HIV/AIDS: Diagnosis & Anti-HIV Therapy
Diagnosis & Anti-HIV Therapy
Diagnosing HIV Infection
A positive diagnosis of HIV infection can be made with several types of tests, including virus culture, antibody testing, and polymerase chain reaction (PCR). Generally, HIV infection is diagnosed by showing that specific antibodies fighting the infection are present in the blood. Antibodies against HIV are usually detectable approximately 25 days after infection, and nearly all infected individuals are HIV antibody-positive after 12 weeks.
One of the major reasons antiretroviral treatment of HIV infections has not been more successful is the development of drug-resistant HIV strains in patients during therapy. Identifying such strains early can help improve the effectiveness of treatment.
False-negative tests can arise because it may take several weeks after initial infection for the body to produce antibodies. Rapid tests can generate results in less than 30 minutes, analyzing blood, saliva, or urine.
Early Anti-HIV Therapy
In 1987, AZT (zidovudine, Retrovir) became the first anti-HIV drug approved by the Food and Drug Administration (FDA). It blocks the activity of the critical HIV enzyme needed to make new virus particles, restricting the virus's ability to replicate. Unlike bacteriocidal antibiotics, which can kill certain infectious bacteria, anti-HIV therapy is bacteriostatic, and only limits production of new virus—it doesn't kill the virus that's already there.
AZT therapy helped HIV-infected patients live longer with fewer opportunistic infections because it helped to reduce viral load. However, drug resistance and side effects limited AZT therapy. Common side effects included nausea, vomiting, headache, fatigue, weakness, and/or muscle pain. Other side effects included inflammation, insomnia, and kidney disorders. Possibly the best application of AZT was its use during pregnancy as a way to reduce the risk of HIV being passed from mother to child.
Effective therapy against HIV is complex and requires that patients take several different drugs at very specific times. Some have to be taken with food, some on an empty stomach. This is one of the reasons why it is difficult to deliver effective therapy in undeveloped countries.
You've Got to Have HAART
Antiretroviral describes a drug that acts against a retrovirus such as HIV.
New approaches were needed to advance HIV therapy. In the mid-1990s, there was a significant breakthrough in therapy with the approval of a new class of drugs called “protease inhibitors.” These drugs are highly active in blocking HIV replication when used alone. Yet HIV's ability to mutate and become resistant threatened to make these new drugs useless. When treating an infection caused by a rapidly mutating virus like HIV, the most effective method is combination therapy with multiple drugs that act in different ways. This way, a single mutation cannot cause resistance.
Today there are a number of antiretroviral agents available as therapeutic options that have several different mechanisms of action.
Highly active antiretroviral therapy (HAART) consists of three-drug combinations of antiretroviral agents. This approach has significantly decreased the incidence of death among HIV-infected people in the United States and has allowed HIV-infected individuals to lead productive lives. Decreasing amounts of HIV in the bloodstream helps restore immune function, so opportunistic infections are less of a problem. During therapy, it's important to measure viral load and T cell counts to monitor the status of HIV disease and to guide recommendations for continued therapy.
But HAART, like all complex medications, has problems. There are serious long-term side effects, such as an accumulation of lactic acid in the bloodstream and physical and metabolic changes that cause changes in fat distribution as well as cholesterol and glucose abnormalities that can lead to a risk of heart disease. Long-term use of the drugs can also promote the development of drug-resistant strains of HIV. Clearly, these problems must be balanced with the alternative of a greatly shortened life. Finally, HAART therapy is expensive and requires strict compliance for proper administration. For this reason, it is not a realistic option for many of the 40 million HIV-infected people in the world.
Excerpted from The Complete Idiot's Guide to Dangerous Diseases and Epidemics © 2002 by David Perlin, Ph.D., and Ann Cohen. All rights reserved including the right of reproduction in whole or in part in any form. Used by arrangement with Alpha Books, a member of Penguin Group (USA) Inc.