Bovine H5N1 influenza virus binds poorly to human-type sialic acid receptors

Abstract

Clade 2.3.4.4b highly pathogenic H5N1 avian influenza (HPAI) viruses started circulating widely in lactating dairy cattle in the United States at the end of 2023. Avian influenza viruses enter cells after binding to glycan receptors with terminally linked α2-3 sialic acid, whereas human influenza viruses typically bind to glycan receptors terminally linked α2-6 sialic acid in the upper respiratory tract. Here, we evaluated the receptor binding properties of hemagglutinin (HA) trimers from a clade 2.3.4.4b avian isolate (A/American Wigeon/South Carolina/22-000345-001/2021) and a cattle isolate (A/dairy cattle/Texas/24-008749-002-v/2024). Using two different methods, we found that both of the 2.3.4.4b H5s bound efficiently to glycan receptors with terminally linked α2-3 sialic acid with no detectable binding to glycan receptors with terminally linked α2-6 sialic acid. Our data suggest that clade 2.3.4.4b H5N1 viruses bind poorly to human receptors. It will be important to continue evaluating receptor binding properties of these viruses as they evolve in cattle.

Fig. 1.. Bovine H5N1 influenza HA binds retains high specificity for avian-type sialic acid receptors.

Glycan binding analysis of avian and cattle clade 2.3.4.4b H5 HAs. Panel A shows list of the biotinylated glycans analyzed in an ELISA based format, with terminal α2–3 or α2–6 linked sialic acids representing avian-type or human-type receptors, respectively. Panel B shows binding of Maackia amurensis agglutinin (MAA) and Sambucus nigra agglutinin (SNA) to assess loading for glycans with α2–3 and α2–6 linked sialic acids, respectively. Panel C displays results for A/South Carolina/2021 and A/Cattle/Texas/2024 H5 HA binding to terminally sialylated linear (L) and biantennary N-linked (N) glycans. Panel D Glycan microarray analysis of (A/South Carolina/2021) and E (A/Cattle/Texas/2024) H5 HAs. The array contains a library of glycans comprising control glycans with no sialic acid (grey), α2–3 sialosides (blue) and α2–6 sialosides (red). Shown is mean and standard error of the mean SEM of 4 replicates. A complete list of glycan structures elaborated on the array are found in Extended Table 1.