Of course, elevations of CSF NFL concentrations are not specific to HIV-related brain injury; CSF NFL concentrations have been shown to be a sensitive indictor of CNS axonal injury in a variety of neurological diseases [56], [58], [74]–[77] including various infections [46], [78]–[82], so other causes of ongoing injury need to be considered in individual cases with elevated CSF NFL. This evidence concerns the gene NEFL and infection.