( rough an alpha-26 bond and another is ...)Changes in amino acids in the 1918 influenza virus cut transmission

rough an alpha-2,6 bond and another is through an alpha-2,3 bond. Hemagglutinins from avian influenza virus prefer binding to alpha 2-3 sialic acids, while hemagglutinins from human influenza viruses prefer binding to alpha 2-6 sialic acids, which are highly abundant in the upper respiratory tract of humans. For an avian virus to be able to jump to humans and to start a new pandemic, it has been hypothesized that the hemagglutinin needs to mutate and change its binding preference from alpha2-3 to alpha2-6 sialic acids.

In this study, the researchers used ferrets as an animal model of human influenza virus infection, due to the presence of alpha2-6 sialic acids in the respiratory tract of ferrets, similar to the human scenario. Groups of ferrets were infected with three types of influenza viruses; two from existing viral strains related to the 1918 flu and taken from human tissue, and the third, which was artificially created in a laboratory and made to look like avian flu. One virus bound to only alpha-2,6, the second bound to both, and the artificially-generated virus bound to only alpha-2,3.

The researchers were surprised to discover that the ferrets infected with all three viruses, including the one with preference for binding to alpha2-3 sialic acids, experienced severe disease, with high levels of virus replication in the respiratory tract. However, only the virus with specificity for binding to alpha2-6 silaic acids was able to transmit by aerosols to contact ferrets. "It appears that when the virus only had an alpha-2,3 binding activity, replication and virulence didn't change," explains Dr. García-Sastre. "These animals still had symptoms, however transmission was practically abolished." Since the artificially-generated virus featured alpha-2,3 sialic acid binding activity, this finding indicated that alpha-2,6 sialic acid binding activity was more important for optimal viral transmission. "Our findings indicate that, to become more
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Source:The Mount Sinai Hospital / Mount Sinai School of Medicine

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