Unsupervised hierarchical clustering identified a large cluster of subjects with active cocaine abuse (primarily via intravenous route), representing 12/17 cocaine users with higher levels of sIL-2R, sCD14, CXCL9, CXCL10, CCL4, and CCL2 compared to non-users (p = 0.0005; data not shown), while no significant clustering was associated with HAND or HCV co-infection. This evidence concerns the gene CXCL9 and cocaine abuse.