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Many forms of flu: one vaccine?

Because the virus is constantly changing, the shot must be updated each season. Scientists are seeking a one-size-fits-all solution.

November 14, 2005|Melissa Healy | Times Staff Writer

As bird flu continues to grab headlines and demand for doses of yearly flu vaccine surges beyond expectations, imagine a different scenario.

Instead of an annual flu shot, you could go anytime of the year to the doctor and get a painless nasal spray that would protect you from this year's flu virus -- and every year after that. The most you might need would be an occasional booster.

Vaccine makers have long wished they could teach the human immune system to recognize and fight all known strains of influenza virus, not just the few that are circulating at one time. The ever-changing nature of the influenza virus has so far made that a fantasy.

Although many hurdles remain, scientists say a universal flu vaccine -- "the dream of every vaccinologist," as noted vaccine designer Dr. Philip Russell puts it -- is closer at hand than ever.

Within at least three companies -- one British, one Israeli and one in the U.S. -- candidate universal vaccines are making their way from the lab bench toward testing. The National Institutes of Health is funding such efforts; the World Health Organization has called for more work on universal vaccines. All three companies and other groups working on this effort will be addressing the WHO in December on their progress.

"It's such a radically different approach, so it's going to require a lot of proof in the clinic to see if it works," says Ashley Birkett, director of viral immunology for Acambis, a British biotechnology firm pursuing such a vaccine. "The potential is huge, but at this point it is still potential."

Scientists are enthusiastic yet tempered in their assessment of the prospects. They question whether a universal flu vaccine will be as effective in blocking development and spread of disease as well as a yearly flu shot.

"There's every reason in the world to look at this," says Dr. Greg Poland, professor of medicine and infectious diseases at the Mayo Clinic. But, he adds, many viruses are tenacious survivors and transform themselves when confronted with a new vaccine. He notes that there's preliminary evidence that the hepatitis B and pertussis viruses have evolved after adopting to vaccines.

So too might a wily virus such as influenza.

An ever-changing enemy

To understand how a universal flu vaccine would work, it is important to understand how the flu virus has plagued our species through history.

Influenza A -- the type of flu most troublesome to humankind -- is a master of disguises, constantly eluding the human immune system by subtly changing its structure. Most years, the virus camouflages itself with just a few slight changes in the proteins that stud its surface.

But sometimes it effects a costume change so dramatic that it can saunter into the respiratory system of the most robust human, completely unrecognized as a potential killer. That's when pandemics of flu, such as the 1918 Spanish flu, which killed as many as 50 million, take hold.

Vaccine makers, armed with design and production methods little changed in half a century, struggle to keep up with this quick-change artist. Each year, international health officials huddle and make an educated guess about which of many strains will circulate most widely.

Starting with a sample of the chosen viruses, pharmaceutical companies use millions of chicken eggs to mass-produce a vaccine against the two Influenza A strains that are the greatest threat at that moment. Each year, the flu shots that result prime humans' natural defenses to recognize and fight those strains.

It's a time-consuming, costly and error-prone process. Flat-footed against this wily virus, humans have always been on the defensive.

A universal influenza vaccine would be different. The master of disguises would be unmasked.

Instead of being bamboozled by the flu virus' showy costume changes, scientists would pick dowdy, less prominent parts of the virus -- the housekeeping features that don't change year to year and are common to all strains. Presenting these pieces to the human immune system would prompt the vaccinated person to recognize and fight off any influenza virus.

Gone would be the need to guess each year's dominant flu strains eight months ahead of flu season, the endless culturing in eggs and the need to deliver the resulting vaccine to millions within a three-month window.

At least three companies as well as others in academia and business are busily at work on that endeavor, each using a slightly different approach.

Acambis uses a protein called M2 that sits on the outside of the virus, although it's buried beneath the other, more prominent proteins that our immune systems normally react to.

BiondVax Ltd., based in Israel, has developed a candidate vaccine based on several fragments of flu virus protein that haven't varied in all the pandemic strains of the 20th century.

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