I am trying to find out about the treatments of AIDS. Most of what I have found are the names of different drugs. Can you give me a simple explanation of how AIDS would be treated, without all the incomprehensible drug names?

J.

Nothing is changing faster in the field of medicine than the treatment of HIV (human immunodeficiency virus), the virus that causes AIDS. To explain how treatment works, I need to first describe how the virus leads to disease. Like all viruses, HIV is an extremely small microbe that requires the cells of a host to replicate itself. In the process, it may sicken the person who is infected. AIDS (acquired immune deficiency syndrome) is a group of illnesses that result from severe infection with HIV.

When people first become infected with HIV, they may get sick with an illness that resembles the flu. After a few weeks, their health returns to normal. For the next five to 10 years, most HIV-infected people will have no symptoms whatsoever. After that, unless treatment is begun, they will usually develop one or more of a group of illnesses that tend to occur in HIV patients. This group consists primarily of infections but also includes some cancers. Some of these illnesses belong to the syndrome of AIDS, while others are just considered symptoms of HIV infection. I generally refer to any illness caused by this virus as "HIV disease."

The drugs used to fight AIDS target HIV's ability to replicate. Unbelievably, 10 billion new viruses are produced in an infected person each day! Each replication requires several steps involving specific proteins called enzymes. Pharmaceutical companies have developed drugs that stop replication by blocking these enzymes. The first such drug was AZT (Retrovir). AZT did have some benefit when given alone, but it did not work for long. That is because HIV randomly changes its genetic makeup (mutates) frequently. By sheer luck (and remember that there are 10 billion daily chances for HIV to get lucky), some mutations enable a strain of the virus to replicate despite being exposed to AZT or any other single drug. Strains that show this ability are called "drug resistant."

Researchers soon discovered that if we attack several steps in the replication process at once, we can prevent, or at least delay, the development of drug resistance. That is why today we always try to give three different drugs when we treat HIV -- what some people refer to as a "drug cocktail."

Exactly when do you start treatment? Most experts like to treat patients relatively early in the infection, before AIDS has developed, in the belief that we may prevent the patient from ever getting ill. I determine how advanced a patient's infection is by measuring the viral load -- that is, determining how much HIV the patient has in his or her body. The greater the viral load, the more quickly the patient will develop AIDS and the higher the risk of death. There are people who, even without treatment, have very low viral loads -- undetectable by our labs -- and have not developed any HIV disease more than 15 years after being infected. That is very rare, but it tells us that if we can keep patients' viral load low, they should do well.

If I have a patient whose viral load is high enough to be detectable by the lab, I usually recommend a combination of three drugs. Then, a few weeks after beginning treatment, I measure the viral load again. Usually, the load has decreased dramatically. If the patient continues to take the medication correctly, the viral load remains low. Some patients can be free of disease for many years.

No one knows how long this good response can persist. We do know that treatment with the "cocktail" can delay the progression to AIDS and decrease the risk of death in the short term. However, it is sometimes extremely difficult for a person to take all of these drugs, most of which have side effects and are tremendously expensive.