Synthetic Meningitis Vaccine Created

More study needs to prove it improves on current version

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By
HealthDay Reporter

THURSDAY, July 22, 2004 (HealthDayNews) -- Cuban and Canadian researchers have developed a synthetic vaccine against a bacterium that can cause meningitis in young children.

However, one expert said the scientific achievement may not be of any practical importance unless further study shows it works better than the current vaccine, which uses molecules extracted from the bacterium itself.

The bacterium is Haemophilus influenzae type b, more commonly known as Hib. It can mount an attack against the lining of the brain, causing meningitis that can be fatal in the early months and years of life.

Vaccines using polysaccharide molecules extracted from bacteria have been available for a decade and have become a routine part of the childhood vaccination schedule in the United States and many other countries. Although the prevalence of the bacterium has declined in developed countries, more than 600,000 infant deaths due to Hib-induced pneumonia or meningitis occur in developing countries each year.

Now researchers at medical research centers in Cuba and the University of Quebec report development of a Hib vaccine using laboratory-made versions of those polysaccharide molecules.

The feat "sets the stage for further development of similar approaches against other human pathogens," said the report, which appears in the July 23 issue of Science.

Such efforts are under way. Several laboratories are working on synthetic vaccines for HIV, the virus that causes AIDS. And a program to develop such a vaccine against cholera is being carried out at the National Institutes of Health, said Paul Kovac, a senior investigator at the National Institute of Diabetes and Digestive and Kidney Diseases.

A synthetic vaccine offers some potential advantages over the traditional approach, Kovac said.

"The traditional vaccine is based on attenuated cells," he said. "When you put it into people to trigger the immune system, in addition to antigenic material against the bacteria, you also create a host of other antigenic material that may result in undesirable side effects. If we put into people only limited antigens, mainly those that are specific for the disease, presumably it can be without those side effects."

A more skeptical reaction comes from Harold Jennings, a vaccine expert who is a group leader at the Institute of Biological Sciences of Canada's National Research Council.

"Scientifically, it's probably pretty good," he said. "I question whether it can be commercially viable."

The Hib vaccines now in use consist of polysaccharides from the bacteria that are laboratory-manipulated to be pure and are attached to proteins, Jennings said. "I don't see an issue at all" in terms of side effects, he added.

The synthetic vaccine "might have an advantage if the performance is better," Jennings said, but there is no proof of that yet.

The Cuban-Canadian report said a trial of the vaccine in more than 1,100 children did show effective protection and that the vaccine "was demonstrated to be as safe and immunogenic in humans as already-licensed vaccines incorporating the native polysaccharides."

"There has been an Hib vaccine around for 10 years," Jennings said. "From my perspective, the thing I question is whether this vaccine would be economically feasible."

More information

The Hib vaccine story is told by the Children's Vaccine Program.

SOURCES: Paul Kovac, Ph.D., senior investigator, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, Md.; Harold Jennings, Ph.D., group leader, Canadian National Research Council Institute of Biological Sciences, Ottawa; July 23, 2004, Science

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