Before viruses can infect cells, they must first get to them, often by traversing layers of the body鈥檚 protective mucus. Understanding how evolution optimised the influenza A virus for this slimy task could help us create new antiviral drugs.
If you just dropped an influenza A virus into mucus, natural diffusion would never carry it to cells fast enough to cause an infection, says at the University of California, Berkeley. Influenza A viruses 鈥� the only influenza known to cause flu pandemics 鈥� get around this problem with specially evolved proteins on their surface.
Mucus molecules are covered in complex sugars called sialic acid, and influenza A鈥檚 outer proteins either stick to or sever them. This lets the virus propel itself forward while leaving severed acids in its trail. The researchers assessed how good influenza A is at this leap-frog motion.
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They simulated this process, tweaking the various factors that could influence the virus鈥檚 movement, including the arrangement of the two types of proteins, how often and how strongly each binds to the sugars, and the friction between the virus and the mucus. That revealed a 鈥淕oldilocks zone鈥� in which every factor was just right for influenza A to move as quickly through the mucus as physics allows.
鈥淭he virus has a lot of tasks to do to be successful,鈥� says team member at George Mason University in Virginia. 鈥淲hat we seem to find is that going through the mucus is one of the important ones.鈥�
The discovery implies that the way viruses move through mucus, which differs between animal species, may be important for how they jump between animals and even cause pandemics, says at the Free University of Brussels in Belgium. But he says more details must be added to simulations to quantify this, including situations where the virus makes twists and turns through the mucus, instead of moving in a straight line.
These insights may also lead to the development of new antiviral drugs that could upset the balance between the virus鈥� sticking and severing proteins, trapping it in the mucus, says team member , also at the University of California, Berkeley.
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