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.
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 Analysts: Beijing Parade a 'Bazaar' of Stolen Technology

Show commemorating victory over Japan in World War II involved long, medium and short range missiles, a range of tanks and 200 fighter aircraft More

Bernie Sanders Surge Reflects US Shift on Socialism

Although most analysts say it is unlikely he will get the Democratic nomination, Sanders' campaign opens up questions and issues that are otherwise marginalized More

Video On IS Frontline, Kurdish Fighters Ready for Offensive

Peshmerga soldiers say although they need more heavy artillery, they are poised to take the fight to the Islamic State extremists on their turf More

Featured Videos

Your JavaScript is turned off or you have an old version of Adobe's Flash Player. Get the latest Flash player.
Drowned Migrant Toddler Photo Triggers European Outragei
X
Henry Ridgwell
September 04, 2015 11:36 AM
The harrowing picture of a drowned three-year-old Syrian boy washed up on a Turkish beach appears to have galvanized Europe’s leaders into doing more to address the refugee crisis. France, Germany and Italy issued a joint call Thursday for compulsory quotas of refugees for all EU states. But there were chaotic scenes in Hungary as police tried to force migrants off a train heading for Austria. Henry Ridgwell has more. And a caution, some of the images in this report may be disturbing.
Video

Video Drowned Migrant Toddler Photo Triggers European Outrage

The harrowing picture of a drowned three-year-old Syrian boy washed up on a Turkish beach appears to have galvanized Europe’s leaders into doing more to address the refugee crisis. France, Germany and Italy issued a joint call Thursday for compulsory quotas of refugees for all EU states. But there were chaotic scenes in Hungary as police tried to force migrants off a train heading for Austria. Henry Ridgwell has more. And a caution, some of the images in this report may be disturbing.
Video

Video Russians Observe 11th Anniversary of Beslan School Attack

This week, Russians have been observing the 11th anniversary of the attack by Islamic militants on a school in Russia's North Caucasus region that killed more than 330 hostages, including 186 children. The three-day siege and massacre that started on September 1, 2004 took place in Beslan, a town in the republic of North Ossetia, and is one of the bloodiest terrorist acts ever in Russia. VOA's Mike Richman reports.
Video

Video Native Americans Debate: Father Serra, Saint or Sinner?

Pope Francis will canonize an 18th century missionary to Spanish California during a papal visit to the United States this month.  But some Native Americans have criticized the elevation to sainthood of the missionary priest, Junipero Serra. VOA's Mike O’Sullivan has more from Los Angeles.
Video

Video Calais School Offers Another Face of Europe’s Migrant Crisis

Europe is facing mounting criticism over how it’s handling its biggest migration crisis since World War II. But not all Europeans believe building walls or passing repressive policies are the answer. A school for migrants in the French port city of Calais, is opening doors and building bonds across nationalities. VOA's Lisa Bryant reports.
Video

Video Kurdish Fighters on IS Frontline Ready for Offensive

Finger on the trigger, the Kurdish Peshmerga soldier stared across the dust at a village taken over by Islamic State extremists. The Kurdistan’s Khazir frontline, just 45 minutes from the Islamic State stronghold of Mosul. And at this point, the militants were less than two kilometers away. VOA's Sharon Behn reports.
Video

Video China Announces Troop Cuts at WWII Parade

Chinese President Xi Jinping Thursday announced plans to cut the world’s largest military force by 300,000 troops. The announcement was made during a massive military parade to commemorate victory over Japan in World War II. The event was shunned by most Western leaders and for some is raising fresh concerns about China’s military ambitions. VOA’s Bill Ide has more from Beijing.
Video

Video Russia-Japan Relations Cool as Putin Visits China for WWII Anniversary

Russian President Vladimir Putin is in Beijing for commemorations of the 70th anniversary of China's WWII victory over Japan. Putin is expected to visit Japan later this year, but tensions between Tokyo and Moscow over islands disputed since the war, and sanctions over Ukraine, could pour cold water on the plan. VOA's Daniel Schearf reports.
Video

Video Yemen ‘on Brink of Disaster’ as Medical Shortages Soar

Aid agencies warn Yemen is on the brink of humanitarian disaster – with up to half a million children facing severe malnutrition, and hospitals running out of basic medicines. There are fears Yemen's civil war could escalate as the coalition led by Saudi Arabia tries to drive back Houthi rebels, who seized control of much of the country earlier this year. Henry Ridgwell reports.
Video

Video Apps Helping Kenyan Businesses Stay Ahead of Counterfeiters

Counterfeit goods in Kenya cost the government as much as $1 billion each year in lost tax revenues. The fake goods also hurt entrepreneurs who find it hard to carve out a niche in the market and retain customers. But as Lenny Ruvaga reports from Nairobi, information technology is being used to try to beat the problem.
Video

Video Nobel Prize Winner Malala Talks to VOA

Nobel Peace Prize winner Malala Yousafzai met with VOA's Deewa service in Washington Sunday to talk about women’s rights and unveil a trailer for her new documentary. VOA's Katherine Gypson has more.
Video

Video War, Drought Threaten Iraq's Marshlands

Iraq's southern wetlands are in crisis. These areas are the spawning ground for Gulf fisheries, a resting place for migrating wildfowl, and source of livelihood for fishermen and herders. Faith Lapidus has more.
Video

Video Colombians Flee Venezuela as Border Crisis Escalates

Hundreds of Colombians have fled Venezuela since last week, amid an escalating border crisis between the two countries. Last week, Venezuelan President Nicolas Maduro ordered the closure of a key border crossing after smugglers injured three Venezuelan soldiers and a civilian. The president also ordered the deportation of Colombians who are in Venezuela illegally. Zlatica Hoke reports.
Video

Video Rebuilding New Orleans' Music Scene

Ten years after Hurricane Katrina inundated New Orleans, threatening to wash away its vibrant musical heritage along with its neighborhoods, the beat goes on. As Bronwyn Benito and Faith Lapidus report, a Musicians' Village is preserving the city's unique sound.
Video

Video In Russia, Auto Industry in Tailspin

Industry insiders say country relies too heavily on imports as inflation cuts too many consumers out of the market. Daniel Schearf has more from Moscow.
Video

Video Scientist Calls Use of Fetal Tissue in Medical Research Essential

An anti-abortion group responsible for secret recordings of workers at a women's health care organization claims the workers shown are offering baby parts for sale, a charge the organization strongly denies. While the selling of fetal tissue is against the law in the United States, abortion and the use of donated fetal tissue for medical research are both legal. VOA’s Julie Taboh reports.

VOA Blogs