Medical DevicesNew Advances On The Long Road To The Development Of An AIDS Vaccine
AIDS Vaccine Day, May 18, marks the occasion in 1997 when U.S. President Bill Clinton challenged researchers to come up with an AIDS vaccine within the following decade, stating that such a vaccine was the only way to eliminate the threat of AIDS. Twelve years later, the goal of an effective HIV vaccine remains unfulfilled, but the need for one remains urgent. AIDS is the number four killer in the world and number one in sub-Saharan Africa. Despite education and prevention campaigns, every day 7,500 people become infected with HIV. Antiretroviral drugs can prolong the lives of those who are infected, but they are not cures, and because of their cost and logistical difficulties, they reach only a minority of those who need them. And for every two individuals who go on antiretroviral treatment, five become HIV infected. As with any major viral pandemic, a vaccine remains the best hope of ending, and not just mitigating, AIDS.
Development of an effective AIDS vaccine will require time and perseverance. Many of today"s licensed vaccines took decades to develop and were the product of many failed attempts. That"s how science works. With each miss, or near hit, researchers learn something-if only what not to do-that advances their progress.
As a result of this kind of incremental learning, we are facing an exciting time in AIDS vaccine science. AIDS vaccine research and development has focused on two arms of the immune system: the arm that dispatches T-cells to seek and destroy human cells that have become HIV infected, and the arm that stimulates the production of antibodies to block HIV from infecting cells in the first place. Today, there are promising new advances on both fronts.
In the past decade, most HIV vaccine development has focused on the T-cell arm, also called cellular immunity. Although vaccine candidates of this type, in the absence of an antibody response, are unlikely to fully prevent HIV infection, in animal studies they have been shown to reduce the amount of virus circulating in the body of the animals that become infected after vaccination. Thus, such a vaccine might keep HIV in check, slowing or preventing progression to AIDS and, perhaps, reducing the chances of transmitting HIV to another person. The only AIDS vaccine candidate of this type to reach efficacy testing failed to show efficacy in the STEP trial in 2007. However, for the first time, researchers have shown in animal studies that a handful of new T-cell vaccine strategies under development can control the amount of virus in infected animals better than approaches previously tested in clinical trials. A subset of these improved T-cell approaches are in early development, heading toward clinical trials.
The greatest scientific challenge impeding AIDS vaccine development is the antibody problem: how to design a vaccine that elicits antibodies that neutralize the many types of HIV in circulation so that the vaccine is protected from infection. But here, too, there is progress to report. Scientists have identified new antibodies capable of neutralizing a wide spectrum of HIV types circulating worldwide. These antibodies may now provide the keys to new vulnerable targets on the surface of HIV, which can be exploited for vaccine design.
There is also an interesting concept now in preclinical testing that aims to use vector-mediated gene transfer to maintain in the body large amounts of broadly neutralizing antibodies against HIV over long periods of time.
Of course, these developments will not lead us directly to an AIDS vaccine. There is much work to do, and more failure ahead, certainly. But the point is, despite disappointments, overall, AIDS vaccine science is progressing.
It does so because of a wide array of participants in the HIV vaccine effort, among them: researchers and technicians who devote themselves to the mission, study and trial participants who make the selfless contribution of volunteering for research, community workers who lend their voices and ears, political leaders who pave the way and donors who make the whole enterprise happen. On the occasion of World AIDS Vaccine Day, we at IAVI salute these individuals and our many partners for their dedication to making an AIDS vaccine a reality.
IAVI