Influenza A is the virus responsible for the Spanish Flu pandemic, which wiped out 3-5% of the human population in the early 20th century. The annual influenza outbreak occurs in the autumn and winter, although it is not normally deadly for healthy adults. There is currently no vaccine providing permanent protection against influenza A because the virus mutates and changes so often, requiring a yearly flu shot. Most viruses come in their own unique packaging (called a viral particle) determined by their DNA, with well-defined surface proteins that allow for long-term recognition by our bodies. However, the influenza virus is infamous for rapidly changing its surface proteins, masquerading itself from our immune system. How can influenza have so much diversity when each viral particle shares the same DNA? Why does the flu virus want to change how it appears?

Researchers created a strain of influenza A virus where they could detect different surface proteins on the virus by attaching different colored markers to each type of surface protein. They infected human cells with this customized virus, which reproduced and released viral offspring. Researchers analyzed the newly made viruses from each individual human cell after one generation, which is quick enough to avoid many genetic mutations. They found that the viral offspring came in different sizes and had different surface proteins. Because the virus did not have a lot of time to mutate, the diverse virus sizes and surfaces were likely due to how the virus randomly packaged and released themselves. The small-sized viruses with a certain type of surface protein could escape an antiviral drug that normally traps the newly-made virus inside the infected cell.

This work demonstrated that the influenza A virus is a master of disguise. With just one DNA script, the virus can take multiple forms, changing its size and appearance. A new understanding of how the flu virus can be so diverse could lead to a more effective antiviral therapy and better flu vaccines.

Managing Correspondent: Veerasak (Jeep) Srisuknimit

Original Paper: Cell

Press article: Nature

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Image Credit: Wikimedia

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