GM-CSF promotes the differentiation and activation of granulocytes, monocytes, macrophages, and dendritic cells and enhances the function of these cells. The various cellular responses (i.e., division, maturation, activation) are induced when GM-CSF binds to specific receptors expressed on the surface of target cells. At higher doses, such as the dose used in this protocol, GM-CSF may result in a rapid rise in white blood cell count. However, further research is necessary to determine the potential antiviral effect of GM-CSF in a potent ART-treated population. It is hoped that GM-CSF can decrease the extent of ongoing HIV replication via alteration of macrophage activation and chemokine receptor expression and that this effect can result in reduction of the pool of latently infected T cells.

Patients are stratified at study entry according to screening CD4 count (below 200 cells/mm3 versus 200 cells/mm3 or higher) and screening HIV-1 RNA copy number (between 1,500 and 10,000 versus 10,000 copies/ml or higher). Then, patients are randomized to receive GM-CSF or GM-CSF placebo subcutaneously 3 times per week for 16 weeks. All patients remain on their current stable potent ART (not provided by this study). During Step 2, all patients receive open-label study treatment, consisting of current potent ART plus GM-CSF subcutaneously 3 times per week for 32 additional weeks. HIV-1 RNA, CD4 counts, and clinical and safety parameters are monitored for all patients periodically until Week 52. Patients who experience an increase in HIV-1 RNA of greater than 1 log 10 from baseline on 2 consecutive determinations or a greater than 50% decrease in CD4 count from baseline (a drop of at least 50 cells) on 2 consecutive determinations at any time during Step 1 or 2 must discontinue all study treatment. Patients who discontinue study treatment for any reason prior to Week 16 continue following the study visit schedule through Week 16.

Additional laboratory samples are performed on patients participating in the immunology substudy (ACTG A5042s) in order to further evaluate the effects of GM-CSF on immune function.