Colorized 3D structure of a prototype universal flu vaccine, containing a protein scaffold (blue) and eight influenza hemagglutinin proteins on the surface (yellow). Image credit: John Gallagher and Audray Harris, Laboratory of Infectious Diseases (CC BY-NC 2.0)
Pathogens are in a constant evolutionary battle to outwit the immune system. For example, influenza viruses rapidly mutate their hemagglutinin protein to evade antibody proteins generated by past infections or vaccinations. This is one reason why people can be repeatedly infected by influenza viruses throughout their lives.
Understanding this process is crucial for selecting the right viral strains for the annual flu vaccine. However, interpreting the evolution of the flu virus is challenging because individuals vary greatly in their exposure histories, resulting in diverse antibody repertoires that target the virus in different ways. Kikawa et al. developed a new method to measure antibody levels against 78 recent flu strains in both children and adults. They discovered that individuals differed significantly in their ability to neutralize various strains. Furthermore, in 2023, viral strains with a higher proportion of people having lower antibody levels appeared to grow much more rapidly in the human population. This suggests that measuring antibody levels against current viral strains can help identify which ones should be included in next year’s vaccine.
Overall, the study by Kikawa et al. shows that experimental approaches capturing the complexity of human immune responses can provide valuable insights into the evolution of flu viruses. Such insights can improve the selection of strains for the annual flu vaccine.
