TreatmentUpdate 68, Volume 8, No 4; May-June 1996
In 1995, researchers in the USA reported that short courses of
interleukin-2 (IL-2) dramatically increased CD4+ cell counts in
6 subjects with HIV-infection. Recently, another research team
has been conducting experiments with IL-2, giving it to a small
group of subjects together with another immune booster thymosin
alpha1. Produced by the thymus gland in the chest, thymosin
alpha1 has increased CD4+ cell counts when used in one study
with AZT (see TreatmentUpdate 52).
The research team in California used 12 HIV-infected and
symptom-free subjects (1 female, 11 male). Before they received
thymosin alpha1, the average CD4+ cell count was 135 cells.
Subjects used AZT 600 mg/day for at least 2 months before
entering this study. The researchers gave subjects a
long-acting form of IL-2 called PEG-IL-2 (polyethylene glycol
IL-2) in a dose of 1 million units/square metre of skin for
half an hour, "every other week for 20 weeks." Eight weeks into
the study researchers gave the subjects thymosin alpha1 0.4
�g/m2 twice weekly injected under the skin. At the 12th week
researchers "increased the dose of [thymosin-alpha1] to 1600
�g/M2 for an additional 8 weeks."
Results---CD4+ cells, HIV production
After each infusion of PEG-IL-2 CD4+ cell counts rose from
pre-study levels of 135 cells to 193 cells. The next week, CD4+
cell counts fell to their pre-study level. Each time subjects
received PEG-IL-2 the same pattern in CD4+ cell changes
occurred. The temporary increase in CD4+ cell counts was
statistically significant only for the first 10 weeks of the
study. After this point, the increased CD4+ cell counts
following the infusion of PEG-IL-2 were no longer statistically
significant. The performance of CD4+ cells in responding to
simulated attack by bacteria, fungi and viruses did not change
during the study. The amount of HIV produced in the subjects
during the study did not significantly change.
When given PEG-IL-2 subjects experienced "fatigue, headache,
nausea, vomiting, fever...muscle pain [for the next 24 hours]."
Giving the subjects the anti-inflammatory drug ibuprofen
(Motrin ) before the infusions "reduced the severity of
symptoms." The combination of drugs used in the study did not
cause life-threatening complications.
Use of the immune booster PEG-IL-2 temporarily increased CD4+
cell counts. After the 10th week the increased numbers were no
longer statistically significant. Use of thymosin alpha1 did
not cause any "significant change in CD4+ cell number[s]." The
California team suggested that testing the combination in
subjects who have more than 200 CD4+ cells may provide better
1. Ramachandran R, Katzenstein DA, Winters MA, et al.
Polyethylene glycol-modified interleukin-2 and thymosin
alpha1 in Human Immunodeficiency Virus type 1 infection.
Journal of Infectious Diseases 1996;173:1005-1008.