Nature Reviews Microbiology | Biological Characteristics, Pathogenicity, Immune Evasion, and Control Strategies of SARS-CoV-2 Variants

This article systematically reviews the evolutionary patterns, antigenic changes, pathogenic mechanisms, and immune evasion characteristics of SARS-CoV-2 variants, and deeply discusses the challenges facing vaccine updates and therapeutic strategies, providing important guidance for future pandemic control.

 

Literature Overview

This article, 'SARS-CoV-2 variants: biology, pathogenicity, immunity, and control,' published in the journal Nature Reviews Microbiology, reviews and summarizes the evolutionary trajectory of SARS-CoV-2 since its emergence, with a focus on analyzing differences among variants in terms of antigenicity, replication capacity, transmissibility, and pathogenicity. The article systematically elaborates on how mutations in the viral spike (S) protein affect neutralizing antibody escape, reveals the potential impact of immune imprinting on vaccine efficacy, and discusses the mechanisms behind the failure of monoclonal antibody therapies and the prospects for small-molecule antiviral drugs. Furthermore, the authors evaluate the limitations of current vaccine strategies and suggest that regular updates, similar to the influenza vaccine model, may be necessary in the future. The entire section is coherent and logically structured, ending with a Chinese period.

Background Knowledge

The coronavirus SARS-CoV-2 is the pathogen responsible for the global pandemic, and its continuous evolution has led to the successive emergence of multiple variants, posing significant challenges to pandemic control. The virus enters host cells via the spike (S) protein binding to the ACE2 receptor, and the S protein—especially the receptor-binding domain (RBD)—is the primary target of neutralizing antibodies, forming the basis for vaccine and therapeutic antibody design. However, as the virus spreads, it accumulates mutations; certain key mutations such as N501Y, E484K, and L452R can enhance ACE2 affinity or enable escape from antibody recognition, resulting in antigenic drift. The World Health Organization (WHO) previously used Greek letters to name important variants (e.g., Alpha, Delta, Omicron), while the Pango lineage system reflects their phylogenetic relationships. The emergence of Omicron marked a significant antigenic shift, with over 30 amino acid substitutions in its S protein, greatly weakening existing immune protection. Subsequently, recombinant variants such as XBB and JN.1 further enhanced immune evasion capabilities. Although vaccines remain effective at preventing severe disease, breakthrough infections are frequent, and monoclonal antibody therapies have successively failed due to mutations in their target sites. Additionally, the phenomenon of immune imprinting may restrict the immune response to new variants based on memory of the original strain, affecting the efficacy of updated vaccines. Animal models such as hACE2-transgenic mice and hamsters are widely used to evaluate variant pathogenicity and transmissibility. Current research focuses on understanding the adaptive advantages of variants, cross-species transmission potential, immune evasion mechanisms, and their impact on therapeutic interventions. Although multiple vaccines and antiviral drugs have been approved, the virus’s ongoing evolution forces the scientific community to continuously adjust response strategies, highlighting the urgent need for more durable, broad-spectrum immune protection and more flexible vaccine update mechanisms.

 

 

Research Methods and Experiments

This study is a systematic review in which the authors integrated extensive data from epidemiological, genomic, structural biology, immunological, and animal model studies since the outbreak of the pandemic in 2019. By analyzing SARS-CoV-2 genomic sequences from public databases such as GISAID, the global transmission dynamics and evolutionary trends of variants were tracked. Pseudovirus or live virus neutralization assays were used to evaluate the ability of different variants to escape sera from vaccinated individuals or convalescent patients. Structural biology methods were employed to elucidate how mutations affect spike protein conformation and ACE2 binding. Replication kinetics, tissue tropism, and pathogenicity of different variants were compared in multiple animal models, including hamsters, K18-hACE2 transgenic mice, and golden Syrian hamsters. Clinical study data were also reviewed to assess real-world effectiveness changes of vaccines and monoclonal antibodies. Deep mutational scanning was used to predict the functional impact of new mutations, and recombination events were analyzed for their role in viral fitness.

