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Scientists Find Key to Avian Flu in Humans


Researchers at the Massachusetts Institute of Technology [MIT] have identified a critical difference between the flu viruses that infect birds and those that infect humans. The discovery could help scientists monitor the evolution of avian flu strains and the development of a vaccine against a deadly flu pandemic.

Influenza is a seasonal virus. What has public health officials worried is the highly pathogenic H5N1 bird flu that's necessitated the destruction of millions of poultry worldwide and caused 212 human deaths since it first appeared in Hong Kong in 1997.

Scientists say it is highly likely that the virus could mutate and spread from person to person — leading to a pandemic that could rival the 1918 Spanish Flu that killed 50 million people.

Massachusetts Institute of Technology bio-engineering professor Ram Sasisekharan has been studying the differences and similarities between avian and human forms of influenza virus. Sasisekharan says sugar, which coats the lungs and nose, is key to how the virus works. "The sugar plays a central role in the ability of the virus to recognize human tissues or human cells as an important step leading to infection eventually."

The protein on the surface of the virus latches on to the sugar or glycan receptors and gains entry into the cell. The virus then replicates itself and spreads infection from the inside out.

What Sasisekharan and colleagues report this week in the Journal Nature Biotechnology is that bird- and human-cell sugars have significantly different shapes. "The avian viruses bind to sugar shapes that typically take a structure that resembles a cone, while the human adapted viruses appear to recognize sugar shapes that resemble that of an umbrella."

Computer modeling and three-dimensional images revealed more detail. Sasisekharan says seasonal human flu viruses bind to this umbrella shape, but not to the H5N1 bird flu strain that health officials fear. "What this enables us to do is to systematically look at the evolving H5N1 strains to see if these viruses are beginning to achieve some sort of specificity or recognition to the umbrella-shaped glycans [sugars] that are there in the upper airways."

Sasisekharan says that can help researchers develop drugs or vaccines that could block the H5N1 virus. "By designing molecules that could mimic the umbrella-shaped structures so that these molecules could potentially act as decoys to trick the virus from binding to the umbrella-shaped structures that are there in the upper airways [respiratory system]."

Sasisekharan says the findings could also speed development of more effective strategies to combat seasonal flu, which kills 36,000 people in the United States alone each year.

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