Influenza viruses can infect cells through a second route of entry

Most flu viruses enter human or animal cells through particular entry routes on the cell floor. Researchers on the College of Zurich bear now found that sure human flu viruses and chicken flu viruses may also utilize a second entry route: a protein advanced of the immune system. This capability helps the viruses to contaminate totally different species – and doubtlessly leap between animals and people.

A lot of the sort A influenza viruses circulating in birds and pigs execute not usually pose a well being danger to people. Nonetheless, the viruses can pose a menace when an outbreak happens, equivalent to the one at present occurring in dairy cows in america, or throughout seasonal epidemics. In uncommon circumstances, a virus can leap from animals to people – with doubtlessly devastating penalties equivalent to a world pandemic.

Further receptor gives various entry route

Most flu viruses penetrate host cells utilizing their envelope proteins, which protrude from the floor like spikes. The so-called hemagglutinin binds to sialic acid, a chemical group on the floor of human cells and the cells of assorted animal species. A global analysis group led by Prof. Silke Stertz from the Institute of Medical Virology on the College of Zurich (UZH) has now proven that flu viruses additionally bear a second methodology of infecting host cells.

Human influenza A viruses of the H2N2 subtype and associated H2N2 avian influenza viruses can enter cells through a second receptor. They utilize another route of entry.”

Prof. Silke Stertz, Institute of Medical Virology, College of Zurich

The researchers discovered that hemagglutinin additionally binds to MHC class II protein complexes. These complexes on the floor of sure immune and respiratory cells are liable for distinguishing between the physique’s personal and international cells. “We discovered that MHC class II complexes enable viruses to penetrate cells in people, pigs, geese, swans and chickens, however not in bats,” says Stertz.

Transmission from animals to people probably

This twin capability to contaminate cells was noticed in cell strains grown within the laboratory and in human respiratory tract cultures. How effectively the viral receptor suits the cell floor buildings performs an important function wherein host species and tissues are contaminated and the way extreme the an infection in the end is. Receptor specificity additionally influences whether or not a virus can infect totally different animal species and even people (zoonosis). “Our outcomes point to that influenza viruses can adapt to totally different entry routes. This might affect their capability to contaminate totally different species and presumably leap between animals and people,” emphasizes the UZH virologist.

So the danger that chicken, swine and different animal influenza viruses might trigger a human influenza pandemic could also be larger than beforehand thought. The capability to utilize MHC class II proteins for cell entry could bear been one among the explanation why H2N2 influenza viruses emerged as a pandemic virus in Asia as early as 1957. That is one other expedient cause to strengthen international influenza surveillance in animals and people.

Supply:

Journal reference:

Karakus, U., . (2024). MHC class II proteins mediate sialic acid-independent entry of human and avian H2N2 influenza A viruses. . doi.org/10.1038/s41564-024-01771-1.

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