Abstract: Influenza A viruses (IAVs) from the H5N1 2.3.4.4b clade are circulating in dairy farms in the USA.; ruminants were presumed not to be hosts for IAVs. Previously, IAV-positive mammalian species were hunters and scavengers, possibly getting infected while feeding on infected birds. It is now recognized that H5N1 viruses that circulate in US dairy cattle transmit through a mammary gland route, in contrast to transmission by aerosols via the respiratory tract. The sialome in the cow mammary and respiratory tract is so far solely defined using plant lectins. Here, we used recombinant HA proteins representing current circulating and classical H5 viruses to determine the distribution of IAV receptors in the respiratory and mammary tract tissues of cows. We complemented our study by mapping the glycan distribution of the upper and lower respiratory tracts of horses and pigs. Most of the sialome of the cow respiratory tract is lined with sialic acid modifications, such as N-glycolyl and O-acetyl, which are not bound by IAV. Interestingly, the H5 protein representing the cow isolates is bound significantly in the mammary gland, whereas classical H5 proteins failed to do so. Furthermore, whereas the 9-O-acetyl modification is prominent in all tissues tested, the 5-N-glycolyl modification is not, resulting in the display of receptors for avian IAV hemagglutinins. This could explain the high levels of virus found in these tissues and milk, adding supporting data to this virus transmission route.IMPORTANCEH5N1 influenza viruses, which usually affect birds, have been found on dairy farms in the USA. Surprisingly, these viruses are spreading among dairy cows, and there is a possibility that they do not spread through the air but through their milk glands. To understand this better, we studied how the virus attaches to tissues in the cow's respiratory tract and mammary glands using specific viral proteins. We found that the cow-associated virus binds strongly to the mammary glands, unlike older versions infecting birds. This might explain why the virus is found in cow's milk, suggesting a new way the virus could be spreading.
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A new strain of the avian H5N1 influenza virus was found in US dairy farms, it is found to attach significantly to the mammary glands of cows. This method is different from its traditional mode of transmission through respiratory tracts via aerosols.
Overview of Research
This research investigates a recently discovered phenomenon where H5N1 influenza viruses, known for affecting birds, are being found circulating among dairy cows in US dairy farms.
The scientists found that the transmittance route of these viruses is unusually through the mammary glands rather than the more common aerosol transmission via the respiratory tract.
In-Depth Investigation
The researchers used recombinant HA proteins, representative of current circulating and classical H5 viruses, to determine the distribution of this virus in the respiratory and mammary tract tissues of cows.
The cow-associated H5 protein was found to be bound significantly in the mammary gland, contrasting older, classical H5 proteins.
The cow’s respiratory tract, typically lined with sialic acid modifications such as N-glycolyl and O-acetyl, was unlikely to bind with the circulating avian influenza A virus (IAV). However, the mammary gland showed a strong binding tendency with the virus.
Findings and Importance
The study confirmed that the newer H5 protein bound significantly to the mammary glands of cows, unlike traditional versions that primarily infected birds.
This significant binding of the cow-associated H5N1 virus to cow’s mammary glands indicates a potential transmission method through cow’s milk. This is a novel insight changing the understanding of the spread of avian flu viruses among mammals.
The high levels of H5N1 virus found in cow’s milk and mammary tissues further supports the probability of this unique transmission route, adding to the understanding of how this virus moves between species.
Cite This Article
APA
Ríos Carrasco M, Gröne A, van den Brand JMA, de Vries RP.
(2024).
The mammary glands of cows abundantly display receptors for circulating avian H5 viruses.
J Virol, e0105224.
https://doi.org/10.1128/jvi.01052-24
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