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Researchers Improve Tuberculosis Vaccine

An international team of researchers plans to begin testing a new vaccine they say shows promise in protecting people against tuberculosis, a disease that infects nine million people each year and kills more than two million. The drug is an improved version of a vaccine that was developed in the early part of the last century.

Since the 1920s when it was developed, almost three billion people around the world have received the BCG vaccine. It's made from a weakened virus that causes a version of tuberculosis in cattle.

For reasons that are poorly understood, BCG protects newborns against TB but not adults, even though they might have been vaccinated as infants.

Immunologist Stephan Kaufmann of the Max Planck Institute in Berlin, Germany, says there are a number of theories as to why BCG does not work in adults, who are most affected by the deadliest form of TB, pulmonary tuberculosis.

"One (theory), which we actually favor, is that BCG can control the bacteria to a certain level, but it can't eradicate them. So, that's sufficient to control disease outbreak in young children. But even these young children that are protected at early ages can develop TB," Dr. Kaufmann says.

English, French, Dutch and German researchers, led by Dr. Kaufmann, have developed a vaccine they hope will work in adults.

In a study involving laboratory mice, scientists gave an improved version of BCG to animals exposed to TB and compared the results to animals inoculated with the older vaccine. Traditional BCG protected 90 percent of the mice exposed to the TB bacteria while 99 percent of exposed mice vaccinated with the improved serum were shielded against the disease.

To further test the vaccine's effectiveness, researchers vaccinated mice exposed to a drug-resistant strain of tuberculosis that's emerging from China and spreading all over the world.

"We found that the conventional BCG is totally ineffective in the mouse model against these clinical isolate from Beijing strains,"Dr. Kaufmann says. "And that was kind of a proof that indeed this pathogen, this strain, is more resistant. But to our rewarding feeling, the new BCG vaccine strain we developed could still protect against this clinical isolate."

Dr. Kaufmann says he hopes the new BCG, which works so well in mice, will work just as well in humans.

Investigators hope to begin clinical trials next January.

The work on the new and improved BCG vaccine against tuberculosis is published in the September 1st issue of the Journal of Clinical Investigation.