News / Africa

Scientists Seek HIV Vaccine Using Monkey Model

 A red ribbon, the symbol of the worldwide campaign against AIDS. A red ribbon, the symbol of the worldwide campaign against AIDS.
x
 A red ribbon, the symbol of the worldwide campaign against AIDS.
A red ribbon, the symbol of the worldwide campaign against AIDS.

Multimedia

Audio
Joe DeCapua
Traditional vaccine methods have been unsuccessful in preventing infection by HIV, the virus that causes AIDS. New techniques are being studied to boost antibodies or other parts of the immune system. But researchers are also working on a method to keep the immune system constantly on guard against HIV.



There are two traditional methods for creating a vaccine. One uses a weakened or attenuated version of a live virus to generate an immune response. The other uses a dead virus. Both methods are proven safe and effective, except when it comes to HIV. Vaccine candidates using these methods simply have not been successful in people when it comes to the AIDS virus.

“HIV has been a very difficult target for a vaccine for a variety of reasons. It’s designed to evade the immune response by evolution,” said Dr. Louis Picker, associate director of Oregon Health and Science University.

While attempts to make an HIV vaccine from a dead virus have failed, Picker said, using a weakened virus holds clues and possibilities when used in primates.

“The live attenuated approach actually was shown to work 20 years ago. But the problem with it was the live attenuated vaccines that actually worked were actually still pathogenic. So they weren’t safe and they could not be moved into humans. This was demonstrated in the non-human primate models – monkey model of AIDS using the virus SIV,” he said.

SIV stands for simian immunodeficiency virus.

“These SIVs that were attenuated, that prevented subsequent infection with the full pathogenic virus, still could cause disease. And people found that if you attenuated them anymore, they didn’t work anymore,” he said.

Picker and his colleagues wanted to understand why the weakened virus offered protection from infection. But at the same time, they needed to prevent it from itself causing disease. They found the answer has to do with T cells, which attack viruses. The weakened, but persistent virus vaccines somehow caused T cells to be ever vigilant. But if the virus was weakened too much, the T cells were not triggered to attack. They concluded that an “effective HIV vaccine might have to persist in the body.”

Picker said, “The unique aspect of the live attenuated vaccines that seem to work was that they were persistent. They weren’t cleared by the host immune system, but they were able to stick around. Of course in the case of HIV/SIV that’s a bad thing, because eventually those live attenuated vaccines would gain strength and cause disease. But probably the fundamental reason, at least what I hypothesized, that they would be able to elicit protection was because of that persistence.”

So, they looked for another persistent virus that was not pathogenic, which might generate T cell immune response.

“The virus that we selected was a virus called cytomegalovirus (CMV), which is actually a virus from a different family of viruses altogether, but it’s one that most people in the world are infected with. But it’s unique in that you can re-infect these people with a virus that now has within its genes HIV genes and then the body would make immune responses to those HIV genes,” he said.

The HIV genes that would be placed in the harmless virus, he said, would not cause disease.

“When they’re introduced into the vaccinee, the immune response recognizes these HIV bits as if they’re part of CMV and raises immune response to it,” he said.

That’s the plan, anyway. The difficult part is making a version of the vaccine that’s safe and effective for humans. That requires an approved vaccine candidate and years of clinical trials.

Meanwhile, in Thailand, a follow-up study is getting underway of the RV 144 vaccine candidate. Several years ago, a study showed that it did indeed provide some measure of protection against HIV, but not enough, being only 31 percent effective.  A clinical study called RV 305 will use the same vaccine components as RV 144, but will attempt to boost and extend the immune response through antibodies.

You May Like

Video On The Scene: In Gaza, Darkness Brings Dread and Death

Palestinians fear nighttime bombardment, VOA correspondent finds More

African Small Farmers Could Be Key to Ending Food Insecurity

Experts say providing access to microloans, crop insurance, better storage facilities, irrigation, road systems and market information could enable greater production More

University of Michigan Wins Solar Car Race

Squad guided its student-designed solar-powered vehicle to fifth consecutive time victory in eight-day bi-annual American Solar Challenge More

Featured Videos

Your JavaScript is turned off or you have an old version of Adobe's Flash Player. Get the latest Flash player.
Vietnamese Staging Chinese Product Boycott After Oil Rig Spati
X
Reasey Poch
July 28, 2014 7:18 PM
China recently pulled an oil rig from an area of the disputed South China Sea that Vietnam also claims. Despite the action, the incident has had a lingering effect on consumers in Vietnam. VOA's Reasey Poch reports from Hanoi on an effort to boycott Chinese products.
Video

Video Vietnamese Staging Chinese Product Boycott After Oil Rig Spat

China recently pulled an oil rig from an area of the disputed South China Sea that Vietnam also claims. Despite the action, the incident has had a lingering effect on consumers in Vietnam. VOA's Reasey Poch reports from Hanoi on an effort to boycott Chinese products.
Video

Video ESA Spacecraft to Land on a Comet

After a long flight through deep space, a European Space Agency probe is finally approaching its target -- a comet millions of kilometers away from earth. Scientists say the mission may lead to some startling discoveries about the origins of the water on earth. VOA’s George Putic has more.
Video

Video Young Africans Arrive in US for Leadership Program

President Barack Obama's Young African Leadership Initiative has brought hundreds of young Africans to the United States for a six-week program aimed at building their knowledge and skills in fields such as public administration and business. Out of the 50,000 young Africans who applied for the program, just one percent was accepted. VOA's Laurel Bowman caught up with some of those who made the cut and has this report.
Video

Video In Honduras, Amnesty Rumors Fuel US Migration Surges

False rumors in Central America are fueling the current surge of undocumented young people being apprehended at the U.S. border. The inaccurate claims suggest the U.S. will give amnesty to young migrants from the region. As VOA's Brian Padden reports from Honduras, these rumors trace back to President Obama's 2012 executive order to halt deportations for some young undocumented immigrants already living in the United States.
Video

Video Students in Business for Themselves

They're only high school students, but they are making accessories for shoes, fabricating backpacks and doing product photography - all through their own businesses. It's the result of a partnership between a non-profit organization that teaches entrepreneurship and their schools. VOA's Mike O'Sullivan and Deyane Moses met the budding entrepreneurs near Los Angeles.
Video

Video Astronauts Train in Underwater Lab

In the world’s only underwater laboratory, four U.S. astronauts train for a planned visit to an asteroid. The lab - called Aquarius- is located five kilometers off Key Largo, in southern Florida. Living in close quarters and making excursions only into the surrounding ocean, they try to simulate the daily routine of a crew that will someday travel to collect samples of a rock orbiting far away from earth. VOA’s George Putic has more.

AppleAndroid