Antonia Netzl, Department of Zoology, writes:

I research vaccination strategies against SARS-CoV-2, the causative agent of COVID-19. SARS-CoV-2 is a virus that evolves, which means that it changes over time. These changes lead to its escape from immunity that was generated against a previous strain – the evolved strain is too different to be recognized by our immune system.  To keep up with virus evolution and ensure continuous protection, SARS-CoV-2 vaccines are regularly updated, similar to influenza vaccines. I study how our immunity responds to and changes with SARS-CoV-2 infection or vaccination, with the aim to improve future vaccines and better understand immune memory. One method I use to do this is called “antigenic cartography”. It is a bioinformatic tool that uses antibody neutralization data to map virus relationships in a 2D “antigenic map” (see Figure 1). Large distances between viruses mean that they are different from each other, and an infection or vaccination with one won’t protect against infection with the other. Mapping virus strains like this allows us to identify strains that evolved far away from previous vaccine strains, and hence strains to test as candidates for updated vaccines. The method was originally developed to map influenza virus’ evolution. Now, the maps my research group and I construct to show influenza’s or SARS-CoV-2’s evolution are an integral part of the vaccine strain selection process at the WHO and other public health institutions.

Figure 1, published as Figure 3 in Rössler, Netzl, et al. (2022): Antigenic map of SARS-CoV-2 variants constructed from single exposure convalescent and double vaccinated sera. Virus variants are shown as colored circles, sera (contain neutralizing antibodies) as open squares with the color corresponding to the infecting variant. The x- and y-axis represent antigenic distances with one grid square corresponding to one two-fold serum dilution of the neutralization titer. The map orientation within x- and y-axis is free as only relative distances can be inferred. Triangles indicate sera positioned outside the central map area and point in the direction where the corresponding serum is positioned. The alpha + E484K variant is shown as smaller circle due to its additional substitution compared to the alpha variant. The table in the right part indicates how many sera from each group were positioned on the map (Ancestral virus conv. n = 10, Alpha conv. n = 10, Beta conv. n = 6, Delta conv. n = 7, BA.1 omicron conv. n = 12, BA.2 omicron conv. n = 12). Each of these serum samples has been titrated against D614G (closes to ancestral virus), alpha, alpha E484K, beta, gamma, delta, BA.1 omicron, BA.2 omicron, and BA.5 omicron variants.

References:

Rössler, A. et al. BA.2 and BA.5 omicron differ immunologically from both BA.1 omicron and pre-omicron variants. Nat. Commun. 13, (2022).