Super-vaccine 94 years later

LOS ANGELES - An improved vaccine against tuberculosis could be ready for testing in people as early as next year.

Researchers say the vaccine is based on a formulation nearly a century old, but was dramatically better and protected all tested guinea pigs against disease.

"It's a pretty potent vaccine," says Dr Marcus Horwitz, a professor at the University of California Los Angeles, who led the study.

"The difference between the unvaccinated guinea pigs and those that were vaccinated is just day and night."

Tuberculosis is highly infectious and can be passed on by sneezing or even by breathing dust into which infected people have spat.

"Tuberculosis is the greatest cause of death from a single infectious agent, killing two million people each year worldwide," says Dr Horwitz.



Aids has recently outpaced TB, killing three million people in 1999, but many Aids victims actually die of tuberculosis because of their weakened immune systems.

A vaccine already exists - the BCG vaccine, developed between 1906 and 1919 from weakened bacteria which infect cattle.

It has been widely used, but is only about 50 per cent effective. No one has been able to make a better vaccine.

Dr Horwitz's team tested guinea pigs, which develop a form of tuberculosis very similar to the human disease. They started with two versions of the BCG vaccine, and added a protein they thought might work, based on previous studies.



"This particular protein helps build the cell wall of the bacterium, and is out in the open where the body's immune system can see it," Dr Horwitz says.

"Tuberculosis is inside white blood cells," he says. "You need a way for the immune system to know that the cell is infected so it can do something about it."

The researchers genetically engineered the BCG vaccine so it also produced this protein.

Dr Horwitz says the vaccine would be cheap and easy to administer.

One drawback is that the vaccine will probably not be useful for people with HIV.

"It can cause disease in immunocompromised patients," he says.

Aids patients who got the vaccine would have to be carefully monitored to make sure they did not develop disease from the vaccine.

- REUTERS