Continued evasion of neutralizing antibody response by Omicron XBB.1.16

Area of Science:

• Virology
• Immunology
• Epidemiology

Background:

• Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) evolution, particularly Omicron variants like XBB, poses challenges to vaccine efficacy.
• The Omicron XBB lineage exhibits substantial immune evasion against antibodies from mRNA vaccination and COVID-19 infection.
• The XBB.1.16 variant, with mutations E180V and K478R, is emerging globally and requires comparative analysis.

Purpose of the Study:

• To compare the immune escape properties of the SARS-CoV-2 XBB.1.16 variant against XBB.1.5 and earlier variants.
• To assess the fusogenicity of the XBB.1.16 spike protein in relation to XBB.1.5.
• To underscore the necessity for continuous monitoring of viral evolution and vaccine updates.

Main Methods:

• Comparative analysis of immune evasion using sera from bivalent-vaccinated and 3-dose-vaccinated healthcare workers.
• Evaluation of sera from individuals convalescent during the BA.4/5 wave.
• Assessment of spike protein fusogenicity linked to specific mutations.

Main Results:

• XBB.1.16 demonstrates strong immune evasion, comparable to XBB.1.5, across various vaccinated and convalescent human sera.
• The XBB.1.16 spike protein exhibits reduced fusogenicity compared to XBB.1.5.
• The diminished fusogenicity phenotype of XBB.1.16 is dependent on the presence of both E180V and K478R mutations.

Conclusions:

• The XBB.1.16 variant presents a significant immune escape threat, necessitating vigilance.
• Updated mRNA vaccine formulations may be required to address the immune evasion posed by emerging variants like XBB.1.16.
• Continuous surveillance of SARS-CoV-2 variants is crucial for public health strategies.