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

Is Air Travel Safe?

Aviation expert says despite tragic losses of Malaysian Airlines flights 370 and 17, industry experienced lowest fatality rate in recorded history last year More

Multimedia 100 Days Later, Nigerian Girls Still Held

Activists holding rallies in Nigeria and several other countries to mark 100th day of captivity for more than 200 schoolgirls being held by Boko Haram More

Chocolate Too Bitter? Swap Sugar for Mushrooms

US food technology company develops fermentation process using mushrooms to reduce bitterness in cocoa beans, believes it will cut sugar content in candy More

Featured Videos

Your JavaScript is turned off or you have an old version of Adobe's Flash Player. Get the latest Flash player.
US Carriers Suspend Travel to Israeli
X
Carolyn Presutti
July 23, 2014 1:21 AM
The United States is prohibiting American carriers from flying to Israel's airport in Tel Aviv for 24 hours, because of rising violence between Israel and Hamas militants. The action was announced on Tuesday, after a rocket fired by Hamas militants in the Gaza Strip landed near the airport. As VOA's Carolyn Presutti tells us, international officials soon may have to determine which combat zones are too dangerous for commercial flights.
Video

Video US Carriers Suspend Travel to Israel

The United States is prohibiting American carriers from flying to Israel's airport in Tel Aviv for 24 hours, because of rising violence between Israel and Hamas militants. The action was announced on Tuesday, after a rocket fired by Hamas militants in the Gaza Strip landed near the airport. As VOA's Carolyn Presutti tells us, international officials soon may have to determine which combat zones are too dangerous for commercial flights.
Video

Video NASA Focuses on Earth-Like Planets

For decades, looking for life elsewhere in the universe meant listening for signals that could be from distant civilizations. But recent breakthroughs in space technology refocused some of that effort toward finding planets that may harbor life, even in its primitive form. VOA’s George Putic reports on a recent panel discussion at NASA’s headquarters, in Washington.
Video

Video IAEA: Iran Turns its Enriched Uranium Into Less Harmful Form

Iran has converted its stockpiles of enriched uranium into a less dangerous form that is more difficult to use for nuclear weapons, according to the United Nations’ Atomic Energy Agency. The move complies with an interim deal reached with Western powers on Iran's nuclear program last year, in exchange for easing of sanctions. Henry Ridgwell reports for VOA from London.
Video

Video Relic of Saint Draws Catholics Worried About Immigration Issue

A Roman Catholic saint who is a figure of devotion for those crossing the border into the United States is attracting believers concerned about the plight of undocumented immigrants. Mike O'Sullivan reports from Los Angeles, where a relic of Saint Toribio has drawn thousands to local churches.
Video

Video US Awards Medal of Honor for Heroics in Bloodiest of Afghan Battles

U.S. combat troops are withdrawing from Afghanistan, on pace to leave the country by the end of this year. But on Monday, U.S. President Barack Obama took time to honor a soldier whose actions while under fire in Afghanistan earned him the Medal of Honor. VOA's Jeff Seldin has more from the Pentagon.
Video

Video Ukraine Rebels Surrender MH17 Black Boxes

After days of negotiations, a senior separatist leader handed over two black boxes from an airliner downed over eastern Ukraine to Malaysian experts early Tuesday. While on Monday, the U.N. Security Council unanimously demanded that armed groups controlling the crash site allow safe and unrestricted access to the wreckage.
Video

Video In Cambodia, HIV Diagnosis Brings Deadly Shame

Although HIV/AIDS is now a treatable condition, a positive diagnosis is still a life altering experience. In Cambodia, people living with HIV are often disowned by friends, family and the community. This humiliation can be unbearable. We bring you one Cambodian woman’s struggle to overcome a life tragedy and her own HIV positive diagnosis.
Video

Video Nature of Space Exploration Enters New Age

Forty-five years ago this month, the first humans walked on the moon. It was during an era of the space race between the United States and the Soviet Union. World politics have changed since then and -- as Elizabeth Lee reports -- so has the nature of space exploration.

AppleAndroid