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Top bird flu scientist says H5N1 is worst flu virus

One of the world’s leading experts on bird flu said Thursday the H5N1 virus is like nothing he’s ever seen, and there are still way too many gaps in planning and knowledge for the world to grapple with it in the event of a pandemic.

“I’ve worked with flu all my life, and this is the worst influenza virus that I have ever seen,’’ said Robert G. Webster, a virologist at the St. Jude Children’s Research Hospital in Memphis, Tennessee. “We have to realize that this influenza virus in poultry becomes systemic ... If that happens in humans, God help us.’’

Webster predicted it would take at least 10 mutations before the H5N1 virus could transmit from human to human. But he said there’s no way to know how long - or if - it would take for that to happen.

“All of those mutations are out there, but ... the virus hasn’t succeeded in bringing it together,’’ he said at the end of a two-day bird flu conference in Singapore organized by The Lancet medical journal.

Experts fear the H5N1 bird flu virus will mutate into a form that easily spreads from person to person, potentially sparking a global pandemic. So far, most human cases have been linked to contact with infected birds.

Webster also called for more pre-pandemic vaccine to be stockpiled, calling current efforts “miserable.’’

He said new research in ferrets suggests that vaccination with a bird flu virus that circulated earlier in Hong Kong, protected the animals from dying when they were infected with the H5N1 virus currently circulating in Vietnam. Such vaccination could also be used as a primer in humans, he said.

If a pandemic strain emerges “you will probably get infected, you will probably get very sick, but you probably won’t die,’’ he said. “So, I think we’re missing out here.’’ Webster said much more research is needed in many areas to understand the virus’s behavior and transmissibility.

He said cultural issues are also preventing autopsies on victims killed by the H5N1 virus, hindering valuable scientific research. In many Asian countries, where most of the human bird flu deaths have occurred, people do not believe in disturbing the body after death.

He said post-mortem examinations have been performed on less than six of the 113 people killed by the bird flu virus since it began ravaging Asian poultry stocks in late 2003.

“The cultural ban in this region on autopsies has to be worked out somehow,’’ he said. “Tissues have to be taken from cadavers to understand the biology of these viruses.’’

Source used in this story:

Associated Press

02 May 2006
U.S. Medical Agency Funds Successful Bird Flu Vaccine Test

New vaccine protected mice, ferrets against lethal H5N1 virus

Washington – A commercially developed vaccine funded by the U.S. National Institutes of Health has protected mice and ferrets against a highly lethal avian influenza virus.

California company Vical Inc., developed the vaccine, and an investigator at St. Jude Children’s Research Hospital in Tennessee led the study, according to a May 2 St. Jude press release.

The finding, coupled with results of previous studies that showed protection against multiple human influenza strains, suggests that such a vaccine would protect humans against multiple variants of the bird and human influenza viruses, said Richard Webby of St. Jude.

Such a vaccine could protect people against an H5N1 bird flu virus that mutates to adapt to humans, not just birds, and easily can spread from person to person, Webby said.

Flu experts and public health officials fear that such a variant of H5N1 would trigger a human pandemic.

The studies included 16 mice or six ferrets in each vaccine or control group, and the investigators used two versions of Vical’s DNA-based vaccine in the studies.

One vaccine was directed against three viral proteins – NP, M2 and H5.

NP and M2 usually do not mutate quickly (they are “conserved”) and are slow to avoid immune responses that a vaccine triggers.

H5 is a mutating (“variable”) protein on the surface of the bird and human flu viruses that is critical to the viruses’ ability to infect cells. The H5 protein easily mutates, so it can avoid immune responses triggered naturally or by a vaccine.

The other vaccine used in the study contained only the two conserved viral proteins, NP and M2.

All test DNA vaccines were formulated with the company’s VaxfectinTM adjuvant. An adjuvant is an additive administered with a vaccine that has little effect by itself, but improves the response of the immune system to the vaccine.

In the St. Jude study, the three-component vaccine (H5, NP, M2) protected the mice completely against potentially lethal challenges with a highly virulent H5N1 avian influenza virus.

Other studies showed that a version of the vaccine containing only the NP and M2 components provided significant protection against several strains of human influenza virus and the H5N1 bird flu strain.

“By stimulating immune responses against targets not likely to mutate,” he added, “the vaccine could trigger an immune defense against a broad range of variants of the virus.”

Even if the bird flu virus mutates to adapt to humans, Webby said, cross protection would let the immune system track and attack such an emerging new variant “without missing a beat.

“We wouldn’t have to wait to start developing a vaccine against it until after the original virus mutated,” he added, which would have to be done now if bird flu adapted to become transmissible between humans, the mutation that could lead to a human pandemic of disease.

Webby’s team showed that all mice and ferrets that received the DNA vaccine survived the challenge with the virulent H5N1 strain; those that received a “blank” (placebo) vaccine did not survive.

The vaccine also prevented weight loss in all animals challenged with the virulent virus, suggesting that the vaccine might also protect humans against serious flu-related sickness. The DNA vaccines targeted NP and M2 – with and without the H5 avian influenza virus surface protein.

The full text of the St. Jude Hospital press release is available on its Web site.

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