In a recent study posted to the bioRxiv* preprint server, researchers assessed the infectivity of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron BA.2.75 variant in comparison with pre-existing variants.

Study: SARS-CoV-2 Omicron BA.2.75 variant could also be far more infective than preexisting variants. Image Credit: Fit Ztudio/Shutterstock

As of July 2022, the SARS-CoV-2 Omicron BA.5 variant has change into an epidemic in Japan. The recently emerged Omicron BA.2.75 has further concerned the world. Studies have developed a mathematical model to predict and compare the infectivities of various SARS-CoV-2 variants comparable to Wuhan, Alpha, Beta, Gamma, Delta, and Omicron BA.1 and BA.2 variants. 

In regards to the study 

In the current study, researchers predicted the comparative risk of infection by recently emerging variants comparable to the SARS-CoV-2 Omicron BA.2.75 variant in comparison with that against preexisting variants.

The team assessed the evolutionary distance of viral spike (S) genes between the Wuhan variant and Omicron BA.4, BA.5, or BA.2.75. The S gene sequences were collected by searching the EpiCoV database of the Global Initiative on Sharing All Influenza Data (GISAID) for the one having an entire S gene sequence. The docking affinity related to the receptor-binding domain (RBD) of every S protein of those variants with angiotensin-converting enzyme-2 (ACE-2) was assessed via cluster evaluation and docking simulation.

The amino acid sequences related to the S proteins were collected from the CoVariants website that classified the variants as per Nextstrain clades, wherein the Omicron BA.4 variant was classified as 22A, Omicron BA.5 as 22B, and Omicron BA.2.75 as 22D. Since BA.4 and BA.5 had similar S proteins, the S gene and amino acid sequences were grouped together for the study.      

Results

The study results showed that the SARS-CoV-2 variants that had an extended evolutionary distance from the SARS-CoV-2 Wuhan variant were more prone to result in an epidemic. The Omicron BA.2.75 variant was found to have the best docking affinity of the viral S protein with the ACE2 protein. In comparison with the Omicron BA.2 variant, while BA.4 and BA.5 had longer S gene evolutionary distances, the docking affinity observed was lower.

Moreover, in comparison with BA.2, BA.2.75 displayed longer evolutionary distances together with higher docking affinity. This indicated that BA.2.75 has the next ability to enter host cells, while the currently available SARS-CoV-2 vaccines are less effective against this variant. 

Conclusion

The study findings showed that the infectivity of the SARS-CoV-2 Omicron BA.2.75 variant was significantly high as a consequence of the long S gene evolutionary distance and the docking simulation for the viral S protein with ACE2. The researchers consider that Omicron BA.2.75 poses the next risk of causing a worldwide health crisis.

*Necessary notice

bioRxiv publishes preliminary scientific reports that usually are not peer-reviewed and, subsequently, mustn’t be considered conclusive, guide clinical practice/health-related behavior, or treated as established information.