A "universal vaccine" is the holy grail of immunisation efforts against the flu, a shapeshifting virus that kills up to half a million people each year, according to the World Health Organisation. There have been several killer pandemics in the past century: the 1918 Spanish Flu outbreak claimed at least 20-million lives.
Existing vaccines target a part of the virus that mutates constantly, forcing drug makers and health officials to concoct new anti-flu cocktails each year.
In the two studies, published in Nature and Science, researchers tested new vaccines on mice, ferrets and monkeys that duplicate another, more stable, part of the virus.
Scientists have long known that the stem of haemagglutinin - a spike-like protein, known as HA, on the surface of the virus - remains largely the same even when the tip, or "head", changes.
But until now, they have not been able to use the stem to provoke an immune reaction in lab animals or humans that would neutralise the virus, or allow the body to attack and destroy infected cells.
To make that happen, a team led by Hadi Yassine of the Vaccine Research Center at the US National Institutes of Health grafted a nano-particlesized protein called ferritin onto a headless HA stem.
The next step was to immunise mice and ferrets, then inject them with the H5N1 "bird flu" that has a mortality rate of more than 50% but is not very contagious.
The mice were completely protected against the flu, the researchers found.
And most of the ferrets, the species that best predicts the success of influenza vaccines on humans, did not fall ill either.
The other study, led by Antonietta Impagliazzo of the Crucell Vaccine Institute in Leiden, the Netherlands, took a similar approach - also creating an HA "stem-only" vaccine. It proved effective in mice. In monkeys, the vaccine provoked a high level of antibodies and significantly reduced fever following infection with the H1N1 virus, which is far less deadly than bird flu, but highly contagious.
Scientists not involved in the studies described them as a major step towards a universal vaccine, but cautioned that a lot of work had to be done, possibly over many years, before a vaccine could be tested on humans.
"This is an exciting development, but the new vaccines now need to be tested in clinical trials to see how well they work in humans," says Sara Gilbert of Oxford University.
"This is an important proof of concept for this vaccine approach," David Morens, a senior adviser at the National Institute of Allergy and Infectious Diseases at the US National Institutes of Health, says of the Nature study.
"If this type of immunity can be elicited, then in theory a vaccinated person could be protected against any influenza virus."
Source: AFP/Business Day via I-Net Bridge
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