Fighting AIDS

AIDS. Fifty years ago, it didn't exist. Fifteen years ago, a few doctors and public health officials noticed the first cases. Within a few years, it was clear that it had reached epidemic status. It has now killed almost 14 million people around the world.

Four years ago, doctors came up with the first treatment to make a dent in the spiraling death rate. Today that treatment works for some patients, but it's not clear how long the results will last. And still there is no cure.

For the nearly 35 million people around the world now living with HIV, there may never be a cure. Once cells are infected with HIV, it's excruciatingly difficult--perhaps impossible--to rid them of the virus. The only sure way to stop the epidemic is to prevent infection in the first place, and only a vaccine can do that.

Unfortunately, HIV is one of the most changeable viruses known to science. After more than a dozen years, researchers are still chasing the moving target through all its mutations, trying to find a few common elements among all the strains in circulation that they can use to concoct an effective vaccine.

So far, about two dozen vaccines have been tested, most made from proteins found on the virus' coat and delivered via another, inactivated virus such as canarypox. While such vaccines are safe and successful in triggering antibodies, it's not clear that any will be sufficiently powerful to combat the strains of the virus that are currently in circulation.

Most of the formulations, for example, fail to get the body to churn out enough of the T cells that are needed to target and destroy HIV-infected cells.

Even without a vaccine, however, there is hope. The arsenal of treatment options has expanded considerably in recent years. Antivirals given to pregnant mothers have proved effective in preventing transmission to newborns, and a new, shorter treatment shows promise for use in developing nations.

For many older patients, protease inhibitors, available since 1995 and taken in combination with other antivirals, have kept HIV at below detectable levels. And while recent studies show that some HIV stubbornly hides from the drugs' reach, early evidence suggests that these sequestered strains may not be infectious. Drug holidays--brief respites from the grueling and complex medication regimen--are also being studied, since some patients who have voluntarily stopped their therapy have experienced no return of symptoms.

The new drugs are not without their problems, however. Patients may have to take them for the rest of their lives, and the expense and complexity of the regimen keep them out of reach for the 9 out of 10 patients who live in developing nations.

Still, the billions of dollars spent on AIDS research over the past 20 years has not been wasted. As scientists learn more about how HIV co-opts the human body to survive, they are realizing that drugs alone may not be enough. To contain the virus effectively, it may take a balance between drug therapy that keeps HIV levels low and a bolstered immune system that can then target and destroy the remaining virus. Until scientists find a vaccine, however, they may control but never cure the century's final scourge.