Unlocking the puzzle: non-defining mutations in SARS-CoV-2 proteome may affect vaccine effectiveness

Area of Science:

• Virology
• Genomics
• Immunology

Background:

• Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) variants possess genome-wide mutations compared to the ancestral Wuhan strain.
• Non-clade-defining mutations, not typically used for variant classification, can alter viral proteins and potentially impact vaccine efficacy.
• Understanding these mutations is critical for assessing and improving COVID-19 vaccine performance against evolving viral strains.

Purpose of the Study:

• To identify SARS-CoV-2 mutations across the entire viral genome, beyond clade-defining mutations, associated with reduced vaccine effectiveness.
• To analyze the physicochemical properties of amino acid substitutions resulting from these mutations.
• To investigate the potential impact of these mutations on viral protein structure and function, and consequently, vaccine protection.

Main Methods:

• Whole-genome consensus sequences of SARS-CoV-2 from COVID-19 patients were obtained from the GISAID database.
• Bioinformatic analyses identified amino acid changes (≥10% frequency) and grouped sequences by identical mutation combinations.
• Focus was placed on specific datasets from Italy and Spain, analyzing mutations in relation to vaccine coverage and variant clades (Omicron, Delta).

Main Results:

• Specific combinations of non-clade-defining mutations in Omicron (clades 21L, 22B/22E, 22F/23A) and Delta (clade 21J) SARS-CoV-2 variants were significantly associated with vaccine failure.
• Four sets of Omicron sequences and two sets of Delta sequences showed strong links to low vaccine coverage.
• Amino acid substitutions were predominantly hydrophobic and polar, suggesting potential alterations in protein structure and function.

Conclusions:

• Non-defining mutations across the SARS-CoV-2 proteome can influence the effectiveness of COVID-19 vaccines.
• Alterations in the physicochemical properties of viral amino acids due to these mutations may disrupt protein structure or function, contributing to vaccine escape.
• Further research into these mutations is essential for developing next-generation vaccines with broader and more durable protection.