Neurofilament light chain protein as a marker of neuronal injury: review of its use in HIV-1 infection and reference values for HIV-negative controls.

INTRODUCTION: Several CSF biomarkers of neuronal injury have been studied in people living with HIV. At this time, the most useful is the light subunit of the neurofilament protein (NFL). This major structural component of myelinated axons is essential to maintain axonal caliber and to facilitate effective nerve conduction. CSF concentrations of NFL provide a sensitive marker of CNS injury in a number of neurological diseases, including HIV-related neuronal injury. Areas Covered: In this review, the authors describe CSF NFL concentrations across the spectrum of HIV-infection, from its early acute phase to severe immunosuppression, with and without neurological conditions, and with and without antiretroviral treatment (n = 516). Furthermore, in order to provide more precise estimates of age-related upper limits of CSF NFL concentrations, the authors present data from a large number (n = 359) of HIV-negative controls. Expert Commentary: Recently a new ultrasensitive diagnostic assay for quantification of NFL in plasma has been developed, providing a convenient way to assess neuronal damage without having to perform a lumbar puncture. This review also considers our current knowledge of plasma NFL in HIV CNS infection.