Key Conclusions and Perspectives

• The evolution of SARS-CoV-2 is driven by dual selective pressures—increased transmissibility and immune evasion—leading to antigenic drift and global replacement events, such as the rapid dominance of D614G, Delta, and Omicron variants
• Omicron variants and their sublineages (e.g., BA.2.86, JN.1) exhibit significant antibody evasion capabilities. Although their replication efficiency in the lower respiratory tract is lower and pathogenicity relatively reduced, their high transmissibility still leads to widespread infection
• Key mutations in the spike protein (e.g., N501Y, E484K, L452R, F456L) can enhance ACE2 binding affinity or disrupt neutralizing antibody recognition, forming the core mechanism of immune evasion
• The immune imprinting phenomenon may limit the generation of broad neutralizing antibodies against new variants, affecting the efficacy of updated vaccines, suggesting that future vaccine design should consider strategies to overcome original antigenic sin
• Although neutralizing antibody therapies have generally become ineffective due to target site mutations, small-molecule antiviral drugs such as nirmatrelvir and remdesivir remain active and have become important treatment options for high-risk patients
• Viral recombination events (e.g., XBB) can rapidly generate new lineages with growth advantages, becoming globally dominant strains, highlighting the importance of genomic surveillance
• Animal models show that although Omicron exhibits reduced pathogenicity in hamsters, certain sublineages (e.g., BA.2.75) still possess strong replication capacity and may cause severe disease in immunocompromised individuals
• Current vaccine strategies need to shift toward a regular update model similar to influenza vaccines, with antigen selection based on predictions of circulating strains to maintain protective efficacy

Research Significance and Prospects

This review comprehensively outlines the evolutionary pathways and biological characteristics of SARS-CoV-2 variants, emphasizing the challenges posed by the virus’s continuous evolution to existing control measures. It provides clear direction for vaccine development: future efforts should focus on developing broad-spectrum coronavirus vaccines targeting conserved epitopes or adopting multivalent vaccine strategies to cover more variants. At the same time, strengthening the global genomic surveillance network and enhancing early detection and functional assessment capabilities for new variants are crucial. For treatment strategies, continued development of antiviral drugs targeting non-S proteins is essential to reduce the risk of resistance. In addition, in-depth research into the role of T-cell immunity in controlling infection will aid in designing more durable immune interventions.

Looking ahead, addressing the long-term circulation of SARS-CoV-2 will require multidimensional strategies: optimizing vaccine update processes, developing broad-spectrum antiviral drugs, establishing more sensitive surveillance systems, and promoting equitable global vaccine distribution. Furthermore, enhanced protection for immunocompromised individuals and exploration of long-acting antibody prophylaxis are needed. This study provides a theoretical foundation for understanding virus–host interactions and offers scientific evidence for formulating sustainable public health policies. As the virus continues to evolve, scientific research must remain agile and promptly adjust response strategies to mitigate future public health burdens.

 

 

Conclusion

This article systematically summarizes the origin and evolutionary patterns of SARS-CoV-2 variants and their impact on viral infectivity, pathogenicity, and immune evasion. The study shows that during transmission, the virus continuously accumulates spike protein mutations, gaining selective advantages by enhancing ACE2 binding or escaping neutralizing antibody recognition, leading to frequent global replacement events. The emergence of Omicron and its sublineages has significantly altered the pandemic landscape; although pathogenicity has somewhat decreased, their strong immune evasion capabilities have reduced the efficacy of vaccines and monoclonal antibodies. The immune imprinting phenomenon further complicates immune responses and may limit the effectiveness of updated vaccines. Although small-molecule antiviral drugs remain effective, the virus’s ongoing evolution necessitates a shift in vaccine strategies toward regular updates. Future research should focus on developing broad-spectrum vaccines and therapies targeting conserved regions, while strengthening global genomic surveillance to enable rapid responses to new variants. This review provides a comprehensive perspective on understanding the adaptive evolution of SARS-CoV-2 and offers valuable guidance for pandemic control and vaccine design.

 

Ryuta Uraki, Bette Korber, Michael S Diamond, and Yoshihiro Kawaoka. SARS-CoV-2 variants: biology, pathogenicity, immunity, and control. Nature reviews. Microbiology.