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

Abstract

The recent emergence of B.1.1.529, the Omicron variant1,2, has raised concerns of escape from protection by vaccines and therapeutic antibodies. A key test for potential countermeasures against B.1.1.529 is their activity in preclinical rodent models of respiratory tract disease. Here, using the collaborative network of the SARS-CoV-2 Assessment of Viral Evolution (SAVE) programme of the National Institute of Allergy and Infectious Diseases (NIAID), we evaluated the ability of several B.1.1.529 isolates to cause infection and disease in immunocompetent and human ACE2 (hACE2)-expressing mice and hamsters. Despite modelling data indicating that B.1.1.529 spike can bind more avidly to mouse ACE2 (refs. 3,4), we observed less infection by B.1.1.529 in 129, C57BL/6, BALB/c and K18-hACE2 transgenic mice than by 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 were also milder than with 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.

A Community Study of SARS-CoV-2 Detection by RT-PCR in Saliva: A Reliable and Effective Method

“…By showing the efficacy and reliability of saliva testing in asymptomatic individuals and given that saliva can be safely self-collected at home, our study supports the use of the oral fluid for widespread COVID-19 testing in the community. Incidentally, while our study was performed when the SARS-CoV-2 alpha variant was predominant, the omicron variant, highly transmissible and with a preferential tropism for the upper respiratory tract [21][22][23][24], became globally widespread at the time this article was written. Since omicron is more efficiently detected in saliva than in nasal swabs compared to other variants [25,26], the use of the oral fluid for diagnosing active SARS-CoV-2 infections in the population is further warranted.…”

Organoid Models of SARS-CoV-2 Infection: What Have We Learned about COVID-19?

“…Early studies with the most recent variant Omicron (B.1.529) in ALI-HNE show more rapid viral kinetics than Delta [231], which may underlie the increased transmissibility and rapid global spread of this variant [48]. However, compared to Delta, syncytia formation is diminished [52,231], as is pathogenicity in mouse and hamster models [232,233] and human lung alveolar organoids [52]. Reduced pathogenicity in human alveolar organoids might indicate decreased severity of disease in the real-world human experience with Omicron.…”

Virological characteristics of SARS-CoV-2 BA.2 variant

“…Notably, BA.2 has initiated outcompeting BA.1 3 , suggesting that BA.2 is more transmissible than BA. 1. In a few months since the emergence of BA.1, we and others revealed the virological characteristics of BA.1 [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] . For instance, BA.1 is highly resistant to the vaccine-induced humoral immunity and antiviral drugs [4][5][6][7][8][9][10][11][16][17][18][19] .…”