Key Cell May Offer Vital AIDS Clue : Health: Researcher says it continues to be active in some long-lived patients and could help others.
The answer to the puzzle of why some AIDS-infected individuals live 10 years or longer without becoming sick may lie in a key immune system cell that appears to block the virus from reproducing, a U.S. researcher told participants at the eighth International Conference on AIDS on Wednesday.
Individuals who develop AIDS symptoms usually experience a drop in the activity of their CD8 cells, one of the white blood cells that play an important role in the body’s immune system, said Dr. Jay Levy, a UC San Francisco researcher who has been studying long-term survivors of the disease.
This reduction of activity precedes the destruction of CD4 cells, which are the primary target of the human immunodeficiency virus, he said.
In some infected people, however, the CD8 cells maintain relatively high activity levels, which, in Levy’s opinion, helps keep them fairly healthy. By learning more about this process, scientists hope they can use it to help other AIDS patients.
“All viral diseases have long-term survivors, and HIV is no exception,” he said. “Through the study of these special individuals, we hope to gain insight into approaches that will permit all infected individuals to achieve a normal life span.”
Levy’s approach is consistent with the feeling of most AIDS researchers that no “magic bullet” cure will be found. They feel that the key to controlling the disease is to keep infected individuals free of symptoms and living a relatively normal life for as long as possible. Many researchers are trying to achieve this in different ways, such as through drug combinations and other therapies.
Immune system cells, although they have different jobs in the body, work in concert to protect an individual against foreign invaders. CD4 cells regulate the immune response, while CD8 cells attack infected cells.
CD8 cells secrete powerful substances known as cytokines, which are like chemical messengers that can call into play other cells and substances, including, for example, elements of the inflammatory response.
Levy said Wednesday that he has found a previously undiscovered cytokine that stops HIV from replicating within CD4 cells in laboratory cultures. The cytokine has been semi-purified so that its size and certain physical and chemical properties are now known, he said, adding that he hopes the substance can be “purified further and identified completely within the next six months.”
The activity of CD8 cells is important in stopping viral replication and is directly related to how long an individual remains free of symptoms, Levy said.
Presumably, the practical application of this research would be to find ways to maintain--or boost--the activity of CD8 cells in order to keep the immune system intact longer and stave off symptoms of the disease.
This could possibly be accomplished by extracting a patient’s own CD8 cells during an early stage of infection--while the cells are still active--and storing them until the remaining CD8 cells in the body begin to decline, Levy said. Then the stored cells could be reintroduced into the patient with the hope that they would reactivate, he said.
“In long-term survivors, CD8 cell activity remains strong,” he said. “Persons who have survived more than 10 years without exhibiting disease symptoms still have high levels of activated CD8 cells.”
He said, however, that he does not know why CD8 cells lose their activity over time, leading to the onset of disease.
Levy said he and his colleagues have identified the subset of CD8 cells responsible for stopping viral replication in the lab and have found cell surface markers that he believes are an indication of activated CD8 cells.
By tagging these markers with fluorescent labels, he said, researchers may be able to count activated CD8 cells and predict the course of the disease in an individual.
In other developments, a U.S. health official said that the cumulative cost of treating all people with AIDS and AIDS infection in the United States will rise by nearly half between now and 1995, in part because of the increasing use of expensive new drugs.
Fred J. Hellinger, director of the division of cost and financing for the Agency for Health Care Policy and Research, said that the total cost of treating all people with AIDS or HIV infection since the beginning of the epidemic in 1981 will increase from $10.3 billion to $15.2 billion by 1995.
Further, Hellinger said, the lifetime cost of treating an AIDS patient--that is, from diagnosis to death--has risen steadily since 1988, when it was $57,000, to $85,333 in 1991, and is now $102,000, he said.
The average annual cost of treating a person with AIDS rose from $32,000 to $38,300 last year, he said. The average yearly cost of treating an individual who is infected but not yet sick is about $10,000, nearly double the $5,100 of a year ago.
In another study, UC San Francisco researchers found that HIV-infected men who were also psychologically depressed suffered more rapid decline and died sooner.
Researchers found that CD4 cell counts dropped 38% faster in the depressed group than in men who were not depressed.
The study, conducted between January, 1985, and January, 1991, was of 330 gay and bisexual men who were part of the San Francisco Men’s Health Study.
Researchers found that if the person was depressed, the average rate of CD4 cell decrease was 81 cells per microliter of blood each year. If the individual was not depressed, the average rate of decline was 59 cells.
During the course of the six-year study, 36% of the 300 participants died. Although the same proportion died, whether or not they were depressed at the start of the study, the depressed men were more likely to die faster, researchers said.
Putting a Price on AIDS
Here are the annual costs of treating AIDS patients and those who are HIV positive. The middle column is for HIV positive patients without AIDS symptoms but with significant immune system damage. The right column is for HIV patients without AIDS symptoms who show little to moderate immune system damage:
*HIV positive **HIV positive with significant with little to With AIDS immune damage moderate damage Inpatient Hospital care $28,700 $7,603 $2,323 Clinic or doctor visits 3,660 3,001 2,635 Home care 1,460 423 81 Drugs 4,060 2,498 1,405 Long-term care 420 -- -- Total 38,300 13,525 6,444
*CD4 counts less than 200; **CD4 counts of 200 or more
Source: Agency for Health Care Policy and Research
