Light at the End of the Tunnel
The search for a vaccine against human immunodeficiency virus (HIV), the virus that causes AIDS, has gone from "an impossible dream" to "a technical problem." At least, so says a team of AIDS researchers who have found and mapped a weak spot in HIV's armor.
The implications of such a find are profound. Nearly 40 million people are infected with HIV worldwide, and around 3 million people die from AIDS each year, despite recent advances in antiretroviral therapies. Many experts say creating an HIV vaccine is our best chance to stop the global AIDS pandemic. Yet an HIV vaccine has proven elusive, leading some to say it's an impossible dream. Why?
Vaccines generally work by stimulating production of tiny proteins called antibodies that surround, bind to, and neutralize invaders in your bloodstream. The antibodies for a particular virus (or other bodily invader) fit together with it like a lock and key. When they find the virus in your body, they latch onto it. Sometimes that's enough to neutralize it. If not, the antibodies call for backup.
Either way, the lock-and-key match between antibody and invader is key. Unfortunately, making a match with HIV is very difficult, for two main reasons. First, HIV comes in a variety of types and subtypes that mix up would-be matches. Second, HIV is a master of mutation. Following infection, an HIV population can rapidly evolve inside the patient's body, shifting shape to escape the immune system's grasp.
As the virus's surface changes, antibodies that might otherwise attack it lose their ability to lock on. That makes the antibodies' job tough--and the would-be vaccine maker's job even tougher. Stimulating production of the right protein "key" for a particular lock is hard enough. Imagine trying to stimulate production of a protein key (or set of keys) to fit multiple locks, each of which keeps changing its shape.
Still, there are limits to how much HIV can mutate without sacrificing its own virulence. One is a glycoprotein on the virus's surface called gp120. HIV uses this structure to latch onto target cells within the human immune system. In effect, gp120 is one of HIV's own keys--one of the structures that enable it to invade human beings.
"So," scientists thought, "why not attack HIV right there, via the very structure it uses to attack us?" Smart thinking. Unfortunately, gp120's chemical and structural properties make it tough to grasp. Only a few rare antibodies bind to it.
That's where the new study comes in. Basically, the researchers devised a way to snap a picture of one of those rare antibodies locking onto HIV via gp120. Now, they have what amounts to a 3D map of the target they hope to attack with more and better antibodies. Of course, that's still a far cry from having an actual vaccine. But better a carefully mapped target than merely a dream.
The implications of such a find are profound. Nearly 40 million people are infected with HIV worldwide, and around 3 million people die from AIDS each year, despite recent advances in antiretroviral therapies. Many experts say creating an HIV vaccine is our best chance to stop the global AIDS pandemic. Yet an HIV vaccine has proven elusive, leading some to say it's an impossible dream. Why?
Vaccines generally work by stimulating production of tiny proteins called antibodies that surround, bind to, and neutralize invaders in your bloodstream. The antibodies for a particular virus (or other bodily invader) fit together with it like a lock and key. When they find the virus in your body, they latch onto it. Sometimes that's enough to neutralize it. If not, the antibodies call for backup.
Either way, the lock-and-key match between antibody and invader is key. Unfortunately, making a match with HIV is very difficult, for two main reasons. First, HIV comes in a variety of types and subtypes that mix up would-be matches. Second, HIV is a master of mutation. Following infection, an HIV population can rapidly evolve inside the patient's body, shifting shape to escape the immune system's grasp.
As the virus's surface changes, antibodies that might otherwise attack it lose their ability to lock on. That makes the antibodies' job tough--and the would-be vaccine maker's job even tougher. Stimulating production of the right protein "key" for a particular lock is hard enough. Imagine trying to stimulate production of a protein key (or set of keys) to fit multiple locks, each of which keeps changing its shape.
Still, there are limits to how much HIV can mutate without sacrificing its own virulence. One is a glycoprotein on the virus's surface called gp120. HIV uses this structure to latch onto target cells within the human immune system. In effect, gp120 is one of HIV's own keys--one of the structures that enable it to invade human beings.
"So," scientists thought, "why not attack HIV right there, via the very structure it uses to attack us?" Smart thinking. Unfortunately, gp120's chemical and structural properties make it tough to grasp. Only a few rare antibodies bind to it.
That's where the new study comes in. Basically, the researchers devised a way to snap a picture of one of those rare antibodies locking onto HIV via gp120. Now, they have what amounts to a 3D map of the target they hope to attack with more and better antibodies. Of course, that's still a far cry from having an actual vaccine. But better a carefully mapped target than merely a dream.