Such cells in HIV-positive patients have a particular gene expression signature [overexpression of APOE (Apolipoprotein E), AXL (Tyrosine-protein kinase receptor UFO), CTSB (Cathepsin B), APOC1 (Apolipoprotein C-I), MSR1 (Macrophage scavenger receptor 1), and TREM2 (Triggering receptor expressed on myeloid cells 2)] that matches significantly with neurodegenerative disease-associated microglia (43). This evidence concerns the gene CTSB and neurodegenerative disease.