Experiments and biosafety
The measurements are all made using a pseudovirus-based deep mutational scanning system that was originally described in Dadonaite et al (2023). See Dadaonaite et al (2024) for details on how this system was applied to H5 HA.
A key aspect of this system is that it utilizes pseudotyped lentiviral virions that encode no viral genes other than the viral entry protein (in this case HA). Pseudotyping is a widely used and safe method to study viral entry proteins, since the pseudoviruses can only undergo a single cycle of infection and therefore pose no risk of transmission or replication in humans or any other animals. For this reason, they provide as safe way to study mutations to proteins from even potential pandemic viruses like H5N1 influenza at biosafety level 2.
See the paper describing this study (In progress, add link when posted to bioRxiv) for more details.