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The treatment of HIV/AIDS has evolved in the last 20 years since the beginning of the epidemic from no treatment to treatment with a single drug (AZT) to dual-drug therapy and, now, to highly active antiretroviral therapy (HAART). HAART is defined as treatment with at least three active anti-retroviral medications (ARV’s), typically two nucleoside or nucleotide reverse transcriptase inhibitors (NRTI’s) plus a non-nucleoside reverse transcriptase inhibitor (NNRTI) or a protease inhibitor (PI) or another NRTI called abacavir (Ziagen). HAART is often called the drug “cocktail” or triple-therapy. HAART affords us a potent way of suppressing viral replication in the blood while attempting to prevent the virus from rapidly developing resistance to the individual ARV’s. Suppressing viral replication with HAART allows the body time to rebuild its immune system and replenish the destroyed CD4 or T cells. HAART has been clearly shown to delay progression to AIDS and prolong life. Note that a curative treatment of HIV/AIDS is not possible at the present time, or in the near future, and when HAART is stopped, HIV becomes detectable in the blood once again.
At the present time, we have seven NRTI’s, three NNRTI’s and six PI’s to choose from that have been approved by the Food and Drug Administration (FDA). What combination of drugs to start in a person who is “naive” to therapy (has never been on HAART) depends on the viral load and the patient’s life circumstances, as the various ARV’s frequently have to be taken at different times of the day and with or without food. This decision is best made in conjunction with a health care provider (HCP) who knows the person well and who is well-versed in the treatment of people with HIV/AIDS. Other medications may also need to be taken depending on what the person’s CD4 cell count is. For example, people who have CD4 counts below 200 are susceptible to Pneumocystis carinii pneumonia (PCP), and taking trimethoprim-sulfamethoxazole (Bactrim) prophylactically significantly reduces the chances of developing this infection.
Failure of HAART
“Failure” of therapy can occur, defined as having a detectable viral load in the blood. Sometimes, the viral load rises only transiently and at low levels, called “blips”. This can occur if the viral load was measured while the person was ill or recently got a vaccine. Blips are not a reason to switch therapy, as the viral load will frequently become undetectable if measured a gain after a few weeks. Failure of HAART is a sustained and high rise in the viral load. People fail their HAART regimens for various reasons: non-adherence to the regimen, side effects from the medications, and development of resistance of HIV to the various medications in the regimen. When this happens, the regimen has to be switched. The HCP will frequently order a genotype or phenotype test (as explained elsewhere), and use the information provided by these tests to devise the best next regimen. The new regimen is called a “salvage” regimen.
The field of HIV/AIDS is rapidly evolving. Treatment strategies for ARV-naive and “experienced” people are evolving as well. What defines optimal naive and salvage regimens is debatable and is the subject of many clinical trials. For example, should a naive regimen contain an NNRTI or a PI? Does directly observed therapy improve adherence to HAART? Does treatment with glucose- or cholesterol-lowering medications improve the metabolic side effects (diabetes and high cholesterol) of HAART? Does monitoring drug levels in the blood and raising the dosages of the ARV’s increase viral suppression and success of a HAART regimen? Does therapeutic vaccination and structured treatment interruption work?
We at the NYU Center For AIDS Research and the NYU/Bellevue Adult AIDS Clinical Trials Unit are trying to answer some of these questions.