Abstract:
Long-term effects of the growing population of HIV-treated people in Southern Africa on individuals and the public health sector at large are not yet understood. This study proposes a
novel ‘ratio’ model that relates CD4+ T-cell counts of HIV-infected individuals to the CD4+ count
reference values from healthy populations. We use mixed-effects regression to fit the model to
data from 1616 children (median age 4.3 years at ART initiation) and 14,542 adults (median age 36
years at ART initiation). We found that the scaled carrying capacity, maximum CD4+ count relative
to an HIV-negative individual of similar age, and baseline scaled CD4+ counts were closer to
healthy values in children than in adults. Post-ART initiation, CD4+ growth rate was inversely
correlated with baseline CD4+ T-cell counts, and consequently higher in adults than children. Our
results highlight the impacts of age on dynamics of the immune system of healthy and HIV-infected
individuals.
