H1N1 virus can infect cells deeper in lungs: Study

The findings of this study could explain why H1N1 virus mutates and spreads more quickly between the cells and causes more severe symptoms in people infected with it than those infected with the seasonal influenza.

The study illustrates that the influenza viruses attach to the bead-like-molecules called receptors found on the surface of the cells and infect them.

If a virus does not find its specific receptor it cannot infect the cell because different viruses have different receptors. But once inside the cell, the virus mutates profusely and disintegrates into multiple copies that are capable of infecting the neighboring cells as well.

Receptor binding of the H1N1 and seasonal influenza
For the purpose of the study, researchers compared the viruses of the H1N1 influenza and seasonal flu. They tried to identify which receptors each virus binds to and observed how both the viruses infect the cells.

It was found that the H1N1 virus has the potential to attach itself to the receptors found even deep inside the lungs, causing more severe lung infection.

On the other hand, the seasonal flu viruses are capable of attaching to the receptors found in the upper respiratory track of the cells like those present in the nose, throat and upper airway. This is why people who get infected with the seasonal flu develop mild symptoms, unlike its more harmful counterpart.

Prof. Ten Feizi of Imperial College London, one of the authors of the study said, "Receptor binding determines how well a virus spreads between cells and causes an infection.

"Our new study adds to our understanding of how swine-origin influenza H1N1 virus is behaving in the current pandemic and shows us changes we need to look out for."

H1N1 virus’s ability to stick to deeper receptors
The study cautions that the pandemic swine flu influenza has high potential to attach itself to more than one receptor, thus infecting more cells. This can lead to a strong binding with the receptors found in the deeper respiratory tract, leading to severe lung infection.

Lead researcher Prof. Feizi 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."

Prof. Feizi added, "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."

A report by World Health Organisation (WHO) also warns that the H1N1 might return for a second strike in winters in a more mutated form, infecting the lungs deeper this time.

The study has been carried out by the scientists at the Imperial College, London.