SARS-CoV-2 Omicron escapes immune

In a recent study published in the journal Vaccines, researchers revealed how Omicron severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) evades neutralizing antibodies (nAbs).

Two days after it was first reported on November 24, 2021, the World Health Organization (WHO) designated SARS-CoV-2 Omicron as a Variant of Concern (VOC). The WHO estimated a potentially higher risk of harm for VOCs from Omicron given the high risk of spreading the COVID-19 pandemic globally and a significantly higher R-value of Omicron than Delta. VOC.

Preliminary studies have revealed a high risk of reinfection and breakthrough infections with the Omicron variant. Nevertheless, the disease caused by the Omicron variant has been relatively mild and health facilities remain functional despite the huge increase in infections. Therefore, it is possible that the pandemic will end with the global spread of Omicron VOC and the resulting widespread immunization with greatly reduced severity and mortality.

In the present study, the researchers reported the mechanisms underlying the increased transmissibility and antibody resistance induced by infection or vaccine of the SARS-CoV-2 Omicron variant. Serum samples were obtained from convalescents infected with the SARS-CoV-2 Wuhan strain, doubly vaccinated subjects and boosted individuals. Participants received BNT162b2 or mRNA-1273 messenger ribonucleic acid (mRNA) vaccines.

The binding kinetics of angiotensin-converting enzyme-2 (ACE2): receptor binding domain (RBD) were assessed. High precision streptavidin (SAX) biosensors were loaded with biotinylated ACE2 and later quenched with biocytin. Serial dilution of RBD in kinetic buffer (KB) was performed. Enzyme immunoassays (ELISA) were performed and a biolayer interferometry (BLI)-based assay was used to test the ability of serum samples to compete with ACE2 for binding to type RBDs. wild (WT), Delta and Omicron variants.

Heat-inactivated serum samples were diluted and incubated with 100 tissue culture median infectious doses (TCID50) of SARS-CoV-2 WT, Delta, or Omicron variant. Then this mixture (serum + virus) was added to Vero cells, incubated for four days and checked for cytopathic effect (CPE). The authors expressed the neutralizing titers as the highest dilution of the sera, completely inhibiting CPE. Statistical significance was measured using the paired or unpaired Student's t test.