Plasma and CSF NfL concentrations in the HAD group were significantly elevated compared to all other subgroups and in the neuroasymptomatic group with <50 CD4+ T-cell counts were significantly elevated compared to the other groups, except compared to the 50–199 CD4+ T-cell counts group and to the primary HIV infection group for CSF NfL only. The gene discussed is CD4; the disease is HIV infectious disease.