021-12-07T03:21:05Z","timestamp":1638847265000},"page":"2434","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":35,"title":["Propagation of SARS-CoV-2 in Calu-3 Cells to Eliminate Mutations in the Furin Cleavage Site of Spike"],"prefix":"10.3390","volume":"13","author":[{"given":"John James","family":"Baczenas","sequence":"first","affiliation":[{"name":"Wisconsin National Primate Center, UW-Madison, Madison, WI 53711, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Hanne","family":"Andersen","sequence":"additional","affiliation":[{"name":"BIOQUAL, Inc., Rockville, MD 20852, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sujatha","family":"Rashid","sequence":"additional","affiliation":[{"name":"American Type Culture Collection (ATCC), 10801 University Boulevard, Manassas, VA 20110, USA"},{"name":"The Biodefense and Emerging Infections Research Resources Repository (BEI Resources), 10801 University Boulevard, Manassas, VA 20110, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"David","family":"Yarmosh","sequence":"additional","affiliation":[{"name":"American Type Culture Collection (ATCC), 10801 University Boulevard, Manassas, VA 20110, USA"},{"name":"The Biodefense and Emerging Infections Research Resources Repository (BEI Resources), 10801 University Boulevard, Manassas, VA 20110, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Nikhita","family":"Puthuveetil","sequence":"additional","affiliation":[{"name":"American Type Culture Collection (ATCC), 10801 University Boulevard, Manassas, VA 20110, USA"},{"name":"The Biodefense and Emerging Infections Research Resources Repository (BEI Resources), 10801 University Boulevard, Manassas, VA 20110, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Michael","family":"Parker","sequence":"additional","affiliation":[{"name":"American Type Culture Collection (ATCC), 10801 University Boulevard, Manassas, VA 20110, USA"},{"name":"The Biodefense and Emerging Infections Research Resources Repository (BEI Resources), 10801 University Boulevard, Manassas, VA 20110, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Rebecca","family":"Bradford","sequence":"additional","affiliation":[{"name":"American Type Culture Collection (ATCC), 10801 University Boulevard, Manassas, VA 20110, USA"},{"name":"The Biodefense and Emerging Infections Research Resources Repository (BEI Resources), 10801 University Boulevard, Manassas, VA 20110, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Clint","family":"Florence","sequence":"additional","affiliation":[{"name":"Office of Biodefense, Research Resources and Translational Research, Division of Microbiology and Infectious Diseases, NIAID, NIH, Bethesda, MD 20892, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kimberly J.","family":"Stemple","sequence":"additional","affiliation":[{"name":"Office of Biodefense, Research Resources and Translational Research, Division of Microbiology and Infectious Diseases, NIAID, NIH, Bethesda, MD 20892, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mark G.","family":"Lewis","sequence":"additional","affiliation":[{"name":"BIOQUAL, Inc., Rockville, MD 20852, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0183-5010","authenticated-orcid":false,"given":"Shelby L.","family":"O\u2019Connor","sequence":"additional","affiliation":[{"name":"Wisconsin National Primate Center, UW-Madison, Madison, WI 53711, USA"},{"name":"Department of Pathology and Laboratory Medicine, UW-Madison, Madison, WI 53705, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2021,12,4]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"585","DOI":"10.1056\/NEJMoa2108891","article-title":"Effectiveness of COVID-19 Vaccines against the B.1.617.2 (Delta) Variant","volume":"385","author":"Andrews","year":"2021","journal-title":"N. 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