Pioneering AIDS doctor turns attention to SARS

Dr David Ho joins a batch of government labs and dozens of private companies racing to develop drugs or vaccines to treat and prevent severe acute respiratory syndrome, which has killed more than 500 people and infected 7,000 across the world.

While it took years to pin down the AIDS virus, the coronavirus that causes SARS was identified and its gene map sequenced and published in less than a month.

Ho, who helped discover the powerful protease inhibitors that proved the key to the HIV “cocktail”, says his lab is working on a drug and a vaccine against SARS. “I wouldn’t say that we switched gears, but we took on an additional load,” said Ho, who heads the Aaron Diamond AIDS Research Centre at Rockefeller University in New York.

Ho and other experts believe it may be easier to find a vaccine that works against SARS than one for HIV: “Animal coronaviruses can be neutralised by antibodies much more easily than HIV. That immediately suggests that a (SARS) vaccine is going to be easier. There’s a lot of wishful thinking there, but it could turn out to be true.”

Some approaches include a “killed” vaccine, which means deactivating the virus so it can do no harm, in the hope it will stimulate the immune system to recognise and attack the “live” virus. One of the polio vaccines is a killed vaccine.

Dr Anthony Fauci, head of the National Institute of Allergy and Infectious Diseases, said a team headed by Dr Brian Murphy is doing that. He hopes to get an experimental “killed” virus vaccine ready to test in animals in a year.

There is a risk this will not work, or even that an “killed” virus could recombine with other viruses and cause harm. So another team at NIAID, headed by Dr Gary Nabel, is working on a vaccine based on tiny bits of the virus.

The idea behind genetic vaccines of this sort is to prime the immune system with the most important parts of the virus.

And a team at the US Army Medical Research Institute for Infectious Diseases, based at Fort Detrick in Maryland, is screening thousands of possible drugs.

So far, nothing looks like it would be workable, although approaches such as cystine protease inhibitors and calcium ion channel inhibitors which attack various processes the virus used to replicate, look the best, said Fauci.

The antiviral rimantidine had worked to kill the virus, said Fauci, but only at dangerously high concentrations.

Interferon beta also worked but only at high levels. “There is nothing that suggests anything we have tested will work,” he said.

Companies such as Merck & Co. and France’s vaccine-maker, Aventis AG, are also working with NIAID and the Food and Drug Administration.

FDA associate commissioner Dr Murray Lumpkin said FDA had identified 16 compounds that interfere with viral replication, made by 10 different companies.

He said any SARS treatments would likely go through the agency’s “fast track” programme.

California-based Medarex is working on a monoclonal antibody, a human immune system protein genetically engineered to target SARS.

Oregon-based AVI BioPharma Inc wants to try its “antisense” technology to immobilise the virus using mirror-image strands of its genetic material.

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