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By Susan Okie
Washington Post Staff Writer
Tuesday, June 4, 2002; Page A08

Preliminary testing of a new tuberculosis vaccine in humans is expected to begin by the end of this year, experts said yesterday. The planned safety trial would mark the first time in about 80 years that a new vaccine has been tested against the tuberculosis bacterium, which infects an estimated one-third of the world's population.

In the past decade, there has been a resurgence of scientific effort and international funding to fight TB, which kills about 2 million people worldwide each year, according to health officials and researchers who spoke to reporters yesterday at the Fourth World Congress on Tuberculosis. However, bacterial strains that resist treatment with existing drugs are becoming increasingly prevalent, making the development of new drugs and vaccines essential to controlling the epidemic.

"We won't even begin to approach the goal of elimination of TB as a global health problem without developing new tools," said Philip Hopewell of the University of California at San Francisco.

There were 15,989 cases of TB reported in the United States last year, half of them among people born in other countries. Tuberculosis infection may remain dormant in the lungs for many years, often for a lifetime. In 5 percent to 10 percent of those infected, the disease becomes active, usually causing fever, night sweats and coughing that can transmit the bacteria to others.

Someone with active TB must take medicines daily for six to nine months to halt progression of the disease. The World Health Organization has spearheaded an approach called DOTS (directly observed treatment, short-course) to ensure that people with TB take their drugs faithfully, which increases cure rates and prevents emergence of resistant strains. But despite expansion of the strategy, especially in China and India, where one-third of TB deaths occur, currently only 27 percent of the world's TB cases are detected and treated within DOTS programs, Hopewell said.

People whose immune systems have been damaged by HIV infection are especially vulnerable to TB, which is a major cause of death among such individuals, especially in developing countries. Although a full course of TB treatment costs only $10, not enough money is available to find and treat all active TB cases worldwide, said Jong-Wook Lee of the World Health Organization. "The gap is $300 million" annually, he said.

About 15 percent of funds from the new Global Fund to Fight HIV, Tuberculosis and Malaria have been allocated to tuberculosis detection and treatment, said Kenneth Castro of the federal Centers for Disease Control and Prevention. The Bill and Melinda Gates Foundation is also funding efforts to develop new vaccines, drugs and tests for TB.

The recent decoding of the genetic sequence of Mycobacterium tuberculosis, the TB bacterium, represents a potential breakthrough for development of new drugs and vaccines, said Douglas Young of London's Imperial College. One discovery stemming from new genetic knowledge is that of isocitrate lyase, an enzyme that TB bacteria apparently need to maintain themselves even when they are quiescent. Current drugs against the disease can kill the bacteria only when they are multiplying. A drug that blocked the action of the enzyme might work better and faster than current treatments, Young suggested.

The TB vaccine slated for testing in humans later this year is a new version of BCG, a partially effective vaccine introduced 80 years ago. BCG is widely used in developing countries to prevent severe TB in childhood. Developed by California researcher Marcus Horwitz, the new vaccine is genetically engineered to prompt production of a specific bacterial protein that has been found to protect mice from the disease, said Carol Nacy of the Rockville-based Sequella Foundation. The clinical trial, currently planned to take place in San Francisco, would test the vaccine's safety, she said.

Other vaccines being developed may be used to boost the immune systems of TB-infected individuals to reduce their likelihood of developing active disease, or as an adjunct to drug treatment to prevent relapses, Nacy said.

"We are not anywhere convinced that any of the vaccines [about to undergo] testing in humans today are going to be the vaccine," she said. "We simply have no way to know what is going to work."