Lipid mediators derived from omega-3 polyunsaturated fatty acids (PUFAs), found in the diet, have anti-inflammatory properties. One of these lipid mediators, protectin D1, is now shown to improve disease in mice infected with influenza by inhibiting viral replication through a mechanism that blocks export of viral transcripts (Cell http://dx.doi.org/10.1016/j.cell.2013.02.027).

Masayuki Morita et al. screened human lung epithelial cells infected with the influenza virus H1N1 to find PUFA-derived lipids that block virus replication. Protectin D1 showed the largest blocking effect, even in cells infected with other human pathogenic influenza strains. In mice, protectin D1 protected from infection with H1N1 and was also therapeutic when given with the antiviral peramivir, even at late time points in infection, when other antiviral drugs are ineffective.

The amounts of endogenous protectin D1 were reduced in infected mice; a reduction that correlated with the pathogenicity of the strain. The authors also found that its production was dependent on a specific enzyme expressed mostly in epithelial cells and leukocytes.

The findings identify a new innate suppressor of influenza virus replication that may be further investigated as a potential antiviral drug and biomarker to protect from and treat severe influenza infections.