ABSTRACT
Highly pathogenic avian influenza virus (HPAIV) H5N1 continues to pose a significant threat to animal and human health. Since 2022, an expanded host range has been observed, as illustrated by the H5N1 outbreak in dairy cows. Other minor livestock species, such as sheep, goats, and alpacas, have also tested positive for H5N1 for the first time, raising concerns about its impact on previously overlooked livestock species. In this study, we first characterized the distribution of sialic acid (SA) receptors across respiratory and non-respiratory tissues of sheep, goats, and alpacas using Maackia amurensis (SA α2,3) and Sambucus nigra (SA α2,6) lectins. We found that both SA receptors are present in all tissues across species, with notable differences in their distribution and abundance. Next, we developed recombinant LPAIV H5N1 viruses over a laboratory-adapted backbone to evaluate tissue-specific virus binding profiles. The results show that a representative H5N1 virus from clade 2.3.4.4b binds effectively to respiratory and non-respiratory tissues across all species. The strongest virus binding was observed in sheep, followed by goats and, lastly, alpacas. Similar binding patterns were observed with an LPAIV version of clade 2.3.4.4b and a Gs/Gd lineage precursor prototype virus. Finally, we show that H1N1 and H3N2 viruses also bind to respiratory tissues of sheep and goats. These findings provide important insights into the potential susceptibility of minor livestock species to HPAIV H5N1 and other influenza subtypes. Our results contribute to a better understanding of influenza tissue tropism across livestock species and its potential implications for zoonotic transmission.
IMPORTANCE
Since 2022, an unprecedented number of Influenza A virus (IAV) H5N1 detections have been reported in mammals. Sheep, goats, and alpacas are often raised in integrated production systems and may serve as hosts at the wildlife-livestock interface. The establishment of H5N1 in any mammalian host also increases its pandemic potential. Our results reveal species- and tissue-dependent patterns of H5N1 attachment and identify tissues that support viral binding. Furthermore, we show that respiratory tissues may be susceptible to other IAV subtypes, suggesting that these species could act as mixing vessels for reassortment events and the emergence of novel IAV strains. These results expand our understanding of the host range and tissue tropism of H5N1 and other IAV subtypes, providing a foundation for targeted surveillance of minor livestock species. Collectively, this work underscores the importance of considering diverse livestock hosts when evaluating the continued spread of H5N1 at the avian-mammalian interface.
Competing Interest Statement
The authors have declared no competing interest.
Source: BioRxIV, https://doi.org/10.64898/2026.10.26.762033
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