Determinants of Restoration of CD4 and CD8 Cell Counts and their Ratio in HIV-1 Positive Individuals with Sustained Virological Suppression on Antiretroviral Therapy

BACKGROUND: An increasing number of HIV-positive individuals now start antiretroviral therapy (ART) with high CD4 cell counts. We investigated whether this makes restoration of CD4 and CD8 cell counts and the CD4:CD8 ratio during virologically suppressive ART to median levels seen in HIV uninfected individuals more likely and whether restoration depends on gender, age and other individual characteristics. METHODS: We determined median and quartile reference values for CD4 and CD8 cell count and their ratio using cross-sectional data from 2,309 HIV-negative individuals. We used longitudinal measurements of 60,997 HIV-positive individuals from the Antiretroviral Therapy Cohort Collaboration in linear mixed effects models. RESULTS: When baseline CD4 cell counts were higher, higher long-term CD4 cell counts and CD4:CD8 ratios were reached. Highest long-term CD4 cell counts were observed in middle-aged individuals. During the first two years median CD8 cell counts converged towards median reference values. However, changes were small thereafter and long-term CD8 cell count levels were higher than median reference values. Median 8-year CD8 cell counts were higher when ART was started with