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SARS-CoV-2 Omicron virus causes attenuated disease in mice and hamsters

The recent emergence of B.1.1.529, the Omicron variant has raised concerns for escape from protection by vaccines and therapeutic antibodies.

A key test for potential countermeasures against B.1.1.529 is their activity in pre-clinical rodent models of respiratory tract disease. Here, using the collaborative network of the SARS-CoV-2 Assessment of Viral Evolution (SAVE) program of the National Institute of Allergy and Infectious Diseases (NIAID), the authors evaluated the ability of multiple B.1.1.529 Omicron isolates to cause infection and disease in immunocompetent and human ACE2 (hACE2) expressing mice and hamsters. Despite modeling data suggesting that B.1.1.529 spike can bind more avidly to murine ACE2, the authors observed less infection in 129, C57BL/6, BALB/c, and K18-hACE2 transgenic mice as compared with previous SARS-CoV-2 variants, with limited weight loss and lower viral burden in the upper and lower respiratory tracts. In wild-type and hACE2 transgenic hamsters, lung infection, clinical disease, and pathology with B.1.1.529 also were milder compared to historical isolates or other SARS-CoV-2 variants of concern. Overall, experiments from the SAVE/NIAID network with several B.1.1.529 isolates demonstrate attenuated lung disease in rodents, which parallels preliminary human clinical data.
Halfmann PJ, Iida S, Iwatsuki-Horimoto K, Maemura T, Kiso M, Scheaffer SM, Darling TL, Joshi A, Loeber S, Singh G, Foster SL, Ying B, Case JB, Chong Z, Whitener B, Moliva J, Floyd K, Ujie M, Nakajima N, Ito M, Wright R, Uraki R, Warang P, Gagne M, Li R, Sakai-Tagawa Y, Liu Y, Larson D, Osorio JE, Hernandez-Ortiz JP, Henry AR, Ciouderis K, Florek KR, Patel M, Odle A, Wong LR, Bateman AC, Wang Z, Edara VV, Chong Z, Franks J, Jeevan T, Fabrizio T, DeBeauchamp J, Kercher L, Seiler P, Gonzalez-Reiche AS, Sordillo EM, Chang LA, van Bakel H, Simon V; Consortium Mount Sinai Pathogen Surveillance (PSP) study group, Douek DC, Sullivan NJ, Thackray LB, Ueki H, Yamayoshi S, Imai M, Perlman S, Webby RJ, Seder RA, Suthar MS, García-Sastre A, Schotsaert M, Suzuki T, Boon ACM, Diamond MS, Kawaoka Y. SARS-CoV-2 Omicron virus causes attenuated disease in mice and hamsters. Nature. 2022 Jan 21.

doi: 10.1038/s41586-022-04441-6.