Acquired Immune Deficiency Syndrome (AIDS)
Every, single medicine taken by people with AIDS today to stay alive has come about only through animal research. The world's leading AIDS researchers and people with the disease know that animals hold the key to finding a cure.
"With animals, we may have a cure for AIDS in 10 years. Without animals we will never cure AIDS in our lifetime." (Robert Gallo, M.D. Co-Discoverer of HIV)
Common Questions About HIV and AIDS
Acquired Immune Deficiency Syndrome (AIDS) is a viral disease that destroys the immune system of its victims, leaving them defenseless against a range of diseases and cancers. A recent study by the World Health Organization has stated that at least 10 million children world-wide will be infected by the AIDS virus by the end of the 20th century. An additional 10 million children will have already lost their parents to this deadly disease.
Progress in AIDS research to date includes identification of the virus that causes the disease; simple and effective methods of detecting it in the blood; and development of drugs that may retard its effect. These advances in the study of AIDS have depended on research conducted in virology, molecular biology and immunology during the past 25 years. Animal models and cell and tissue culture studies all played very important roles.
The human AIDS virus (HIV-1) belongs to the family called retroviruses, which are characterized by the presence of an enzyme that allows them to convert their genetic material (RNA) into DNA. This enables the virus to integrate the AIDS gene into the DNA of the host. The existence of this enzyme was discovered through cell culture research.
Development and testing of drugs for safety and efficacy against a range of retroviruses in order to treat AIDS have been conducted in tissue culture, as well as in live animals. The drug AZT, for example, now being used by AIDS patients to prolong their lives, was developed and tested in animals. Several new drugs are being studied in animals for their enhanced ability to delay progression of the disease and for their limited side effects.
In 1989, initial reports were published that researchers have been able to protect monkeys against simian AIDS with a vaccine. Biomedical researchers are now working on the possibility of developing a similar vaccine for humans against AIDS.
One difficulty in studying vaccine effectiveness based on human trials is the long incubation period of the virus, now estimated at 9-11 years. For this reason, researchers have developed a mouse with a fully human immune system. (Mice, like humans, suffer from a genetically-induced severe combined immunodeficiency disease.) The use of these mice as a model in AIDS research allows researchers to study the complex interactions between immune cells and to evaluate promising drugs and vaccines. Because the mice develop disease after a few weeks following infection with HIV, the problem of long incubation times for the AIDS virus is solved.
Questions and Answers about HIV and AIDS
World AIDS Day, December 1, 1999, was dedicated to increasing public awareness and understanding of HIV and the AIDS epidemic. The struggle against this epidemic requires not only excellent science and compassionate treatment, but a well-informed, supportive public. Partners in Research is pleased to present answers to some common questions about HIV and AIDS:
- A recent report said that AIDS deaths were decreasing. Is the epidemic over?
- How do we know that HIV is really the cause of AIDS?
- What is so special about HIV?
- Can infection be prevented?
- What type of contact is safe?
- What are the symptoms? How long does it take for a person to develop symptoms?
- How can I tell if I have been infected with HIV?
- I think I might be infected....
- What is the outlook for an infected person?
- Why is there no vaccine?
- Can other animals get AIDS?
- Are animal models relevant in AIDS research?
- Will the disease be eradicated soon?
- Is there anything that can be done?
- Won't sex education just encourage teenagers to have sex at an earlier age and increase the spread of AIDS?
- Wouldn't it be a good idea to require identification of persons infected with HIV and notification of their spouses and sexual partners?
- "AIDS affects mostly gay guys, doesn't it? As long as I have sex with girls, I should be okay."
- Find out more
A recent report said that AIDS deaths were decreasing. Is the epidemic over?
No. Effective treatments have certainly improved survival, but the number of new HIV infections is rising in Canada, the United States, and around the world. Every day, about a dozen more Canadians become infected. In fact, the average age of those newly-infected is dropping. Today, a growing number of Canadians in their teens are now living with HIV.
How do we know that HIV is really the cause of AIDS?
Tests for HIV antibody in persons with AIDS show that they are invariably infected with the virus.
HIV has been isolated from persons with AIDS and grown in pure culture.
Before the development of sensitive diagnostic tests for antibodies to HIV, many units of contaminated blood were transfused into previously uninfected people. These persons subsequently developed AIDS.
What is so special about HIV?
