TreatmentUpdate 74 - Volume 8, No 10; December 1996
Sean Hosein

IL-2 is a chemical produced by the immune system that can cause T cells to divide and produce copies of themselves. Since HIV/AIDS is associated with less than normal levels of CD4+ cells, some researchers think infusions of IL-2 will increase the CD4+ cell count, perhaps delaying or stopping the development of AIDS.

Study details

Doctors reported results from their experiments on 30 adult, HIV-infected subjects (1 female, 29 males) assigned to receive IL-2 and 29 others assigned to receive continued anti-HIV therapy (and no IL-2). On average, subjects had about 400 CD4+ cells and did not have AIDS when they entered the study. Their average HIV viral load was about 40,000 copies/ml of blood.

The protocol called for subjects to receive infusions of IL-2 over 5 days while in a hospital, every other month. Subjects were first given 18 million IU (international units) and if side effects were severe the dose could be reduced. While in the study subjects were encouraged to use AZT, ddC, ddI, d4T alone or in combination as they chose on their doctors' advice.

Results

The CD4+ counts of subjects receiving IL-2 rose on average by 37 cells/month. By the 14th month of the study, their average CD4+ count rose by over 400 cells. In 5 subjects, their CD4+ counts rose above 1,000 cells for about 18 months after they stopped using IL-2. In the control group (which did not receive IL-2) the CD4+ cell count fell by about 5 cells/month. Over all, this group lost about 50 CD4+ cells by the 14th month.

HIV

Amazingly, researchers claim that there were no significant increases in the amount of HIV in the blood of subjects in both study groups.

The control group

By the 14th month of the study all subjects who were not already receiving IL-2 were allowed access to the drug and nineteen of 29 subjects chose to do so. Twelve of the 19 are still in the study.

Survival

Five subjects died of complications associated with AIDS, three in the control group and two in the IL-2 group. During the first 14 months of the study one subject receiving IL-2 died of complications from a viral infection of the brain.

Toxicity

Common side effects among subjects receiving IL-2 were:

* persistent tiredness

* muscle pain

* fever

* headache

Two subjects receiving IL-2 had to take thyroid hormone supplements because of the drug's toxicity.

Extra CD4+ cells

Where did the extra CD4+ cells seen in IL-2 users come from? The researchers involved in the study claim that the cells were new and not redistributed from lymph nodes/tissues. Yet results from cutting edge immunologic research suggests that IL-2 "rescues" T cells destined for destruction. These cells were to be destroyed because they were immunologically exhausted, defective or no longer needed. IL-2 therefore appears to increase CD4+ cell counts by maintaining in circulation cells that would normally have been removed. Even when rescued by IL-2, these cells would not be able to perform any useful function. The higher the pre-IL-2 CD4+ cell count, the greater the proportion of CD4+ cells rescued. So far, data from this and other IL-2 studies have not shown that IL-2 treatment delays the appearance of AIDS.

References:

1. Kovacs JA, Vogel S, Albert JM, et al. Controlled trial of interleukin-2 infusions in patients infected with the Human Immunodeficiency Virus. New England Journal of Medicine 1996;335:1350-1356.

2. Adachi Y, Oyaizu N, Than S, et al. IL-2 rescues in vitro lymphocyte apoptosis in patients with HIV infection. Journal of Immunology 1996;157:4184-4193.

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Copyright © 1996 - TreatmentUpdate. Reproduced with permission. Reproduction of this article (other than one copy for personal reference) must be cleared through the Editor, The Canadian AIDS Treatment Information Exchange, 555 Richmond St. West, Suite 505, Box 1104, Toronto, ON, M5V 3B1 • Phone: 416-203-7122 • Toll Free: 1-800-263-1638 • Fax: 416-203-8284  http://www.catie.ca