AIDS Therapies and Vaccines

The eleventh World AIDS conference held in Vancouver, British Columbia, Canada, in 1996 provided the turning point for treatment. Several groups of researchers presented information on a combination of drugs (also referred to as an AIDS "cocktail") that, when used together, could virtually erase any traces of the virus from the bloodstream of infected individuals. A new blood test that could detect HIV much earlier than previously available tests was also introduced.

This blood test changed early treatment options and established new ideas about how the disease works. Within a year, these novel HIV and AIDS treatments were being duplicated in medical offices and clinics around the world. By the late 1990s, HIV had moved from a progressively terminal disease to one that could be managed over the long-term, at least for those who have access to and can afford these new treatment options.

The combined drugs therapy first introduced at the 1996 conference is now the standard of care for those with HIV. Eleven different drugs that fall into three categories make up the treatment strategy. Five of the drugs are known as nucleoside analogs. That is, the drugs mimic the structure of some components of the viral genetic material. The incorporation of the analogs into viral genetic material can stop the virus from making new copies of itself. A well-known nucleoside analog is azidothymidine (AZT, which is marketed under the name Retrovir®). Other drugs block the action of protein-degrading enzymes (proteases) that are made by HIV. Still other drugs block the action of reverse transcriptase (an enzyme that HIV uses to duplicate its genetic material).

The differently acting drugs are used in combination (the AIDS cocktail) to block the disease's progression. All three types of drugs act to halt the manufacture of new virus inside the immune cells of the human body, where HIV has already established an active infection.

The mortality rate has since fallen sharply as more HIV-positive patients are prescribed this three-drug combination. The use of the improved blood test has also been expanded to measure the amount of HIV in the blood during drug treatment, which can help to pinpoint the most effective combination of drugs for each individual. In all cases, the goal of treatment is to keep the level of HIV in the body as low as possible, for as long as possible. Presently, a "cure" for AIDS does not exist.

Despite the treatment advances, questions remain concerning the effectiveness of such treatments over the long term. The average annual cost per patient for the three-drug combination treatment is US$15,000. This is exorbitantly expensive for the majority of AIDS patients who live in developing countries.

As well, while treatments can almost completely eliminate the virus in as few as two or more years, the immune system remains impaired. Patients may be just as susceptible to other illnesses that their immune systems cannot withstand. Furthermore, because HIV can "hide" from the immune system by occupying healthy cells, the absence of detectable HIV is no guarantee that the viral infection is truly eliminated.

A strict medicine administration schedule and diet must be maintained for the drugs to be successful. The regimen is difficult for many patients to follow, either because of privacy constraints or the side effects some of the drugs can cause.

Perhaps the most basic questions researchers are still struggling with are when to provide treatment, which drugs to begin with, how to identify when alterations are needed in the therapy, and which drugs to try next.