Bird flu vaccine has its neigh-sayers

[Fred Derf Veteran]

Bird flu vaccine has its neigh-sayers

HELEN BRANSWELL

Canadian Press

Chinese researchers have shown antibodies to H5N1 avian flu generated by vaccinating horses protected mice from what should have been a lethal challenge with the virus.

But while the researchers suggest horse antibodies might provide a stop-gap answer to an expected global shortage of vaccine in the next flu pandemic, others say this type of therapy is unlikely to make it into the pandemic influenza medicine chest.

?This is horse serum (blood),? Dr. David Fedson, a retired vaccine industry executive and virologist, said from his home in France.

?You couldn't get any regulator authority, certainly in a developed country, to allow any horse serum preparation to be used for anything. It would be with great reluctance that they would do that.?

Infectious disease expert Dr. Michael Osterholm saw other problems. The challenges of generating huge amounts of horse serum would make the idea unworkable, he said.

?It surely makes for interesting science,? said Dr. Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota.

?But today we have to actually also look at the applicability of any technology to solving the problem. And the number of horses and the processing requirements that it would take to have a meaningful supply of H5N1 anti-sera is almost mindboggling for a worldwide pandemic.?

The scientific paper, by scientists from Sun Yat-sen University in Guangzhou, Kunming General Hospital and Harbin Veterinary Research Institute, showed that the antibodies horses made after being vaccinated with an H5N1 vaccine were protective in mice given a fatal dose of the virus.

The paper was published in the journal Respiratory Research.

Mice were deliberately infected with the virus, then inoculated 24 hours later with the horse anti-sera. Three different doses of anti-sera were tested ? 50, 100 and 200 micrograms ? and a control group was given blood from unvaccinated horses.

All mice in the control group died. Seventy per cent of the mice which received a 50 mcg dose survived. At the two higher doses, all the mice survived.

The authors noted that in the absence of an effective vaccine or drugs against H5N1, this form of avian influenza is likely to remain a global health threat.

?In this article, we have attempted to provide an alternative pathway of prevention and treatment of H5N1 infection,? the authors wrote, adding they hoped this therapy could play ?a potent role in combatting the H5N1 virus.?

The world faces a shortage of treatment options for pandemic influenza, particularly if the virulent H5N1 virus triggers the next pandemic. There are only four antiviral drugs that target influenza and they aren't made in the quantities the world would need.

A number of countries, including Canada, see vaccine as a cornerstone of the pandemic preparations. But vaccine will take months to make. And the global vaccine production output is so limited only a fraction of the world's people can hope to be protected this way from infection.

These realities have led to a vigorous exploration of novel alternatives. But experts said the one identified by the Chinese team is unlikely to win widespread acceptance.

Horse anti-sera, used to treat pneumococcal pneumonia before the development of antibiotics, can cause serum sickness. That condition, the body's attempt to deal with a foreign substance, can lead to joint pain and nausea ? and in acute cases, death.

Dr. Mark Loeb, an infectious diseases specialist at McMaster University in Hamilton, was cautious about the potential role horse anti-sera might play.

?I don't think it's something that should be ignored,? Dr. Loeb said. ?But I don't think this is something that's going to be mainline therapy.?

http://www.theglobeandmail.com/servlet/sto...eandHealth/home