A team of Chinese scientists has conducted a groundbreaking study to classify SARS-CoV-2 variants into serotypes based on their antigenic properties. The research focused on the receptor-binding domain (RBD) in the viral spike protein, which plays a crucial role in determining the virus’s ability to infect human cells and trigger an immune response. By evaluating 23 representative variants, including pre-Omicron variants and Omicron sub-variants, the scientists identified five distinct serotypes. This classification could serve as a foundation for the rapid identification and evaluation of emerging variants and inform the development of more effective vaccines and neutralizing antibodies against COVID-19.
The continuous evolution of the SARS-CoV-2 virus has led to the emergence of new variants that can evade the immune response triggered by existing vaccines and treatments. This has been a major challenge in the battle against COVID-19, with breakthrough infections occurring despite vaccination efforts. The receptor-binding domain (RBD) in the spike protein of SARS-CoV-2 is particularly important for immune recognition and response. Variants with more mutations in the RBD have been shown to possess increased immune evasion capabilities while remaining highly transmissible.
Several variants of concern (VOCs) have emerged throughout the pandemic, including the Beta and Gamma variants, which possess specific RBD mutations associated with breakthrough infections and immune evasion. The Omicron variants, which appeared towards the end of 2021, carry a large number of mutations in the RBD that have reduced the efficacy of previously approved vaccines and monoclonal antibodies. As Omicron continues to evolve, it has given rise to sub-variants with enhanced immune evasion capabilities, raising concerns about multiple serotypes of the virus.
The concept of serotypes in viral classification is not new and has been crucial in understanding and combating various viruses. Adenoviruses, for example, have been classified into more than 100 serotypes based on their distinctive antigenic properties. The establishment of serotypes has been instrumental in developing broad-spectrum vaccines, antibodies, and evaluating the antigenicity of newly emerged variants.
The Chinese scientists conducted a comprehensive study to classify SARS-CoV-2 variants into serotypes based on their RBD antigenicities. They selected 23 representative variants, including pre-Omicron VOCs, VOIs, and Omicron sub-variants. By constructing mRNA vaccines containing the RBDs derived from these variants and evaluating the neutralizing capabilities of the mice’s antisera, the researchers were able to classify the variants into five distinct serotypes.
The serotype classification revealed five serotypes with different cross-neutralization properties. Serotype-I encompassed all pre-Omicron variants and had two subtypes. Serotype-II consisted of the BA.1 and BA.1.1 sub-variants. Serotype-III included the BA.3, BA.2, BA.2.12.1, and BA.2.75 sub-variants. Serotype-IV comprised the BA.5, BF.7, BQ.1, and BQ.1.1 sub-variants. Serotype-V consisted of the XBB and XBB.1.5 sub-variants. These serotypes exhibited varying degrees of cross-neutralization against different sub-variants.
The classification of SARS-CoV-2 variants into serotypes based on their RBD antigenicities has significant implications for the development of broad-spectrum COVID-19 vaccines. It provides valuable insights into the complex world of COVID-19 variants and can aid in timely risk assessment and the selection of appropriate vaccines. The study’s findings, published in the peer-reviewed journal Science Bulletin, represent a crucial milestone in our ongoing battle against the pandemic.