DURBAN, S. Africa (Reuters) - Intermittent use of the cancer
drug interleukin 2 (IL-2) can boost the immune system of
HIV-infected patients already taking standard antiretroviral
drugs, conclude researchers from the US National Institutes of
Health (NIH), in Bethesda, Maryland.
"After a year there was a substantial increase in CD4 (immune
cell) counts," in patients taking combination therapy,
explained study co-author Dr. H. Clifford Lane. He presented
the findings, which are to be published in the July 12th issue
of The Journal of The American Medical Association, at a press
briefing held here Saturday as part of the XIII International
Antiretroviral drug cocktails--powerful combinations of
protease inhibitors and other HIV-suppressing medications--have
helped many HIV-infected patients keep the symptoms of AIDS at
bay over the long term.
The NIH researchers speculate that IL-2, which has long proven
useful against certain cancers despite its sometimes toxic side
effects, might also give 'added value,' to standard HIV
Although IL-2 has no direct effect in suppressing the
proliferation of HIV, it does have a stimulating effect on the
growth of immune system CD4 cells, which are white blood cells
that are the prime targets of the virus that causes AIDS. In
fact, low levels of CD4 cells in the blood are an ominous
indicator of a weakened immune system, signaling that the
patient may be vulnerable to the infections and illnesses that
In their study, Lane and his colleagues assigned 39
HIV-positive adults a combination of standard anti-retroviral
therapy and 5-day courses of twice-daily injections of IL-2,
given once every two months over the course of a year. Another
group of 43 patients received anti-retroviral therapy alone.
"After one year there was a very substantial increase in the
CD4 count in the IL-2 treated group" compared with those who
went without the drug, Lane told reporters. Patients on
IL-2/antiretroviral therapy saw their CD4 cell counts rise an
average of 112% over the course of treatment, compared with a
rise of just 18% in those receiving standard therapy.
The researchers note that improvements in immune function
seemed to rise with increasing dosage of IL-2, with those
receiving the highest dose charting a 207% rise in CD4 cell
counts compared with the average 39% increase seen in patients
on the lowest dose.
Finally, the NIH team was pleased to report that the viral
load--a measure of the amount of virus found in a patient's
blood--actually fell slightly in those taking IL-2 compared
with those not taking the drug. In fact, two-thirds (67%) of
patients taking IL-2 saw their viral load level decline to the
very low level of fewer than 50 copies of HIV per milliliter of
blood. In contrast, just 37% of those who did not take the drug
achieved that goal.
There was a down side to the combo therapy, however. IL-2,
while safe over the long term, does have side effects. "Toxic
effects were common among patients," on the IL-2 therapy, the
researchers report, and included flu-like complaints such as
fever, fatigue, and muscle aches. However, most patients were
able to minimize these effects by skipping or re-scheduling
IL-2 dosages, or by using pain-relievers such as ibuprofen or
Lane also pointed out that once IL-2 nudges CD4 to healthier
levels, treatments can be stretched out over longer and longer
intervals before the next booster treatment is required.
"You get the (CD4) pool large enough and it replicates and
replenishes," he told Reuters Health. "We've had patients who
haven't had a cycle of therapy for three, four years."
The next step, he said, will be to find out if IL-2-generated
CD4 cells are as functional and effective as immune cells
produced the natural way. Two international trials, involving
thousands of patients are underway to assess whether the rise
in CD4 prompted by IL-2 is of lasting clinical benefit.
Lane is betting the results will be positive. "As best we can
tell in tests in the laboratory these cells are
indistinguishable from other CD4 cells," he said.
SOURCE: The Journal of the American Medical Association (JAMA)