Nasal solution joins SARS race
Vaccine against fatal virus works in monkeys.
As human trials of a vaccine for severe acute respiratory syndrome (SARS) kick off in China, US researchers are developing the first nasal vaccine for the disease.
"The nose is where the infection attacks, so it is very effective," says Peter Collins, an infectious disease scientist at the National Institute of Allergy and Infectious Diseases in Bethesda, Maryland, who is involved in the study.
SARS, caused by a virus similar to the common cold, emerged in Southeast Asia in late 2002 and killed nearly 800 people in 2003. Outbreaks have been controlled but there is the possibility that the disease might re-emerge.
In preparation, scientists worldwide are racing to develop SARS vaccines using various approaches, most of which are designed for injection into the bloodstream rather than the nose.
These vaccines consist of either dead or live versions of the SARS virus, or parts of the virus, that stimulate the body to produce protective antibodies against the disease. Some vaccines contain the antibodies themselves.
The new nose vaccine, described in The Lancet, is a weakened version of a flu virus11. Inserted into that virus is a gene from the SARS virus that is sufficient to trigger an immune response against the disease. Details of the gene itself have just been published in the Proceedings of the National Academy of Sciences22.
The US team have tested their nasal vaccine in monkeys and found that it prevented SARS infection with a single dose.
"This is good news; monkeys are very similar to humans," comments Albert Osterhaus, a virologist at the Erasmus Medical Centre in Rotterdam, the Netherlands.
In the experiment, the team gave a single dose of the vaccine to one of two groups of four African green monkeys (Cercopithecus aethiops). After four weeks, swabs were taken from the animals' noses and throats and analysed for the SARS virus.
In the vaccine-treated group, the SARS virus did not multiply and infection was prevented. In the untreated group, the virus was able to replicate.
As it is, the vaccine is only effective in children, because adults are immune to the flu virus being used. "Now we will try a different virus for adults," Collins told Nature Science Update.
Collins acknowledges that his approach to developing a SARS vaccine is just one of many, and others may be equally successful. "All the approaches are good and worth pursuing," he says.
A Chinese company, Sinovac Biotech, based in Beijing, began the world's first clinical trial in May. Their trial involves inoculating humans with a dead version of the SARS virus. So far, four volunteers have been injected. The vaccine appears to be safe, but the researchers do not yet know whether it will provide protection against SARS by stimulating the production of protective antibodies.
Osterhaus has also been developing a SARS vaccine. His vaccine, which he has tested on a group of four ferrets, consists of the SARS antibodies themselves33. Four days after contact with the SARS virus, levels of the virus were 2,000 times lower in treated ferrets than in untreated animals.
But although progress is certainly promising, experts warn that other disease control measures, such as minimizing the spread of the disease, are also important. "My view is that the future lies in public health, not vaccines," says David Brown, a molecular biologist at the University of Cambridge.
Meanwhile, Swiss vaccine company Berna Biotech, based in Bern, announced earlier this month that it is abandoning trials of its own SARS vaccine, saying that fears of another epidemic have waned.
- Bukreyev A, et al. The Lancet, 363, 2122 - 2126, (2004).
- Buchholz U. J., et al. PNAS, (2004)doi:10.1073/pnas.0403492101.
- ter Meulen, J. et al. The Lancet, 363, 2139 - 2141, (2004) http://www.thelancet.com.