In a recent study published in bioRxiv* preprint server, researchers evaluated the infectivity of the Omicron BA.2.75 variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) compared to pre-existing variants.
As of July 2022, SARS-CoV-2 variant Omicron BA.5 has become an epidemic in Japan. The recently released Omicron BA.2.75 has further troubled the world. The studies developed a mathematical model to predict and compare the infectivity of different SARS-CoV-2 variants such as Wuhan, Alpha, Beta, Gamma, Delta and Omicron BA.1 and BA.2 variants.
About the study
In the present study, the investigators predicted the relative risk of infection with newly emerging variants, such as the SARS-CoV-2 Omicron BA.2.75 variant, compared to pre-existing variants.
The team estimated the evolutionary distance of the viral spike genes (S) between the Wuhan variant and Omicron BA.4, BA.5, or BA.2.75. The S gene sequences were assembled by searching the Global Initiative for the Sharing of All Influenza Data (GISAID) EpiCoV database for the full S gene sequence. -2 (ACE-2) were evaluated using cluster analysis and docking simulation.
The amino acid sequences associated with the S proteins were collected from the CoVariants website, which classified the variants according to Nextstrain clades, where the Omicron BA.4 variant was classified as 22A, Omicron BA.5 as 22B, and Omicron BA.2.75 as 22D . . Because BA.4 and BA.5 had similar S proteins, the S gene and amino acid sequences were pooled for study.
The results of the study showed that SARS-CoV-2 variants that had a greater evolutionary distance from the Wuhan SARS-CoV-2 variant were more likely to lead to an epidemic. The Omicron BA.2.75 variant was found to have the highest docking affinity of the viral S protein to the ACE2 protein. Compared to the Omicron variant BA.2, while BA.4 and BA.5 had longer evolutionary distances of the S gene, the observed docking affinity was lower.
In addition, compared to BA.2, BA.2.75 exhibited longer evolutionary distances along with a higher docking affinity. This indicated that BA.2.75 has a higher ability to enter host cells, while currently available SARS-CoV-2 vaccines are less effective against this variant.
The results of the study showed that the infectivity of the SARS-CoV-2 Omicron BA.2.75 variant was significantly higher due to the large evolutionary distance of the S gene and the imitation of viral S protein docking with ACE2. The researchers believe that Omicron BA.2.75 poses a higher risk of triggering a global health crisis.
bioRxiv publishes preliminary scientific reports that are not peer-reviewed and therefore should not be considered definitive, guiding clinical practice/health-related behavior, or considered as established information.