CD4 and HIV infectious disease: Next, to assess the relationship between CSF markers of neurodegeneration, monocyte activation, and systemic HIV infection and to determine whether markers of monocyte/macrophage activation correlate with neuronal injury in HAND, each of the above candidate biomarkers was examined in association with each other and with plasma HIV-1 RNA viral load and CD4+ T-lymphocyte count in all subjects, regardless of cognitive impairment.