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SCIENCE IN THE NEWS #2099 - Digest

By StaffThis is Steve Ember.And this is Bob Doughty with SCIENCE IN THE NEWS, a VOA Special English program about recent developments in science. Today, we tell about an experimental vaccine against the disease AIDS. We tell about an international conference on climate change. And we tell about a special operation to treat a little girl with a rare and deadly blood disease.

American scientists say an experimental AIDS vaccine has successfully prevented monkeys from developing the disease. The vaccine is designed to make the animals' immune system attack and control H-I-V, the virus that causes AIDS.

The vaccine did not prevent the monkeys from becoming infected with the virus. But it did prevent them from getting sick. The results suggest that a similar vaccine might be developed that could help control the virus in humans.

More than thirty-five-million people are infected with the AIDS virus around the world. AIDS researchers say a vaccine is the only way to slow the rate of infections. But efforts to develop a vaccine have been slow. And many earlier vaccine trials have failed.Norman Letvin led the team that developed the vaccine. He is an AIDS researcher at the Harvard Medical School in Boston, Massachusetts. He said most research today only deals with ways to prevent AIDS. He says a vaccine is needed to help people from becoming sick after they become infected.

Most vaccines contain parts of a virus. This causes the body to produce proteins called antibodies. Antibodies attach to a virus and help other immune cells find and kill the virus. But this does not work with H-I-V. Scientists say this is probably because the virus changes so quickly.

Doctor Letvin said the new vaccine works by strengthening another part of the immune system called killer T-cells. These cells kill cells the virus has already infected. Doctor Letvin's research showed that T-cells alone could help control H-I-V.The scientists made the experimental vaccine with a combination of genetic material from two kinds of AIDS virus. They used genetic material from H-I-V, which infects humans, and S-I-V, which infects only monkeys. The researchers added a natural protein to the vaccine to increase T-cell activity.

The researchers worked with a team at Merck Research Labs in West Point, Pennsylvania. They tested twenty monkeys. They injected the experimental vaccine in some of the monkeys. They gave a false vaccine to other monkeys. The researchers infected all the monkeys with an AIDS virus that causes the disease very quickly.

The monkeys that received the false vaccine all became sick. Half of them died within one-hundred-forty days. However, none of the monkeys that were given the experimental vaccine became sick after eight months. The vaccinated monkeys produced killer T-cells that attacked the virus. The vaccine appeared to help suppress the amount of the virus in the blood.But scientists say even a small amount of virus in the blood may be dangerous. H-I-V can cause disease in people who suppress the disease for many years.

The researchers do not know how long the vaccine will remain effective in the animals. They say more injections of the vaccine may be needed. But they say the work provides hope that a human version of the vaccine might be able to replace costly AIDS drugs. And they say the vaccine may make it less likely that infected people could pass the virus to other people. However, researchers warn that a vaccine that is effective in monkeys may not be effective in humans.

((MUSIC BRIDGE))You are listening to the Special English program SCIENCE IN THE NEWS on VOA. This is Steve Ember with Bob Doughty in Washington.

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An international conference on climate change is being held in the Netherlands. Delegates in The Hague are discussing ways to deal with rising temperatures on earth.

Three years ago, representatives of more than one-hundred-sixty nations signed a treaty designed to slow climate change. The treaty urges industrial nations to reduce gases produced by factories and vehicles. Many scientists believe that carbon dioxide and other industrial gases trap heat in earth's atmosphere. However, many nations still have not approved the treaty.

The conference delegates are attempting to negotiate details of the agreement. They also are studying new information about climate change.Last month, an international team of scientists reported that human activity is partly to blame for the rising temperatures. The scientists also said the earth could get warmer than earlier studies had suggested.

Their findings are included in a report prepared for the United Nations. The report is expected to get final approval at a U-N conference next year. The findings are expected to widely influence climate debate over the next several years.

Five years ago, scientists said they expected average temperatures to rise about three degrees Celsius during the next century. The new report suggests that temperatures could rise as much as six degrees Celsius during the period. However, not everyone is satisfied with the report. Some scientists say there is little solid evidence that any climate change would have harmful effects.A new American study examines the possible effects of climate change across the United States. A federal science agency prepared the study for Congress.

The study found that average temperatures will rise by three to five degrees Celsius over the next century. It warns that climate changes will damage environmental systems. The American government report says these changes will influence water supplies in every area. And, it calls for actions to protect food supplies and the public health.

((MUSIC BRIDGE))Doctors are closely watching the condition of six-year-old Molly Nash. The girl is fighting a rare and deadly blood disease. Recently, doctors in Minneapolis, Minnesota performed a special operation to treat Molly. She received special cells from the blood of a baby who was created to save his sister's life. Doctors say that tests show the treatment is a success.

Molly was born with a disease called Fanconi anemia. The disease prevented her body from making bone marrow. Her bone marrow could not produce red blood cells to carry oxygen. She could not produce white blood cells to fight infections. And she could not produce platelets to help blood clot.The only proven treatment is a bone marrow transplant operation. The rate of success is highest when the patient's brother or sister provides bone marrow for the treatment. Molly did not have a brother or sister so her parents decided to create one.

Doctors took eggs from Molly's mother and sperm from her father to create embryos in the laboratory. The scientists tested the genes of the embryos for the presence of Fanconi anemia. They also used tests to identify an embryo that was able to provide special cells for the transplant operation. Doctors then placed the embryo in Molly's mother. She gave birth to a boy, Adam, at the end of August. Doctors saved blood from the umbilical cord that had connected Adam with his mother. They placed special stem cells from the blood into Molly. Stem cells are able to grow into many kinds of tissue, including bone marrow.John Wagner of the University of Minnesota performed Molly's transplant operation in September. Three weeks later, he announced that tests show Molly is carrying bone marrow cells belonging to Adam. Doctor Wagner says she is producing platelets and white blood cells for the first time in years.

This was the first known case in which parents used genetic tests to choose a baby because of its ability to save their other child's life. Some observers say this raises important questions for society. Doctor Wagner says the medical community should hold a public debate about the issue.

This SCIENCE IN THE NEWS program was written by Cynthia Kirk and George Grow. It was produced by George Grow. This is Steve Ember.And this is Bob Doughty. Join us again next week for more news about science in Special English on the Voice of America.