|
|
           
| tHERE IS NO CURE FOR HIV/AIDS!!!! CONTENTS Antiviral drugs that attack HIV exploit vulnerable spots in the viral replication cycle. One target is the process of reverse transcription葉hat is, the conversion of the viral ribonucleic acid (RNA) into deoxyribonucleic acid (DNA)葉hat HIV must undergo to be infectious. Reverse transcription is a process unique to retroviruses and is performed by the viral enzyme reverse transcriptase (RT). One class of anti-HIV drugs, known as nucleosides, are all RT inhibitors. Five nucleosides are currently licensed by the U.S. Food and Drug Administration (FDA): zidovudine (Retrovir, AZT), didanosine (Videx, ddI), zalcitabine (Hivid, ddC), stavudine (Zerit, d4T), and lamivudine (Epivir, 3TC). These drugs work as DNA-chain terminators. Because the drug appears to be a normal nucleotide base (the building block of DNA), the RT enzyme mistakenly inserts the drug into the growing viral DNA chain. Once the drug is inserted, no additional DNA bases can be added, and therefore viral DNA synthesis is terminated. Although the nucleosides are more likely to interact with the viral RT enzyme, they also can be incorporated by the enzyme responsible for normal cellular DNA synthesis in the person receiving the drug, leading to toxicity (poisoning) and side effects. Such drug incorporation is usually observed in rapidly dividing cell types, such as the cells of the bone marrow, spongy tissue filling the cavities within bones. A second problem is the emergence of drug-resistant forms of HIV in people receiving these drugs. Studies on early treatment of HIV infection with AZT have presented contradictory results as to whether such early treatment prolongs life. Because HIV replicates rapidly and mutates frequently during the earliest period of infection, an HIV-infected person carries many different strains of HIV, some of which may be drug-resistant. The limited variety of HIV in the early stage is thought to make it more susceptible to AZT and related drugs. Although RT inhibitors were never considered a cure for HIV infection, it was hoped that they would slow the progression of AIDS, and AZT has been shown effective in reducing HIV transmission from pregnant women to their babies. However, the clinical benefit of RT inhibitors when used alone has been largely disappointing; they have extended the lives of people with AIDS by only about six months. When taken in conjunction with other RT inhibitors, however, they have been more effective. For example, AZT combined with lamivudine prevents the AIDS virus from developing resistance to AZT even though the virus quickly develops resistance to lamivudine. The combination also has been shown to boost CD4 T-cell counts and to lower levels of HIV in the blood. In November 1995 the FDA approved the combined use of AZT and lamivudine for early treatment of AIDS. RT inhibitors are also effective when used with a new class of anti-HIV drugs known as protease inhibitors, approved by the FDA in December 1995. Protease inhibitors work by crippling a key viral enzyme called protease, which is vital to the reproduction of HIV in the later stages of its replication cycle.After HIV replicates葉hat is, makes copies of its own protein components葉hese proteins must be cut to specific sizes before they can assemble into a mature virus. Protease is responsible for trimming the new HIV proteins to their required dimensions. When protease is blocked熔r inhibited葉he proteins are not cut andthe defective HIV cannot infect new cells. The first protease inhibitor drug, saquinavir (Invirase), was approved for use in combination with nucleoside drugs such as AZT. In March 1996 two additional drugs, ritonavir (Norvir) and indinavir (Crivaxin), were rapidly approved for use alone or in combination with nucleosides. A fourth drug, nelfinavir (Viracept), was approved by the FDA in March 1997 for both adult and child use. Ritonavir, formerly allowed for adult use only, was also approved for adult and child use. Preliminary results from four American and European studies indicate that these drugs cause dramatic increases in the number of CD4 T-cells and decreases in the amount of virus in the blood. These results are about two to three times more powerful than those seen with the nucleoside drugs. Researchers cautioned that new studies show also that HIV can quickly develop resistance to these new drugs, at least when they are used alone. However, researchers suspect that the resistance can be delayed when the agents are combined with other anti-HIV drugs庸or example, the nucleosides. In fact, the most effective treatment