SARS-CoV-2 ORF7a Mutation Found in BF.5 and BF.7 Sublineages Impacts Its Functions

Area of Science:

• Virology
• Molecular Biology
• Immunology

Background:

• SARS-CoV-2 Omicron subvariants BF.5 and BF.7 showed a high prevalence of the ORF7a: H47Y mutation.
• The SARS-CoV-2 ORF7a protein has multiple functions, including immune evasion and modulation of host cell surface proteins.

Purpose of the Study:

• To investigate the functional impact of the ORF7a: H47Y mutation on SARS-CoV-2 ORF7a protein functions.
• To determine how this mutation affects the virus's interaction with the host immune system and cellular processes.

Main Methods:

• Site-directed mutagenesis to introduce the H47Y mutation into the SARS-CoV-2 ORF7a gene.
• Functional assays to assess the protein's ability to antagonize type I interferon (IFN-I) response.
• Analysis of major histocompatibility complex I (MHC-I) cell surface levels.
• Evaluation of the anti-SERINC5 function.

Main Results:

• The H47Y mutation significantly impaired the ORF7a protein's ability to antagonize the type I interferon (IFN-I) response.
• The mutation led to a downregulation of major histocompatibility complex I (MHC-I) cell surface levels.
• The H47Y mutation did not affect the anti-SERINC5 function of the ORF7a protein.

Conclusions:

• The ORF7a: H47Y mutation alters key functions of the SARS-CoV-2 ORF7a protein.
• These functional changes may contribute to altered virus pathogenesis observed in Omicron subvariants.
• Understanding these molecular mechanisms is crucial for tracking viral evolution and developing countermeasures.