September 13th, 2011
06:02 PM ET
After 2 years of analyzing the results of the largest AIDS vaccine clinical trial ever held – called RV144 - researchers say they have found 2 ways the immune system can respond, which could predict whether those inoculated will be protected or are more likely to become infected with HIV.
The new data was released at the annual AIDS Vaccine conference, the largest scientific venue that brings together the world's top scientists, policy makers, community advocates and funders who focus exclusively on AIDS vaccine research. The conference is hosted by the Global HIV Vaccine Enterprise. This year's co-hosts are Mahidol University where RV144 trial was conducted and Thailand's Ministry of Public Health.
According to the World Health Organization (WHO), in 2009 33.3 million people were living with HIV, there were 2.6 million new infections and 1.8 million AIDS-related deaths worldwide. Since the epidemic started more than 60 million people have been infected and nearly 30 million have died of the disease.
RV-144 was a phase III clinical trial of more than 16,000 healthy Thai adults. Trial results that were released in September 2009 found the vaccine was 31% effective in preventing HIV infections. Study investigators called it "modestly protective." They also suggested the study provided proof that a vaccine might be possible. Since then researchers have culled data from the study looking for clues as to why the vaccine protected some but not others. In this new study, they found that the vaccine produced 2 types of immune responses: One led to an increased vaccine efficacy, which means the vaccine would prevent infection. The other immune response led to the same infection rate as a placebo, according to Dr. Barton Haynes, Director of the Duke Human Vaccine Institute at Duke University School of Medicine.
Antibodies are proteins made by the immune system to identify and fight off things foreign to the body like viruses and bacteria.
Barton, who oversaw much of the research, says this new information will be helpful in the design of future clinical trials. "We now have an informed hypothesis, we have signals. Now we know where we want to go"
The news generated excitement among other scientists at the conference.
"What we now have are clues, why it might work," Dr. Carl Dieffenbach. "Something we haven't had over the last 30 years, so that's very important."
Still, Dieffenbach says, "We cannot put all our eggs in a single basket and we will continue to pursue other approaches."
This latest advance comes on the heels of a number of scientific breakthroughs in HIV/AIDS research. In 2010, the CAPRISA 004 (Centre for the AIDS Programme of Research In South Africa) showed a 39% reduction in new HIV infections in sexually active, HIV-negative South African women using tenofovir gel, an antiretroviral (ARV) microbicide. Tenofovir helped prevent the virus from reproducing inside cells.
In another 2010 study, the iPrEx trial, men who have sex with men (MSM) took the antiretroviral pill Truvada daily. HIV transmission was reduced 44% over those who got the placebo. A study in May by the HIV Prevention Trials Network–HPTN 052, found giving people with the infection antiviral therapy reduced the risk of HIV transmission to their uninfected partner by 96%. And this summer, more positive news from two separate trials. In Botswana the PrEP or pre-exposure prophylaxis trial found heterosexuals reduced their risk of infection by 63% if the uninfected partner took an antiretroviral drug daily. In Kenya and Uganda, a separate PrEP study using different ARV drugs also found between 62-73% fewer infections in couples with one infected partner.
But some researchers here say the vaccine is still the "holy grail." Which is why this news is getting such buzz at the conference.
"It's exciting because it's the first time getting a glimpse of how an HIV vaccine works." Catherine Hankins, Chief Scientific Advisor, UNIAIDS said. "We need a vaccine if we are going to end the epidemic."
Haynes says the next step is to continue mining the data for clues that will help them determine how researchers can anticipate what will happen in future trials.
"Vaccines like HIV are difficult [to develop] because of the nature of the bug. It's requiring a more intense effort. There has never been a vaccine against a retrovirus in humans, so this is a new paradigm."
But even with this modest advance researchers say, there's still a lot to be done before a vaccine is ready globally and for the general public.
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