against HIV is now considered to be a combinationof three drugs taken together葉wo nucleoside RT inhibitors and one protease inhibitor. Although these drug combinations may cause severe side effects (such as diarrhea, abdominal cramps, and anemia), when taken properly they can reduce blood levels of the virus to undetectable levels. Each drug must be taken according to specific guidelines, however, and one missed dose can allow the virus to quickly mutate to a strain that resists the drugs. These drug combinations can also consist of two nucleoside RT inhibitors and one non-nucleoside RT inhibitor, a new class of anti-HIV drug first recommended for approval by the FDA in June 1996. These drugs work similarly to nucleoside RT inhibitors in that they bind to the HIV reverse transcriptase enzyme. However, they do not compete with other nucleosides for binding sites. The first drug of this type to be developed was nevirapine (Viramune), which was appproved by the FDA in April 1997. A second non-nucleoside RT inhibitor, delavirdine (Rescriptin), is currently available only in test settings. Both drugs are effective only when taken with nucleoside RT inhibitors; they should not be used with protease inhibitors. No matter which drug combination is administered, researchers believe that the earlier a patient is treated for HIV, the greater the chance that the treatment will be effective. The development of antiviral therapies for HIV is complex, and each new approach and drug must be extensively evaluated for safety and effectiveness. The general perception that this evaluation process causes unnecessary delays in providing therapies spurred public demonstrations against the FDA. These demonstrations have resulted in policy changes that make experimental drugs and approaches more readily available to people with AIDS, even before the drugs or approaches are approved. Although early availability of a drug entails the risk that it may be used in people before its toxicity and side effects are fully understood, many people with AIDS are willing to take this risk with the hope that the drug may prove effective. Effective drug treatments are available to fight many AIDS-associated opportunistic infections, and these treatments have provided clinical benefit and prolonged survival for individuals with AIDS. Recent drug treatments for PCP have dramatically decreased illness and death due to this opportunistic infection. Antifungal drugs such as amphotericin B and fluconazole are effective against AIDS-related fungal infections. The antiherpes drugs ganciclovir and foscarnet are used to treat CMV retinitis and other herpes diseases. Because these therapies require medical supervision and are often needed on an extended basis, a network of community hospices (see Hospital) has been established to provide low-cost outpatient care for individuals with AIDS. Some hospices provide shelter and compassionate support for people living with AIDS. Gene therapy, an approach that involves altering the genes of the infected person to help prevent the virus from spreading to uninfected cells, might someday be used to treat HIV infection. Gene therapy has been used in clinical trials to inhibit HIV by introducing into cells a new gene that interferes with the viral regulatory proteins. In other trials, gene therapy has been used to introduce a new gene that protects the cells from becoming infected by HIV. Efforts also are under way to develop an effective immunization that could be either protective, preventing infection if an immunized person is exposed to HIV, or therapeutic, prolonging survival or decreasing immune destruction in people already infected with HIV. The World Health Organization (WHO) is currently sponsoring a large-scale trial of a protective-vaccine candidate in areas of the world where the rate of HIV infection is just beginning to rise dramatically. In 1996 the FDA for the first time gave researchers in the United States permission to inject a vaccine made from simple DNA into healthy, uninfected volunteers. The vaccine in this trial is made from a gene that codes for one of the proteins that form the surface of HIV. Consequently, this DNA vaccine should generate antibodies to the AIDS virus and activate immune cells that kill the virus. With the discovery in 1996 that HIV must bind to chemokine receptors as well as CD4 molecules, researchers also began to develop laboratory chemokines that might block HIV from attaching to these receptors and casing infection. Individuals who lack CCR5 receptors due to a genetic defect appear to be protected from contracting the disease.