The surface of the virus contains proteins which enable it to identify, attach to, enter, and ultimately destroy the very cells which are supposed to promote immunity.
Immediately after infecting the cell, the virus transforms its genetic material, RNA, into a DNA form and splices it into the host's DNA. This unusual reversal of the flow of genetic information is restricted to retroviruses. The unique enzyme which carries out this task is called the reverse transcriptase.
The virus may remain latent in the cell for years.
Eventually the virus replicates. Assembly of new viruses requires rearrangement of viral proteins, a process regulated by viral proteases. The new viruses then lyse the host cell and infect nearby helper T cells and macrophages. [The proteases and reverse transcriptases have been targets for the development of chemotherapeutic drugs.]
The virus mutates frequently, changing its susceptibility to drugs and to antibodies.
Can infection be prevented?
Yes. The virus is present in blood, semen, and vaginal fluids. Since it does not survive for long outside the body, it can be transmitted in only a few ways:
By unprotected sexual intercourse. You can avoid HIV by not having sex at all, or by making sure that you protect yourself by always practicing 'safer sex'. Discuss HIV with your partner, and have sex only with a partner who agrees to protect both of you by using a latex condom.
By contaminated sharp objects. Avoid using instruments that pierce skin unless you are sure they have been sterilized. Do not share personal items such as razors and toothbrushes.
During childbirth or breast-feeding. A pregnant woman should ask for an HIV test. If she is positive, early drug treatment will greatly reduce the chances of infecting the baby and will improve her long-term survival.
After transfusion of contaminated blood. Donated blood in Canada is always checked for HIV, so the chances of getting it from a blood transfusion are also very, very low. Some people worry that they can get HIV by donating blood, but this isn't true. A new needle is used every time.
What type of contact is safe?
HIV is not spread by everyday social contact. Touching, hugging and shaking hands with an infected person is safe. Insects and pets cannot spread HIV.
What are the symptoms? How long does it take for a person to develop symptoms?
It is important to distinguish between HIV infection and AIDS. About half of those infected remain free of symptoms for more than ten years after HIV infection. They do not have AIDS, but they can transmit the virus to others.
Others develop a fever and rash a few weeks after infection, but recover and remain symptom-free for years (but infectious). During this long "latent period", the virus is inactive in some cells and slowly replicates in others. Subsequent infections with other pathogens may trigger CD4+ replication and activation of latent HIV.
When the virus has killed enough CD4+ T cells to reduce the count to less than 200/mm3, the person is said to have AIDS. Symptoms may include fever, enlarged lymph glands, opportunistic infections, tumors, and dementia.
How can I tell if I have been infected with HIV?
A simple blood test, called the "HIV Antibody Test," can tell if you are infected with HIV. A positive test result means that you have been infected with HIV, and that you can spread it to others. A negative result means that no antibodies to HIV were found in your blood at the time of testing. Most positive tests will show up at three months, but HIV antibodies can take as long as six months to develop, so you need to get tested again to be sure you don't have the virus.
I think I might be infected....
If you have taken chances, and are worried that you might be infected with HIV, please see your doctor right away, or go to an HIV testing clinic or STD clinic. The blood test for HIV will be done, and all your information will be kept private.
If you have been exposed to HIV, then your sex partners, or anyone with whom you have shared needles and syringes must be told that they also may have been exposed to the virus. They will have to decide if they wish to be tested for HIV infection. You might want to tell them yourself, but if you are not comfortable, talk to your doctor or nurse--they can help.
What is the outlook for an infected person?
The longer the virus can be kept at very low levels, the better the prognosis. The aggressive HAART (Highly Active Anti-Retroviral Therapy) treatment is the preferred approach. A variety of drugs target the viral reverse transcriptase and protease. Researchers are now trying to develop a new class of drugs that will target the nucleocapsid. These drugs can preserve health and prolong life for many years.
Using drugs in combination reduces the problem of resistance. Highly-sensitive tests can determine the number of viruses in the blood and can quickly determine whether a treatment approach is working. If it is not, a switch can be made early. However, these medications are very expensive ($12,000 per year per patient) and the regimens are complex. Affluent or well-insured recipients must be well organized and committed to staying with difficult, expensive therapy for the rest of their lives, even with the knowledge that they are not cured.
Why is there no vaccine?
