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Scientist discover why H1N1 flu causes pneumonia and death in some people

Kathleen Blanchard's picture

Spanish researchers, for the first time, have identified a first immunological clue as to why some patients with H1N1 flu develop pneumonia and die. The researchers studied patients in Spanish hospitals during the first wave of H1N1 pandemic in July and August 2009, finding high levels of an important molecule, Interleukin 17, in the blood of patients with severe cases of H1N1 flu.

The molecule, Interleukin 17, is an important regulator of white blood cells needed to fight infection. Patients with mild symptoms of H1N1 flu were found to have lower levels of Interleukin 17. When high levels of the molecule are present widespread inflammation and cytokine release occurs.

High levels of Interleukin 17 are linked to autoimmune diseases such as rheumatoid arthritis. The molecule is widely implicated for promoting inflammation. Identifying individuals with high levels of Interleukin 17 found in patients with severe illness and pneumonia from H1N1 flu could lead to earlier intervention and treatment strategies.

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According to David Kelvin, leader of the Canadian team, Head of the Experimental Therapeutics Division, Toronto General Hospital Research Institute, University Health Network and Professor of Immunology, University of Toronto, "In rare cases, the [H1N1] virus causes lung infections requiring patients to be treated in hospital. By targeting or blocking TH17 in the future, we could potentially reduce the amount of inflammation in the lungs and speed up recovery." TH17 cells produce Interleukin 17. Kelvin adds that it would be years before the treatment could be developed for clinical application.

Research is needed to find ways to block Interleukin 17, but the scientists say a blood test could be developed in the near future that would identify individuals at risk for developing severe illness and deadly pneumonia from H1N1 flu.

"A diagnostic test could let us know early who is at risk for the severe form of this illness quickly," says Kelvin. High levels of Interleukin 17 could indicate the body's inability to rid itself of the H1N1 flu virus, also found during the 1918 Spanish flu pandemic that caused high numbers of deaths.

For the first time, scientists have targeted an important immunological reason that explains why some individuals develop severe H1N1 flu symptoms and death. Identifying high levels of the molecule Interleukin 17, that the scientists say becomes "out of control" when H1N1 flu is severe, could help target those who are at highest risk for severe illness from pneumonia associated with H1N1 flu.