At any given time, prevention is better than cure - remember this ... Because there is as yet no successful vaccination against HIV, prevention efforts have focused mainly on educating the public about routes of HIV transmission and about personal measures that reduce the risk of infection. The CDC has established the National AIDS Clearinghouse, a hotline to disseminate educational literature and current statistics on AIDS. Safe-sex campaigns encourage sexual abstinence or monogamy (sexual relations with only one partner) and the use of latex condoms to provide a protective barrier during sexual intercourse (see Birth Control). Needle-exchange programs have been implemented to reduce needle sharing and consequent HIV transmission among IV drug abusers. The U.S. government has set strict guidelines for health-care settings, including use of protective clothing and proper instrument disposal, to decrease the risk of transmission to both the patient and the health care provider. On a national scale, screening of the blood supply has greatly reduced the risk of contracting HIV from blood products. However, with the exception of blood screening, these prevention programs have had only limited success. WHAT TO DO IF YOUR TEST IS POSITIVE? A positive HIV test does not mean that you have AIDS. It means that you are infected with the HIV virus and must take steps to protect your health and prevent transmission.
Your positive test is only part of the picture--your overall health counts for a great deal. Your doctor may suggest drugs or other treatment that can help you stay healthy and avoid other infections. Drugs such as AZT are proving beneficial in slowing the progression of HIV infection. And a great deal of research is under way to find other treatments and, hopefully, a cure. You should be alert for changes in your body because HIV-positive people are more susceptible to other infections. See your doctor if a sudden acute illness occurs or if you notice a change (e.g., fever, pain, cough, shortness of breath, bleeding, or an unusual skin condition).
THE IMPORTANCE OF A HEALTHY LIFE-STYLE The better you care for your body, the better your body can fight the HIV infection. A nutritious diet and adequate rest are essential. Exercise is important because it strengthens your body, increases your energy and stamina, and makes you feel better mentally. Do not abuse alcohol or inject drugs because they can make the HIV infection worse and you will be more likely to develop AIDS. Alcohol and drugs can also impair your judgment, and you might take risks you ordinarily would not. If you have a problem with drugs or alcohol, get help to quit.
Coping with a diagnosis of HIV can be difficult. Many people feel they are all alone, that no one can understand what they are going through. But help is out there--you don't have to face this alone. Seek professional help from a trained counselor, psychologist, or psychiatrist. These professionals can provide emotional support and guidance in helping you cope with the variety of social problems that HIV-positive people may face. Friends and family members can be valuable in helping you cope. Share information about HIV infection and AIDS with these people so they can better help you.
Most people would not deliberately place their friends, sex partner(s), or even total strangers in jeopardy by exposing them to the AIDS virus. Sex. The only sure way to protect your sexual partner(s) is to not have sex. It is safe to hug, cuddle, masturbate each other (as long as the skin isn't broken), rub, or "dry kiss." If you have sex, here are ways to minimize the chance of spreading the infection: (1) Use a latex condom from start to finish, with a birth control foam or jelly that contains nonoxynol-9. (2) Do not do anything that might cause a tear, abrasion, or bleeding (such as anal intercourse). (3) Use only a water-based lubricant, such as K-Y Jelly. Do not use saliva or oily lubricants, such as petroleum jelly or vegetable oil. (4) Avoid oral sex. (5) Avoid deep, wet, or "French" kissing. Drug use. If you inject drugs, please get help to quit because drugs can make your HIV infection worse. Until you quit: (1) do not share "works" with anyone else, (2) never use works that someone else has used, and (3) if you reuse your own works, clean them with bleach and water between uses. Women. If you don't want to pass the virus to your child, do not get pregnant, because there is a strong chance you could pass the virus to your unborn baby. Babies with the AIDS virus usually die before age 2 years. If you already have a baby, do not breast-feed, because you could pass the virus to your baby in your milk. Personal items. Even during normal use, some personal items may carry small amounts of blood that can be passed on to other people if you share them. Items such as toothbrushes, razors, and sex toys should not be shared. Donations: Do not donate blood, sperm, or body organs.
 ｩ Copyright 2000, ThinkQuest Team C005315 All rights reserved. thinkquest.org/C005315F/solutions.htm
|
