Flu viruses join forces
Two influenza viruses infect more cells when they cooperate.
Viruses like influenza mutate fast. When you get the flu, the virus hijacks your cells, and your body becomes home to millions of viruses, many of which are genetically different from each other. Previous research had suggested that variants of rapidly evolving viruses sometimes cooperate with one another to survive, but few studies have pinpointed specific cooperative interactions.
In the past decade, influenza surveillance groups noticed that one particular mutant virus appears again and again when influenza viruses are grown in the laboratory. Katherine Xue and colleagues thought that this mutant virus shouldn’t be able to grow on its own because the mutation disrupted the protein that influenza viruses use to detach from host cells. So, they asked if the mutant was cooperating with the non-mutated virus to survive.
Xue and colleagues revealed that the two influenza viruses, which differ by just one mutation, cooperate with each other when grown in cells in the laboratory. The mutant virus often appeared following a random mutation in a population of non-mutated virus, and vice versa. Instead of competing with each other until one virus went extinct, the two viruses actually grew better together than they did apart. Xue and colleagues suggest that this is because one of the viruses is good at entering new cells, while the other is better at exiting cells to spread the infection. A mixed population combines these two strengths.
Following on from this work, it remains unclear whether influenza viruses cooperate in other settings — for example, during infections in people. Further studies are also needed to determine exactly how the two viruses help each other at the molecular level.
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To find out more
Read the eLife research paper on which this eLife digest is based: “Cooperation between distinct viral variants promotes growth of H3N2 influenza in cell culture” (March 15, 2016).
