NEFL and Cognitive impairment: CSF NFL is elevated in early and later infection in subjects with and without cognitive impairment (Peluso et al. 2013; Jessen Krut et al. 2014), although levels are highest in HIV-associated dementia (HAD) (Gisslen et al. 2007; Abdulle et al. 2007; Mellgren et al. 2007) and fluctuate in response to combined antiretroviral therapy (increase with interruption and decrease with initiation) (Abdulle et al. 2007).