SARS-CoV-2 Omicron-B.1.1.529 leads to widespread escape from neutralizing antibody responses

On 24th November 2021, the sequence of a new SARS-CoV-2 viral isolate Omicron-B.1.1.529 was announced, containing far more mutations in Spike (S) than previously reported variants. Neutralization titers of Omicron by sera from vaccinees and convalescent subjects infected with early pandemic Alpha, Beta, Gamma, or Delta are substantially reduced, or the sera failed to neutralize. Titers against Omicron are boosted by third vaccine doses and are high in both vaccinated individuals and those infected by Delta. Mutations in Omicron knock out or substantially reduce neutralization by most of the large panel of potent monoclonal antibodies and antibodies under commercial development. Omicron S has structural changes from earlier viruses and uses mutations that confer tight binding to ACE2 to unleash evolution driven by immune escape. This leads to a large number of mutations in the ACE2 binding site and rebalances receptor affinity to that of earlier pandemic viruses.

Automated summary

On November 24, 2021, the sequence of a new SARS-CoV-2 variant, Omicron-B.1.1.529, was announced. Compared to previous variants, Omicron has a higher number of mutations in the Spike (S) protein. Serum neutralization of Omicron by individuals vaccinated or previously infected with Alpha, Beta, Gamma, or Delta variants is significantly reduced or ineffective. Third vaccine doses can boost neutralization titers against Omicron, and high titers are observed in both vaccinated individuals and those infected with the Delta variant. Most potent monoclonal antibodies and antibodies under development are unable to effectively neutralize Omicron due to mutations in its Spike protein. Omicron has structural changes compared to earlier viruses and utilizes mutations that enhance its binding to ACE2, allowing for immune escape. This results in a large number of mutations in the ACE2 binding site and a rebalancing of receptor affinity similar to earlier pandemic viruses.