London - Scientists have developed a flu vaccine that works against more than one strain of influenza virus, that has raised the prospect of a “universal” vaccine against all types of flu.
Currently, seasonal flu vaccines are designed against specific viral strains thought to pose the greatest threat. This means that a vaccine is often not effective if a known viral strain starts to mutate - a constant problem with influenza viruses.
This happened last winter, when health officials said that the flu vaccine they had prepared in anticipation of the influenza season protected only three percent of those who were inoculated instead of a more typical 50 percent.
Researchers have made many attempts in the past at making broader vaccines without success. Now, two groups working independently of one another have made breakthroughs by developing vaccines based on a part of the influenza virus that rarely mutates.
Both sets of researchers developed their vaccines by concentrating on the “stem” of a viral protein known as haemagglutinin (H) rather than the rapidly mutating “head” of the protein.
The flu virus uses haemagglutinin to latch on to human cells, and it is the head of the protein that changes rapidly to evade the body's immune defences. Each research team showed that the new kind of vaccine completely protects laboratory mice against several strains of the H1 subtype of influenza virus. They also found that the vaccine - based on the H1N1 flu virus - also worked against the H5N1 subtype of avian flu.
However a study in the journal Nature Medicine, led by Gary Nabel and Barney Graham, of the US National Institute of Allergy and Infectious Diseases in Bethesda, Maryland, also showed that the new vaccine protected immunised ferrets against H5N1. Ferrets are the closest animal model to human influenza because both humans and ferrets share the same receptor protein that flu uses to infect cells.
“It's really moving us in the direction of extending the breadth of protection of an influenza vaccine. We hope eventually to protect against any flu viruses that we encounter - and this is a potential step in that direction,” Dr Nabel said.
“A universal vaccine is an awfully grand ambition - that is to protect against all flu viruses to a high degree. But if we can improve current vaccines by giving them broader protection, then that would be good,” he said.
It will take between three and five years to carry out further development and testing before the vaccine could be tried on human volunteers, he added. The team built the vaccine by isolating the stem section of the virus's haemagglutinin protein and fusing it with nanoparticles made from the ferritin protein, which normally carries oxygen around the body. These particles stimulated the immune system to make antibodies against flu viruses.
The second study, to be published in the journal Science, was led by Antonietta Impagliazzo, of the Crucell Vaccine Institute in Leiden, the Netherlands, and Ian Wilson, of the Scripps Research Institute in La Jolla, California.
Professor Sarah Gilbert, of Oxford University, said: “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. This will be the next stage of research, which will take several years. So we are still some way from having better flu vaccines for humans.”
Professor Sanjaya Senanayake, a specialist in infectious diseases at the Australian National University in Canberra, added a note of caution to the findings:
“Some limitations are that these are animal studies, rather than human ones, and it is not clear how long the immunity will last from a dose of this novel vaccine.”
The Independent