Successful vaccines against polio, measles, mumps, rubella, and hepatitis B generate antibodies. These bind to viruses and prevent them from entering cells and causing disease. Most of the vaccines under development are based on the viral surface protein gp120. In a US study, one of these proved to be safe and did produce antibodies, but the antibodies failed to recognize HIV newly isolated from patients. A trial of a similar vaccine is now under way in Thailand.
Even if the antibodies recognized "wild" virus, they would not be sufficient. Since the virus can remain within cells for years, an optimal vaccine must produce cytotoxic immune cells that would destroy infected cells and expose the virus to antibodies. Such vaccines are technically very difficult to prepare. A live vaccine with this aim has been tested on primates, but the vaccine itself may cause disease in some animals. Other approaches are promising, but are at an earlier stage of development.
Can other animals get AIDS?
Yes and No. Similar viruses infect sheep, monkeys, birds, cats, and mice. Some cause cancers, and others affect the immune system. For example, domestic cats suffer from feline immunodeficiency virus and feline leukemia virus, for which vaccines are available.
Non-human primates are susceptible to HIV-1 infections, but they do not develop human AIDS-like disease. Such animals can, however, be used to evaluate promising drugs and vaccines. The simian immunodeficiency virus (SIV), a close relative of HIV, does cause an AIDS-like syndrome in monkeys, and this model is being used to evaluate vaccines.
Are animal models relevant in AIDS research?
Yes. Primates have been used to help evaluate the safety and efficacy of drugs and vaccines. Another promising animal model is the SCID-hu mouse. This mouse suffers from a genetic defect that prevents it from having immune cells of its own. When such mice are reconstituted with human immune cells, they develop a fully competent human immune system, including the CD4+ receptor which allows the HIV to enter cells. These mice have been superb tools for evaluation of promising new drugs and vaccines.
Will the disease be eradicated soon?
No. On the positive side, we know more about the human immunodeficiency virus (HIV) that causes AIDS than we do about any other virus. Study of the virus has greatly expanded our understanding of the human immune system. Researchers have developed treatment strategies that can maintain good health in infected patients, often for many years. Sadly, these are not a cure, and the disease is fatal. No vaccine will be available for at least the next five years.
Social and economic issues further complicate the problem. Behavioral change is the only really effective prevention, but complacency and ignorance often get in the way of good behavior. Furthermore, although more than 90 percent of HIV-infected people live in the developing world, over 90 percent of the money spent on prevention and care are spent in developed countries. Effective therapy is beyond economic reach to most.
Since clean needles and diagnostic kits are also less widely available, so transmission by infected blood is more common. Condoms are unaffordable to many, so the disease is most commonly transmitted by unprotected heterosexual activity. Since the early 1980's more than 40 million persons have been infected and over 12 million have died. Each day 16,000 new infections occur in the world.
Is there anything that can be done?
Yes! Education is necessary to promote healthful behavior. Specific, easily-understood motivational information on prevention of sexually transmitted diseases, and convenient, private access to condoms and to HIV testing must be directed to different high-risk target groups. Needle exchange programs can be set up to provide addicts not only with needles, but with health information and counseling to improve their lifestyles.
Won't sex education just encourage teenagers to have sex at an earlier age and increase the spread of AIDS?
No. The World Health Organization (WHO) found that there was no evidence of sex education leading to earlier or increased sexual activity in the young people who were exposed to it. Six studies showed that sex education led either to a delay in the onset of sexual activity or to a decrease in overall sexual activity. Ten studies showed that education programs increased safer sex practices among young people who were already sexually active.
Wouldn't it be a good idea to require identification of persons infected with HIV and notification of their spouses and sexual partners?
No. The newer therapies are very promising, especially if begun during the early stages of infection. Thus people at risk must be motivated to take the HIV antibody test early. A mandatory reporting policy would undermine faith and comfort in the health care system and delay testing. Such a plan would backfire.
"AIDS affects mostly gay guys, doesn't it? As long as I have sex with girls, I should be okay."
Not true. HIV (the virus that causes AIDS) is spread by contact with an infected person of either sex. When you have unprotected sex, you are also in contact with every person your partner has had sex with. Don't take chances! Always use a latex condom.
To find out more about HIV and AIDS, check out the following website:
- http://www.cdc.gov/nchstp/hiv_aids/pubs/facts.htm
Prepared for Partners in Research by:
Dr. Sarah B. Galsworthy, The University of Western Ontario
info@pirweb.org
London, ON N6A 4V6
Phone: (519) 433-7866
Fax: (519) 645-8899