H5N1 proteins from one patient bound weakly in receptor tests
Scientists tested surface proteins reconstructed from H5N1 sequences found in a severely ill Canadian patient in 2024. In laboratory assays, the variants bound tested bird-type and human-type receptor sugars weakly or below the measurement threshold, although the proteins retained some membrane-fusion activity. Researchers used sequences rather than a recovered whole virus. These protein results do not establish how the infection occurred or whether the variants could spread between people.
Science··Night
Protein sequences came from one severe case
A respiratory sample from a person who became severely ill with H5N1 in British Columbia, Canada, in 2024 provided the starting sequences for the new study. Those sequences indicated a mixed viral population; the researchers did not isolate intact live virus from the patient. Hemagglutinin, a protein on the influenza surface, helps the virus attach to cell sugars and merge membranes. The team made proteins corresponding to the patient sequences for laboratory comparison.[1]
Binding was weak while fusion persisted
The team tested two changes, E190D and Q226H, separately and together. On glycan arrays, the patient-derived variants attached very weakly to the tested bird-type and human-type structures, or showed no measurable binding. Cryo-electron microscopy did not show an N169-linked sugar at the same position where it appeared in comparison proteins. Full-length protein expressed in human lung-derived cells still supported membrane fusion, though less strongly than the comparison proteins.[1]
Protein assays did not measure transmission
Serum collected after the patient’s infection bound strongly to the hemagglutinin studied by the team. Like the receptor-binding and membrane-fusion assays, this result describes behavior of selected proteins recreated from a single severe case. The study did not determine the source of the patient’s infection or test whether these variants spread between people. Weak binding on the selected glycan arrays also does not establish that attachment to every kind of human cell is impossible.[1]
