Distinct phenotype of SARS-CoV-2 Omicron BA.1 in human primary cells but no increased host range in cell lines of putative mammalian reservoir species

SARS-CoV-2s genetic plasticity has led to several variants of concern (VOCs). Here we studied replicative capacity for seven SARS-CoV-2 isolates (B.1, Alpha, Beta, Gamma, Delta, Zeta, and Omicron BA.1) in primary reconstituted airway epithelia (HAE) and lung-derived cell lines. Furthermore, to investigate the host range of Delta and Omicron compared to ancestral SARS-CoV-2, we assessed replication in 17 cell lines from 11 non-primate mammalian species, including bats, rodents, insectivores and carnivores. Only Omicrons phenotype differed in vitro, with rapid but short replication and efficient production of infectious virus in nasal HAEs, in contrast to other VOCs, but not in lung cell lines. No increased infection efficiency for other species was observed, but Delta and Omicron infection efficiency was increased in A549 cells. Notably replication in A549 and Calu3 cells was lower than in nasal HAE. Our results suggest better adaptation of VOCs towards humans, without an extended host range.

Analytical sensitivity of seven SARS-CoV-2 antigen-detecting rapid tests for Omicron variant

BackgroundThe emergence of each novel SARS-CoV-2 variants of concern (VOCs) requires investigation of its potential impact on the performance of diagnostic tests in use, including Antigen-detecting rapid diagnostic tests (Ag-RDT). Although anecdotal reports have been circulating that the newly emerged Omicron variant is in principle detectable by Ag-RDTs, few data on sensitivity are available. MethodsWe have performed 1) analytical sensitivity testing with cultured virus in eight Ag-RDTs and 2) retrospective testing in duplicates with clinical samples from vaccinated individuals with Omicron (n=18) or Delta (n=17) breakthrough infection on seven Ag-RDTs. FindingsOverall, we have found large heterogenicity between Ag-RDTs for detecting Omicron. When using cultured virus, we observed a trend towards lower sensitivity for Omicron detection compared to earlier circulating SARS-CoV-2 and the other VOCs. When comparing performance for Delta and Omicron in a comparable set of clinical samples in seven Ag-RDTs, 124/252 (49.2%) of all test performed showed a positive result for Omicron compared to 156/238 (65.6%) for Delta samples. Sensitivity for both Omicron and Delta between Ag-RDTs was highly variable. Four out of seven Ag-RDTs showed significantly lower sensitivity (p<0.001) to detect Omicron when compared to Delta while three had comparable sensitivity to Delta. InterpretationSensitivity for detecting Omicron is highly variable between Ag-RDTs, necessitating a careful consideration when using these tests to guide infection prevention measures. While analytical and retrospective testing may be a proxy and timely solution to generate performance data, it is not a replacement for clinical evaluations which are urgently needed. Biological and technical reasons for detection failure by some Ag-RDTs need to be further investigated. FundingThis work was supported by the Swiss National Science Foundation (grant numbers 196383, 196644 and 198412), the Fondation Ancrage Bienfaisance du Groupe Pictet, the Fondation Privee des Hopiteaux Universitaires de Geneve and FIND, the global alliance for diagnostics.

SARS-CoV-2 infections in nasal epithelial cells from smokers versus non-smokers

Whether smoking exacerbates Coronavirus disease 2019 is still debated. Ex-vivo Infection of reconstituted epithelial tissues from smoker versus non-smoker donors suggested comparable susceptibility to SARS-CoV-2 in epithelia from both groups.