AIDS TREATMENT UPDATE, Issue 28 - April 1995
Interleukin-2 (IL-2) is a cytokine which becomes depleted in
HIV infection. In the test-tube IL-2 encourages the growth of
CD4 cells. American researchers have been studying IL-2 for
over three years, and in March reported some startling examples
of immune system re-constitution among treated people.
The participants in the study were given infusions of 6 to 18
million units of IL-2 every 8 weeks, plus anti-retroviral
therapy. The infusions last about five days and had to be done
on an in-patient basis, but experiments are now being carried
out with infusion methods which can be performed at home.
Six out of ten people with baseline CD4 counts above 200
enjoyed CD4 count increases of at least 50% that lasted two
months after each infusion. Although participants' counts then
started to drop again, they didn't fall back to their starting
values, and the next infusion increased them again. In some
cases CD4 counts had risen to 1000 after two years of
treatment. The number of functional CD8 cells also increased.
Treatment Issues last month reported that similar responses
appear to be occurring in the randomised IL-2 trial now taking
place in the US and Australia.
The effects were less among 12 people with lower CD4 counts.
Only two out of six people with a baseline CD4 count between
100 and 200 had a 50% increase, and none of the six people with
counts below 100 seemed to benefit. IL-2 also caused sustained
increases in levels of HIV in 10 out of 12 people in this
group, and caused more severe side-effects.
IL-2 has unpleasant side-effects; it causes a severe flu-like
illness during the infusion period, described by one recipient
as "worse than the worst flu I've ever had", and trials have
been slow to recruit because many otherwise healthy people find
the prospect of hospitalisation every two months unacceptable.
Experiments are now going on to find agents which can reduce
the severity of IL-2's side effects.
A French trial sponsored by the ANRS, the French national
clinical trials body, has just opened and aims to recruit 100
people. Plans for a UK trial of IL-2 plus anti-retroviral
therapy are still at an early stage.