'Flu's Hidden Gene

01 July 2012
Posted by Chris Smith.

A new gene has been found in the Influenza A genome, and it seems to alter the immune response to infection with the virus.

Influenza VirusEach 'flu virus particle carries RNA inside it - this is the genetic material which provides all the information needed to make more viruses.  When the 'flu virus enters a host cell, it hijacks the cell's protein-making machinery and forces it to make viral proteins - effectively turning the cell into a virus factory.

In order to make protein, a piece of cellular machinery known as the ribosome 'reads' the RNA from the 'flu virus.  This RNA is made up of groups of three bases, which form the code for amino acids, the building blocks of protein.  In one particular stretch of the 'flu RNA known as segment 3, there's an unusual code, which causes the ribosome to 'stumble' about 1.3% of the time - causing a 'ribosomal frameshift'.  Rather than reading the RNA bases as 123, 123, 123, the ribosome starts to read 231, 231, 231.  Normally, this would make a nonsense of the genetic code - but in this particular case, it instead causes a completely new protein to be made.

The scientists, from Cambridge in the UK and research institutions across the US, showed that this protein is made in cells infected with the 'flu virus, and that it causes the total output of protein from these cells to be less.  It seems the novel protein prevents any cellular proteins from being made at all - so the cell is making exclusively viral proteins.

This has the effect of suppressing the immune response to the 'flu infection - in particular, the pathways which activate immune cells called T-cells, and cause inflammation and cell death are affected.  These are the mechanisms which make an episode of the 'flu so unpleasant, but by suppressing them the viral protein not only makes you feel better but also probably increases the length of time it can spend in any one host individual.

While this can't explain all the variability we see in how severe a bout of the 'flu can be, it could turn out to be an important part of the puzzle - and because this protein is only made by the virus, it could provide a new way to target the bug.

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