VOA常速英语:Research Group Has High Hopes for New TB Vaccine

Physicians have long known that the so-called "BCG" vaccine for tuberculosis does not provide the same level of protection against the disease in all parts of the world.  Some also say the vaccine's effectiveness has been declining since its development in the 1920s, and that it protects against only certain kinds of TB infections.  Now, a non-profit health organization says a new gene-based vaccine it's developing has shown promise as a better source of immunity against tuberculosis, a disease that kills nearly two million people every year. 

Aeras is a U.S. based non-profit group dedicated to the development of tuberculosis vaccines.  It currently has five vaccines in the pipeline, two of which are being tested for safety and efficacy.

Michelle Stone, the director of Vaccine Discovery at Aeras, says one of the new vaccines successfully induced complete immunity in laboratory mice - a result she calls unique:

“In most of the vaccines that we have been putting through clinical trials, you see a reduction of one to two blocks of bacterial burden [amount of infection] in an animal," said Stone. "And in this one, in some - not all - they saw complete elimination of bacteria from the animal.”

The new vaccine is based on research at New York's Albert Einstein College of Medicine.  Dr. William Jacobs, who led the project, says the vaccine development team used cutting-edge scientific techniques - to genetically engineer 26 different strains of TB bacterium.  He says those altered bacteria, when injected into lab mice in large doses, provided the mice with absolute immunity to TB.

“It's different from any other vaccine that is out there and different at this point is good because people have tried a lot of things," said Jacobs. "Before we did these studies I didn’t even think that was possible but now I have hope.  Now that we have actually seen it we can make this happen in humans.”

But Michelle Stone says it will not be easy to replicate the results from the experiments on mice - to produce a similar vaccine for humans.

“Putting back 26 different genes is unique but then that also makes it difficult for them because by putting that gene sequence in they now need to go back and figure out which specific ones are responsible for yielding protection, so that when you are making a product out of it,  you are only giving the genes or the proteins that are responsible for protection and not just an extra sequence that’s not yielding any protection," she said.

Experts say developing a TB vaccine has been a challenge because the bacterium that causes it keeps evolving and developing resistance to drugs, making the pathogen a more difficult, moving target.

Stone believes the promising results at Aeras mean the global scourge of this persistent and deadly disease may one day be ended.  She says Aeras hopes to have an effective new vaccine against TB by the end of this decade.