AIDS therapies and vaccines
AIDS therapies and vaccines
Acquired immunodeficiency syndrome (AIDS) is a disease characterized by the destruction of the immune system. More than 16,000 new AIDS patients are diagnosed each day. AIDS is caused by several types of a virus designated as the human immunodeficiency virus (HIV).
The immune system is the principle defense system of the body to a variety of infections. Thus, individuals diagnosed with AIDS are prone to illness and, in many cases, eventual death from microbiological illnesses, organ failures, or cancer.
AIDS was recognized in the early 1980s. Soon thereafter came the discovery of the various types of HIV and their association with AIDS. Since then, scientists and researchers around the world have spent billions of dollars and thousands of hours to discover how AIDS is caused and what options are available to stop the progression of the disease.
Once the scientific community became mobilized to fight AIDS, international conferences were held in the mid-1980s. Exchange of data on AIDS and HIV led to the development of blood tests to detect the virus or its genetic material, and to diagnose the infection. Only then did the severity of the illness and the extent of the worldwide epidemic become known.
By the late 1980s, treatments for the virus became available, and so treatment of infections that prey on the severely weakened immune systems of those with AIDS could be managed to some extent. The death toll internationally was still extremely high, and remained so until the mid-1990s when the research collectively began to identify the best range of treatments for the 11 or more strains of HIV.
AIDS treatment
The eleventh World AIDS conference held in Vancouver, British Columbia, Canada, in 1996 provided the turning point for treatment. Several groups of researchers presented information on a combination of drugs (also referred to as an AIDS “cocktail”) that, when used together, could virtually erase any traces of the virus from the bloodstream of infected individuals. A new blood test that could detect HIV much earlier than previously available tests was also introduced.
This blood test changed early treatment options and established new ideas about how the disease works. Within a year, these novel HIV and AIDS treatments were being duplicated in medical offices and clinics around the world. By the late 1990s, HIV had moved from a progressively terminal disease to one that could be managed over the long-term, at least for those who had access to and could afford these new treatment options.
Combined drug therapy similar to those first introduced at the 1996 conference is now the standard of care for those with HIV. Twenty-nine different drugs that fall into four categories are available to make up the treatment strategy, and Atripla®, a new drug approved for use in mid-2006, combines different classes of drugs used to treat HIV infection in one tablet. Thirteen of the drugs are known as nucleoside analogs. That is, the drugs mimic the structure of some components of the viral genetic material. The incorporation of the analogs into viral genetic material can stop the virus from making new copies of itself. A well-known nucleoside analog is azidothymidine (AZT, which is marketed under the name Retrovir®). Other drugs block the action of protein-degrading enzymes (proteases) that are made by HIV. Still other drugs block the action of reverse transcriptase (an enzyme that HIV uses to duplicate its genetic material).
The differently acting drugs are used in combination to block the disease’s progression. All classes of these drugs act to halt the manufacture of new virus inside the immune cells of the human body, where HIV has already established an active infection.
The mortality rate has since fallen sharply as more HIV-positive patients are prescribed this three-drug combination. The use of the improved blood test has also been expanded to measure the amount of HIV in the blood during drug treatment, which can help to pinpoint the most effective combination of drugs for each individual. In all cases, the goal of treatment is to keep the level of HIV in the body as low as possible, for as long as possible. Presently, a “cure” for AIDS does not exist.
Despite the treatment advances, questions remain concerning the effectiveness of such treatments over the long term. While treatments can almost completely eliminate the virus in as few as two or more years, the immune system remains impaired. Patients may be just as susceptible to other illnesses that their immune systems cannot withstand. Furthermore, because HIV can “hide” from the immune system by occupying healthy cells, the absence of detectable HIV is no guarantee that the viral infection is truly eliminated.
The average annual cost per patient for the brand name three-drug combination treatment can reach $15,000, but by 2006, more than twenty generic drugs were approved for use in treating AIDS, bringing the cost down significantly for people who take the generic versions of the drugs. In 2003, President George W. Bush launched a $15-billion initiative to fight AIDS in 15 countries, particularly in SubSaharan Africa. Many of the drugs distributed in the program were generic versions of the combination pill.
A strict medicine administration schedule and diet must be maintained for the drugs to be successful. The regimen is difficult for many patients to follow, either because of privacy constraints or the side effects some of the drugs can cause.
Perhaps the most basic questions researchers are still struggling with are when to provide treatment, which drugs to begin with, how to identify when alterations are needed in the therapy, and which drugs to try next.
Vaccine development
The search for a vaccine that would protect people from HIV infection by blocking the entry of the virus into the immune cells, has been ongoing almost as long as the search for AIDS treatment strategies. At least 25 experimental vaccines have been created since identification of the disease. Unfortunately, few have proved even promising enough to complete the large-scale testing on human volunteers that is required to demonstrate the vaccine’s success.
Some initial vaccine trials, however, have occurred. In June 1998, the first AIDS vaccine to be tested on humans began with 5,000 volunteers in 30 cities in the United States, and a smaller group in Thailand. Volunteers were given a series of injections intended to stimulate the immune system to resist the two most common strains of the AIDS virus. Results announced in 2003 were disappointing, with little immunity protection for the general public noted, although blacks and Asians who were given the vaccine showed a two-thirds-lower infection rate than participants who received a placebo. Since then, more than twenty new candidate AIDS vaccine trials were launched under the auspices of the International AIDS Vaccine Initiative in small-scale human clinical trials around the world.
See also Molecular biology; T cells.
Resources
BOOKS
Bartlett, John G. and Finkbeiner, Ann K. The Guide to Living with HIV Infection, 5th ed. Baltimore: Johns Hopkins, 2001.
PERIODICALS
Gaschen, B., J. Taylor, K. Yusin, et al. “AIDS-Diversity Considerations in HIV-1 Vaccine Selection.” Science 296 (June 2002): 2354–2360.
Vastag, B. “HIV Vaccine Efforts Inch Forward.” Journal of the American Medical Association 286 (October 2001): 1826–1828.
OTHER
United States National Institutes of Health. “National Institute of Allergy and Infectious Diseases- HIV/AIDS Vaccines” <http://www.niaid.nih.gov/daids/vaccine> (accessed November 21, 2006).
Brian Hoyle