CD4 and HIV-1 infection: LTNP within the Chelsea and Westminster HIV cohort are defined by a duration of HIV-1 infection longer than 7 years from time of HIV-1+ diagnosis, in the absence of ART and clinical symptoms, and the stable maintenance of CD4+ T-cell count within the normal reference range used by the laboratory and HIV clinicians during routine clinical follow-up (450–1650 cells/μl blood) [3], [5], [7].