The discovery comes at a time when fear of a global pandemic is heightened and available antiviral drugs are losing their potency. Governments worldwide have been preparing for a potential bird flu pandemic that has already seen 200 people infected and 113 have died worldwide since its onset in Asia in 2003.
The study describes the discovery of a peptide that blocks the influenza virus from attaching to and entering the cells of its host. The virus is unable to replicate and infect more cells.
The new drug is a fragment of a larger human protein whose role is to assist things to pass through membranes such as those that encapsulate cells.
Although the peptide's precise mechanism for thwarting flu remains unknown it seems to work by blocking the virus' ability to latch onto a key cell surface molecule that the virus uses to get inside cells.
"This gives us another tool," said Stacey Schultz-Cherry, a University of Wisconsin-Madison professor of medical microbiology and immunology and the senior author of the new report. "We're quickly losing our antivirals."
Currently, there are a few effective antiviral medications on the market for influenza, but they are beginning to show signs that they are losing their effectiveness.
Scientists are worried that the flu virus, and especially the H5N1 bird flu virus, will evolve to the point where existing drugs are no longer effective.
The new drug, which was tested on cells in culture and in mice, demonstrated complete protection against infection and was effective in treating animals in the early stages of infection.
The research found that untreated infected animals typically died within a week. All of the infected animals treated with small doses of the drug at the onset of symptoms survived.
"Pre-treatment with (the peptide) provided 100 per cent protection against numerous subtypes (of flu), including the highly pathogenic H5N1 viruses," according to the report.
"It attacks a completely different part of the virus life cycle," said Curtis Brandt, a co-author of the study and a UW-Madison professor of medical microbiology and immunology and of ophthalmology and visual sciences.
"The virus can't even get into the cell. The peptide is blocking the very earliest step in infection."
Antiviral drugs are considered to be a critical line of defence in the event of an influenza epidemic or pandemic. Vaccines are the most important defence, but new vaccines must be customised in response to an outbreak of disease and it can take as long as a year to formulate and manufacture vaccine in quantity.
Antiviral drugs, it is anticipated, would be used to buy time to produce a vaccine in the event of a flu pandemic.
The scientific team emphasised that while the new drug shows great promise, much work remains to determine optimal dosage, efficacy and safety before the drug can be tested in a human patient.
One possibility is that the new agent could be used as part of an anti-influenza cocktail of drugs, much like those used to treat HIV infection. The team hopes to move the research into preclinical phase as quickly as possible.
The study appears online this week (Oct. 4, 2006) in the Journal of Virology,