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Replication of SARS-CoV-2 Omicron BA.2 Variant in Ex Vivo Cultures of the Human Upper and Lower Respiratory Tract
33 Pages Posted: 30 May 2022
More...Abstract
Background: The Omicron BA.2 sublineage has replaced BA.1 worldwide and has comparable levels of immune evasion to BA.1. These observations suggest that enhanced antibody evasion is not related to increased transmissibility of BA.2.
Methods: Here, we characterized the replication competence and tissue tropism of three Omicron BA.1, BA.1.1, BA.2 variants in comparison with the wild-type virus and Delta variants, in human nasal, bronchial and lung tissues cultured ex vivo.
Findings: BA.2 replicated more efficiently in nasal and bronchial tissues at 33°C than wild-type, Delta and BA.1. Both BA.2 and BA.1 had higher replication competence than wild-type and Delta viruses in bronchial tissues at 37°C. BA.1, BA.1.1 and BA.2 replicated less well in lung parenchymal tissues compared to wild-type and Delta viruses.
Interpretation: Higher replication competence of Omicron BA.2 in the human upper airway at 33°C than BA.1 may help to explain the current expansion of BA.2 over BA.1. A lower replication level of the tested Omicron variants in human lung tissues is in line with the clinical manifestations of decreased disease severity of patients infected with the Omicron strain compared with other ancestral strains.
Funding Information: This work was supported by US National Institute of Allergy and Infectious Diseases and the Theme-Based Research Scheme under University Grants Committee of Hong Kong Special Administrative Region, China.
Declaration of Interests: The authors declare no competing financial interests.
Ethics Approval Statement: All experiments were carried out in a Bio-safety Level 3 (BSL-3) facility. Informed consent was obtained from all subjects and approval was granted by the Institutional Review Board (IRB) of the University of Hong Kong and the Hospital Authority (Hong Kong West) (IRB approval no: UW 20-862 and UW 20-588).
Keywords: SARS-CoV-2, Omicron BA.2, Nasal tissue, Bronchial tissue, Transmission, Pathogenicity
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