A recent study published in the journal Nature has investigated the receptor affinity and antigenicity of the highly mutated SARS-CoV-2 BA.2.86 variant, also known as the Omicron sub-variant. This variant is genetically distinct from existing variants and has been detected in more than 400 sequences across 28 countries, raising concerns about its potential to evade antibodies induced by infection or vaccination.
The study aimed to characterize the antigenicity of BA.2.86 by analyzing serum samples from three cohorts. The first cohort included individuals who received three doses of the monovalent vaccine followed by two bivalent doses. The second and third cohorts consisted of patients who experienced breakthrough infections with BA.2 and XBB variants after vaccination, respectively.
The researchers generated vesicular stomatitis virus (VSV) pseudoviruses to assess the antigenicity of the BA.2.86 spike. They created two versions of the spike, one with the absence and one with the presence of a specific mutation. Pseudoviruses representing other SARS-CoV-2 variants were also generated for comparison.
The pseudoviruses were tested for neutralization by sera from the three cohorts. The BA.2 variant was found to be most sensitive to serum neutralization, while the EG.5.1 variant was the most resistant. BA.2.86 demonstrated higher sensitivity to neutralization than EG.5.1 in two of the cohorts. These findings suggest that exposure to the XBB.1.5 variant could elicit an effective immune response against prevailing SARS-CoV-2 variants.
The researchers also tested the susceptibility of BA.2.86 to 26 monoclonal antibodies (mAbs) targeting different epitopes. BA.2.86 was found to be highly resistant to certain mAbs that target specific regions of the virus, including the N-terminal domain (NTD), receptor-binding domain (RBD) class 2 and 3 epitopes, and sub-domain 1 (SD1). However, it was more sensitive to neutralization by most mAbs targeting other epitopes compared to the EG.5.1 variant.
To better understand the impact of specific mutations in BA.2.86, the researchers synthesized genes for all 34 mutations and tested their neutralization resistance. Several mutations were found to confer resistance to specific mAbs, while others had little or no impact on antigenicity.
Lastly, the researchers evaluated the receptor affinity of the BA.2.86 spike using surface plasmon resonance. The BA.2.86 spike demonstrated significantly higher binding affinity to the ACE2 receptor compared to the BA.2, EG.5.1, and XBB.1.5 spikes.
In conclusion, the SARS-CoV-2 BA.2.86 variant did not exhibit higher resistance to neutralization by human sera compared to other variants like EG.5.1 and XBB.1.5. However, it did display a higher receptor affinity, which could potentially contribute to its transmissibility. Further research is needed to fully understand the significance of these findings and the implications for the spread of the variant. Continued surveillance of emerging variants is crucial to monitor their evolution and assess their potential impact on public health.
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- Source: Coherent Market Insights, Public sources, Desk research
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