Kicking Up A (cytokine) Storm

The New Year brings with it many new possibilities, including, unfortunately a new flu season.

So far, the number of flu cases in 2012 is down, thanks largely to the unprecedented mild weather over most of the US. A sharp contrast to 2009 when H1N1 (or swine flu) killed more than 18,000 people worldwide or 1918 when the flu virus infected around a third of the world’s population and killed at least 50 million people.

New research shows that the reason so many people died in both of those years wasn’t the influenza virus itself, but the immune system’s reaction to it.  It turns out that the virus destroys its host by turning the body’s own defenses against itself.

While trying to destroy flu-infected cells, your immune system also destroys legions of perfectly healthy cells all over your body. This is why, even though the virus itself rarely ventures outside the lungs, the symptoms of the flu are so widespread” says , Michael Oldstone, a virologist at the Scripps Research Institute in La Jolla, Calif.

Most of the time this immune response isn’t too severe. As the virus runs its course, the response subsides. But in some cases, an infection can trigger a reaction so destructive it can be fatal. Scientists call this a cytokine storm, because of the violent way immune cells respond to a virus. Cytokines usually help fight off infections by telling the immune system which specific viral cells it should be attacking, but sometimes an overabundance of cytokines floods into a part of the body, and that’s when you get a storm.

Cytokine storms are rare, but they may be more common among younger people because they have stronger immune systems, and are more prone to overreactions. This may explain one of the more surprising outcomes of the 2009 swine flu: that it was deadlier among young people than it was among the elderly.

Cytokine storms can cause serious damage throughout the body, especially in the lungs, which is why most flu deaths are attributed to pneumonia.

After 5 years of research, Oldstone and his colleagues have identified a cell — they call S1P1 – that responds to cytokines. More importantly they’ve also figured out how to turn off that cell’s signals. This could pave the way for a new class of immune-reaction-blocking drugs that could provide protection against cytokine storms and be more effective than antiviral drugs.

Cytokine-blocking drugs could target the flu effects that cause the most damage to the body and would avoid the problems of virus mutation because they don’t affect the virus itself.

Still, it will probably be many years before those drugs reach your local pharmacy. Although preliminary experiments in mice have shown very promising results they still have to replicate these in ferrets, then primates and finally, humans.

Do you have any flu stories to share? SRxA’s Word on Health would love to hear from you.

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