Understanding SARS-CoV-2 virus variants

Researchers continue to discover more about the SARS-CoV-2 virus, including how it impacts the body and what effects variants may have on transmission and disease severity. The structure and shape of the virus is key to understanding its effects and impact, as this determines what the virus can or cannot do as it infects cells and interacts with the immune system. 

What is the spike protein on the SARS-CoV-2 virus?

The spike protein is found on the surface of the SARS-CoV-2 virus and allows the virus to attach to and enter cells within the body. There is potential for immune cells to recognise and interact with this part of the virus surface.

What are the current SARS-CoV-2 variants of concern and what do we know about the mutations and their effect?

As the SARS-CoV-2 virus replicates, genetic changes can occur through random mutations, altering the structure of the virus and cause virus variants. The scientific community tracks variants and closely monitors the impact they might have on infection rates and disease severity. Those that significantly increase transmission of the virus or disease severity, and/or potentially reduce the impact of preventative measures are labelled variants of concern.

The four current variants of concern according to the World Health Organization – Alpha, Beta, Gamma and Delta – have spike protein mutations, which impact the way the SARS-CoV-2 virus interacts with the body [Figure 1]. Some of the variants share the same mutations which gives rise to similar effects, for instance how easily they spread between individuals and the severity of illness they cause.

Figure 1. SARS-CoV-2 variants of concern and spike protein mutations

Spike protein structure adapted from Harvey et al.1
Variant functional implications adapted from SARS-CoV-2 (hCoV-19) Mutation Reports.2
Only mutations with major functional consequences that appear in at least 75% of all sequences are shown

Specific spike protein changes include:1,2

  • In all four variants of concern, mutation D614G has increased the ability of the SARS-CoV-2 virus to infect cells.
  • Mutations E484K and N501Y, seen across several variants of concern, give the spike protein a greater ability to hook onto and infect cells.
  • All the variants of concern have mutations which impact the role of antibodies in dealing with the virus. For example:
  • The L18F mutation seen in the Gamma variant means that virus-fighting antibodies cannot bind to the spike protein as well.
  • The K417N/T mutation in the Beta variant impairs the ability of antibodies to prevent the virus from entering cells of the body.

As the body produces many different antibodies in response to the SARS-CoV-2 virus, along with other immune cells such as T-cells, the immune system has a range of potential ways in which it can respond to virus variants.


1. Harvey WT, et al. SARS-CoV-2 variants, spike mutations and immune escape. Nat Rev Microbiol 2021;19:409–424. Available at: https://www.nature.com/articles/s41579-021-00573-0. Last accessed: September 2021.

2. Outbreak.info. SARS-CoV-2 (hCoV-19) Mutation Reports. Lineage Mutation Tracker. Available at: https://outbreak.info/situation-reports#voc. Last accessed: September 2021.


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Veeva ID: Z4-36501
Date of preparation: August 2021