Researchers led by Dr Homayoun Shams of the University of Texas Health Science Centre studied such therapy in a group of mice.
They found that mice given an immune-priming chemical in the lungs had reduced viral burden and improved resistance when infected with flu. Further work in this area could lead to new ways of treating flu in humans, they said.
Control of flu infection has focused on adaptive immunity through the use of vaccines, but these are variably effective as viruses mutate and prevalence shifts from season to season.
Recent studies have suggested that innate immunity is vital to flu resistance, with alveolar macrophages helping clear flu virus from the lungs.
The University of Texas researchers said that enhancing this action would increase resistance to flu infection.
The team bred mice so that their lungs either overexpressed or lacked granulocyte-macrophage colony stimulating factor (GM-CSF). GM-CSF encourages white blood cells to mature and is already used to treat Neutropenia in humans.
These two types of mice, along with wild types, were then infected with various flu strains. Only the mice with enhanced GM-CSF survived. These mice also had reduced lung injury and alveolar damage after infection.
The researchers concluded that GM-CSF mice were highly resistant to flu including the H1N1 pandemic strain.
They then delivered GM-CSF into the lungs of wild type mice and found that this recruited immune cells to infection sites, conferring resistance to flu.
Researchers hope GM-CSF can be used to prevent flu in humans. ‘This strategy has the potential to represent a new therapeutic approach to reduce morbidity and mortality from influenza in humans,’ they said.