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According to estimates of the World Health Organization WHO, each year about three to five million people are afflicted by influenza throughout the world. This infection can take a moderate course, or a severe one that leads to fatality in ten to 15 percent of the afflicted individuals. While early antiviral treatment might alleviate the course of the disease, there is no solid evidence known that allows for reliable prognosis early in the infection process. Instead, patients are often given antibiotics that are ineffective against influenza viruses and therefore fail to contain the infection.
A researcher team directed by Klaus Schughart from the Helmholtz Centre for Infection Research (HZI), Benjamin Tang from the University of Sydney and Jens Schreiber from the Otto von Guericke University Magdeburg tested blood samples of influenza patients for markers that might be indicative of the course of the disease. The majority of the control samples from healthy individuals was taken at the HZI. "We selected blood samples from influenza patients with a moderate versus severe course of the disease and from healthy individuals as well, and produced transcription profiles of the three groups," says Klaus Schughart. "This analysis shows us which genes are active in the patients and which are not. Without the contribution of the volunteers from the HZI, it would not have been possible to complete the study the way it was done and I'm very grateful to everybody who volunteered to participate in our study."
The study aimed to find genes that distinguish the three test groups from each other. Patients who were hospitalized for influenza and released early were considered to have a moderate course of the disease. Severe courses included patients who needed to be artificially ventilated. "In the first step, we were able to show that the IFI27 gene is upregulated in all influenza patients. This makes IFI27 a unique biomarker for differentiation of an influenza infection from a bacterial respiratory infection," says Schughart.
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In the next step, the researchers searched for a marker of the severity of the course of the disease – and they found a gene that is particularly active in all patients suffering from a severe course. "The result has not been published yet. This new marker is now being tested in larger studies to determine the point in time at which it is upregulated," says Schughart.
The study also showed neutrophils – a type of immune cells – to be activated. Neutrophils can be seen as the first line of defence at the site of infection, where they shoot oxygen radicals at infected cells or capture the pathogens with DNA nets. This reaction seems to overshoot in influenza cases with a severe course though and possibly increase the fatality. "The activity of neutrophils can be controlled and this may be a potential new approach for future therapies," says Schughart.