Inhaling a protein that boosts the immune system could help in the fight against flu, tests on mice suggest.
US experts found it reduced symptoms and prevented death despite “lethal” doses of flu.
Writing in the American Journal of Respiratory and Critical Care Medicine, they say the nasal aerosol treatment has “great potential”.
A UK flu expert said the work could be useful in directing research, even if it was not directly transferable.
The World Health Organization (WHO) says there are three to five million cases of flu worldwide each year, and it is linked to 250,000 to 500,000 deaths annually.
Every year a vaccine is produced to act against the most commonly circulating types of flu.
Flu virus
But the researchers say vaccines are “variably effective”, largely because of the way viruses change.
In this study, they looked at the effect of a protein called granulocyte macrophage-colony stimulating factor (GM-CSF).
It is known to boost the activity of alveolar macrophages (AM), the first line of defence against inhaled organisms and molecules.
They compared mice given GM-CSF with some who were not.
The animals were infected with lethal doses of a flu virus.
All the untreated mice lost weight and died within days. But all those treated survived, and while they lost weight initially, they regained it after a short period.
The effect was seen for a number of different flu strains, including swine flu (H1N1).
Dr Homayoun Shams, from the University of Texas, who led the study, said: “Such unique and unambiguous results demonstrate the great potential of GM-CSF and may be the remedy for a critical public health priority – developing strategies to reduce the morbidity and mortality from influenza.
He added: “Despite the widespread use of vaccines, influenza causes significant morbidity and mortality throughout the world, and those with poor immune systems are particularly more susceptible—such as very young, elderly or immunocompromised individuals.
“Unlike a vaccine, GM-SCF does not rely heavily on the body’s ability to mount an immune counter-attack against a specific antigen or virus strain, but enhances the speed of local responses to virus infection and delicately balances the host immune responses.”
GM-SCF is already used to treat people with neutropenia, a blood disorder.
Professor John Oxford, a virologist based at Queen Mary, University of London, said it was “cutting edge” research.
But he added: “Transferring it into humans can be quite difficult. We don’t know the sort of problems that could occur if you start meddling with the immune system, as we saw with the Northwick Park trial [in which six men became seriously ill after taking a drug which was meant to "retune" the immune system].
“So first we’ll see how it pans out in mice, then see how it can possibly apply to humans.
“But it could also help our understanding of the pathology of flu.”
Over 12 million Brazilians have been vaccinated for flu during the ongoing nationwide campaign, according to an official report.
The campaign that began April 25 ends May 13, Prensa Latina said.
The health ministry’s latest report, which contains data from across the country till May 6, said 50 percent of the 24 million Brazilians targeted for vaccination have received their shots.
The 24-million plan accounts for 80 percent of all citizens included in the “at-risk” groups, including people over 60, pregnant women, indigenous people, children aged seven months to two years, and health workers.
The vaccine administered this year not only protects against three main flu viruses circulating in the southern hemisphere, but also against A(H1N1) influenza.
Health Minister Alexander Padilha asked people to go to one of the 65,000 medical centres designated for the campaign.
The health ministry has acquired 33 million doses of vaccine, he added.
A new approach by researchers has shown ‘great potential to reduce the morbidity and mortality from flu’.
A research on mice has shown that the pulmonary administration of granulocyte macrophage-colony stimulating factor (GM-CSF) significantly reduces flu symptoms and prevents death after a lethal dose of influenza virus.
While GM-SCF therapy for humans as a flu prophylaxis or treatment may be years away, the study results were striking: All of the mice treated with GM-SCF survived after being infected with the influenza virus, whereas untreated mice all died from the same infection.
“Such unique and unambiguous results demonstrate the great potential of GM-CSF and may be the remedy for a critical public health priority: developing strategies to reduce the morbidity and mortality from influenza,” said Homayoun Shams, principal investigator of the study.
Genetic mutations of influenza virus reduce the potency of flu vaccines, and a vaccinated person may contract flu, develop complications and even die due to poor host immune responses to vaccine or mutated virus strains.
GM-SCF boosts innate immunity to make it immediately effective against the virus, and its protective effect has not been shown to be strain dependant so far. Alveolar macrophages (AM), which are enhanced by GM-SCF, are an essential piece of the innate immune response and are known to contribute to host defense against flu infections in animal models.
“Unlike a vaccine, GM-SCF does not rely heavily on the body”s ability to mount an immune counter-attack against a specific antigen or virus strain, but enhances the speed of local responses to virus infection and delicately balances the host immune responses,” explained Shams.
The study has been published in the American Journal of Respiratory and Critical Care Medicine.