Can swine-flu infect deep inside lungs?

A new study funded by the EU has found that between the pandemic swine-flu and the seasonal common-flu, swine-flu is far more likely to infect cells deep inside the lungs. Published in the journal Nature Biotechnology, the findings suggest that, because of how the swine virus attaches to specific receptors in the body, patients infected with the pandemic strain of the H1N1 virus will probably experience more severe symptoms than patients infected with the seasonal strain of flu.

The research was jointly funded by the FLUPATH (Avian influenza: impact of virus-host interactions on pathogenesis and ecology) and FLUINNATE (Innate immunity in influenza virus infection of mammalian airways) projects under the 'Policies support' activity of the EU's Sixth Framework Programme (FP6). The funding is reported to be worth almost EUR4 million.

The researchers, consisting of scientists from Germany, Japan, Portugal, Spain and the UK, warn that scientists should closely watch how cells are infected in current swine-flu patients, as it could lead to more serious problems.

The researchers say flu viruses attach to protein molecules on the exterior of the cell called receptors. They are embedded in either the plasma membrane or the cytoplasm of a cell. Each virus then attaches itself to a specific receptor, but when a virus fails to find its specific receptor, it also fails to enter the cell. However, if a virus succeeds in entering the cell, it can then manipulate the cell's machinery to produce the components that are needed to assemble new viruses. The viruses then leave the cell and infect other cells, resulting in infection.

World Pharma News reports how scientists, using a glass surface with 86 different receptors attached, could identify exactly which receptors the virus bound to. The study shows how pandemic H1H1 influenza can bind strongly to receptors called alpha2-6 that are located in the nose, throat and upper airway, as well as to alpha2-3 receptors, located deeper inside the lungs. Seasonal H1N1 influenza, they observed, attaches only to alpha2-6 receptors.

Professor Ten Feizi of The Glycosciences Laboratory at Imperial College London said, "Most people infected with swine-origin flu in the current pandemic have experienced relatively mild symptoms... However, some people have had more severe lung infections, which can be worse than those caused by seasonal flu. Our new research shows how the virus does this: by attaching to receptors mostly found on cells deep in the lungs. This is something seasonal flu cannot do."

"If the flu virus mutates in the future, it may attach to the receptors deep inside the lungs more strongly, and this could mean that more people would experience serious symptoms."

"We think scientists should be on the lookout for these kinds of changes in the virus so we can try to find ways of minimising the impact of such changes."

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